fixie/single speed electric bike build

Hey guys, its been a long time but i finally put an e-bike together!

long story short with the hub motor. i gave a bike shop 5 weeks to lace the wheel with the hub but when i finally came to collect it, it wasn't ready so i decided to cancel the job and picked up a mid drive system in which i could easily install myself at home..

i picked up a TSDZ2 350w system from BMS battery for around 420 euro's after postage and import duties to Germany. link below

https://bmsbattery.com/home/803-sdz2-torque-sensor-central-motor.html

i was a little worried that a mid drive system wont really like to work with a single speed bike such as this, but it proved me wrong. 36Kph top speed is good for me and awesome at climbing hills! only downside is that on the flat straights the motor will cut off once you reach the top speed due the motors maximum speed not being able to keep up.. i will fix this problem soon once the DC to DC boost converter arrives, the converter will boost my 36v battery up to 49 volts with up to 20 amps at the input, hopefully it will give the motors RPM so i'm able to reach 40+ Kph.. the controllers speed limit of 25Kph has been disabled by the way ;)

i desperately need to purchase some better non-painted wheels and purchase the brake system mentioned above! the stock brakes just can't keep up.

any questions, just ask

i've posted a picture of the bike below and a little video :)

https://www.youtube.com/watch?v=zV7BZI8zSWA&feature=youtu.be

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This is nuts. I love it. Get some better brakes though!

haha!, i totally agree
the stock brake system is horrific! urgently need upgrading

i'm waiting on a front and rear set of Magura HS33 R Urban's.. should do the job!

when i brake at the moment using my high end 1,99 euro supermarket special brake pads its going something like this

braking.. braking... starting to fade.. fully fading.. still fading.. pads starting to melt... heavily melting.... still melting.... metal vs aluminium..... aannddd......stopped

spent a few hours scraping and removing the melted brake pads from my rim's last weekend... they lasted for a grand total of 4.3Km's

that's 46 cents per Km in "cheap" brake pads xD

Ha, that sounds equally funny and scary! In the long run, it might be worth getting something like an on-one pompetamine with disc brakes. Keep us updated!

possibly yer :) i think i will reverently purchase new wheels and a front folk, one that will take a disc brake.. 100% need one!

i have a questions in relation to gearing, hoping one of you guys could help?

my bike has a flip-flop bub with a 16T freewheel on one side and a 16t fixed gear on the other..

would it be possible for me to fit another freewheel on the other side to replace the fixed gear with let say.. a 13-14 tooth freewheel?

my current gearing is 16/44t. this is too easy for the motor, it easily drags me up any hill and it also hits maximum RPM when attempting top speeds, the motor will even turn off at top speed due to the lack of pressure i'm applying to the peddles

my idea.. 16th freewheel for hill's and rides to unknown destinations
13-14 tooth freewheel on the otherside of the hub for flat ground and top speed attempts ;)

does anybody know which size freewheel i need to replace the fixed gear in terms of the thread size? and can anybody recommend a 13-14t freewheel that will fit?

Cheers!

one more question..

where i can purchase singlespeed freewheel spacers? my chain line is not the best and i could do with moving the freewheel out by 2-3mm

the only spacers i can find are for cassette type hubs

I don't know if you can get a 13/14t freewheel for standard diameter hub threads... I'd say your best bet is getting a larger chainring on the front.

And maybe go 16/19 or 16/20 on the rear

a larger chain ring up front is not possible, even tho the chain ring is 110/5 hole the chain ring is offset by around 4-5mm.. a normal chain ring will push my chain line even further out of line :(

does a flip-flop hub have the same size thread on both sides?

sometimes it'll be fixed / free or fixed / fixed but the threaded part that takes the cog or the freewheel will be the same size in my experience

ah i see, thank you!

i will have to do some more research.. this may be tricky!

how about the freewheel spacers to bring the freewheel out a little ( 2-4mm )
i can't to find anything at all online about them.. every link take me to spacers for cassette type hubs

do they exist? :D

how about this one?

https://www.amazon.com/Odyssey-BMX-free-hub-sprocket/dp/B009GIBNS0/ref=pd_sbs_468_39?_encoding=UTF8&refRID=P2N14BD6QM8KB915S374

FW1213 Threads onto metric (small) side of flip flop hub

If you have metric (small) threads on either side of your hub then sure. If you want to check take the freewheel you already have and try to thread it onto the other side.

hmmmmm, i will have to check later on.

another idea is to just use a small 12-14t fixed gear, the mid drive unit has a freewheeling chain ring / crank so i may still be able to freewheel, i need to confirm this later on this evening tho

This is very cool. A bit late but if you'd built it around a Pompetamine you could have used disc brakes for better braking.

Maybe something for V2?

possibly yer!, i think my next step after improving the brakes will be to find some front folks with a caliper mount and a new set of wheels which will accept a disc upfront.

at this very moment in time im fully focused on reaching a higher top speed, due to my 16/44t gearing i'm limited to 40-45Kph and the motor turns off at this speed due to me applying next to no force on the peddles (torque sensing mid drive)

i'm almost certain this motor can reach up to 55-60Kph with the correct gearing.. it has so much torque to offer which i just can't access with the current gearing!

Personally I'd sort the braking out first :)!

Jeremy Clarkson — 'Speed has never killed anyone. Suddenly becoming stationary, that's what gets you.'

but correct, i need better brakes.. although i have solved this issue, its just currently in the post.

turns out that the freewheel at the crank/chain ring will work with a fixed gear at the rear.. the chain will always be turning but the pedals will stay still.. there is a slight form of friction coming from the crank when the chain is turning it but its definitely not turning the actual motor, i'm just a little curious where the friction is coming from exactly.... might just be because the system is still new and not worn in just yet.

Can we see more pictures? Close up of the motor and batteries etc? Can hardly tell it has a motor in above picture. Very neat and also very impressive!

yer sure, i will probably take some tonight.

i might just make another video showing the bike in more detail

Some wheels with a proper braking surface will help too.