Brompton electrification

[shemozzle999]

What I am trying to establish is whether the existing SA torque washer and nut can be modified to fit the hub shaft and still have enough meat left to do their original jobs, for that I need to know the shaft diameter i.e. what is the biggest measurement/width across the shaft Cwah?

 

[jerrysimon]

This shows how it works.

Regards

Jerry

 

[jerrysimon]

Ok I had my rear Brompton wheel off anyway so I have done some pictures to show it more clearly using my Tongxin as a substitute. Man I am so kind

Bare with me whilst I post them.

Shown my Tongxin held up to the rear droputs. Notice the flats and how they fit in the dropout.

Anti rotation washer that comes with the Tongxin. One either side. The hole would have to be enlarged to get the motor shaft right into the dropout.

 

[jerrysimon]

Single speed tensioner with anti rotation washer and non flanged nut.

Almost fits.

No way with the flanged nut

Regards

Jerry

 

[jerrysimon]

Shown with washer on the inside which may work better. You will then need another nut on the outside to hold the tensioner on.

Shown held up in stock position.

Regards

Jerry

 

[jerrysimon]

Ok cwah I think it is now time to take stock

These are my thoughts.

It will probably be ok and work with the above if you keep everything at 36v, don't over volt it and restrict assistance to 15mph. This is with the caveat that you're carrying a lot of extra weight in the rear triangle and putting extra stress on the pivot bolt every time you fold it under. This will probably lead to a failure of the bolt before its time. This is also going to be no lightweight portable bike to carry.

To be honest though, if you are going to over volt the motor and zip along at 30mph, I think you would be crazy to rely on this fixing!

My advice is to just forget about making this a 16" wheeled fold-able moped

I hope you find the photos and my thoughts here helpful.

No criticism is intended just some friendly safety advice. I think I speak for all when I say that whilst we all want to help you with the project, none of us want to help contribute to you building a bike which would subsequently result in you having a nasty accident and injuring yourself.

Regards

Jerry

 

[cwah]

I really want to ride at 30 mph!! it's going to be too slow otherwise!

I'm going to beef up the forkend as much as possible. Your advice are really really helpful and will allow me to run safely at 30 mph!

It's not that fast, and much more secure when all cars are trying to go faster than me.


ps: Thanks a lot for all these pictures. That's really kind.

 

[cwah]

Just did all the pictures:
Shaft flat width of 10mm:

Shaft max width of 14mm:

That's quite a big shaft, but at least I know it's tought

 

[cwah]

I have 28 mm to play with:

When the derailler is fitted, I still have a bit of space:

 

[cwah]

And I can probably file the derailleur in order to fit the anti-rotation washer:

 

[jerrysimon]

I really want to ride at 30 mph!! it's going to be too slow otherwise!

I'm going to beef up the forkend as much as possible. Your advice are really really helpful and will allow me to run safely at 30 mph!

It's not that fast, and much more secure when all cars are trying to go faster than me.


ps: Thanks a lot for all these pictures. That's really kind.

You are very welcome in terms of the pictures. However you miss the point completely. It may be a language problem or just that I am an old cautious fart and you are young.

My intention is NOT to allow you to ride safely on your Brompton, assisted to 30 mph as I believe that is not possible both in terms of your or others safety.

My intention is to help to support you in this project to build a safe eBrompton. As such if you feel that riding at 30mph assisted is the only acceptable option, and I consider that not viable in terms of safety, then I must now decline to support you any further in this project.

Regards

Jerry

 

[johnc461165]

Wish we lived closer cwah, we could solve this problem so easily by making a custom bracket for the tensioner and torque washer, anyway best of luck with the project.

 

[cwah]

I'm sooo close to completion. I spent so much time on it. I really have to make this bike live! That's going to be the first brompton with rear motor on it!!

Jerry, sorry for the misunderstanding, I will certainly not reach 30 mph. I'm planning to have an usual speed around 20-23mph. But for some cases I'd like to reach higher speed (If I'm in highway or tunnel full of cars low speed is really dangerous)

So I'm looking for the maximum protection possible for a bike that'll probably still have a strong acceleration.

Anyway, with this actual motor (24V mini-hub) I can't reach 30 mph with my actual battery (74V). The RPM is so low that to reach 30 mph I would have to go over 100V.. With my actual batteries, I'd be around 20-23mph. So no worries


John, you're really one of the most helpful in the forum. Especially for this e-brompton project. Can't ask for your help everytime, I'll try to sort this chain tensioner using my own skill.


It's soon live guys, so looking forward for the bike completion

 

[cwah]

Guys, the nightly update about my brompton build:

I installed the rear rack with easy wheel... now my brompton rolls once folded!!!! Yeeeeey

However, installation of the rear rack was quite tought, dimension were different and I had to force a bit... and a result it narrowed the dropout width. Now I can only fit 1 washer rather than the 2 initially.

I decided to only put the torque washer on the area with the chain tensionner. The side of the inner dropout don't have washer because of the lack of space. I hope it's not going to be a problem.

 

[cwah]

More info about the build. It's my crazy night build topic

I'm now adding all the torque arms to my bike. I've 2 anti-rotation washer and:
- Conhistmotor torque arm (thinner) on the gear side:

- Cyclezee torque arm (stronger) on the other side:

This configuration should be enough to handle some torque

 

[cwah]

I'm lucky, I received the new Marathon "greenguard" tyre and they are thinner than the standard tyre. The tyre isn't rubbing anymore with the rear fork:

Just sometime I hear a minor sound but that should be ok


I'm trying to put the chain tensionner on top of the torque arm:

 

[cwah]

The chain tensioner is not yet aligned with the chain:

I'll have to keep filing the chain tensioner inside to allow it to go closer to the bike.. Will keep doing that tomorrow.

Now my biggest problem is that I've put too much strenght when I tried to tighten the motor shaft bolt. Now it's getting loose and I may need to change the shaft... but for that I'd probably need to purchase a new motor

 

[cwah]

Night build update:

I filed the tensioner like crazy in order to make it fit with the torque arm


Result:

It's almost there, just a minor misalignement... leave it like this for now because there is not much plastic remaining to file on the chain tensioner

 

[cwah]

Now I've put my 4 lipo in a carton box:

When it's closed, just the cable is reachable:

 

[cwah]

For a total weight of 4.5kg:

I'll for now put that on my brompton front bag