Advice required on a brompton conversion

[Deleted member 4366]

201 rpm will be too slow for a Brompton. It'll do about 9 mph on the road. To get torque for hill-climbing, it'll be down to 4.5mph or less.

 

[jerrysimon]

Yes good point Dave.

My Brompton Tongxins are all 260RPM. These give me 15mph on the flat and aboyt 13-14mph up hills.

Jerry

 

[schiller]

Thank you all for the advice, Jerry i have red everything you've wrote about your conversions, very helpfull and inspiring.
I haven't seen a 28h version of the q85, only 36 seems to be available. Thinking to go with it as per d8veh's suggestion regarding reliability, which makes sense, gears are less prone to failure than rollers.
Yes it is slow, if the simulator of ebikes.ca is trustworthy, at 6-7% inclines about 12kph - 7mph- . With an additional 100w pedaling about 15kph.
Compared to the current situation (walking aside the bike) it is supersonic for me. But maybe you are right: After a while i may find it slow too. I' think about it, thanks for pointing out.

Jerry if am not mistaken, you use an extension block for the hook, which is not available now. Without it, i have seen that the cable protection scratches the rear stay and it seems that force must be applied to get the hook in place.

I fold it regularly, this is a potential problem. I could do the slight modification of the fork, not a big deal, but i would like to retain the fold as close to the original as possible.
This is the reason that i have not definitely ditched the DD option:
Bike folds normally. Of course handling will be at least questionable and it is really a pity to add twice the weight of the tongxin in the front wheel and have about the same power.
It more reliable too, but with the small wheels and current limiting, the q85 should live quite long..

Greetings
Konstantinos