A big bike with two motors needs a big battery. Lets take advantage of the frontloader design to hide the battery.
A big issue with an ebike – particularly one that is left outside on its own all the time – is battery security. The battery is maybe the most expensive component on an ebike and its a big theft target. So typically you have to carry the thing inside with you, and hey… thats a real pain in the neck. Not only is it a really heavy black brick, but you have to dismount it and re-mount it to the bike, and disconnect and reconnect it to the motor (forget about your display keeping the correct time and date), every single time. I have come up with my own way to make the best of this bad situation for my other cargo bikes, but with the Bullitt, we can make the problem go away.
The Kinda-Secret Compartment
Take a look at the picture above. See the big black box under the cargo area, near the ground? Thats it: the battery box. You’d be surprised by how many people don’t notice it. Even if they do, what are they going to do about it?
I had seen a few other Bullitt builds with battery boxes and they seemed like great ideas: The battery goes out of sight, out of mind under the floor of the bike. It lets you get creative on battery size (as in you can go bigger if you like since there’s lots of room down there). It may even be made secure enough that you can just leave it on the bike – eliminating maybe the biggest inconvenience of using an ebike for daily errands and shopping.
Also, just as with electric auto designs, a ‘skateboard’ config for the battery puts it centered and below the floor – down as low as it can go. That is as good as it can get for performance.
But I was thinking of none of these things when I was putting together my build sheet. I was still thinking I would do another quick-carry sling pack with the battery inside, and toss that pack into the cargo bay for easy removal and replacement. It wouldn’t be secured to anything but I would see about figuring that out later on.
But while the parts were still trickling in, I was participating in a discussion on the Bullitt Universal Owners Group on Facebook. Another Bullitt owner showed off his own build and mentioned his battery box – and that he had gotten it from Splendid Cycles – the same shop where I got my Bullitt frame and parts. I gave them a call and in short order one of the last examples they had on hand was on its way to me. I was told up front the box was a blank canvas, and I would need my own elbow grease to add mounting holes and any other refinements, such as waterproofing, cable exits etc.
As-delivered, the battery box looked as you see it below. A simple slot holds it up on the back. Its front at first seems unnecessarily complicated, but is quite clever. Its seamless, unbroken face prevents any direct channel for water ingress from the front, just behind the tire. The cutouts necessary to let the box slide into place doubled as my exit points for the power, charging and temperature sensor cables, so no need to cut any holes. It fits absolutely flush to the near side of the frame so no insulation is needed or wanted. Its shape is angled on one side to clear the steering tube.
The first step was to drill the box so it could be fixed in place. As-designed, it would stay put. But I am sure there would be some shifting and rattling… and I can’t abide rattles. Also, the existence of the box complicated the installation of the honeycomb floorboard. The floorboard expects to be able to drop a bolt straight down and use a nut underneath to lock it down. Well, now that bolt hole is completely inside the box on the front left corner. Its outside on the right front, but not by much. I needed to change those two mounts to fixed studs going from the bottom up.
I also wanted to add an entirely separate bolt on the front dedicated to strongly fixing the box in place. I decided to use an oversized hole, and used a hand file to enlarge it to a rectangle. Following that, a combination of an oversized, hardened washer and a flush-fit M8 bolt gives a flat fit that works under the honeycomb board fitting directly down on top of it.
The new ‘studs’ are common, long M6 socket caps with – get this – a Presta valve nut to hold them in place. I needed a low profile nut and there’s nothing lower-profile than the common presta nut, which even fits snugly inside the bolt hole manufactured into the LvH honeycomb board.
For the rear of the box, to match up with the honeycomb board’s rear mounting hole, I had to use another M6 rather than go with another big M8. I drilled a thin hole thru the box’s top flap and the honeycomb board’s rear mounting bolt goes thru there. However to be consistent – because I wanted to use security nuts to make getting into the box that much more difficult – I made it go in from the bottom-up like the others (we’ll show those security nuts etc. in more detail when we talk about the cargo box installation).
Now Install The Battery
At this point, the next step in the installation process – which, maddeningly, has to be done in this order whether you like it or not – was to install the battery.
You can see how I accomplished that below. All of the padding is closed-cell, and I left as much of the battery untouched by foam as I could. The battery lays on the bare alloy of the box with no padding (a solid metal wall is plenty of protection). It is surrounded on four sides such that it cannot move, even after months of pothole pounding commutes and store visits. I disassembled the bike after 500 miles and looked inside to be sure of this. No water had gotten in either despite riding in rainstorms.
There is a brake cable braze-on above the pack underneath the center bar. It is perfectly positioned to smash into the cells underneath if the pack bounces up to meet it. I prevented this possibility via some left over Minicel T600 EVA foam (you’ll see what I used it for in the Cargo Box episode) to fix the battery in position (i.e. keep it from bouncing). Two pieces are used, one on each side of the braze-on. Underneath this area the visible green rectangle is a piece of thin metal fence strapping which provides a last but certain line of defense against that braze-on ever contacting the bare pack.
The battery is literally incapable of movement on any axis. It is held solidly – but not enough to smoosh anything. Rapping on the box with your knuckles yields a satisfying thunk as if you are rapping on a solid block of metal.
Lets Talk About The Battery
An AWD bike needs a lot of power. Even one where I have toned down the power to civilized levels. You must have a pack whose Battery Management System is strong enough to run two motors at once, and if you get into the subject and learn the specifics, you will find out real fast that commercially-manufactured battery packs can’t cut the mustard (this is why commercial AWD bikes have two separate batteries). If you want to build the bike right as opposed to building it cheap and sucky, you have to get yourself a custom pack built that is tailored to the job.
The battery itself was built custom to my specs after some discussion with Matt Bzura at Bicycle Motorworks. This is one of several packs I have purchased from his firm, after hearing nothing but good things about his work from other builders over the span of a few years. I’ve had nothing but good experience working with him as well.
I knew that an AWD bike needs more power, so the battery pack needs to be bigger than usual. And the Splendid Cycles battery box is a big sucker. If I put in a battery that filled that box it would be TOO big. Looking at the box dimensions and knowing what I wanted to do for crash padding gave me one half of the picture. Matt @ BicycleMotorworks filled in the blanks with the dimensional details of the cells and battery management system chosen for the job.
Samsung 40T (21700’s)
70a Continuous output
XT90S / 8ga
XT60 / 12 ga
The 40T cells in the larger 21700 size, and overall pack design allows it to operate under load without voltage sag, and without heating up, despite the enclosed space and the dense, closed cell padding that holds the pack fast. A temperature sensor is attached to the pack top and runs outside of the box for easy visibility from the saddle.
What About Heat?
In use in a normal climate - bearing in mind its sealed in a big metal box - the pack does not get noticeably warm over and above ambient air temperature - nothing over 5 degrees Fahrenheit above ambient. However, 5 degrees over ambient is a lot when its 105 in the shade, where in the sun, the pavement is radiating heat at 130. In severe heat (as I write this, the end of next week is scheduled to reach 114°F, which is more than 45°C) I need to plan ahead for where the bike is going to be parked, and plan my route to provide the shortest, shadiest path to my destination. Our local area has already experienced several days where the temperature has exceeded 110°F / 43°C. Even though the battery cells are not thermally coupled to the case, I ringed the box with heat sinks to help keep the pack a bit closer to ambient temperature. They have reduced pack surface temperature by up to 5 degrees.
The battery charge cable is routed outside of the box along with the power cables, and comes up as shown in the photo below (the green plug). This plug is semi-rigid thanks to the manner in which I insulated the end connector, as well as how its braced against other secured wiring. It is easy to access, protected from the elements via the plug cap and not going anywhere. In winter months a rubber band and some plastic will ensure nothing can get through and cause any fireworks.
And last but not least… this is a 52v battery that has a capacity of 32 amp hours. I like having batteries big enough that range anxiety doesn’t exist. You simply go ride the bike and do what you need to do. Considering the bike – thanks to its motor configs – eats only 400-500w at cruise… my ass will wear out in the seat before the battery charge does…
So long as I remember to charge it. But even then – and this has happened to me already – the battery is big enough to maybe rescue me from that faux pas.
(not) The End
Thats about all I have on the battery and battery box. We’ll stick to the same area of the bike in the next article in the series, as the two of them are linked together:
And now for something completely different. The Bullitt from Larry vs. Harry is a bucket list bike that (now that its finally done) I love to ride. This series will cover the details of a frame-up build that includes AWD electrification.
Originally, this was going to be a single article that covered everything. However, as time progressed and I got more and more of the details written down, I found I was at almost 6800 words, and could easily hit 8-10,000 before completion. Thats too damn big, so it had to be broken up. This opening post will cover some of the introductory bits. Then we’ll split off into followups that hit the high points of the various things worth bringing up.
Looking at all those different pictures, they all look sort of like 2- or 3-wheeled dump trucks. Not exactly a fun ride. But thats to be expected of freight haulers, right?
So, What the hell is a Bullitt?
A Bullitt is a frontloader-style cargo bike made by Larry vs. Harry in Copenhagen, Denmark. It does its cargo carrying job, but its also specifically designed to be nimble, on a frame that is relatively rigid. Its also meant to be those things in a lightweight package, where that frame is lightweight alloy (whose inherent rigidity is mitigated by the sheer length of the frame. A Bullitt is also a very comfortable bike to ride).
In short, the Bullitt is a cargo bike for people who still want to have fun riding their bike. You aren’t schlepping around in the bicycle equivalent of a minivan.
When I originally decided to build up a Bullitt, I set up my build sheet and began listing out components. But before I finished, the cost crossed my pain threshold and I chickened out. This was going to be my first cargo bike. I had no experience with the platform, and wasn’t even sure I would like the idea, never mind throwing in the funkiness of a frontloader. I wasn’t ready to make such a big financial commitment.
So I went the budget route with the Mongoose Envoy. I used that frame and fork as a donor platform to develop a really nice lower-cost cargo solution. After some use I decided 1)this whole cargo bike thing was really cool and 2)the Envoy wasn’t big enough for the XXL jobs I wanted to give it.
When I was doing my research prior to buying the Envoy, I had almost bought the much larger Surly Big Fat Dummy, but bailed on that one too due to the same kinds of newbie uncertainties that led me to bail on the Bullitt project.
So, wanting to upsize, I went there next. That bike has been a thing of beauty. I loved it and still do for a variety of reasons beyond its utility as a cargo bike (and a bikepacking bike. And a take-the-trails-route-instead commuter. And an unstoppable freight train that terrifies all who cross its path). The Big Fat Dummy truly is a BFD.
Using the BFD for all things, every day, I could see room for improvement. Stuff that bugged me and worse – slowed me down.
At the shops, you have to bring the battery in with you or risk getting it stolen. I had a solution for this but it still takes effort to deal with and is a pain. Additionally it limits the size of the battery as the bigger it is, the more trouble it is to carry around.
The BFD has two panniers that hold more than 275L (not 27.5… Two Hundred and Seventy Five). Who can ask for more? Except bags that big aren’t kept opened up and ready for use. They’re folded up and strapped to the frame. Expanding them requires some fussing and fiddling with the straps. Not the end of the world but it has to be done. And then you need to cinch those four to six straps down to secure the load. And balance your load between the bags or bad things can happen. When you are doing this every day at multiple stops, you start wanting things to be easier… but how?
Enter The Dragon
A Bullitt from Larry vs. Harry. Thats how. A bike purpose-built for a narrow type of use-case: urban utility. The Bullitt is the most nimble and rigidly-framed of the genre: the sports car of the frontloader world. The battery on this bike will be locked in a quasi-concealed, sealed box under the cargo floor of the bike; out of sight from prying eyes and prybars. No more lugging it into the store with me. Most importantly, the bike has a floor in the first place. Cargo is held in a great big open box. I can just walk up, dump my shit in and and take off. No more pre-flight prep.
Also I kind of liked that it looked weird… and I had no idea whether I could ride such a contraption. I don’t get that kind of uncertainty with bikes much these days and I looked forward to the challenge.
Oh, and since LvH decided to call the green paint on the bike Lizzard King, well that makes for an obvious name for the bike.
Bullitts are – wonderfully – built up from frames and customized by a great many of their owners. So even though I am doing a lot of writing-up here, there’s not much point in doing full how-to’s, since thats how most everyone does it already, anyway. So my focus will for the most part be more of a high-level one rather than getting down and into the finer details of Tab A inserting into Slot B etc.
So Lets Build It Already!
So much going on… Where do we start?
The Frame Kit
Your local Larry vs. Harry dealer will happily sell you a complete bike, or even one whose frame has been purpose-built to integrate an electric motor. You can choose an internally geared hub, and the frame has a split in it to allow a belt drive. Lots of options for a complete bike, or buy their frame kit and build your own.
I chose the frame kit route. The kit comes with the frame, fork, steering arm, headsets (plural) installed and a number of other components that are unique to a Bullitt’s construction, so you don’t have to go searching all over creation for weird parts. I also purchased the “honeycomb floor board” (the cargo deck) and the “side panels” (hard sides to the cargo area that turn it into a big bucket). It all arrived in one giant box, too big for UPS so it was a LTL freight carrier in a full sized semi-hauler that brought it in. The truck was so big it had to meet me on the street.
I purchased the frame kit from Splendid Cycles up in Portland, Oregon. I handled the transaction entirely over the phone and the folks at Splendid were both helpful and generous with their time, answering my technical and build questions and making sure I was taken care of. Delivery was prompt and I was frankly amazed at how well the frame was packaged once I got the box opened up. Oddly enough I met the tech who packed my frame online, in the Bullitt Facebook group, who was happy to see I got the frame and confirmed what was visually obvious: he had spent time making sure it was packed well so it would get to me in the same shape it left their shop.
All Wheel Drive
Even though the bike only took me about a month to build so it was at least roadworthy, there was a lot going on with this bike. Most of the reason it was such a pain revolved around this one feature. In the end, it was worth it, but the added complexity of an AWD ebike is not for the faint of heart.
I have built several all wheel drive ebikes, but not recently. I decided the Bullitt was going to be the proof-of-concept behind a different, more civilized/everyman form of ebike AWD that I had been mulling over for years but never did anything about. That subject, the merits of an AWD ebike and the specifics surrounding it are all dealt with in a separate case study in my dual-motor AWD ebike series. I’ll let that post and its companions stand on their own and just say that the sort of cooperative, drama-free AWD that was put into the Bullitt is, in my estimation, a tremendous success with regard to making it a viable all-day, everyday auto replacement.
On the surface, it seems I left a hole in my description of my Surly Big Fat Dummy build. I omitted this episode and thought I was done. In my defense, there are zillions of BBSHD installation tutorials out there, and I have described a BBSHD install myself – on a cargo bike no less – right here in this blog.
However, I haven’t done a writeup geared to THIS bike. Since this blog is dedicated to answering questions that I see asked a lot (and I have seen this one more than a few times), I’ll do something a little more focused on the BFD.
Bear in mind the bike has been in near-daily use for months already. I had to dig thru my archives for pics rather than taking them as I went along. So illustrationwise, there’s not much to see. On the flip side of that, there doesn’t need to be as the Big Fat Dummy is an easy (easy!) build.
Since I have covered this ground elsewhere, I’ll be leaving generic details out, and providing links to related content more so than I will be doing in depth step-by-step instructions.
Get On With It Already!
Yeah, yeah sure … here we go.
Step 1: Buy What You Need
This can be very simple or very involved. Especially if you are a first-timer and don’t know what you need and maybe not even what you want. In my opinion the best motor for the job is a Bafang BBSHD. I typically buy my motors from Luna Cycle, and here is their page for their kit. They may or may not be selling a battery along with that kit. I am using a different source for the pack as you will see further below.
If you buy the kit, you don’t have to worry about buying individual bits, with the exception of needing a speed sensor cable extension, and a proper chainring.
But, lets go over the individual bits. Myself personally, I just buy the bare motor from Luna, and add the parts I need to complete the installation. This lets me use exactly what I want, which is not quite possible if buying the packaged kit. Here are all my parts:
Bare Motor: Purchased from Luna Cycle here. The Surly Big Fat Dummy requires the 100mm sized motor (It will be a perfect fit). if its available you can buy the optional spacer and mounting kit on that page. At the moment, Luna is not selling the 100mm mounting kit – the only difference is some M6 bolts and spacers… you can source that yourself to the correct size if needed. Or just buy the needed parts separately. Go ahead and accept the 46T chainring (aka ‘The Disk of Death’) as its a free throwaway item you would (should) never use. Secondary Source: California Ebike is a reliable alternative and one of my go-to sellers for parts, but their motors cost an additional $100 or so. Here is their BBSHD motor page.
Motor Mounting Parts:
Triangle Mounting Plate: This is what puts the bite on your bottom bracket to firmly affix the motor. You can buy these plates at Luna Cycle, BafangUSA Direct or Amazon.
M6 bolts, washers, spacers: Needed to affix the Triangle Mounting Plate, these are commonly available. If you work on bikes you probably already have them in the garage. If you buy a mounting kit they may have them but in all cases I recommend you do not use them and instead go out and buy stainless hardware.
Lockrings: I use two inner rings stacked atop one another. If you like, you can buy the more conventional inner and the aesthetically-pleasing outer. More on the reasoning behind the choices below. Buy the rings at Luna Cycle, Bafang USA Direct or Amazon.
Speed Sensor & Cable Extension: You will need the sensor (which integrates a length of cable to plug into the motor), the sensor magnet and an extension thanks to the Surly Big Fat Dummy’s long tail. I have seen builders route the sensor to the front fork but by necessity this puts the sensor inside of the tire rim’s width, which makes for issues taking that tire off. Put it on the back where it belongs and forget about it. I described the sensor in a fair bit of detail here. Don’t mess with multiple magnets unless you feel a need to experiment, but I do provide a link to what I think is a lighter weight, superior magnet that you may want to substitute for the Bafang wheel weight that comes with their sensor. The speed sensors themselves are available in a wide variety of places, cheapest at Luna but also at California Ebike and many other sources. You can get the speed sensor extension anywhere you can find the speed sensor. California Ebike or Bafang USA Direct or many other sources, including Amazon with Prime Delivery. Notice all of the options I linked are different lengths. Measure the gap you have when you are routing your cabling and decide which one you want, accordingly.
A Proper Chainring: I am going to skip most of the detail here and refer you to this blog post on BBSHD chainrings. It was written with the Mongoose Envoy build in mind but the Surly Big Fat Dummy is essentially an identical set of problems and solutions. I will say this: For a combination of mostly street with some mild trail use I settled on the 46T Lekkie Bling Ring, which biases chain line towards the bottom half of the 11 speed cluster. This is the ring that has the most miles on my bike and its the best all-rounder. At the moment I am set up mostly for trails, though, and as such I am running the Luna Eclipse 42T which biases chainline heavily toward the inner half of the rear cluster, giving me good access to the inner cogs. You cannot go below 42T in the front without compromising chainline to the inner cogs.
Note with a BBSHD, the stock My Other Brother Darryl rims and the stock Edna tires, you will not be fully able to use all cogs simply because chainline will not be acceptable for a 1x drivetrain pumping out 1000 to 1750w. You8 can do it, but the chainring teeth and maybe the chain will not last very long if you run at either extreme – say… the biggest cog and the Lekkie chainring.
Two of the pics below show a 130 BCD adapter which really biases chainline to the lower cogs, and is best for the street. Both of these use 48T, 130 BCD chainrings. Even though most of my mileage on this bike is with the Lekkie ring, it doesn’t appear as if I ever took a picture of the bike with the thing installed.
Crankarms: In two of the pictures above you can see I used Lekkie Buzz Bars, and with their forged construction and left offset to correct the misalignment under your saddle that will happen with standard crankarms. Luna Cycle sells a less-expensive clone worth looking at if you can’t handle the price of the Lekkies. As a last resort you can also use the standard Bafang crankarms that are cheap and cheaply made, but good enough for many riders. Make sure you buy BBSHD-specific arms or they will not have the left offset.
Display: I have used many displays and hands down, at the present time the Bafang/Luna 860C is the best out there. It is fully visible in blinding sunlight and can be set to display both real time amp output as well as real time wattage. The Luna version reads battery voltage level accurately up to 60v, meaning it works with 52v batteries. Bafang versions of the 860C may not. There are many other options for a display including a low-visibility-but-clean/low profile EggRider v2. For my money the 860C is worth waiting for if its temporarily out of stock, and its my go-to for bikes I build.
Throttle: I like the basic el cheapo Bafang universal thumb throttle. Its an easy fit and unobtrusive. If you follow my lead on BBSHD settings for it, its annoyingly short throw will still be well controllable and allow for fine adjustments while riding. Buy it at Luna, California Ebike or Bafang USA Direct.
Main Bus Cable: You have options here. the main bus cable is available in short and long lengths, and there are also extensions available. However nothing fancy is required on the Surly Big Fat Dummy. You can buy this standard one from Luna or many, many other sources. If you opt to use Magura MT5e brakes, California Ebike has a specially modified harness to plug in the red Julet cutoff connectors the MT5e uses. I am using this bus cable and MT5e’s, myself. NOTE: If you opt to keep the SRAM hydraulic brakes you will not have brake-actuated motor cutoffs. This is no big deal. They’re nice but the stock brakes can overpower the motor in a pinch. If you like, you can invest in some hydraulic cutoff conversions that involve gluing on a magnet to your levers and strapping on some wires. the alternative is a brake upgrade (not a bad thing, but not cheap, either).
Installation tool(s): Using one of the many Bafang-inspired toy wrenches to install a BBSHD is a cruel joke on the inexperienced. You have to use a proper torque wrench and special socket to do the job right, where the motor doesn’t move. I’ll leave the torque wrench choice to you (I use a Wera B2). The socket you need for the inner ring is often out of stock. Buy it here at Luna Cycle or hunt around… its available elsewhere if you look. The tool for the outer ring can either be hand-tightened – if you must – with a stainless steel version of the cheesy Bafang wrench. I bought this one on Amazon so I know it fits. But it is absolutely a sucky solution. Better is to use a 16-notch bottom bracket tool that you can fit onto a torque wrench and do a proper job of applying the manufacturer’s torque spec, written right on that outer ring. Note if you use two inner rings you do not need the special outer ring tool.
OK so you have all of your parts for the motor… Time to take things off so you are ready to do the installation. Its a simple list: Remove the crankarms, bottom bracket and chainrings.
You’ll also want to pull off one of your handlebar grips in preparation for installing your throttle. Which one depends on how you want to set up the bars. You will also likely want to loosen up and shift around your brake levers and the remaining rear shifter so your throttle is butted up directly against your hald-grip, rather than the brake being there. this is a bridge you should cross when you come to it, disassemblywise.
Thats it. You’re ready to install your motor.
Step 3: Install The Motor
Here again I’m not going to get too deep into the specifics of motor installation. I’ve already covered it myself elsewhere for a similar bike, and God knows there are plenty of video and written tutorials out there on the interwebs. However I will note that the 100mm motor is a perfect fit on the Surly Big Fat Dummy, which requires no spacers of any kind. Just put it in like it belongs there and clamp it down tight.
About that clamping part, I will go into that a bit:
I mentioned above that I like to use two inner (gray) lockrings: I stack them atop one another in jam-nut fashion where each is tightened to 100 ft lbs. Thats quite a lot more than the Bafang specification for using just one inner lockring. I am going off of installation advice provided by Luna Cycle – not in their official installation video linked above. At one time there was a supplemental vid made in their shop that discussed their learning to do this on their shop bikes. It went hand in hand with the use of a big 1/2″ torque wrench to apply the necessary force, and that wrench in turn used a specially made Luna tool for the lockrings (that sadly is no longer available, although you can see them on the site still). The use of 100 ft lbs and some additional info on it is in the link to the tool above.
I have stuck to that 100 ft lb specification and it has never let me down. I have also added to it by using a second inner lock ring rather than the ‘beauty’ trim ring that is more typically used. the number of threads needed for another inner ring is about the same. You gain the benefit of a serious jam nut holding down the first ring. Also, something we are not doing here but you can see elsewhere: If you are building an AWD bike, the use of two rings lets you mount the front wheel’s PAS ring in between the two.
I do not use the outer trim / beauty ring at all.
Lastly on the subject of lockrings, here’s a technique to tell at a glance whether the rings are loosening or your motor is shifting (or about to): Make a registration line along the frame and the lockrings. If the line ever breaks apart, something is loosening. You can tell with a simple glance down as you are mounting the bike.
Next, I’ll make note of how I did the speed sensor installation, both with the factory SRAM brakes and my later MT5e upgrade.
Using the SRAM Brakes / No Helpers
Attaching a speed sensor on a Surly Big Fat Dummy is not as straightforward as it is on a typical bicycle. In addition to the added distance – addressed with an extension cable – there’s no place to put the thing! The frame is different enough that nothing appears to work – on first glance.
Keep looking! the SRAM brakes that come stock with the bike have a weird sort of tail hanging off the caliper, and this is a handy, if unusual, place to mount the speed sensor.
I first wrapped this tail with a length of 3M mastik tape to enlarge its diameter and give the sensor more to grab onto. Then I simply zip tied it on as if it were a chainstay, and aligned the magnet as usual. These pictures show a dusty bike as they were taken just before I uninstalled the sensor and upgraded the brakes to the Magura MT5e’s.
Using Other Brakes – And a Crutch
For the Maguras, there was no such luck as the calipers have no tails or anything else I could glom onto. So I had to add something: I used a simple small handlebar extension, and built up the frame to a proper larger diameter to mount it by wrapping the frame with gorilla tape, which I then faced with silicone tape to provide a grippy surface for the bar mount. Next, I used more zip ties (!) to clamp the new ‘frame tube’ to the upper part of the Big Fat Dummy’s … superstructure. Once this was done, I had a tube close enough to the spokes to re-mount the speed sensor as shown.
Well, a bunch I suppose if you were looking for a bolt-by-bolt conversion tutorial specific to this one bike. But really, between the other pages already on this site and the links I have given off-world up above, you’ve got everything here that you need to buy – and build – your own.
52v, 32ah single battery, skateboard config (box under cargo floor)
KT and Bafang displays
160 Nm rear, 45Nm front
This bike had a fairly involved build with lots of neat details. However, thats not what this article is about. Build details will be discussed in a near-future article dedicated to the subject.
My previous AWD builds all used effectively the same front wheel setup: A 35a controller mated to a Bafang geared fat motor packing an 80 Nm punch. It was so powerful, on my early commuter bikes I needed to turn down acceleration via a slow-start setting. When I graduated to a combination mid drive+hub, I found best results on rough trails came from the same slow start, but also using the front power sparingly: little if any throttle and gentle PAS.
There things stayed for a few years – roughly from the middle of 2017 to early 2021. During this period I concentrated on riding and refining the use and configuration of these AWD bikes. I built other bikes during this time- all more traditional single-motor mid drives. As part of that work I came up with tuning settings that worked very well with pedaling and a cycling mindset. These changes worked great with the 2Fat AWD bike as well.
With regard to tuning, I concentrated on backing off the BBSHD’s power when delivered in ‘pedelec’ mode: limited use of throttle and pedal assist only. The point of this was to have a bike that did not run away from me, still delivered measurable, useful levels of assist, lacked the common complaints against cadence-type assist and did not suffer from any of the weaknesses of torque-sensing.
When 2021 arrived and I wanted to build a bucket-list bike – the Larry vs. Harry Bullitt cargo bike – I decided to go all out and make it AWD. Further, I wanted to prove a concept I had been mulling over for the last few years. For lack of a better term, lets call it Drama-Free AWD: what a normal person who just wanted a reliable automobile replacement would want to ride.
Its a pretty short list:
Low power High power in a front wheel can be fun, but its not necessary to gain the traction benefits that come with AWD. Use a smaller, lighter, relatively low-powered motor (45 Nm vs. the prior 80 Nm) as part of its design. Also use a smaller controller that peaks at 25 amps rather than the previous 35. Continue to use the slow-start setting to ensure … Drama Free AWD. 25 amps on a smaller diameter wheel will still be a strong assist, but those amps will be rolled on slowly so no surprises.
Fast Wind Front Motor The Bullitt has a 20″ front wheel. A ‘fast wind’ motor favors torque off the starting line at the expense of higher top speed. This is normal for a small wheel build and further solidifies the emphasis on slow, strong startup power that melts away on its own as speed increases.
Toned-Down Rear Motor My revised motor settings keep the BBSHD from engaging until speed goes past 5 mph if I rely on pedal assist. I learned how important that is to drivetrain longevity when I built 2Fat. We’ll re-use those identical settings.
What I Expected
On a bike destined to carry heavy loads, the front motor is intended to get the bike off to a painless start. It does this job very nicely. Despite the relatively low power, it still gets the bike rolling from a stop, and effectively takes out the BBSHD’s shock to the drivetrain when that second motor kicks in at 6 mph.
That reduced sting will translate into reduced wear and tear, and reduced parts replacement over time. Its too early to pull hubs apart and look inside to verify this assumption, but since I have seen and verified the effect before on similar hardware, there’s no reason to assume different results.
It was a short list of things to expect and… it all panned out. But there were also some pleasant surprises. This turned out better than I thought it would.
What Surprised Me
I noted above the motor is ‘fast wind’; built for low-speed torque, not high speed rpms, and how this plays into the smaller front wheel size. Intellectually, thats easy to understand. Less obvious was the fact that, in practice, there will be a lot less motor usage than there was before.
With The Great Pumpkin, I usually run both motors at equal levels (usually full blast) all the time. The bike and flat, straight streets just lend themselves to a high speed cruise. Two identical motors and identical controllers gulping juice from one battery mean a big power drain. No surprise.
With 2Fat, while I reduce power to the front motor, I was often giving the bike hard use on trails. More often than not the bike is fighting its way up a hill, thru a bunch of sand etc.
So even though The Lizzard King is not dramatically different than 2Fat in terms of its configuration, the world it lives in is quite different: level and smooth city streets. Easy acceleration and long periods of the motors spinning fast while running at an efficient cruising speed.
More different still: Off the line, the front motor kicks in slowly and then power melts away as wheel revolutions increase. It pulls strong from zero to about 16 mph. But from 17+, it starts scaling back as the motor approaches its rpm limit. By the time 20 mph rolls around, on typical level 2 assist you are down to about 200 watts of output. By the time you hit 23-24 mph on flat ground, wattage to the front wheel has minimized to a steady… 37 watts. Just enough of a dribble to ease the wheel’s free spin.
If you hit an incline, you’ll slow down a tad and see wattage output creep up again. But rolling down the street on the flats, the front motor takes itself out of the picture. Its time for…
… The rear motor to kick in. As noted, pedal assist does not engage the rear motor until it crosses past 5 mph. So when the front motor is eating the most juice, the rear motor hasn’t even started. As the mid kicks in and spools up, the hub begins making its graceful exit.
The two motors never really run hard together at the same time, unless climbing a hill. Then you can see watts climb on the front rather than fading away. Cruising at an energetic cadence around 24+ mph , you are on the single rear motor, being given a small boost from the front motor (remember those 37 watts?).
With the two motors staying out of each others’ way, this translates to an overall reduction in expected battery drain, consisting of both reduced peak and continuous draws. It gets better though.
The rear BBSHD is also using a lot less power than its siblings in The Pacific Fleet.
At 20 mph, on PAS 2 in the front and maybe PAS 4 or 5 in the back, looking at both displays, I can see 250-300w being output from the rear motor, and another 150-200w being output from the front. 500w or kess are being drawn between the two motors, on a great big cargo bike. All the way up and down the speed curve, watt and amp output for the BBSHD is much less than it is on any of my other bikes.
Not So Fast!
All of this wonderfulness is only true when running under pedal assist. If I mash the rear throttle the BBSHD will, as usual, peg the output gauge until I release. And that means it will burn thru my battery range lickety-split. Not a surprise. There is no free lunch in this world, but if we stay off the throttle we still get a hefty discount.
And I still configured my big single battery (custom-built for this bike) to the usual theoretical limits: A 25a peak front controller and a 30a peak rear controller mean I must have a battery management system with a bare minimum of a 55a continuous rating, and preferably 60 (mine is 70). I would rather not take any chances, but clearly I have a bigger safety margin than I figured on originally.
And despite the capability of the bike, reality is it rides more comfortably around 20 mph. So power consumption is lower still simply because of the type of bike it is. But the big takeaway is its lower power use is lower across the board. It was an unexpected gain in efficiency, but looking back on it, it should not have been. The benefit was hidden by my hard use of the other bikes.
Should a commercial bike be made with this Drama Free AWD kind of approach in mind, a thoughtfully designed system could manage power in such a way as to map out the curves on the individual motors. Develop something that never bumps into the limits of a much more conventional BMS. That makes for a battery system less expensive and easier to source in volume. And a street machine is going to have lower power needs than is generally understood to be the case with an AWD bike.
Lower power means safety for the casual rider, lower cost and smaller battery sizes.
Lower power on a street bike could look like – in the USA at least – dual motors fitted to bikes that still remain legal within both federal manufacturing standards and individual state vehicle codes. A 249w front motor and a 500w rear for example. Or even a 250/350.
Whats the Takeaway?
The fact that I can operate a great big bike like The Lizzard King at power levels well below allowed USA ebike power limits is testimony to the fact that viable, useful AWD can operate well within the legal framework of ebikes in this country.
Just because you have two motors does not mean they both have to be running simultaneously at full blast. Turns out… not doing that can be kind of a big deal.
Back when I put together the Mongoose Envoy Project, I used a skateboard deck to cover over the long, but only marginally-useful-on-its-own rear framework to create what ended up being an aircraft carrier landing deck.
I started out with a 33″x10″ double kicktail which I mounted on top of eight 25mm tall by 13mm dia. spacer posts. The idea behind the spacers was to give me some working room to attach a net to the top of the deck, and have room to easily mount its hooks to those posts. It worked well, but I left money on the table with only a 33″ deck. I could go longer. So I did. I found a 40″ longboard with a single kick and mounted it on 10 posts, this time.
It was great, but of course, I thought I could go one better. So I scored a 44″ double-kick longboard, and – since the 25mm posts were a bit fiddly trying to get my fingers in that small space – swapped out for taller 40mm replacements. I also made some other improvements, and that deck remains on that bike as you see it here to this day.
Fast Forward To The Present…
Now I have a Surly Big Fat Dummy, and I want to do the deck idea one better (AGAIN!). I still have the 40″ deck left over from the Mongoose build. Since the BFD is already like 8 feet long I don’t need something that makes it longer, so this ‘shorter’ deck will do just fine. I drilled some new holes, repainted it and took the spacers a step further.
The Next Level (literally)
Unlike the Mongoose, which had nothing but a framework, the Surly Big Fat Dummy already has a pretty good deck as it is. On the Mongoose Envoy I was trying to cover over the bare framework and make something useful. This time I am trying to make something already useful more so.
To preserve the utility of the existing deck, I went with much larger spacers. That created a ‘hangar’ under the deck of this aircraft carrier of a bike. This new hangar’s purpose is to house things that need to be carried along, but generally kept out of sight. Stuff where I can benefit from it being reasonably handy, but kept out of the way.
Great Idea. But first I had to assemble the parts and make the thing.
Like my previous decks, I wanted to use enough spacers and bolt anchor points to make the deck an integral, structural part of the frame. No wiggling possible. Part of what it takes to do that is to use the widest spacers I can find (the 5/8″ OD are it, and dictated why I couldn’t stay metric). To further solidify the connection laterally, I needed washers everywhere clamping everything.
And excepting the spacers themselves, its all Grade 8 hardened steel. Its. Not. Moving.
Notice also I used hex bolts and did not bother to work with countersunk heads, matching washers etc. as with the previous decks. This thing is spray painted in truck bedliner to help keep things from sliding around, and the hex bolt edges do the same job.
Airframe bolts exist in a wide variety of very finely diced sizes. I am not giving the size I used because the ones you may need will vary according to the thickness of your top deck.
Here’s what the finished assembly looks like up close:
Now that the aircraft carrier has a landing deck, we find out what we stuff down underneath in the hanger.
Take the crap off the top of the deck and you have yourself a work table. Or a coffee table. Or a picnic table. Its 40″ long so use your imagination.
See that net? Its 30″ long before it gets stretched out, and since I ordinarily have the Great Big Bags on the bike, I generally do not need to use the top deck for storage of items up so high. But when I do, that nice long cargo net does a great job.
Got a Big Fat Dummy? And a drill? And a skateboard? Make yourself one of these. Next time you have to sign a peace treaty, host a banquet or make off with an emergency supply of toilet paper… you got this!
Parking your ebike outdoors all alone? When shopping, my cargo bikes are locked but out on the street… but the battery goes in with me. Here’s how I do it without people thinking I am carrying a bomb.
Yes You Can Take ‘it’ With You
An ebike used for utility purposes is, by its nature, going to be left out a lot. You go to the store, load up a shopping cart, come back and fill up your saddlebags. You really want all the parts on the bike when you left to still be there. Especially after loading on 50 lbs of cat food, Oreos and diapers.
The most obvious way you keep the bike itself is to use a good locking strategy. I’ll save that for a different discussion. This time I will focus on how I protect the single most-expensive component on any ebike – the battery. Not by locking it up, but by making it so I can do a quick grab and carry it in with me.
By removing that battery, we are making that big heavy ebike into a boat anchor, which we can hope makes it at least a little less attractive to thieves.
Size (and Shape) Matters
What I am describing can be made to work with any shape battery, kept anywhere on your bike. What you see here works best with a squarish, oblong battery. In the pics below I am using a 17.5ah Luna Storm battery, which is pretty big and heavy (in part thanks to its powerful but not-so-energy-dense 25R cells). More likely, if you have a similar heat-shrink battery pack like this one, its quite a bit smaller and lighter.
I also keep a Luna Wolf Pack battery like this and do not use its magnetic mount. The battery is easy to quickly get off that mount, but leaving it inside of a bag like I describe here is, overall, easier than stuffing it in every time, taking it back out and so on. For packs like this (Wolf, Shark, Dolphin etc.) you could certainly bring a small pack and put it in/take it out as a part of your routine.
There’s more than one way to skin this cat, so what you see here is just a jumping off point.
Lets Get to It
This is the battery in its bag, just like it would be if I rolled up to the local Costco.
If we zip open the bag, we don’t see a battery. We see an inner bag, along with that charger cable extending thru to the rear. The controller cable is in there too just out of sight (look closely and you can see it)
If we look inside the bag, we see the battery charge cable is in fact an extension running from the rear of the interior bag up and out the front. The motor cable – an XT90S connector – also has a short extension between the battery cable and the motor cable. The idea is this: when routinely, frequently detaching and reattaching the cable, if there is any wear its on a cheap, replaceable extension and not a critical, live/hot cable coming directly off the battery.
Disconnect the cables and give a tug to the inner bag. Here its shown halfway out but you will just pull the thing out in one motion.
Annnd here we are. the cables are shown sticking out of the inner bag. You will want to cap those for safety’s sake. I use cheap plugs I got a bagful of on Fleabay for a couple bucks.
And yes… as-is I have had someone ask me “what is that a bomb?” … only half joking and ready to clock me if I make a sudden move. So stuff the wires in the bag so they don’t stick out.
Done! Wires are capped and stuffed into the bag in 5 seconds. The sling strap goes over your shoulder for easy carry. I just lug it to the nearest shopping cart and put it in the bottom rack with my helmet and off I go.
Its a really short list with one item on it.
You see above the Blackhawk S.T.R.I.K.E. carrier in use. Purchase link is here. Yes, the name is a tad ridiculous. But this pack is minimalist and is just durable cloth with no insulation or padding. Its easier to stuff into a confined space. Mine came with a super sturdy velcro sling strap.
Another that is well made (and a tad smaller for a tighter fit is sold by Voodoo Tactical. It comes with thin backpack-style shoulder straps that don’t take up *too* much space in your triangle bag and are not enormously fiddly when stuffing back in there.
Another one I use (with my Luna Wolf pack) is this government-issue USMC carrier. The link is to a brand new unit. I got mine surplus and cheaper on Fleabay. This pouch has no straps (you can clip on your own from a duffel bag if you like) and it is the opposite of the Blackhawk carrier: Its thick and padded. I can still stuff it into any triangle bag I have despite this. Its great as a protective layer over a battery.
Wrapping It Up
There are lots of ways to do this. How I do it is no big deal. Key takeaway here is to find a method that works for you so you can swiftly grab the battery, go off to your next adventure and then come back and plug right back in again.
“Wideloaders” are a load-supporting framework that sit level to the rear axle on a cargo bike. They are not made for the Surly Big Fat Dummy, but the frame has fittings to attach them. Here is how I made mine with no special tools or fabrication skills.
Wideloaders go hand in hand with the use of XL panniers like Great Big Bags 2.0. If you have Wideloaders that your bags sit on, it lets the frame support part of the load directly and increases carry capacity. So, for my Surly Big Fat Dummy, I definitely wanted these.
Big Fat Problem
The Big Fat Dummy is a unique frame design. It is similar to the Surly Big Dummy. There’s a family resemblance to XtraCycle-compatible frames. There are many factory-original and aftermarket options for those bikes, but similar is not ‘identical’ or even ‘compatible’. BFD owners figure this out pretty quick.
The image below shows a bright green Surly Big Dummy frame overlaid onto a Big Fat Dummy frame. The front wideloader mounting points are lined up (look for the frame hole/white circle on the bottom tube extension, aft of the bottom bracket). This overlay makes it clear the rear mount holes don’t match. You need Wideloaders designed specifically for the Big Fat Dummy frame.
Unfortunately that product doesn’t exist. If you want them, you make them. So I did.
Lets Get Started
Your wideloaders are going to mount in the front and rear hollow tubes that already exist in the frame. These cross-tubes are both 7/8″ Inside Diameter (ID), so you will need to buy 7/8″ Outside Diameter (OD) tubing. Luckily, this is widely available. However you will find a variety of thicknesses, heat treatments and alloys. I’ll pass along what I think is the best to use, and, well, what I used. I’ll let you decide whether or not to follow my lead or make some changes, as what I did turned out to be really REALLY heavy duty, but also heavy for what it is.
What about copper tubes? You can go a different way and use copper tubing and soldered joints for a very, very cool look. But its no lighter than the alloy and screw-together approach I used, requires semi-permanent solder connections and a whole lot more effort (and money) to put together. It will look incredible when its done though. If you go this route yourself, note that copper tubing is designed to have a specific liquid flow rate, so it is measured via its Inside Diameter rather than Outside. So while I am using 7/8″ tubing, your typical copper tubing that fits is going to be known as 3/4″ tubing. The deciding factor to proper fit will be wall thickness so pay attention when doing your buying.
Total project cost (not counting shipping): About $230.00. $304 with the optional tools added in.
Notes on the Parts List
Your life will be a lot easier with the tube cutter and ratcheting attachment. It makes doing the job of making repeated cuts easy and gives a perfect cut every time.
Once you are done cutting a tube, even if done with the tube cutter it will still have sharp and somewhat bulged edges. Use the reamer to give a finished bevel to the outer and inner edges. You could use a straight file, or a tiny long round file, and eyeball it until done. But this specialized tool does a quick, clean job in just a couple seconds.
You need a few passes with a flat file on the flat of your cut pipe to smooth out the surface after the cut. Well actually you don’t need it, but between this Flat Bastard and the reamer you will never cut yourself on a sharp edge. And yes I picked this file to link in because they called it a Flat Bastard (any bastard cut will do, or even a fine cut).
If you choose the 6063-T5 tubing you likely also will need a hacksaw. I am not linking one or giving a price. If you don’t already have a hacksaw in your toolbox you may as well pull your toga up over your head and accept your fate.
This is an extreme-duty choice. With a wall thickness of just under 1/4″, it is heavy stuff. But use two of these as thru-frame cross-pieces and your wideloaders will not bend even with well over 100 lbs of cargo loaded on them. My record is about 160 lbs (72.5 kg) and I was glad I over-did it, especially when hitting road bumps… an overloaded bike that weighs over 500 lbs with the rider onboard is a runaway freight train: you have to just hang on and bulldoze thru things you would otherwise avoid on the ride home.
This tubing is too thick for the tube cutter. You can use the cutter to get it started, then switch to a standard-issue hacksaw, or find some other method of cutting this very thick tubing. Me, I went cutter+hacksaw. It worked fine, but was something of a pain in the ass.
This stuff is sold in metric measurements since it is coming from a bicycle frame tube supplier, but the measurements translate to 7/8″ OD tubing with walls about 0.071″ thick, in individual lengths of 39″. That is roughly the thickness of bicycle handlebars. As aluminum tubing goes, its thicker than most reasonably-priced alternatives, which is good. Its also much lighter than the 6063 I used for the crossbars. You can sub in two tubes of this 7005 for crossbars less insanely thick than the 6063. They will still be strong.
Stainless Boat Rail Fittings
Being thick stainless steel, these marine boat fittings are all about durability and strength. Also they are heavy as hell for bicycle components. Once again, this is a job where weight weenies need not apply. You put these suckers on and screw down their grub screws into the softer alloy tubing and they will hold fast, regardless of whether or not you forget how wide the bike is and walk it into the corner of a wall … in that contest, the wall loses.
Worth Noting: In many of the pics here, you will see I am using tee and quad-fittings that allow more connections than are necessary for the project in this post. Thats because I was building with an additional integrated center-mount kickstand in mind. We’ll save that for a separate article. Stick to the parts in the parts list to just build the wideloaders.
Garbage Disposal Hose
What in the hell is that doing on this list? Fact is, I didn’t build my wideloaders originally with this in mind. You will see many pics here with the older bushings, washers and heatshrink tubing for coating. I got the idea a few months afterwards. Covering the outer tubes in thick tubing permanently dingproofs them and helps protect whatever I lean the bike up against.
Once I found cheap PVC garbage disposal hose, I realized I could further use it to replace almost all of the washers and spacers in the build.
Since I had already built mine, I personally only used the disposal hose on the outer facing tubes, leaving the two inner lengthwise tubes covered in heatshrink. However, you could buy two units of the disposal hose and sheathe all of your tubing with it. Simpler, looks kinda neat and about the same cost.
25 feet of Heat Shrink
The need for this stuff was largely eliminated with the use of the garbage disposal hose. However, you still need about 2 feet of it (20″, actually) to line the crossbars inside the frame. In a cruel lesson in Chinese capitalism, 10 feet of 2:1 heat shrink is one cent more expensive than 25 feet. So what the hell lets get some extra. Also, the 3:1 that is widely available in shorter lengths is the marine grade with adhesive glue inside and thats too thick for our crossbar liners. So… maybe its not a bad idea to check your local hardware store before buying this stuff. Its not going to be any cheaper but if you don’t want an extra 23 feet of 1″ heat shrink tubing sitting in a drawer for the next decade, a local buy might fix that.
The Sleeve Bearings and Washers
I used these in my original build and you can see them in all the pics. They were optional then and, later on when I discovered the garbage disposal tubing, were replaceable in the project. The one remnant I would still use regardless are the “mil spec” steel washers. Why mil spec? They are cut to closer tolerances than ordinary washers. If you want a really snug fit to your tubing, with a not-gigantic OD to go along with it, these washers are pretty much the best option.
If you use the disposal hose to replace the cushioning washers and bushings for spacing, I would still use the mil spec washers up against the frame to ensure the most solid contact possible.
Construction / Assembly
NOTE: While I often go into painful levels of detail, I won’t be specifying measurements on cut dimensions. I don’t want you taking my word for what works on your bike and your fittings. I’ll make one exception to this: The width of the crossbars, since that requires some thought and is worth discussion. We’ll get into that below.
Step 1: Cut the Crossbars to Desired Width
This is maybe your most important project decision. How wide do you go? Your answer will help determine what you bump into while trying to move the bike around, or smash into as you try and negotiate a narrow passageway (like a shared use path entrance). At a glance, a good rule of thumb for maximum width would seem to be ‘no wider than your handlebars’. That will mean whatever you are riding thru, if your handlebars fit then most likely the wideloaders will not snag, either.
While you are figuring this width out, know the center section of the Surly Big Fat Dummy is exactly 10″ wide.
The BFD 26″ bike in Bliolet uses Answer ProTaper bars; 810mm wide. That works out to almost 32″ of width, give or take. So knock 10″ off of 32″ (the width of the center section) and divide by two. Following the no-wider-than-handlebars thinking, you would have wideloaders 11″ wide on each side. The 1-piece crossbar would be a total of 32″ in width.
Thats way too wide. Forget about the handlebar rule. It sounds like a good thing to have that nice big shelf, but it will be VERY ungainly to have that much hanging off the side. Don’t even think about it. Another issue is trying to get the bike thru a door. Think how much fun it will be to get a bike 32″ wide (and almost 8 feet long) thru a doorway that is commonly no more than 36″ wide. And some doors are 32″ wide.
I settled on a bar that is 26″ in length. Subtracting the 10″ center section and dividing the remainder means I have an 8″ crossbar extension. The elbow will extend my width a bit more. So figure in the end, I have about a 28″ wide rear platform. Here again the dictating factor is getting thru a doorway (I park in a garage every day and bring the bike in thru a door at a sharp angle).
If you are unsure, its better to guess on the too-wide side. It is a whole lot easier to file or cut metal off than it is to put it back on again (fun fact: this is also the First Rule of Gunsmithing).
Step 2: Drill And Fit the Crossbars
This part is easy. I took the 26″ cut crossbar and measured it to 13″. Then I used a red Sharpie to mark the center. In the pic below, a test-fit, you can see the red mark coming thru the centered frame hole. Once you have confirmed the spot is in the right place (measure!), pull the tube out and drill a centered hole straight thru at the spot of that marker dot. Drill large enough for an M6 bolt.
Finalize Crossbar Fitment
Once you have drilled that hole you can fit the tubing right inside the 7/8″ ID frame tubing and attach the crossbar, centered exactly to the frame and fixed in place with a stainless M6 socket cap bolt, nylock nut and a washer on each side. However, there will be a small amount of play between the crossbar and the frame, which means these things will rattle. We can’t have that.
Add a length of heatshrink – cut to a 10″ length to the center section of the crossbar. Using your heat gun, shrink the tubing so it sits tight on the very center of the crossbar. The hole you drilled will be a clearly visible depression on the bar.
Get a bit of dishwashing liquid or similar non-permanent lubricant and smear it over the now-snug heatshrink.
Push the crossbar into the frame. It will now be very snug thanks to the added diameter of the heatshrink. The dishwashing liquid will let you push the bar into the hole while leaving the heatshrink attached and placed on the center. You may have to experiment with lesser lengths of heatshrink as it might want to be pushed back by the frame as you get further into the frame and closer to centering it (I had to spiral wrap sandpaper on a wooden dowel and run it thru a few times to debur the interior of the frame. If you already own a cylinder hone of the right size this is a place you might carefully use it).
As you push thru, when you see the depression in the center frame hole where heatshrink sags in under your drilled bolt hole, stop. Now just shove the washer’d bolt into that hole. It will break the heatshrink on its own. Clamp in with the nut on the other side.
Repeat the process with the other bar.
Your crossbars are now tightly, permanently fit. Bolted into the frame and lined with a thin rubbery material, they will not rattle.
Step 3: Fit the Tee’s and Inner Lengthwise Bars
Now that the crossbars are bolted in, its time to attach the inner bars. What you see in the pic below is a test fit where I hadn’t yet finished Step 1 above. The crossbars aren’t yet bolted in. But the procedure is well-illustrated. Loosen the grub screw on your front tee. Stuff the bar into it until it stops. Measure how far it went in. Position the bar atop the rear tee. Its going to go in the same distance, so measure accordingly. Thats your tube length. Cut to size and if it fits, do one more like it for the other tube on the other side.
To do the actual fitting once the tube is cut, loosen the grub screws in the tees so they are still in place, but do not intrude at all into their opening (or remove them completely and stash in a safe place). Place the cut tube into each of the tees. Make sure the grub screw holes are facing up for both tees. Now slide this assembly over the attached crossbars and slide them inward to their final position. If they do not slide smoothly to the interior – if they hang up halfway down the crossbar for instance – you may have cut your tube a bit too long and need to make a second cut, or do some filing if its a near thing.
This is a good time to mention that for placement on the drive side, you want the inner bar to clear the derailleur when it is on the smallest cog, with some extra room to spare that allows for frame flex (although these wideloaders can’t help but stiffen the frame). Keep this in mind when you are deciding final placement on the drive side inner bar.
When the tees and tube are sitting, unbolted, in place, move on to the next step.
Step 4: Fit the Elbows and Outer Lengthwise Bars.
Repeat the process from Step 3 for the outer bars. This time measure fitment with the 90-degree elbows. In the pic below note I had a tee in place in the rear – I was considering doing an extension out behind. In the end I thought an 8-foot-long bicycle was plenty and squared it up with an elbow.
After cutting the tubes, do the same procedure as in the previous step with regard to placing the bar and elbows onto the frame without permanently attaching anything.
When the tubes are all cut, everything is lined up and you know it all fits, its time for Step 5.
Step 5: Add The Bumpers / Final Assembly
Since you didn’t actually tighten anything down in Steps 3 and 4 above, its easy to take it all back apart. Do so now, leaving only the crossbars, which should already be firmly assembled. Your next moves, in order:
Straighten out Your lengthwise (long) pieces of Disposal Hose
OK this is out of order because you should do this a day or two in advance of your actual build party. You want to give the hose some time to uncurl itself.
Off the shelf the hose is kind of a pain in the ass to deal with, considering between two and four lengths of it need to be cut fairly precisely to a bit under a 3-foot length. I found two ways to deal with this (and used both of them). First, the easiest way:
If you have some long lengths of 1 1/2″ hard PVC pipe laying around, stuff this curved tubing inside of it. Let it sit like this. You can do it with 1 1/4″ PVC but its a tight fit and really tough to get it thru in lengths any longer than about 3 feet.
If you don’t have PVC, use your actual wideloader tubing. If you are following the parts list above you have four individual tubes that are longer than you will need. Work with those. This is going to be a snug fit and require some elbow grease to stuff it on there. I stuffed on a couple of feet, then dripped on some WD40 and let it penetrate (there’s a bit of slack to let it dribble in) and just worked it. Once I had used enough of it (used… not over-used), and let it spread, they slid on and off easily. But it takes a little time and patience. Afterwards, wipe off the tubes. I didn’t worry about the residual WD40 inside the hose itself. Just enough remained to make final assembly straightforward.
Cut spacers for frame-to-inner-tee fitting
You will cut spacers to desired lengths from the disposal hose. On each corner, use one of the milspec washers up against the frame for a total of 4 washers needed. The milspec sizing will give the washer a nice even fit.
On the build you see pictured, I used 1.5″ corrosion resistant bushings in the rear for a nice look and exactly the spacing from the frame I wanted. In the front, I stacked three of the rubber cushioning washers, sandwiched by two milspec washers. This front scheme was a leftover from earlier plans that did not include bolting in the front crossbar. Thats what you get when you plan a build and buy parts before you get the bike in hand to work with directly. You will want to just cut a short length of hose and back it with a washer.
Line the inner lengthwise bars
You are going to do one of three things here:
Line the inner bar with 2 or 3 layers of heatshrink. Do multiple layers in case you scuff or ding the bar. Just one layer is easily torn. This was my initial build because its all I had figured out how to do at the time.
Line the inner bar with a length of garbage disposal hose. to match all the other bars. Using the disposal hose is cosmetic on the inner bar, but it is more durable and will give you a consistent, beefy look. Doing this is almost the same cost as using the comparatively fragile heatshrink. If starting over from scratch, I would go this route.
Do nothing and leave the bar bare. If you like the bare look then great you are done.
Install the inner lengthwise bars
At this point you are ready to do the final install of the inner lengthwise bars. Having attached any desired covering to the bar, loosely reattach the tees to the bar and slide it on just as in Step 3, again making sure the grub screws for the tee fitting are facing up. When in place up against the spacers you cut and installed above, its time to tighten the screws.
This is one of the few times a thread locker is properly in order vs. being a misused crutch. I personally prefer Vibra Tite. The blue gel is easy to apply, never hardens and holds tight regardless of vibration and impacts over time. Goop up the threads of each grub screw and tighten them into the softer alloy tubing until they are roughly flush-fit to the fitting. Nothing is going anywhere once that is done.
Line the remainder of the crossbar
Now you need to line the next section of crossbar if you care to do so. At this point I will say that heatshrink should not be an option – go with the flexible PVC (or do nothing if thats your bag). Cut each length to size and slide onto the tube.
Line the outer bars (or don’t)
Almost the same procedure as the inners: Affix your elbows to the tube and attach the tube assembly to the crossbars. Now you know how much exposed crossbar there is. measure this and cut your outer bar liner/bumper. Tighten ONE of the elbows onto the outer bar and remove the elbow from the crossbars. Now you are holding the outer bar with one elbow attached. Take your cut liner and slide it down until it is snug against the installed elbow. If you cut the liner to the proper length, it is now installed perfectly centered.
Install the outer bars
Loosely attach the second elbow to the outer bar. Slide the assembly over the crossbars. Tighten all the grub screws down so there are no gaps, using thread locker and again tightening so the grub screws are roughly flush with the outer wall of the fitting.
We’re almost done .
Step 6: Add the Floor (Straps)
Up to this point we’ve created an empty framework. It needs a floor to help hold up the Great Big Bags that will be sitting on top of it. I opted to use 2″ x 30″ hook-and-loop cinch straps, 4 on each side, which are movable, super lightweight, have some give to them but at the same time are very strong.
I had to buy two 6-packs of straps to get what I want, so I could add more straps, but 4 is enough and more importantly I can space the straps in such a way they work in complement to the four pannier straps I use to provide additional support on heavy loads.
Since the bag straps also have to wrap around the inner bars of the wideloaders, the floor straps have to be out of the way, and what you see is spaced out to let me interleave the bag straps between the floor straps.
A Final Note on the Floor
At around $30, the floor straps added a noticeable bump up in job cost. Is there a cheaper way to do this? Probably. I considered a bunch of ideas including diagonally weaving super thick bungee cord into a floor. I have a spool of the stuff in my garage.
What about more tees and crossbars with the leftover tubing bits? Without question that would look great and be supremely sturdy… but is it necessary? I don’t think so, and I didn’t feel like taking the time, adding the weight or going to the expense. But for sure, it would look great. In the end I felt the straps got me to the finish line immediately and were easiest to manage over time.
What about skateboards?
Well, that would work great. If you are a parent and your wideloaders need to serve as platforms for little feet, and maybe you want your kids to be able to stand on them, then a skateboard is a great option. If you use the really thick 6063-T5 tubing it will for sure be well-suited to a couple of M5 holes drilled thru each bar to attach that board, front and rear. From there, find a blank deck to your liking and bolt that sucker on.
Job Done. They Work Great!
These pics are from the initial build, and reflect the parts I used for spacers at that time, along with some showing a different strap setup. Your results may vary so the bags you buy or build may dictate a still different approach.
My first set of Big Bags were 77L each, almost the same size as the largest generally available cargo bike pannier (and 1/3 the price). It turns out you can go a lot bigger than that and stay practical.
When I put together my first set of Big and Cheap DIY Cargo Bike Bags, I thought two 77L panniers were huge! I fit them onto my Mongoose Envoy cargo bike project, and for several months they have been great, but not quite perfect. Not because of the capacity of the things. They were perfectly sized for that mid tail frame. But there were a few convenience issues … you’ll see below what my solutions were.
Why go bigger?
Well, I liked the Mongoose mid tail so much (it was my first dedicated cargo bike) I decided to jump all in and go for a full sized longtail with as much capacity as I could get my hands on. The Surly Big Fat Dummy was a bike I had *almost* bought before the Mongoose, and I decided with its fat tires, sheer size and very stiff frame it would offer the larger carry capacity and greater versatility I was after.
Going from a mid tail to a long tail meant I had more room for bigger bags. I could do the Rothco 77L canvas bags again, but after quite a bit of shopping around, I found Rothco’s larger, heavy-canvas 34″ long, square zipper’d duffel bag was dimensionally just about perfect to fit the BFD’s rear cargo area.
Total Project Cost: About $221.00. Result: 276L of pannier space. Two Hundred and Seventy Six Liters.
Notes on the Parts List
Foam I am sure you can find something cheaper. I wanted something bright yellow so I could see the contents of the bag easily. Cross linked polyethylene is essentially a thin version of gym mat material. Extremely fine-celled. I have used Foam Factory for some esoteric jobs in business for custom cut stuff and found they had what I was after. What you want here is a big single sheet of foam that wraps entirely around the bag interior. The large foam sheet specified here is just over double what you need. Cut it in half, shave a few inches off one side and its a perfect fit. As an alternative you might try a couple of the Therma Rest mattresses that I used in my original bags, and some gorilla tape.
Grommets You can also use #6 grommets just like I did with the original Big And Cheap Bags. It all depends on what tools you have in your garage. If you have no grommeting tools whatsoever, this #5 size midget grommet kit will give you everything you need – the tool and plenty of grommets. Cost is about $56 and you will have plenty of grommets left over so you can hammer reinforced holes into more things.
The Wooden Dowels You can go to Home Depot and pay about half what you will at Amazon. Thats what I did, and HD has a handy manual-cut station you can use to cut the rod down if you don’t have a saw (please buy a saw instead). I only put Amazon as a source so there is an online purchase choice.
The Luggage Straps, Part 1 I specified four 2-paks for a total of 8 straps. 4 per side. Generally you only need two. But when carrying really heavy items, like the pictured load below (still in the shopping cart) that weighed about 128 lbs (58 kilos) … you want more straps to help take the burden off of your wideloaders. So, you can buy fewer straps. Or you can buy the max that will fit and toss the spares into your cavernous panniers and forget about them until they are needed. Your choice.
The Luggage Straps, Part 2 Notice in the pic above, and in my previous Big Bag posts, I used 2″ and then 3″ wide velcro straps (a single 3″ above). these hold fine, but in daily use, velcro is… velcro. It is constantly sticking to things it decides to stick to, and generally making my life more difficult. The straps do indeed do their job, but first and foremost just finding 3″ wide straps long enough to work with these bags is very difficult (and a process I will not describe since I abandoned them). Also these 3″ extra-long unicorns are just too damned expensive. Kydex buckled straps unbuckle in an instant, don’t stick to themselves or anything else, fit 4 to a side which is plenty and cost less to boot. Lastly, the luggage straps I am specifying adjust from 40″ to 74″ which is perfect for folding the bags up, empty, and expanding them out when full. Since the excess strap length is captured via a sewn-on sleeve, nothing is ever flopping around.
Whats With The Dowels?
My original Big Bags used hooks, and I went to a fair amount of trouble to make sure they were absolutely planted and rattle-free. And they are all that. But still, I thought there has to be a better way, and I ended up coming up with one.
Using dowels and cargo loops for hanging the bag has major benefits over hooks:
It doesn’t rattle
It is light weight (lighter still if you use an alloy tube)
It is cheap (less so if you go alloy)
It distributes the load on the bags evenly across their entire length
It holds them fully secure
There are no points of excessive wear/rubbing.
And last but not least, they make bag removal and reattachment a snap. The process described in a nutshell:
STEP 1: Loop-tie five cargo loops per side to the Dummy rails, and loop those up thru the deck itself so they drape down. If you are not making bags for a Surly or Xtracycle-compatible cargo bike, use as many loops per side as you can, as well-spaced as you can make them.
Here is one of my early fitments when I was figuring this all out.
STEP 2: Create 5 grommet holes in the top inside edge of each bag. One on each top corner, and the remaining three positioned so they are roughly equally spaced down the side of your rack. the exact positions will vary depending on your rack. I illustrated the whole grommet-creation process in the original bag creation post. But worth noting for these bags I used smaller #5 grommets and I really prefer this smaller size.
STEP 3: Line up your now-holey bag with the dangly loops and, one at a time, put each loop into each corresponding bag hole. As you do this, thread your dowel thru the loop on the inside of the bag.
Here is what this looks like with no bag in the middle
Annnnnd with the bag:
STEP 4: Remember the rubber chair feet? Put one on each end of the wooden dowel. This keeps the bag from rubbing on a relatively sharp edge of cut wood. Sooner or later it will rub enough to wear thru the canvas. But not if you have a big soft round rubber bumper on that edge.
Note the above pics show a 1.25″ wooden dowel. I downsized to 7/8″ and its much easier to fit the loops thru when putting the bag back on. You can see the smaller version in the pics below. Original concern was the dowel bending, but there are so many cargo loops to suspend it… thats not going to happen.
Spend a few minutes with some fine-grit sandpaper to make the imperfect surface of your dowel silky smooth.
Bag Removal and Re-Attachment
Here it is in a few easy steps. I photographed my first bag removal as you see, and I timed the second with a stopwatch. It took 30 seconds to detach the bag and another 15 seconds to toss the straps in and zip the bag up.
You can forget about making something that fast and easy with hooks.
STEP 1: Unbuckle the two bag straps. Pull the top inside corners of the bag back so each end of the wooden dowel is visible.
STEP 2: Pull off the rubber foot from one side. I removed the rear one this time. STEP 3: Pull the dowel out from the other side. Its only halfway out in the picture. It will slide out quickly and easily.
STEP 4: DONE. The bag is now free. It is now a big duffel bag with handles you can lug into the house with all its contents. Feel free to use the shoulder strap that came with it.
Did I Mention The Kangaroo Pouch?
Yes really. Just like the original bags, Big Bags 2.0 are typically folded up when empty. The foam liner inside means the folds are fairly thick and a pouch is created in the fold. For bags this big, its pretty deep, too. And almost three feet long. Check out how I almost disappear a 2 lb sledgehammer into it, standing on its end, below.
That makes for secure storage of most daily-use items. On a typical day, a small backpack with my work clothes, pouch with my keys and alarm remote and garage door opener, and another with my wallet and phone are all snuggled in one side or the other. Road bounces and vibrations don’t disturb them, and there is enough room left over that I don’t have to open the bags up at all unless I am on a shopping trip. So as big as these things are, if anything they handle small jobs just as well as the the large ones they were designed for.
I used to think the 77L bags were crazy big. I spent a lot of time agonizing over whether I was wasting time and money even attempting to go bigger with these duffel bags. Now, having had some time to live with them and on more than one occasion to stuff them full, I can’t imagine why I would want to go smaller.
Less than a year ago, I started the Mongoose Envoy Project. I loved the bike and – after dabbling with fast-carry-stuff ebikes for a few years (that ended up looking more like zombie-apocalypse bikes), it was my first actual purpose-built cargo bike.
With respect to the cargo platform, I. Freaking. Loved. It. I am not a recreational rider. I never have been since I started riding in the 1970’s. I put in long commute rides, and I try and do as much as I can of my daily errands on a bike vs. uh… one of my automobiles. Yes I have to admit that while I am doing the whole save-the-planet schtick and trying not to drive, its because I love riding bikes and I always have.
Anyway, where was I? Right. Cargo bikes. So… I built the Mongoose out until it was truly as perfect as it can be for its intended purpose. Its even a good value and componentwise I would put it up with just about any high end cargo bike. With that said, it has some problems.
It doesn’t fit me quite right. Mostly in the upper body. I have done pretty much what I can to deal with this. A LOT of the problem has absolutely nothing to do with the bicycle and has everything to do with lingering injuries from when I was T-boned by an inattentive driver in a SMIDSY type collision. I did a passable Superman impression on the arc upwards… and a decent impression of Vinko Bokataj for the landing.
It hurts to ride the damn thing. Again, this is all about residual pain from the above-referenced accident and has nothing to do with the bike. My wrists remain in bad shape, probably permanently, and while the Jones bars help by putting my hands at a better angle, I need both a higher upright riding position to take weight off my wrists, and a suspension fork to reduce the impacts that are part of normal street riding.
As the cargo bike platform expanded my idea of what a bike could accomplish, I wanted more than the Envoy, with its mid-tail size and only plus-sized (after upgrading) tires could deliver. Go big or go home as the saying goes, and the Big Fat Dummy is arguably, physically the largest production 2-wheel bike on the planet.
The addition of the larger 2.8″ plus sized tires on the Envoy worked so well, and I have done so much work with the fat tire platform, I wanted to go fat on a cargo bike and take advantage of the added capacity the fat tires give (and since my very first serious Costco run weighed in at a total of over 500 lbs counting me and the bike… good decision!)
So, this section of the blog, of which this page is only a teaser that will eventually house the episode menu, will document the custom work I have done on this bike. What is worth mentioning that is. This is not going to be a rivet-scraping pass over the bike. We’ll just hit the high points.
One bike to rule them all? So far yeah. Its all that.
I had an aftermarket kickstand that was too short. Here’s a way to add a tough-as-shoe-leather extension that should last forever.
My Mongoose Envoy received a much-needed upgrade to its kickstand when I upgraded to an Ursus Jumbo, whose much-wider (18″) leg platform keeps the bike stable on uneven pavement or when it was heavily loaded.
The stock Envoy stand works well unless you have 100 lbs of groceries loaded up. Do that and .. oops you gently bumped the bike! Over it goes and boy does your life suck. You’ll have to unload the bags, stand the bike back up, uncrack the eggs and load back up again. Same deal happens when parked on an incline.
The Jumbo solved this problem given its obvious mechanical advantage.
… until I put some big poofy 26×2.8 Vee Speedster tires on the bike, which raised the frame up probably a full inch; maybe more. That meant of the two legs that Ursus kickstand has, only one of them was on the ground at any one time. At first it was kind of fun to be able to lower the stand and roll the bike around, or out of my way with ease. Then I saw what a bad idea it was on a sloping driveway. The bike was happy to tip over. For a cargo bike that will be loaded, that has to change.
A couple of methods presented themselves. The first was to lower the stand by shimming the base. While I would have been able to find a longer M10 bolt to do the job, making a shim that will actually work is a lot more complex than just throwing in some washers and calling it good. Absent a mill and some billet to do some custom fabrication, shimming was a no-go. So, since I can’t make the base longer, that leaves only the legs. I had to make them longer.
Shoe Goo… To The Rescue!
I should be brought up on charges for that header. Couldn’t help myself, and besides its true. Shoe Goo is a shoe repair tool that is essentially replacement shoe leather. Or shoe adhesive to hold your precious Converse All Stars together after they came apart. Or both. For you shade tree mechanics, if you think of it as a hard rubber equivalent of JB Weld … you have it down.
So what I decided to do is to stick my kickstand upside down in a vise, block off the bottom of each leg with some painter’s tape, fill the resulting cup with goo and let it dry. Peel off the tape and I’ll have a longer kickstand with a new, tough-as-nails rubber foot.
It turned out to be a bit longer than that, and took quite a bit more time to cure. But layering on a bunch of goop to the bottom of the kickstand is the short version of what I did here. And best of all, it actually worked.
Time For Plan B
What you see above is only the first attempt, using green painter’s tape. And while it worked (see photos sans tape) it became clear just by looking at it I could expand the ‘foot’ to a much greater size if I taped off the base and poured in more goo. You can see this in the last two photos where the tape has been removed. the foot of the Jumbo has essentially a large hole in it that you can further tape off, then fill in. this time you need to tape halfway up the leg as that hole runs thru to the front of the stand, and your tape will provide a deep chamber for the goo to fill and harden into.
This time I used silicone tape, which I discovered by accident does not stick to Shoe Goo! Knowing that, I was able to use a scrap of tape to help sculpt the slowly hardening-but-still-pliable glob of goo. That matters because as this stuff dries – and then cures – it shrinks into itself. You will need to come back every couple of days to apply another layer. And when at some point you call the job done, you will want to let this material sit for at least another five days.
So if you are doing the math here, that means this is going to take time. I spent a total of about two weeks applying, filling again after it shrinks down and then letting it cure so its stable with a bike standing on it.
Is it worth the trouble? Well, I spent about $8 on two of the big tubes of goo and another nickel or so on a length of black rubber mastik tape around each foot to pretty them up. When I was done, I had a kickstand that completely solved my problem, and I can expect to be able to use for the life of the bike. If you want, Shoe Goo comes in a black formula that will have a matching look… but it costs more than double what the clear stuff does.
If You Do This…
I felt my way thru this project and learned as I went. The way YOU want to do it is skip the first stage with the green tape entirely. Use the silicone tape to wrap the entire foot. Wrap snugly at the bottom of the channel you want to fill, and as you get to the top – the actual extension to the base – do not wrap that tight, just do it loosely and make sure the tape wrap adheres to itself. Then inject the goo with a narrow nozzle (there are kits out there that have them) deep into the channel you just created, filling it from bottom to top until you have a single large ‘sole’ wrapped in the silicone tape.
Then, walk away from it for 24 hours. Add more goo as it cures and shrinks down. Use a scrap of silicone to pat down the added goo so it forms a nice smooth surface. If it seems solid, remember thats just the outer layer and inside its still like jelly. I went on a week’s vacation after I thought I had it done and it was pretty solid.