You thought the last post on LED strip lights for a Larry vs. Harry Bullitt was a quickee? Lets be even quickee-er for this followup.
This post is a continuation of this one where I did the full description of how I added low-power-consumption LED strip lights to my Larry vs. Harry Bullitt… In less than an hour and with no wiring skills. No skills at all in fact.
I Moved The Switches & Batteries
I could stop right there with that heading and just show off a couple pics, but lets do a little better than that.
When we last left off with this little project, I had put together a neat set of working strip lights in a very short time. However, since I just slapped it together, there was one glaring omission: The on/off switches for the lights were inside the cargo bay, just sitting in a little unsecured bag.
Considering the Bullitt is a really stable ride, this was not such a big deal. But I shouldn’t need to go into the cargo bay to turn the lights on. Gotta fix that.
That little bag was already there, holding the battery packs for my two front-wheel-mounted headlights. So it wasn’t much of a stretch to just toss in the USB power bank for the strip lights, and run the on/off switches over to it. While we are at it, we’re going to move and secure the power packs for those lights as well, and eliminate this little brown bag completely.
As you can see in Figure 1 above, I lined my cargo bay with a sort of 1-piece tub of super-dense closed cell foam. It is bolted down at the rear but nowhere else. Its easy to just pull the ‘tub’ up and run the wires underneath it, back to the cockpit.
Lets Keep It Simple
This is going to be real easy: I already have a handlebar bag. It holds my front motor controller. That bag is not right for this job, but it is also a MOLLE bag, so I can easily attach additional bags directly to it. I had a small, cheap bag in my leftover parts pile. It will hold the power packs for both the head and strip lights, along with the strip light power switches.
Now we need a way to connect the wires up front to the batteries in the bag. Since they are nothing more than USB 2.0 plugs on both sides, I used simple USB 2.0 extension cables. The ideal length is 2 meters and these can be had from Amazon via their Amazon Basics USB 2.0 cable in a 2-meter length. Its possible to use USB 3.0 cables, but those are quite a bit more expensive versus the 2.0 cables that run about $5 each. I needed 4 of them.
I connected one to each of my four plugs at the front. Two to the headlights and two to the strip lights. Then run the cables along the floor back to the rear… bulkhead or whatever its called.
From there, run the wires up the bulkhead, out of the cargo bay and up into the handlebar bag. For the top portion, I zip-tied the 4 cables together for the sake of a neat appearance.
There is a fair bit of extra cable, which works to my benefit as it let me route the cables into the bag at precisely the point where the zipper opens it. I bundled the wires together with some non-permanent velcro ties; again for neatness’ sake.
Inside the bag, the battery packs line the bottom, ends-facing-up, so I can plug directly into them.
The USB on/off switches from the strip lights are stuffed in here rather than getting creative and surface mounting them on the bag via the MOLLE webbing. My thinking is I want them kept out of the elements.
Batteries and wiring are secure and out of sight.
Switches are easily accessible.
There is more than enough room in the bag, which is only half full at most.
Batteries are convenient to pull out when bike is left outside at a shop and I pull everything not nailed down and take it in with me. It is just as convenient to reconnect upon return.
One Last Thing!
My LED strips have an extension soldered onto each of them from the factory. They were originally 1.6M long and both, at the same point in their length, have a visible solder joint where they were extended. Since this is open, unsealed solder, thats an open connection. I’m not sure if a bad thing would happen if water ended up bridging the gap between those bits of solder, but lets not find out. I used a narrow bit of that same 3M mastic sealing tape I described in the original article to cover that connecting point and waterproof it.
That little strip of tape makes no difference in the appearance of the light when its turned on.
I knocked this project out in maybe an hour, start to finish. I’m doing the same with this quickee explainer post.
There is a Part 2 followup to this article detailing some improvements. See it here.
What It Is
Not too long ago I saw someone show off some LED strip lights lining the front and bottom of their Larry vs. Harry Bullitt. Since I am fooling around with and writing up bike lights recently, I thought this looked pretty cool, so I decided to spring a few bucks to do a simpler version of the project myself.
What I Did
I have a reputation for not taking the easy way out, with careful planning and meticulous execution.
None of that happened here. I just slapped this sucker together, kind-of. Actually the way it went down … I was mocking up a couple different layouts in the garage, a light bulb went off for a simple setup, decided “how tough can it be?” and from there did the complete installation in under an hour.
I will probably pretty this up at some point but for now I’ll just enjoy what I have and see how I like it as-is. Before I get into the strip lights themselves, I need to back up a step and describe a mod I made awhile back that led me directly to lining the side panels rather than doing the usual and lining the frame.
M6x25mm stainless socket cap screws with washers (2).
I wanted to use the big countersunk washers and screws on all of the attachment points, but the front two don’t have enough room for the washer to fit so I just used standard socket caps.
Pictures of the parts installed will do a better job of explaining how this all came together than writing it up:
The spacers add 8mm of width and the skinny washers sandwiching it together give a bit of extra strength. They also add about 2mm total for a roughly 1cm widening of the panel mounting on each side (so 2 cm total width increase). The countersunk washers and screws give a nice flat facing, with broad contact to the mounting bracket. The socket caps worked fine too, so the expensive option of the countersunk washers can be considered optional although I think its a nice touch, and prefer the facing to the cargo area be nice and flat.
I could have gone a lot wider as you can see if you explore the site linked above, but that would spoil my ability to use my LvH tonneau cover. As it stands its tight but it fits.
On To The Light Show
So… coming into the game this is what I bought:
4000k LED Strip Lights If you want something to match your typical bicycle headlight, choose a strip with a 6000k color temp. I decided to go a little warmer and it turned out to be a good choice, although I didn’t know why this was yet.
I chose this set of lights because it was a longer 1.5M (just in case), it used 3M adhesive tape for mounting – these kinds of lights are infamous for coming off after exposure to weather – and it had a simple, switch-free USB plug.
Inline LED Switches I thought when I bought the parts that I might not use switches at all – I would just plug and unplug my lights from the power bank I planned to use (more on that later) or use the power bank’s on/off switch to do the same job without extra parts. If I had been thinking I would have bought the white ones to match the USB wire coming off the strip lights.
0.4″ (10mm) -wide 3M VHB Double-SidedTape VHB – aka “3M red body tape” is a weatherproof, super-durable rubber tape available in a variety of widths and thicknesses. The bigger stuff can literally be used to stick smaller body panels (trim pieces and such) permanently to a car. Most modern car badging uses this stuff to stick on the vehicle make and model logos. Its strong and weatherproof. I had a roll already in my garage. Use the link above to get yourself some.
My idea was to lay down the VHB on the bike frame, and then stick the lights to the VHB – essentially: stick tape on the lights to tape on the frame. It’ll never come off.
Anker 13000 mah USB Power Bank I already had this power bank in a drawer. It has two USB output ports and works perfectly to power both strips. Looks like it will last for a full week (I recharge all my stuff once a week).
I started out trying to rig something up by running a USB extension up the steering tube to the handlebars where I have a bag already. I could have mounted the switches on the bags. This meant I would need to run the USB connections from the lights from the rear of the frame, and hiding that connection wasn’t going to happen since the light strips only bend on one axis. Plus I’d be gaining two more wires running up the steering tube and more visible wires are never a good thing.
While I was pondering that, I realized I had an overhang created by my side panel extensions. This gave me a rubberized surface to stick my base layer of VHB, which will only make for a more firm connection. Also this would bring the wiring up further away from the ground, splashes and shield it from ground impacts.
After poking at it a bit more from this panel-mount angle, I realized I could run the power connections from the front, directly into the front of the cargo box. Since I already had a small bag located there holding two power banks for my lower front headlights, I could just add this to the bag that was already there.
Dang thats good enough to just get it done in a few minutes. I can mess with cleaning up the wires later if I feel like it. And so, here again I’ll use pictures to show the install result:
You can see the light strip is sitting directly on a ‘bed’ of thin black rubber. That is the 3M VHB, which I laid down first as a complete strip, front to back. From there I peeled and stuck the lights atop that. Since I was sticking sticky tape onto sticky tape I had to be careful to get it right the first time, but it wasn’t difficult. The light strip can be cut at specific, marked spots along its length and it was easy to do that.
You can see on each end there is a rubber cap. This is 3M 2229 mastic electrical sealing tape. Essentially its tape-shaped rubber goo. You cut a thin strip of it and lay it over what you want to insulate. Then you work it a little like clay until its formed into a shape that gives you a watertight seal. Mastic is one of those things everyone should have in their tool box. There is a thinner version – 3M 2228 – that is commonly available in big box hardware stores in the USA (much cheaper than found on Amazon).
And yeah I know that bag just sitting there is kinda cheesy, but it was already there holding the power for the two fork-mounted headlights. Thats a spot where my lock is always sitting (in that black bag) so its not taking up space I use for anything else.
Whatsit Look Like Turned On?
Well, before you scroll down to see the pics, know this: The camera gives you a false impression of how bright it is. It is nowhere near as blindingly bright as you see in the night time pics, and its brighter than it seems in the daytime pics.
At night, mounting the strips on the panels – which thanks to the mods I did create a narrow overhang ideally suited to mounting these lights – the effect is to light up the frame as if it was a billboard. Its bright and legible and really cool looking. The camera makes it look like its a blinding washout of light and thats the camera, not reality. Also, the 4000k warm color temp I chose meshes perfectly with my green frame. Different color frames (Moondog – navy blue – comes to mind) might take better to a 6000k color temp, and I bet Pepper (hot red) would like 3000k better than 4000k.
The bike jumps out in the night, which is the idea insofar as visibility in traffic is concerned. Also, the lights face downwards and illuminate the ground in a nice big circle around me. Thats useful to me in a minor way (whatever I smash into will be brightly lit up), but also helps increase my visibility to oncoming and overtaking traffic. The forward facing lights provide a minor benefit to illuminating the road close up.
During the day, the effect is minor but on a cloudy day the bike does look a bit ‘brighter’ from the side, and for sure the forward facing portion of the lights provide a daytime running light effect. On sunny days? No idea I just did all this last night.
As near as I can tell, power usage is minimal. I was unable to dent the battery in my testing and trials. We’ll see how that goes after a week of daily use.
Down the road, I may play around with USB extensions and move the switches back towards the rear – I can run them behind the padding that lines the box – so I don’t have to open the tonneau to switch the lights on. I have a couple extension cables and smaller power banks without a job that may work well in this regard. We’ll see. For now this is quick and dirty and pretty slick.
Seeding BBSHD aftermarket controllers has gotten more complicated in 2021. The 2021 choices have seen BBSHD market gorilla Luna up their controller game. To take on start up ERT in the F.O.C category, Luna has recently beta tested their Ludi V2 BBSHD controller. Luna explicitly states to “use this controller in off road only situations”.
I installed a Luna Ludi V2 FOC controller on my Specialized Pitch BBSHD conversion that utilizes a 42T Eclipse and wears Schwalbe 27.5 Moto X tires. Prior to upgrading the controller, the Luna 860c display showed a little over 30 hrs of riding time. I ride the same 25mi route of asphalt with this bike. It’s powered by a Luna Dire Wolf 52v 21aH battery that contains 84 LG MJ-1 18650 cells configured 14s6p.
My commuter routine is about 12 mi asphalt in AM. Charge at work to 80%. Then ride home same route. Without changing gearing between the stock BBSHD controller loaded with Karl’s Sauce Settings and the Luna Ludi V2 controller, I have gained about 8 mph top end speed and my battery consumption has remain the same or slightly decreased.
The only issue so far with the controller upgrade is that the battery indicator goes red during acceleration or hill climbs when below about 50v. Previously the stock controller with Karl’s settings at the same mph and same gear selection did not trip the battery icon to red on the Luna 860c display .
On average, I am consuming about 3v less of total battery upon arrival at work, which is the 12 mi mark, before charging the battery to 80% using the Luna battery charger. My transit time is about 45 minutes to work and is nearly all ghost pedaling.
I am basically maintaining the same speed covering the same distance arriving at the same time to work but using less battery. This is possible because I am using less wattage/requiring less PAS as observed on the display.
The efficiencies can not be attributable to becoming a better ebike rider; getting more efficient in gear selection, braking, running stop light etc. If anything, I have greatly decreased gear changes. I am staying in my most effective cassette gear of 24T, 3rd biggest cassette gear, and not downshifting to provide more leg drive. 24T provides maximum chain wrap with out stripping. The previous 25hr of bike time I stripped out the lower tooth gears to the point I can’t use them under BBSHD power or human only power; the chain just skips terrible in those smaller cogs due to not enough chain wrap and the cassette teeth being worn down.
How much did I pay? This was beta and I did pay my own $. This is not available stand alone from Luna right now. If you want the Luna Ludi V2 FOC controller you have to buy a Luna BBSHD bike. In the past I did buy a Luna Ludi V1 controller for over $200 and I did buy an ERT NXT BAC 855 BBSHD kit for over $500. This beta was somewhere in between.
Is the Luna Ludi V2 desirable? YES!!! At the very least you can extend the range of your current battery. You can get more top end out of your bike and using throttle only you can reach a higher mph.
It was very straight forward to install. I have previously removed BBSHD controllers. I am familiar with how the PAS clip and 6 halls/temp clip operate etc. After you get familiar with this, it took under 1 hour to remove the stock BBSHD controller and install the Luna Ludi V2. It took about 10 minutes to silicone/water proof the connections.
Pro Tip!! When connecting the 3 BBSHD phase connection spade connectors, make double sure the spade goes into the female socket …… Plus look at the 4 pin PAS and 6 PIN halls/temp connector on your V2. Hints can be found how to disconnect your stock controller by actuating the retainer clip of the connector. When you disconnect wiring looms do you generally just grab and yank??!! No. Look at what came with the kit and carefully disconnect the stock controller by actuating the retainer tangs!
2nd Pro Tip!! Elevate the bike. Hang your bike by the front wheel and try to get the BBSHD/bottom bracket as close to eye level as possible. I had the luxury of a ceiling hoist. But you can use your garage door track or a ceiling hook as well. This will make it much easier to remove the stock controller and install the upgrade after mkt controller. You have to water proof all connection in the BBSHD before screwing down the controller and this is much easier at eye level.
Luna has posted a firmware update. Using the VESC app, my nephew flashed the controller wirelessly using his Android phone and the blue tooth connection via the small antenna sticking out of the controller case. The flash upgrade included a pseudo-motor idle function that helps keep the chain semi-tight when letting off the throttle, helping to reduce chain slap. The amount of idle is increased by increasing the PAS level.
Performance into a 15MPH wind flat ground 55v at full sag during these observations.
Throttle only in PAS 5 and the biggest cassette gear of 34T gives 25MPH at 800 Watts; over 30+MPH at 1200 Watts. Full throttle made the LUNA Dire Wolf battery icon go red so I did not hold it there long but it was very fast acceleration and speed.
PAS 5 ghost pedaling and the biggest cassette gear of 34T gives 16.5MPH at 500 Watts; 24T gives 22.5MPH at 500 Watts.
In PAS the speed controller would stick to a MPH level and increase or decrease the Watts to maintain that speed; almost like a governor.
The BBSHD never got too hot to hold your hand on the motor or the controller. The motor never got hotter than 110 F.
Overall the Luna Ludi V2 is very good. It’s $ well spent even if just considering the battery range extension. If you are looking to scooter throttle only you won’t be disappointed in acceleration and top speed. As a PAS ghost peddler, it does not seem that different from the stock Bafang controller loaded up with Karl’s Sauce Settings. VESC app analytics dashboard looks cool but I don’t have an Android device nor the time to play around with those features. Luna warns not to change parameters on the controller without considering the consequences and locked out some of the most dangerous ones to the motor and rider.
P.S. At the time of publishing another field weakened BBSHD after market controller has burst on the scene. Enthusiasts of ASI BAC 855 have banded together via Discord collaboration to present a potential product challenge to Luna Ludi V2. The High Voltage team of Captain Codswallop, Mike and Greg bring a formidable grass roots business plan. I’ve done business with Captain on 3D printing for ebike items and was blown away at the exceptional level of quality and customer service. Captain told me High Voltage is “…new to the market but are providing a high quality product that customers are very happy with…focus…on customer service and quality. We are looking to expand to other motors in the near future.”
The High Voltage brand graphic to look for on authentic products:
So, my Gen 1, 1.5 and 3 bike layouts are all twin geared hub designs. What was Gen 2?
750w, 35a geared Bafang G060 front hub motor
30a BBSHD mid drive
52v, 12.5ah rear motor battery in triangle
52v, 12.5ah front motor battery on rack top
Batteries connected in parallel to form a single ‘virtual’ 25ah power source to both motors
KT and Bafang displays
160Nm rear… 80 Nm front (do the math on that one!)
I live part-time in two towns: The first, an extended work visa, is in Fresno California, smack in the middle of California’s San Joaquin Valley and flat as a table. I built The Colonel, The Purple Thing and The Great Pumpkin for commuting in Fresno.
After a fashion, I finally was able to get a big enough bike rack on the back of my SUV to bring the Colonel to my actual home in Pacific Grove, California. My house is at the top of the hill there. Unlike in Fresno, nothing in or around the area is flat. You are either going up a steep hill, or down one, or both.
My intention was to be able to use the Colonel like I did in Fresno, as local errand transport and a light duty cargo-shopper. Unfortunately, I found out the first day about the limitations of hub drives: They suck in hills.
Hubs are Single Speed
Hub drives power an ebike via the axle. They don’t – and they can’t – use the gears of the bike. Forcing a single speed hub motor up a hill makes it just as miserable as a human stuck with no gears. So even though I have very powerful hubs, and they were geared hubs that put down the most torque of any on the market… they still struggled. Even with two of them. I could hear the gears groaning inside the motor casings and I could tell that, while I could get up the hills, my motors were not happy about it. I did not want to lug them into an early grave. I had already gone to a lot of trouble to make the bike bulletproof and had no desire to ignore the problem and inevitably kill it.
I Need To Build a New Bike
Everybody knows mid drives are the solution to the hill problem for an ebike. A hub motor is single speed and at least relatively weak on torque, but a mid drive uses the gears in the drivetrain, plus it has double or more the torque output of a hub, and thats before you factor in the multiplier of the gears. Wonderful right? Except mid drive motors – especially DIY builds – are notorious for putting drivetrains into an early grave. Why? Well because they pour a LOT more power through the chainring, chain, rear cluster and cassette body (i.e. “the drivetrain”) than a bicycle was ever meant to withstand.
A normal cyclist can pump out maybe 300 watts for a minute or so, but typically normal sustained – strong – output is about 100 watts.
EU-market electric motors must peak at 250w of output to stay legal (pssst… they don’t).
A 25-amp BBS02 on a 48v system puts out in excess of 1250 watts peak
Your garden variety 30-amp BBSHD running under a 52v battery is peaking – and can sustain – about 1750 watts of output.
That gives some perspective on how much abuse is heaped upon a drivetrain with a mid drive. Coming off the successful builds of The Colonel (v1.0) and the Purple Thing (v1.5), I knew AWD reduced load on the individual motors dramatically when they work together as a team.
Given that, I thought about how I could use a front hub to reduce or eliminate the shock that a mid-drive puts onto the ebike’s drivetrain. Not only would I gain the traction benefits of AWD, and the benefit of reduced load from the team effort – things I already knew were a big positive – the front hub would also, if used in a slightly different way, provide an important added benefit: eliminating all the extra wear and tear that goes with having a mid drive.
If it worked, it would give me a bike with all the original AWD performance benefits, plus the ability to effortlessly climb walls, without tearing the bike up.
SPOILER ALERT: It worked unbelievably well.
In fact this bike is a showcase on how AWD can almost eliminate mid-drive wear and tear. Making a bike that climbs hills and bombs trails really well is almost an afterthought.
So that is what I am going to focus on here in this article. What was built and how was it used?
Briefly, this bike is the Great Pumpkin on the front wheel, and a typical mid-drive installation on the back. In between is the usual extra wiring scattered all over the place to deal with powering two motors, set up dual PAS etc..
The Front Motor
2Fat has another Bafang G060 80Nm front fat motor installed – this time its inside of a custom-built 100mm double-wall Weinmann (branded as an Origin8) rim. Go fat or go home. Attached are the same two torque arms as seen on the Pumpkin’s installation, and once again the controller is sitting in a grommeted handlebar bag that doubles as a wallet/keys/phone holder. It also serves to disguise the uncut steering tube I used to give me a more upright – but not too upright – riding position.
Different from the Pumpkin is the battery setup. This bike was built before the v3.0 Pumpkin came onto this Earth (The Purple Thing had just been born). So, lacking the wherewithal to commission a big custom battery for the triangle, I used two packs, one for each motor. The front motor’s 12ah 52v battery was located in the rack trunk at the back of the bike. I had already learned I did not want to put a battery on the front rack as it made the steering too heavy. The rear motor’s 17.5ah pack was in the triangle.
Additionally, due to the very low standover of 2Fat’s Large sized frame thanks to its top tube (it is a titanium, USA-made Chumba Ursa Major) there is not enough room to plug in a properly big battery in the triangle to handle both motors. So I had to do two batteries and live with the awful choice of putting one on the back rack.
After running the two dissimilar, separate batteries from its initial build in 2017 to March 2021, I switched to two identical, now-parallel’d-together packs in the same locations. Each is 12.5ah (14S6P) with Samsung 25R cells. Each has a 50a continuous BMS. As such, the system has a single 25ah power supply with a BMS capable of handling 100 continuous amps. Considering I can never peak past 65, I’m in great shape. I purchased the packs from Bicycle Motorworks, who builds their packs in the USA and constructs them at time of order.
Running battery packs in parallel should only be done by those who have done the research and know exactly what they are getting into. In this case, both packs are identical, being manufactured to-order together, and have the same charge cycle count. Their voltages were matched before they were joined and there is some additional babysitting that will be necessary for charging and balancing. If you can avoid running packs in parallel and use just one battery: Do that instead.
Using two entirely separate batteries is a kludge and your last resort. Not only will you have to charge them separately, you will also draw down the two batteries separately at different rates which will result in uneven remaining power, lesser range and more frequent recharges.
The Rear Motor
This is pretty much your garden-variety 52v BBSHD installation. It has a couple of nice spiffs in the form of a 42T Lekkie Bling Ring, and Lekkie Buzz Bars, but neither of those things are a requirement of the AWD approach we’re discussing here.
The rear wheel is another matching Weinmann 100mm rim, again with DT Champion 2.0 spokes and 16mm brass nipples. The rear hub is a DT 350 Big Ride, which has sealed cartridge bearings and has been upgraded to a steel cassette body. Additionally a 9-speed Shimano HG400 cluster gives me steel cogs literally welded together into a single cluster, that spreads the enormous torque of the BBSHD across the entire steel cassette body. The DT350’s ratchet engagement mechanism is one of the few known bombproof rear hub mechanisms when faced with the power of the Dark Side 30a BBSHD motor.
A solid rear wheel build with extra strength parts throughout is crucial to a successful mid drive ebike.
The Special Bits
There is a bit more that went into making these motors work together. The complete integration possible on the Pumpkin thanks to the use of identical motors and controllers wouldn’t work here.
Trying to share cutoff signals between the motors again – using adapters for the red-to-yellow connections found on the BBSHD – resulted in bricking both motors. I tried everything to share the signals. It can’t be done unless you are willing to install a second, independent set of hydraulic magnet style cutoffs, zip tied to the integrated MT5e cutoffs and connected via a ‘y’ further down the line. That would work but it would look like crap, for very little benefit over what I ended up doing: I set up the front brake to engage the front motor cutoff, and the rear – with a red-to-yellow HIGO adapter – to cut off the rear motor. Since I always use both levers to do my braking I get an effective result.
PAS for the BBSHD is built into its motor casing, so it just works. PAS for the front motor was another matter entirely. Ordinarily the assist disc and sensor runs on the right-hand, drive side of the bike and hides behind the front chainring. This is not possible with the BBSHD’s secondary gear housing being there instead. So PAS had to be made to work on the left hand side. The KT controller has left-hand PAS sensor installation settings.
What was needed then was a left-hand install. This was quite a bit trickier, since the 120mm motor running in front of 5″ tire-compatible chainstays had zero extra spindle length to mount the disk. Lacking a bottom bracket cup to mount the PAS sensor ring, I set it behind a second inner lockring – I used two inner lock rings stacked like jam nuts rather than the usual inner+outer ring. These doubled inner rings had the secondary benefit of being a more aggressive, solid mounting for the motor.
With the sensor mounted, next I had the sensor ring to deal with. As noted above… there was no length available period for the sensor disk as the crankarms mounted pretty much flush to the bottom bracket.
The eventual solution involved hogging out the center of the PAS sensor disc so it could sit on the inner flange of the Lekkie crankarm instead of the spindle. I prepped the crankarm with… thin strips of thick duct tape so the disk would sit tightly on the flange. It was a bodge but it worked, and with just one improvement since installation in 2017 it has held perfectly. That improvement is a zip tie to help hold the disk steady in position (of course I used a zip tie. We have duct tape in the mix; all thats missing is a zip tie).
Worth noting: I used this identical PAS ring mounting when I built the Lizzard King AWD cargo bike in 2021. Not only did I have enough extra spindle so I did not have to do this surgery on the ring, I also realized I could unscrew and reverse the sensor in its mounting ring. This eliminated the need to use the reverse settings in the display/controller. Since the inset ring was reversed, it was outset now… and that held the sensor closer to the magnets (they work fine inset as seen here, but closer is better).
Here’s where the eagle-eyed may spot a preview of how I ride this bike to soften up the mid drive.
On the right, we have the grip, then the brake lever, followed by the 9-speed shifter. Here again we see a v2.0 feature that v3.0 fixed: A SRAM drivetrain gives us a SRAM, not Shimano shifter. The Shimano shifter needs so much real estate on the grip it is impossible to put a throttle on that side of the handlebars. Look at the cockpit of The Great Pumpkin and the Lizzard King to see how a SRAM shifter solves this and lets me do one throttle per thumb.
Being unable to do that at the time – and believe me I tried EVERY possible combination of throttles. I still have most of them in a box in my garage. I settled on two styles of thumb throttle, side by side on the left, with the innermost throttle being for the hub/front and the outermost for the BBSHD/rear. As for the eagle-eyed part: The front throttle is cocked higher so between that and its longer throw, it is engaged first and when at 100% it follows the natural curve of my thumb. Both throttles can then be at 100% and my hand stays comfortable at WFO.
How To Ride It
At last we get to the point!
I already let the cat out of the bag earlier: The biggest deal associated with this bike is not that it can climb really well (REALLY well). Nor is its ability to handle trails and rotten conditions its star quality.
No, the real point of having a mid drive teamed with a front hub motor is to use that hub motor to take the shock off the drivetrain that mid drives deliver. Do that and you also take away the excess wear and tear on the parts (if we are being fair, a lot of this comes from doofus riders who don’t know what they are doing).
When starting, start with the hub
This is most of the deal right here. Don’t make the mid drive haul the bike up from a dead stop. Its got the torque to do it. But everything takes a beating in the process. The nylon gears inside of the mid drive. The chainring. The poor chain. The suffering cogs. The cassette body being dug into by the cogs. The pawls inside of the cassette body that are straining against the hub. Your ebike hates you for doing this to it.
By using a mid-drive-strong chain, a steel cluster and a steel cassette body with a ratchet engagement mechanism, we harden the drivetrain to be very tolerant of this abuse. Between that and learning how to use a mid drive, wear and tear really isn’t bad at all. Maybe no worse than a quality analog bike used hard. But still… even with the hardened drivetrain it sure would be nice to take things easier.
By using a hub motor to get the bike rolling – even by just a few mph – we accomplish this mission. Using my pedaling-friendly BBSHD programming or something like it, the BBSHD will not kick in on pedaling until the bike crosses about 5 mph. So from a stop, you hit the front throttle for about one full second. That throttle is cocked up a bit higher on 2Fat to make that a natural move. The bike starts up from its dead stop without any strain on the drivetrain since the BBSHD is not even running. Simultaneously, you also start pedaling. This engages the cassette mechanism.
When speed crosses 5 mph, the BBSHD’s pedal assist now kicks in on a drivetrain that is already engaged. There is no longer a risk of having the motor jerk the chain and smash the cluster into engagement. And with this gentle engagement, the motor starts working on a bike that is already moving. So you get the doubled benefit of a lighter effort against all components to get your fat bike off its fat ass. Instead, you get smooth – and strong – acceleration. The lack of lugging the motor has the further benefit of not generating anywhere near as much heat since the motor is no longer running at low rpms for anywhere near as long. And those nylon gears inside the motor are writing you a nice thank-you card.
Rather than using the throttle, you could also just start pedaling. I have set the KT controller to engage PAS as quickly as possible. Combine that with the BBSHD’s controller being told to hang back for the initial startup, and you have a completely thumbs-off solution that implements at a nice gentle pace.
So… It just works.
Or you can force it! Remember with this setup you have two throttles. There’s no law that says if you need it, you can’t jump the gun and either hit the rear throttle early, or hit it so the motor engages harder than it would have in your designated PAS mode. So if you need a little extra push thanks to an XL load of groceries, or a steep hill, you have options at your disposal.
One of the mantras associated with smart mid drive riding is that you always Always ALWAYS freaking downshift the bike when you come to a stop. The LAST thing you want is to lug the motor up from a dead stop because of all the brutality it visits on your chain, your cogs blah blah blah. So that means you remember to downshift one or two… maybe even three times before you come to a stop. When the light turns green you upshift in sequence one gear at a time as you get back up to speed again. Thus as we all understand: you row thru the gears.
Another rule mid drive mavens repeat ad nauseum is – if you have an 11T small rear cog… stay the hell off of it. Its too small to use on a mid drive. It bogs the bejesus out of the motor from a stop, its too small to be able to get up to speed before the sun sets and if thats not bad enough, the teeny cog on even the steel Shimano clusters is alloy and it is not attached like all the others are. Its an individual. So not only do they dig into the cassette body harder, they die fast. Like Really Fast. As in a few hundred miles tops.
Well, on AWD mid drives like 2Fat, you can forget about all that. Because of the powered front hub doing its part (either thru a quick dab of throttle or just letting PAS start the bike), there is no longer a need to shift at a light. You can forget about the whole process. Just leave it and it’ll be fine as if it was a hub motor! In fact the front motor allows the bike to increase its speed so it gets up and goes fast just like a hub motor does.
I found this out within a day of building the bike, and since then learned from experience the 11T cog will last about 1500 miles before it typically cracks (two so far). Thats not so bad for a readily available US$7 part. And if I wanted it to live longer, well it wouldn’t kill me to go up a gear at a light once in a while.
Wrapping It All Up
2Fat itself is not the ideal example of how to execute this concept. It is a product of when it was built and my knowledge level at that time. In the present day, I for sure would not want to build a bike with two batteries, and if I did I would NEVER put one on the back rack. But thats partly the limits of the frame I used. I came within a hair of using a Salsa Blackborow frame kit for this bike until, at the last minute, this titanium beauty fell into my lap for a song… but thats another story.
Next, I wouldn’t use Shimano components thanks to the real estate problems introduced by the shifter. Instead I’d use SRAM components so I could do one throttle per thumb.
Really the Great Pumpkin with its XL size and XL triangle, plus its SRAM shifters – would be ideal here. But them’s the breaks. This is what I’ve got. Boo hoo.
With that said… I did learn as I went along, and in 2021 I returned to dual motor bikes with the Lizzard King, a bike meant to prove a different kind of AWD could be awesome: You don’t need the 80Nm, 35a punch of the Pumpkin’s or 2Fat’s front hub to gain the benefits of AWD. A low power implementation, done a little differently, should be very effective and appeal to a much broader range of everyday, low-speed, low-drama ebike use. And…
1 x 52v, 30ah battery with Samsung 30Q cells, 90a continuous BMS
2 x 35a KT brand controllers
2 x KT brand displays
160 Nm total power
The Great Pumpkin remains my fast commuter workhorse. This bike is meant for transportation to and from a destination, not sightseeing. As such it is designed to travel as close to the safe, legal speed limit as possible. Here in California the assist limit is 28 mph, I stay on the street (no shared-use bike paths allowed) and this bike’s gears are made to let me power it up past that 28 mph limit to about 34 mph – if I am strong enough to pull it off.
A note on speeds and our local roads here, and how they influence the design and capabilities of this ebike: in California the law limits ebikes to 28 mph (45 km/h) of assist. Thats an assist limit, not a speed limit. The maximum lawful speed is the posted motor vehicle speed limit, adjusted downward if necessary to maintain safety. So if you can pedal the bike faster than 28, thats fine so long as doing that is "safe for conditions". These speeds seem like a lot to readers in some parts of the world. But remember here in the USA we've got open roads that are nothing like you see in many urban centers in, for example, the EU. The two pictures above come from two different places along my 15-mile commute route. The speed limit signs are in mph not km/h. Bear in mind drivers regularly exceed these limits by a significant margin so in rush hour traffic a 30 mph bike is by far the slowest thing on the tarmac, with no pedestrian issues to speak of.So, on streets like this, if I can pedal to 34 mph - and oftentimes I can - thats perfectly legal. In fact I have been paced and radar'd by police cruisers and motorcycle traffic enforcement many times without incident.
So the secondary purpose of this bike is to enable me to work hard while still transporting me to Point B at a practical speed. You’ve heard how ebikes let you arrive at your destination without getting all sweaty? Well, this one lets you arrive all sweaty on purpose if you like.
The geared hub motors let it accelerate fast in traffic, and despite its necessary lack of suspension, the fat tires (and the suspension seatpost) let it ride well on lousy pavement. It has over 7000 miles on it at present (March 2021), and benefits from all of the learning I got the hard way building its predecessors. In fact, I am using the same set of wheels I had built for my very first AWD ebike: The Colonel. This is a testament to finding a good wheelbuilder at the Local Bike Shop of your choice and have them build you a quality wheel with quality components.
The Pumpkin is a flat-country bike. Dual geared hubs are powerful, but hub motors – since they power thru the axle and cannot use gears – are just single-speed. Despite their power and ability to handle lots of current, they can get the bike up steep hillside streets, but they struggle doing it. Riding this bike in the Carmel/Pacific Grove portion of the Monterey Bay Area, where nothing is flat, I found it could climb anything but it lugged its motors mightily doing so, to the point I feared for their long life. But if you live on flat land (and this bike’s permanent home is in the table-flat San Joaquin Valley), this is the design that will gobble up pavement for lunch. It will get you where you need to be safely and quickly as an ebike can legally travel.
Why didn’t I choose maintenance-free direct drive hubs? Because they lack torque, and that means slow acceleration unless I load the bike down with bigger, higher voltage batteries and motors with much more unsprung mass.
Having done it the wrong way before out of necessity (translation: too expensive) I put in a single big battery on this bike. It has the biggest battery I could fit into the triangle of this XL-sized frame (A Chumba Ursa Major made with chromoly tubing). A 14S9p (52v) pack that uses Samsung 30Q cells to give me about 30ah. That means it takes awhile to charge. But it also takes awhile to drain, and this single battery is placed down in the triangle where it does not reduce the carry capacity of the bike, or screw up its performance with schlocky placement of a battery on the rear rack.
But doing an AWD bike with a single battery means you have to address more than just size. The Battery Management System (BMS) has to be able to handle the amp draw of two motors simultaneously. Looking for batteries out in the wild that can do this… you’ll find almost none that are capable of it.
How do you calculate the sort of battery you need? You take the peak output of both of your motors and add them together. Your BMS’ “continuous” power rating has to be more than that peak to ensure your motors never trip the BMS’ limits. If they do, to reset the battery you have to hook it up to a charger, which is unlikely to be handy on the side of any road you’re traveling on.
So, with a 35a rear controller and a 35a front controller, I need a battery with a 70a continuous (or more) BMS, and thats a special order item. In my case, the BMS can handle 80a continuous current.
Controllers and Wiring
The 35 amp KT brand rear motor controller is sitting under the saddle, zip-tied neatly with small clear, low-visibility ties to the seatpost mounting arms of the rear rack. This puts the controller in open air to keep its heat down. It will reach temperatures of 135 degrees fahrenheit if stored enclosed. A home-made fender comprising of an extended commercial mudguard and cut-to-size flexible cutting board provides complete coverage from water coming up off the rear tire.
The front motor controller is an identical 35 amp KT, housed in the handlebar bag. This bag has had reinforced brass grommet holes placed strategically inside and out so cables can pass thru its inside compartments to the outside of the bag, without creating issues of splashing water (here again extended fenders help). The top of the bag is left zipped open and this keeps heat from becoming a problem. The front motor cable travels directly up and into this bag, while cables for pedal assist, brake cutoffs, display and throttle exit out either a grommeted side entry or out the open top of the bag. The bag itself essentially hides all of the front motor cabling rats’ nest, both by housing excess wire inside itself and via natural camouflage, providing a black backdrop to black cables running along and woven into its MOLLE exterior. Cables exiting and entering are carefully bundled together for neatness.
The center triangle bag is stuffed mostly full with the custom-sized triangle battery. Like any triangle bag on an ebike, it also serves to hide excess wiring, and given the dual custom splitters for brake cutoff signals and pedal assist (one sensor signal is split off to both motors for simultaneous PAS power) there is plenty of wiring that thankfully remains invisible thanks to this bag, which seldom needs to be opened. The bag has forward and rear-facing cable holes that don’t suffer from water ingestion, again thanks to the fender setup. A capped XT60 charger plug is coming out the front of the bag just behind (and shielded by) the head tube, and this cap is removed and a charger is plugged in here to recharge the battery.
Ergonomically, the cockpit is very well designed and reflects this being my third or fourth try at doing the job. There is one throttle for each thumb in easy reach, and both throttles are clocked so when fully engaged, the paddle is pointing straight down. If you hit a pothole your thumb doesn’t push thru and break the throttle. It slips off instead. The PAS panel is also one-per-side, and also within thumb reach without losing your grip on the bars. SRAM 9-speed shifters are in use, because a SRAM shifter gives you enough real estate on a handgrip (vs. Shimano) to stack multiple hand controls and still be able to easily reach everything.
Despite the duplicated motors and controllers, the displays are mismatched simply because I am re-using parts from older bikes no longer on the front line (in this case parts came off The Purple Thing). For this build I needed a new display and the KT model LCD8H was available, so I grabbed one. It is the same display as the KT model LCD3 above it, used for the front motor. The LCD8H is just in color and easier to configure.
And in case you noticed… yes this is a bike with Class 3/Speed Pedelec performance that has throttles. Reality is, though, the bike is designed specifically as a pedelec. Pedaling acceleration via PAS is plenty fast and is in fact (thanks to controller settings) a little faster than using the throttles. They are only put into use typically for a split second on take-off from a standing start while I regain my balance on the bike and settle in to pedaling. If I am crossing a 4-lane street, I am off the throttles before I get past the first lane while crossing and won’t touch them again until the next stop at the next intersection.
Power (too hot)
These two 80Nm motors have controllers feeding 35a to each axle provide giggle-inducing acceleration. So much so I found performance needs to be turned down for multiple reasons:
#1– (Safety). Come to a stop at an intersection. Acceleration is so strong from a stop, you leap forward so fast you are always the first vehicle that gets to the other side, and you’d better be hanging on. Thats fine if you meant to do that. If on the other hand you accidentally engaged pedal assist, you could be throwing yourself – literally – into the path of a car.
#2 – (Safety). Come to a stop at an intersection. Put your feet down, release the bars and take a drink or something. If you engage again (pedal assist or throttle) and forget to put your handlebars straight, your front wheel will shoot off in the direction its pointed in. Typically a bad thing.
#3 – (Fork survival). With this much torque pulling on the front fork, things start to happen that a bicycle was never stressed or designed for. A front fork was never designed to be pulled on hard, for extended periods or in sudden jerks. Especially not day after day for days and weeks stretching into years.
#4 – (Frame survival). This one was unexpected: Even though I am using a highly durable hand-made-in-USA frame, I still found it was straining under the repeated daily stress of stoplight-to-stoplight acceleration from the rear motor. Specifically I started to hear creaks from the rear triangle and dropouts. eek.
#5 – (Safety again for crying out loud!). I use fat street-smoothie tires in summer. Doing that with the motors unrestrained makes for about a half rotation of front wheel spin on full throttle, and maybe a 1/4 spin on pedal assist… and a goodly chirp out of the back, at the least (lots more if the ground is not clean, dry pavement). Thats fun for an afternoon showing off but more than that and its just plain dangerous.
Power (just right)
To slow down the bike so it accelerates at a safe rate on city streets, and doesn’t wear itself out from all the extra stress of doing this day in and day out, I utilize a setting in each of the two KT brand controllers that sets the power curve to ‘slow start’: C5=00 is undocumented on all but the newest KT display manuals. Where it is documented, it is listed as the most restricted of the three ‘slow start’ modes.
What this does is create an acceleration curve slope that is shallow at tip-in but increasingly steep as it continues forward. Here’s the crazy-cool part: Even dialed way down on both motors this bike is still typically faster than anything else crossing the intersection from a standing start. So you aren’t missing out on much in the way of fun if you want to pour on the amps. Its just safe, sane and controllable when its put on a leash.
Torque Arms (!)
I’m not going to get too deep into the specifics of this topic, but I will say if you use hub motors you have to use torque arms. Gotta do it. Thats for any motor that has ‘flats’ on its axle to allow their use (which is almost all of them). It is true many motors do not need torque arms because they are of such low power. I will say having suffered the consequences of not using one, its WAY better to be safe than sorry and just go ahead and install them regardless of motor power.
What could happen? If you don’t use a torque arm, the force of the motor will overwhelm your bicycle’s dropouts and the motor will “spin out”. That means your steel dropouts will not be able to contain the motor’s axle, which will spin (instead of the motor casing spinning) and when that happens the dropouts spread. Your frame or fork is effectively destroyed and unsalvageable at that point. These 750w, 80Nm motors are right on the edge of demanding two torque arms. For sure they need one. I have used two on the front motor and one on the rear, where the stronger rear dropouts are much less likely to have an issue.
Last but not least… take a look at the pictures on this page and you will see the biggest front chainring ever on a fat bike. Look to the back axle and you may be looking at the smallest cluster. And the derailleur is a mid-length cage, to boot. Fact is, this bike was geared to be pedaled fast on the street, not overland on trails as is the norm for fat bikes.
The front chainring is a 50T ring, while the rear cluster has an 11T small cog. Frankly I forget the size of the biggest cog because I never use it. Its 28T… Maybe 30. And since the hubs on this bike are the motors, powering the bike thru the axle, not the drivetrain, gearing is largely useless unless I want to pedal faster while going slow. This almost never happens because this bike should not be taken on pedestrian paths or similar where such slow travel is necessary.
For a daily driver bike that is transportation, not recreation, you need to address many areas to ensure reliable, day-in, day-out operation. There are many issues addressed on that topic with this bike, but I’ll only touch on the AWD-specific ones here. In a word: Redundancy. If you do a general overview of this bike’s propulsion systems, you will see almost everything but the battery is a separate, independent system. None of this is accidental or done because I was forced to do so (you can buy controller solutions that reach out to two motors at once, for instance). Its done this way because its better. Dual throttles are better. Setting PAS independently per wheel is better than combining the two. Even two different displays let you focus on different bits of each (although that one I could do without if push came to shove).
Redundancy on a dual motor bike can be a big benefit. I’ve had one unfortunate lesson in this: I went over the handlebars and slammed straight down on the pavement, cracking some ribs. I also bent my front fork (just a little) and smashed my rear throttle, among other things. That broken throttle disabled the rear motor despite all other components being in working order. I was able to limp the bike home without pedaling, which I really needed given the cracked ribs and various and sundry other minor injuries.
This is one more reason by the way, why I want throttles on the bike. If I am physically unable to pedal I want to be able to get me and the bike home, or to the emergency room as the case may be.