Electric bicycle building

[hzoltaan]

Ok, we arrived to the step of transferring the power to the wheel...
the question is how...?

The structure of the motor and the grinder is that it turns only to one direction. (I think, even if it would be possible to reverse the motors polarity, the nut which holds the smaller cog would loosen up...) This direction forces me to drive the rear wheel from the left side.

So, how do we put a sprocket on the left side? (the 6 gear gearbox is on the other one)

My idea is that I get a big sprocket (some 40 teeth) with a small hole in the middle and put that one on the left side of the hub, fastening it with M6 or maybe M8 bolts going through the little triangles formed by the spokes by the hub... I could carve out some rubber pieces which would ensure that the sprocket is nicely mounted to the spokes / on the hub...

The good candidate for such a sprocket is a BMX front sprocket, being a full disc so I can drill wherever I want. It's also a bit wider than usual bike sprockets. size is: 1/2 x 1/8. chain is 410

to match it, I found that the front sprocket from an old german moped (it was really popular here, parts are abundant) Simson could fit nicely on the grinder shaft. That sprocket needs chain 420, which is only wider, the pitch and the roller diameter is the same. Get 420 chain, and we are done...

Better idea?

I was also considering putting a rearwheel hub to the front and have the bike front driven. I'm a bit reluctant to do so... probably because I never saw a front driven bike.

[NeilBlanchard]

There are some e-bikes that have front wheel drive; using a hub motor. The advantage is it leaves room for the rear gear cluster, and the possibility of better regenerative braking.

[hzoltaan]

Yes, I saw quite a number of those fromt wheel driven, hub motor powered bikes. (last week I saw a hub motor in a wheel for chips on the fleahmarket... GRRRRR ) I'm reluctant to put this huge motor/gerbox assembly to the front though. It is really bulky.

[hzoltaan]

I got the idea:
I'll get a whel hub which can have a disk brake and on the disk brake mounts I fasten the big 44 teeth BMX sprocket.

soon it will be done.

[hzoltaan]

wow it was logn ago when I wrote last time...
Still, the project is alive... interferred with another project named: refurbishing the house
So, The idea of the power transfer is:
Motor - gearbox - small freewheel (like 16 teeth) - chain 1/8 - big sprocket (BMX pedal sprocket) fixed on a wheelhub which has thread on both sides for freewheel / fixed gear. (stunt bikes and delivery-boys use them... calling the bikes fixie)

so the main "invention" is the new wheel hub which has the thread on both ends. It will allow me to put a normal 3/32 freewheel on the right side to be driven by the pedal, while on the left side there will be a fix threaded sprocket locked with a locknut. (all can be ordered from bike shops for chips) The sprocket I choose has some holes on it for weight reduction. They gonna be perfect to bolt the BMX sprocket on. I could get a wheel hub which takes a disc brake too, but let's face it: this is much cheaper and I can place the sprocket much closer to the wheel... I gonna need it as the frame we not designed top have anything on the left side.

So here we are at the moment, haggling with the internet shop.