Conversion of an old gents bike

[Situpandbeg]

I have two old but very comfortable and well-built upright 26" gents bikes (rod brakes, horizontal cross-bar, "sit up and beg style") which I think would be ideal for rehabilitation with a bit of electrical power assistence for my short (8 miles return) but hilly local trips to the nearest shops etc. Looking at the available kits I think a front wheel motor is my only option since the rear wheels have hub (or no) gears and all the kits seem to be built for deraileur gears. But I am running up against the problem of the front dropout width being too narrow (85-90 mm) for the hub motors that I have found. I am not worried about how the end product looks, in fact to deter theft I wouldn't mind it looking somewhat old and cranky, like the owner. I would just love to upgrade and recycle (sic) these sturdy and comfortable old machines at a relatively low cost. I'm now considering swapping out the front forks with those from a s/h modern bike, except I don't know if they will fit. Has anyone managed to convert such a bike or got any suggestions?

 

[flecc]

There are forks still available for the old style of stem mounting and headstock bearing adjustment, but there are also some motors suitable for 80 mm width. Tongxin is one, and the Electric Wheel Company amongst others handle these kits. Stress 80 mm if you speak to them, since most of their kits are for 100 mm. Some of the Chinese Direct Drive units are also narrow enough, and others may be able to advise of examples.

I do have some concerns over braking efficiency with e-bike higher average speeds. Your rod brakes acting on steel V section rims are not very efficient and can be very poor in wet conditions, so you'd need to exercise caution once you get familiar with the overall higher performance and use it fully.

 

[JuicyBike]

If your forks will stand a little widening then 15mm isn't a great deal of extra distance. Certainly the cost of kits that require 100mm are hundreds of pounds (often) less than the few available that are 80mm.

I think Flecc makes an extremely valid point regarding brakes and perhaps new forks would help the move away from those lovely, beautiful, memory-inducing, rod brakes (which would need electrical switches adding somehow...).

 

[Deleted member 4366]

I'm sure it'll be easy enough to open up those forks to 100mm, as they'll certainly be steel. Just give them a big heave. If you want to keep your rod brakes, it should be very easy to use reed switches on them to work the brake cut-out on the controller.

 

[catsnapper]

I'm about to order some 83mm front hubs for 20" + 26" wheels, and classic steel rims for old Raleigh's etc are still available, so it's quite feasible to build a wheel with the correct hub if that helps solve the problem The other parts to make a kit are readily available from plenty of suppliers.

I would be a little bit worried about rod brakes, steel rims and hills, especially in the rain....

A rear hub might be feasible despite the older type of narrow dropout on the frame. If you look at a typical small/medium Bafang rear hub, the flanges are closer together than most normal bike hubs. Add the high degree of dishing needed to centre the rim for a 135mm dropout with a 6 or 7spd freewheel, then you have a less than ideal wheel.
Assuming most Chinese hubs were originally for the domestic market with its massive numbers of trad style single speed bikes, they would probably have a single speed freewheel and fitted in a 120-126mm dropout - the hub would now be nicely centred with almost no dishing.
By extending the drive side axle the manufacturers created a simple but flawed fix to use multiple gears.

We've modded a Bafang BPM rear hub axle back to 126mm for a 60's classic frame with encouraging results.

Alan

 

[johnc461165]

It is quite easy to open up the forks using threaded bar. Brake performance in my opinion is related to how fast you go, if you ride at normal speeds then the extra weight should not be a problem, all I can say is good luck do what you want to do and enjoy your cycling.

 

[Situpandbeg]

Thanks to you all for this most useful info and advice. I think I will start by looking around for a good value new kit or break up a second-hand bike, preferably 80mm width motor, and ask my local shop to build it into a new rim for the front wheel (it needs one anyway) so that I can keep the rear hub gears. I can think about other scenarios (eg new forks/brakes/rear wheel) if road tests prove to be too exciting (or tiring)after that.

 

[Situpandbeg]

I'm about to order some 83mm front hubs for 20" + 26" wheels

. Can you tell me where I can get a 26" one, how much are they and do they supply the rest of the kit? Thanks.