# A2B e-bike upgrade - build



## rishimaze (May 23, 2021)

I've had this A2B since 2018. The frames are pretty nice, but a lot of the components are pretty cheap. It's seen on again and off again development. Then I moved and it has basicly stalled out for the past year. Hopefully once I get my Zap scooter build done, I'll get back to my first ever e-bike build. The bike was a show room floor bike. It still had the plastic on the seat and had seen maybe 5 or 10 miles of use. I paid $250 for it. Even the battery pack was charged...not that I cared!

It's in really clean condition under the dust.


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## rishimaze (May 23, 2021)

Like my Zap scooter build, I won't go in chronological order. Instead, I'll present areas that I improved or modded.

The brakes on it were cheap mechanicals that didn't work very well. Looking at the wear on the pads, they were clearly very new.


























The rectangular Shimano pad is clearly larger and semi-metalic. They ought to brake better than the organic pads and wear better.










These are the cheapest Shimano hydraulic brakes there are, but they seem to do pretty well. The big difference between them and the more expensive versions is mostly details like cast handles or being able to add cooling fins to the pads. It's almost completely finish details that are not as nice, but the braking capability is the same.


















































This is the complete Shimano brake kit. I believe I paid less than $100 for all of it on Amazon.










The factory 180mm rotors got replaced with 203mm rotors. It doesn't seem like much, but larger rotors warm up more slowly for less brake fade and they provide more braking power for the same amount of clamping force. 203mm is the largest bike brake rotors I could find.


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## rishimaze (May 23, 2021)

The factory Kenda tires on these bikes are pretty aweful. The side walls are very weak and no part of the tires are meant for more than 30 mph.










I bought a set of expensive Schwalbe tires and I wanted to go tubeless, but the tire beads on them have ridges and they would not seal up. No amount of Stans tubeless sealer would close up all those ridges in the tire beads. I tried keeping pressure from my air compressor on one of the tires over night in hopes that the Stans would eventually seal up the tire beads. By the next morning, all the Stans had blown out of the tire beads and the only thing keeping them inflated was the air compressor.


































I discovered that a 16" moto tire fits a 20" bike wheel perfectly so that's what I ended up using. They are much tougher tires and provide wear wear and grip than bike tires. I found a set of Shinko moto tires good up to 75 mph. I was somewhat concerned that the evenly spaced mold marks on the beads would keep them from sealing to the rim, but they have been filled with air for over a year now and never gone soft even a little. The Stans tubeless sealer closed up any small gaps nicely.


















Making a bike wheel air tight so you can go tubeless is pretty easy. You need the inner surface of the rim to be very clean. PET or Poly Ethylene Tape works really well for sealing up over the spoke holes. I laid down 4 layers of tape over the holes. This is more than enough to make a permanent seal. I've heard of people using duct tape or black electrical tape. I wanted something long lasting and reliable that would last nearly forever...aka PET.


















A tubeless valve stem finishes it off. I used aluminum ones because they are light. However the annodizing on them wears off the threads so they lose their black luster pretty quickly.


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## rishimaze (May 23, 2021)

The wheels were not strung particularly well and I wanted to reinforce them. I bought Sapim spokes and nipples for the rear wheel. I replaced all the cheap spoke nipples for the front wheel and reused the existing spokes. While I had the bike wheels apart, I added brass washers under all the spoke nipples to reinforce them on the rim inner wall. This was more important for the back wheel since it will see 10kw on those spokes.

The back wheel got restrung with a track hub in place of the pathetic 500w hub motor. This allows me to thread on a brake rotor on one side and use the freewheel threads on the other side for mounting side by side sprockets. 


































Here's both wheels after restringing next to a 26" bike wheel.


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## rishimaze (May 23, 2021)

The rear shock is just a spring so I replaced that with a DNM shock. I needed a stiffer shock and I definitely wanted damping like a real shock produces. The DNM is a bit longer than the factory shock and that makes the bike sit about 1" taller. It's not enough to really matter and this is still unloaded so adding motor, battery and rider will compress that a good bit.

Factory shock:


















DNM shock:


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## rishimaze (May 23, 2021)

The factory cranks and chain ring got pulled off and replaced with a 3 sprocket set. This will be all the gearing the rider gets for pedaling as the back wheel has a fixie sprocket on it and won't be changing gears via a rear derailleur. The bike chain spins all the time and there is a freewheel in the cranks so the pedals can stay stationary. I need to mount a derailleur near the 3 chain rings for gear changes.

I found these parts from a reseller of specialty bike conversion parts. They had a large selection of sprockets, crank arms and other parts for adding a motor to a bike. I already owned a White Industries freewheel so I reused that with these crank parts.










The M5 screws bolting the freewheel to the sprockets were too tall so I had to machine them down a bit so they cleared the crank arm. The 3 sprockets spin with the rear wheel and the crank arms stay stationary except when you are pedaling.










Those bolt heads juuuust miss the crank arm by about .5mm. I might find a lower profile solution later if they end up grazing the crank arm.










The nuts on the back side of the chain rings clear the frame by about 5mm.










These 3 sprockets are pretty close to the cadence of 2, 3 and 4th gears on the middle chain ring of most bikes.


























The right crank arm has freewheel threads on it for mounting the freewheel and then the 3 sprockets are bolted to the freewheel bolt flange. The sprockets spin around the free wheel and the pedals engage them only when you pedal.


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## rishimaze (May 23, 2021)

The track hub on the back wheel allows me to do some interesting things.

This side has about 1/2" of threads so I used that for the 2 sprockets since it would provide the most support for the motor power.










This side has 2 sizes of threads that are about 1/4" deep each. The larger size fits a standard brake rotor adapter.










The rear brake rotor mounted.










The drive side uses 2 brake rotor adapters locked together so that all the threads are engaged on the track hub. Conveniently I found 2 with the right internal threads and that the M5 threaded holes lined up perfectly. If this doesn't hold up, I may need to make my own adapter.


























I machined the SOMA track cog sprocket to have the 6 bolt pattern of the dual rotor adapters. The steel in these sprockets is VERY tough and hard. Typical HSS drills will not cut it. I used a carbide drill to make the 6 bolt holes. The threaded flange was milled off with a carbide end mill.


































I got a bunch of these adapter plates laser cut. The outer bolt pattern is the same as is common on 219 wheel sprockets. The inner bolt pattern matches the brake rotor adapter bolt pattern. I then mount the 219 sprocket to the adapter plate and then bolt it to the brake rotor adapters. This is the rear sprocket I'll use. It's so large since I'm gearing in a single stage from the 74kv motor to the wheel. It needs to opened up a good bit to take out weight and to make it into less of a speaker cone so it doesn't amplify chain noise.


































The bike chain clears the bolt heads by about 2mm. I think this will be OK. Worst case, I mill them down a bit like I did on the crank bolt heads.










Test fit of the 219 sprocket next to the tire. I have a straight edge in there to make sure the 219 chain will clear the tire. It's close, but OK. This sprocket looks huge on a 20" wheel. It will look lots better once I open up slots in it. It is a custom made sprocket from Azusa Engineering. You can't find ready made 117T wheel sprockets!


















The final sprocket set up. The derailleur is just keeping the bike chain tensioned.


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## rishimaze (May 23, 2021)

I removed the 500w hub motor. The swing arm spacing is pretty wide to accommodate the motor. I was not able to find an axle long enough that didn't have threads under the hub bearings. This made the bearing inner races have a small gap as the the threads compressd. It was pretty easy to get this to happen and then the slight rocking in the back wheel got noticable. I got some 10mm hardened shaft and made one myself with threads only where I needed them. I really need to make a slight longer one as there is more to go behind the axle nuts than my axle can handle. That wide swing arm spacing was a good thing since I later mounted side by side chain lines in there.

The top axle is one I found online. It is barely long enough to span the swing arm gap. Notice how close the threads are to the center of the shaft. This put them well under the rear hub bearing inner races where they would compress and create slop. The lower axle is the one I made. Getting the fine threads to cut straight on the steel was not easy. I had to hold the axel dead vertical and the dye dead horizontal so they could not wander off from each other as the threads cut. These threads stop just outside the hub bearings.


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## rishimaze (May 23, 2021)

I intend to use a Revolt RV-100Em outrunner and a Nucular 24 fet controller on the bike. This outrunner is wound for 74kv and is capable of 12kw peaks. Nucular 24 fet controllers can handle around 20kw so this is a good match for the motor.










This is a Nucular 24 fet in front of an 8kw Kelly controller. They are quite power dense.










The motor will get a custom bracket made that fits behind the shock. Making a bracket won't be too hard. I've made several. This is the strongest section of the swing arms so securing the motor bracket to it should work well. The important details is to clear the shock and to not extend beyond that curved cross brace so I don't run into the back tire. The rear brake line will need to move and the cable on the other side is already gone.


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## rishimaze (May 23, 2021)

Battery placement will be in 2 locations:
1. The V in the main tubes will make for a nice cradle for a pack.
2. Under the bike rack is a set of rails. A2B made a 36v pack to mount here. I'll probably reuse this at 82v for a pack.


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## rishimaze (May 23, 2021)

Here's the A2B as it is right now. I'll probably get rid of the awful seat. There's so many things left to do yet! This is hours and hours of work and it looks like hardly anything has been done.


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