Brompton build with torque in mind

[cwah]

Hello there,

Here is another electric brompton build, as it seems that everyone on this forum is trying to do that too.

My actual brompton is super nice but I need a spare bike because I know I'll one day have problem with the bike and I don't want to wait weeks before I get my bike fixed.

So I'm planning for another Brompton build with much better requirement:
- I don't need high speed. 30 mph is too much and too dangerous.
- What I need in the city is high torque
- That would also make it much efficient


I purchased an 8T Mac motor for good torque and much better acceleration


Here is the picture of the mac close to the rear frame:

It seems that it's not going to go in without spreading quite a lot the rear frame.


Next step:
- Get my motor laced to a 16" rim
- Find the previous metal worker shop that told me that my previous request was impossible, and show them my actual brompton.
- Then ask them to cut the crossbar, spread the dropouts, weld back the dropouts.
- And keep working to reinforce the forkend with additional welding and the area in which torque will be distributed on the rear frame


Seems to be quite a challenge!!



ps: John I'm extremely thankful for your help and without you I wouldn't be able to plan for a second Brompton. I will however not ask you again for that as I can't accept free service and it would be great if I can solve it myself

 

[johnc461165]

Hi cwah, all I can say is same free service from me is always available. It was no problem to do your other Brompton so if you need me I am here. John

PS. cwah I only do it for free

 

[cwah]

Hello John, thanks again for this proposition.

I'll try to sort it in a welding shop, it should be fine when they'll see the great work you've done. You made the impossible possible

 

[johnc461165]

Thanks for that cwah, but I am happy to help if you need me. John

 

[daniel.weck]

Hi, good luck with your build!
Although I tend to use my Tongxin wheel more often on my e-Brompton, I also have a spare wheel equipped with the 8-Fun (modern Bafang) motor, which produces tons of useful torque (i.e. without uncontrollable wheel spin) and relatively decent speed too (for a 16" rim, that is).
I wouldn't be brave enough to modify the rear forks though, so good luck with that! (someone on this forum recently succeeded though, do a search to find the discussion thread)
Cheers, Dan

 

[cwah]

Hello guys,

I didn't post since a while, but my new Brompton project evolved thanks to John, again. Can't thanks him enough

Thanks also to Catsnapper that provide super good wheel lacing service for very good price. I recommend him to anyone that wants to lace his wheel

Here is the wheel with the mac motor plugged:

Thanks to John, it's very professional and the bike can still fold

 

[cwah]

I've put a bit of painting on the rear cross for the rust, and also filed it a bit because it was rubbing against the bar:

Now, the main part is to handle the torque. This is an 8T mac on a 16" wheel. So the speed wouldn't be very fast, but it has enough torque to do wheelie and kill the dropout.

I have to be very careful on the torque arm to be sure I can ride safely, and that my dropout won't break during acceleration.


Option 1:
Use Dr. Bass ultra thick torque arm on the dropouts:

This torque arm is really strong. I tried to hacksaw it and it killed my blade. The dropout won't bend for sure.

However, I'm worried about the rear fork that may not be able to handle the torque.

 

[cwah]

Option 2:
I'll use a small washer to support the dropout (I'll need to file the hole in order to fit it):

And use a longer torque arm to spread the pressure along the bike:

I'm thinking about going toward the second option and use longer torque arm, that seems safer. But not completely sure yet. Using super thick torque arm seems to be a good option too.

A good night of sleep may help me decide

 

[cwah]

I finally decided to go through longer torque arm to spread the load/torque on the rear fork, rather than beefing the dropout.


Here's the left torque arm:

I've put the leg of this torque arm far away in order to have a maximum leverage.

And here's the right torque arm:

This one was more difficult due to the derailleur, I'm hesitating to fix the arm to another location (rather than the screw) in order to have better support.


What do you think guys? Power and safety in mind? This setup is not about speed, but about power

 

[johnc461165]

Good to see you progressing with No2 Brompton look forward to more updates. John

 

[cwah]

Thanks John! I'm making progress, and I am so excited to test my bike that I went outside at midnight to try it lol

There are still wires everywhere, I still need to clean all of this, but it's already a bike I can ride


This mac 8T motor is quite noisy actually, but seems much more efficient than the direct drive. Will do further test and see how it goes


I love torque finally, much more than speed.

 

[cwah]

Yesterday I had too much beer and did some reverse polarity with my battery harness...

My battery wires have melted!

And half of my mofset have blown.


I probably have to buy a new controller now...


Not having fuses was a big BIG mistake

 

[banbury frank]

Hi Cwah


Send me a Mail with your address and I will send you 20 X recovered Mosfets change them all


I will post free

frank@xipi.co.uk


Frank

 

[cwah]

Thanks Frank, I sent you a message. You have spare Mosfets you do not want?

 

[cwah]

Finally received the new controller from Cellman, I hope this one isn't going to die..


Little update on my brompton with the good, the bad, and the ugly:

Here's the ugly first:

I applied some waterproof gel from amazon to seal my bag:
GELERT TENT/GEAR SEAM SEALER/WATERPROOFING/WATERPROOF: Amazon.co.uk: Sports & Outdoors

This geal made my bag completely white, it isn't waterproof and I can't even remove that!!! So a big mistake. I should have tested it first on another bag before spoiling my nice little brompton bag...


You can see the bag here, and good thing, I have a main kill switch:

Can you see the hidden switch?

 

[cwah]

The wires inside the bag are still a furious mess, I'm not sure how I'm going to sort that out, but I think first I need a new bag/case for my battery and controller:

And here's the best! I've managed to have my flasher working and added a 3 mode switch on my handlebar:

Check the flasher working
[video=youtube;58tOY14lNy8]http://www.youtube.com/watch?v=58tOY14lNy8&feature=youtu.be[/video]


I still think that the 3 mode switch is a bit bulky, and using 2 metal hose to hold it is an overkill. Still thinking about a better solution but that's working fine for now