Quick Release, Easy-Carry Ebike Battery Setup

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.

Ignore the charger cable in the front. I took this pic at work in my ebike garage.

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.

When I leave, I generally put the cables back inside and zip it only halfway-ish, so its obvious there’s nothing worthwhile to steal inside. Move along.

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.

Tell the Bomb Squad to cut the red wire

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.

This is just a 3L hydration bladder pouch, the sling strap that comes with it and a shoulder pad I swiped off another strap I wasn’t using.

Parts

Its a really short list with one item on it.

Hydration Carrier

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.

Surly Big Fat Dummy Wideloaders

“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.

The Surly BFD Project Menu
Prologue
Episode 1: 138L (each) Panniers… Seriously?!
Episode 2: Big Fat Dumb Wideloaders (you are here)
Episode 3: Kickstand Kaos
Episode 4: Add a Flight Deck. And a Hangar
Episode 5: Odds and Ends

Do It Yourself (its not like you have a choice)

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.

Image credit: Surly Bikes (click image for original page)

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.

Parts List

27.49  6063-T5 7/8" OD x 7/16" ID (0.219" wall) x 8 ft
43.00  AL7005 22.2mm OD x 1.8mm wall x 1000mm len (qty 4)
43.96  Stainless boat hand rail 90-degree elbow (qty 4)
43.92  Stainless boat hand rail Tee (qty 4)
12.88  Stainless Mil Spec 0.89" ID Washer 10 pak
11.98  2:1 1" heat shrink - 25 ft
14.98  Reinforced 7/8" ID garbage disposal hose
       (10 ft) (qty 2 optional)
 3.00  Stainless steel M6 socket caps
       flat washers
       nylock nuts (2 ea)
29.74  2" x 30" hook/loop cinch straps 6 pak (qty 2)
31.90  Ratcheting tube cutter (optional)
29.99  Inner/Outer Pipe Reamer (optional)
10.99  12" Flat Bastard cut file (optional)
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In original build but replaceable with disposal hose
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12.74  Corrosion resistant sleeve bearing (2)
 6.24  Abrasion-resistant cushioning washer 10 pak

Total project cost (not counting shipping): About $230.00. $304 with the optional tools added in.

Notes on the Parts List

Tools

  • 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.

6063-T5 Tubing

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.

AL7005 Tubing

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.

The pipe cutter makes life a whole lot easier.

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.

hmmm… This piece is not on the parts list

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.

Originally I used 3 layers of cheap heatshrink to cover the tubes, plus bushings and washers. The garbage disposal tubing replaces all of it and saves about $30 on project cost.

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.

Set the fastening screws facing UP on your tee fittings. If they come loose you stand a chance of seeing the problem before they become UFOs.

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.

  1. 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.
  2. Get a bit of dishwashing liquid or similar non-permanent lubricant and smear it over the now-snug heatshrink.
  3. 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).
  4. 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.
  5. 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.

Position the inner tube on the drive side so it doesn’t hit the derailleur in high gear.

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.

I let this sit overnight and added a length of PVC on the still curly side to help straighten the rest of it

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:

  1. 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.
  2. 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.
  3. 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.

Since I did my bumpers after the initial build, I lined the outer bars first – the crossbars are bare in this pic.

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.

The floor straps are spaced so I can interleave two more bag straps between the two center floor straps for extra support with heavy loads.

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.

Great Big Bags 2.0 – 138L (each) Panniers… Seriously?!

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.

The Surly BFD Project Menu
Prologue
Episode 1: 138L (each) Panniers… Seriously?! (you are here)
Episode 2: Big Fat Dumb Wideloaders
Episode 3: Kickstand Kaos
Episode 4: Add a Flight Deck. And a Hangar
Episode 5: Odds and Ends

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.

But, I am getting ahead of myself.

Parts List

$92.00 Rothco Jumbo Canvas Cargo Bag (qty 2)
  7.08 C.S. Osborne #5 5/8" hole Brass Grommets (qty 10)
 44.00 Cross Linked Polyethylene - 2lb, yellow 72"x48
 15.00 7/8" thick hardwood dowel (qty 2)
 20.00 12" soft cargo loops, 6 pak (qty 2)
  7.21 7/8" rubber chair feet 4 pak
 36.00 74" buckled 2" wide luggage strap 2 pak (qty 4)

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.

My first shopping trip with these bags was a Costco run. I didn’t realize I had almost 130 lbs in the cart. The duffel in the bottom goes onto the deck and was at least another 20 (Just the lock is 15 lbs).

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.

The Surly Big Fat Dummy Project

Prologue (you are here)
Episode 1: 138L (each) Panniers… Seriously?!
Episode 2: Big Fat Dumb Wideloaders
Episode 3: Kickstand Kaos
Episode 4: Add a Flight Deck. And a Hangar
Episode 5: Odds and Ends

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.

The Mongoose Envoy, in its final form with the 44″ skateboard deck, indestructo wheels and big poofy tires

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.

I bought a station wagon because i hate bike racks and could put a bike in the back. Things got out of hand.

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.

  1. 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.
  2. 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.
  3. 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.
  4. 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.

Planned (so far) Project Episodes

One bike to rule them all? So far yeah. Its all that.

The BBSHD: Musical Chainrings

It seems inevitable.  When I build a bike, I go through front chainrings trying to get the gearing just to my liking.  My Mongoose Envoy build has pretty much set the world record for tweaks in this regard.  But gearing wasn’t the problem so much as chain alignment.  Alignment is one of the most talked about issues with mid drives and up to this point I have not had to work too hard to get it right.  This build, not so much but I think I finally got it (like $350 later).

While dealing with this I have fooled around with three different sets of crankarms (160’s, 170’s and 175’s).  Not the subject here so if you notice the different crankarms in the pics, I am ignoring them on purpose.

Sidebar:  When building the Surly Big Fat Dummy, I found exactly the same thing as I did here insofar as chain alignment is concerned.  And used the same solution – the USAMade adapter listed as an Honorable Mention below got pulled out of the parts pile and put to use.

The Right Tool For The Job

The Mongoose build is a first for me in many ways.  One thing in particular:  the BBSHD fits the frame really well.  Its a 68mm bottom bracket with absolutely zero chainstay obstruction for the secondary housing.  So I can butt the motor right up against the bottom bracket.  Further, its a lonnnng way back there so chain alignment and misalignment – an inevitable concern with an HD build – is a lot more forgiving since the angles are gentler thanks to the longer reach.  On this bike, if I want I can even forego the offset non-drive side crankarm and the pedals are still easily centered under me.  So the HD is a great fit here.

About That Job…

The Mongoose is a cargo bike.  So it hauls heavy stuff (usually groceries).  It has a secondary job as an unladen backup commuter, but primarily it needs to be optimized to start from a stop while the entire system – with me – weighs 400-450 lbs (180-204kg).  I have really loaded it that heavily so this is not a theoretical exercise.  So I want a big-ish chainring for when I am pedaling fast and light, and still need to be able to get to the big cogs in the back for when I am loaded up and chugging along like a two-wheeled freight train.

Plan A:  Luna Eclipse (42T)

The Luna Eclipse is one of the best BBSHD chainring setups on the market, with a unique ‘wicked’ tooth profile meant to eliminate the possibility of a chain drop under extreme use.  It also has the most extreme internal offset of any chainring option.  This will do the most to overcome the grief visited upon the BBSHD builder by that drive’s secondary housing sending the chainring way out to right field.

Its also gorgeous.  The gunmetal finish I chose matched beautifully with the dark grey frame.  Unfortunately 42T (which is the standard for full-offset chainrings as any smaller and you can’t clear the secondary housing) was not large enough to keep me from clown-pedaling when riding the bike as a commuter.  There was another problem:  Chain alignment.  Running that smaller 42T ring with the smallest rear cog resulted in, after only a few weeks, a whole lot of wear on the inside.  This is why mid drive builds demand the most out of the builder in terms of thinking things thru.  Time for Plan B.

IMG_20200503_123800
Its not ruined yet, but its lifespan sure has been shortened.  this was only a couple hundred miles of wear.

The Eclipse is a proprietary chainring platform, but fortunately other sizes are available.  the largest of which is what I tried next.

Plan B:  Luna Eclipse (48T)

So Plan B was to swap in a Luna 48T ring onto the Eclipse center section to fix the clown pedaling, and to stay the hell off the 12T small rear cog to deal with the alignment issue (I am using a welded together steel cluster for durability and the 12T is alloy and not a part of the welded cluster, so its better to stay off it for the sake of longevity anyway).  I thought that 48T/14T on this bike was the perfect sweet spot.  A small front ring is best when its on cargo duty, and a large one is best when its a commuter.  48T, when used in conjunction with upshifts, gave me pretty much everything I needed.

Pretty much but not everything.  First of all, remember the deep offset of the Luna ring?  It moves the chain inboard 24.8mm which *usually* eliminates the damage the BBSHD does to chain alignment.  Not on the Mongoose, whose narrow bottom bracket effectively papers over all of the sins committed by the motor (at this time I had not yet fully figured this out).  So, as I found with the 42T ring, it was inset too far, even when I stayed off the smallest cog.

So Plan B helped, but it didn’t solve the problem.  After only a couple weeks (I am now checking carefully and frequently) I saw the beginnings of the same wear on the inside of the chainring.  Like the 42T, I had to retire this thing fast so I could use it on some future project.

IMG_20200503_123820
Not as bad as the 42T, but still bad.  Both this one and the 42T looked perfect on the other side.

Sidebar: A mid drive chain powered by a 1500w motor is a chain saw when it comes to components rubbing against it.  That is just a reality of a mid drive and you have to deal with it as part of your design/build process.  When you get it right, you are golden for thousands of happy miles.  Get it wrong and you are sawing thru chainrings and cogs like nobody’s business.

Plan C: Lekkie Bling Ring (46T)

So now what?  42T was too small.  48T was more or less just right.  And the chainring offset that lets me use the inner cogs at great alignment still needs to be reduced or I can’t use anything but the lower gears.  Lekkie has a Bling Ring available in 46T.  It has the same internal offset their 42T ring has and, since I use them on two other bikes I know they are top quality.  At 18.3 mm its offset is quite a bit less than the Luna.  So I got a 46T.  I also added a 2mm spacer underneath it, further reducing the chainring offset to 16.3mm.  That is a whopping 8.5mm less than before so I hoped I would be good on the smaller outer cogs and still let me use the big inners.

And, pretty much, it was.  Chain alignment didn’t seem to be much of an issue, although it still wore down a bit more on the inside.   I was also able to shift up to the biggest cogs in the rear for very low gearing options.  Those are important on a full cargo load and if I am dealing with hills.

But… I flat out missed that 48T high gear for commuting.  And I was still seeing – very slight but noticeable – wear on  the inside of the chainring teeth from the chain, which was still visibly angling outboard a fair distance.

IMG_20200503_123847
This one was on for a few months and had 8.5mm less offset.  But it still shows signs of premature aging.  This was undesirable but livable.

I decided to try an extreme option I had not previously considered.  But on this bike, where all of the normal chainring offset stuff doesn’t seem necessary, it might actually work.

Plan D: Luna 130 BCD Adapter and Wolf Tooth 48T Ring

BBSHD chainrings are generally all proprietary to the platform.  Not so in the cycling world, where chainrings are universal, needing only to match the proper Bolt Circle Diameter for the chainring bolts.  Match the BCD between crankset and chainring and you are good to go.  There are adapters out there in the world that allow a Bafang motor to use standard 104mm and 130mm BCD chainrings.  The problem is they don’t give you anywhere near as much inward offset.  But given my experience so far, maybe I can live with that.  They should fix my alignment on my ‘commuter’ cogs, but will I still be able to use my ‘cargo’ cogs?

In addition to the LunaCycle 130 BCD adapter, I also chose the Wolf Tooth Drop Stop chainring as those rings are best-in-show for this sort of thing on a mid drive.  Attachment to the adapter was a little different than the usual chainring-to-crank operation in that its backwards.  The chainring bolts onto the inside.  I was able to play some games to good effect:  I reversed the chainring so it is logo-side-inward.  Not as pretty, but doing that lets me take advantage of the countersunk bolt holes on what is normally the outboard side.  The countersinking let me mount a bolt so it is almost flush with the ring, which in turn is butted up almost on top of the secondary motor housing.  With the countersinking it now has plenty of clearance.

Plan D Results

FINALLY.  Everything is working right.  The reduced chainring offset means my 14T cog (still not using the 12T for the reliability issues mentioned above) lines up straight back.  This outboard shift did affect my inner cog alignments but I can still get to all of them but the biggest 32T.  I’m comfortable with the angles on all but the second-largest 30T for long term use, and in a pinch, that 30T will work fine.  I just don’t want to stay on it for a week.  So this 9-speed is now a 7-speed and as DIY mid drives go thats still better than a lot of builds can manage.

And worth mentioning, like a lot of what they do, the CNC-machined Luna adapter is freaking gorgeous, and very precisely manufactured.  So much so it really stands head and shoulders above another adapter I got my hands on and was able to compare it directly to.

Honorable Mention: USAMade 130 BCD Adapter

I was surprised at how well this worked and how nicely it was made.  The part only cost me $29.99 on Amazon.  Still, it was Made in USA, well machined and rock solid.  The only things I didn’t like about it was the fact it was machined a bit too heavily, which meant it placed the chainring a millimeter or two further outboard than was necessary, and in this game millimeters count.  Further, as you can see above I was able to reverse the WolfTooth ring and take advantage of the bolt head countersinks.  That didn’t work with this part as USAMade countersunk the outside edge of their part, which made the bolts too long to allow my trying the same trick on the inside, where I needed it.  For a different build it might work fine so I am keeping it for my parts pile.

As for the Stone chainring seen on the USAMade adapter (scroll up to the title image at the top of the page), thats a Chinese Special that ran less than the godawfully expensive Wolf Tooth.  Its noticeably lighter in construction than the WT and I’m not sure I am sold on the tooth profile.  This ring will sit in my parts pile waiting in the wings as an emergency replacement.