Brompton forks spreading for hub motor.

[opeRaptor]

Good day to all.

I have been working on installing a hub motor to my Brompton.

I have a 83mm hub motor from the company Ciclotek with the following specifications:

This is the link to the product: https://www.ciclotekstore.eu/b2c/producto/2201200/2/platinium-motor

From my research it looks very similar to the "Tongxin" or "nano" motors, correct me if I am wrong.
I have found this video that shows installation:

What I am most worried about is widening the forks of my beloved Brompton...

I have found a few threads talking about the process:
http://www.pedelecs.co.uk/forum/threads/freedom-ebikes-brompton-kit-installation.11547/
and of course the excellent thread by JerrySimon:
http://www.pedelecs.co.uk/forum/threads/wheel-building-tongxin-in-brompton-wheel.5090/page-2#post-65911

I am worried about the amount I have to spread, will the legs be strong enough to be widen by this amount?
Furthermore will it be possible to spread the legs evenly, from my experience it is difficult to bed metal, even worst tubing, and when one starts going, the now weak leg will keep bending creating a weak, bent out leg.

TLDR; can I really safely and evenly spread the forks apart without ruining the forks of my Brompton or myself with it?
Is the threaded rod technique the way to go?

 

[jerrysimon]

Spread mine over 9 years ago now still going strong after over 10k miles of use.. As per my thread likely you will have to spread them more than 83mm as they spring back.

Make up a threaded rod like many have done before. You may also have to open the dropouts a little for the motor shaft. I also adjusted (drilled out the holes for lock washer) so I could use the supplied wahsers with tabs.

Unlikely that they will spread evenly and you may have to use washers to space the motor so it does not foul the fork sides.

Brompton certainly don't recommend it and you will of course invalidate any warranty. You could always get another pair of forks if it all goes horribly wrong.

Many have done it without any problems. I have even spread a set of £250 Ti forks though they failed when I had a crash.

Also note the Tongxin motors are only 2kg in weight and rated at 180W over your 2.7kg and 250W motor.

 

[opeRaptor]

Thank you very much for your reply.

Would you be able to give tips and tricks on how to do this *right*? What to look out for?

The video shows widening done almost carelessly which makes me uneasy just by watching...

From the video, it seems I will need the washers to clear lower down the fork.

Have you noticed a difference in stance after the widening? Does the bike stand funny, fold funny? is stretching the soft metal from 75mm to 100odd mm as bad as it sound?

Overall would you recommend it?

Thank you very much for your help!

 

[jerrysimon]

The bike stands fine though in its folded state it will sit wonky on the ground as the forks are wider. It does still fold ok but you may need to play around with the cable that exits the hub (cable tie the wire to the forks) as it can effect the clip mech.

Yes widening the forks does seem a little blunt/industrial. I have done it several times now on others Brompton's as well. It does require a little brute force but you are only widening it by about 10mm (wider but it springs back) and these forks are steel and constructed well. Like you I was a little concerned when I widened mine but in the end just got on and did it. As I said you can always buy a new pair of forks if it all goes wrong.

Would I recommend it ?

Well as I said mine has been fine for 9 years and with 10K miles done on it, but at the end of the day its your bike and the choice is yours