Shimano Nexus alternatives..

[Karl Rowlands]

This is an odd one. I have my yamaha XPC26 with the crank drive, and Shimano Nexus inter4 gears and roller brake.

However, 2 weeks ago, it died. Contacting Yamaha got me a service manual, following troubleshooting in that got me to "Replace controller".

Now, parts for this bike are NLA..so, I knew I had a good battery, and a good motor..I bought a twist-throttle motor controller and throttle, and fitted that to the bike instead.

Yesterday, it worked brilliantly...BUT, for some reason the gears damaged themselves..the selector arm spun round on the hub twice, bending itself and snapping the cable (!).

I can only assume the hub failed, or was too weak to cope with the torque..possibly.

Does anyone have any alternative suggestions? Can I convert a nexus to single speed freewheel, or will I need to replace the whole wheel, in which case I lose the roller brake..if that happens, what are my alternatives? The frame doesn't have provision for frame mounted brakes...

At a bit of a loss...can anyone help? Thanks all.

 

[shemozzle999]

After a quick google I found this, you will need to contact the seller for delivery charges and expect to pay import duty:

http://www.ebay.com/itm/Shimano-Nexus-Rear-HUB-Coaster-Brake-Hub-36H-INTERNAL-4-SPEED-NOS-Bike-SG-4C30-/252206006861?hash=item3ab8a6424d:g:~OsAAOSwCQNWcVtF

 

[flecc]

SRAM have a three speed hub gear with coaster brake, and altnough one less gear it covers exactly the same 200% gear range as your old 4 speed. It's on this link. Because coaster brakes are very unpopular in the UK, you may have to source one from Germany or the Netherlands.

Your Shimano inter 4 hub gear was discontinued by Shimano in 2005 following many failures, so any existing new ones are very old stock. However, if you buy one from Shemozzle's link, you can just remove the whole insert from your hub shell and insert the whole core from the new one, avoiding building another wheel. I've done this myself on a few occasions and at one time inserts were offered as spares for this purpose. If you don't feel up to doing that, an experienced bike mechanic can swap in the new insert for you.

The photo below shows a hub shell with gear insert removed, indicating how you can remove your old one, wash out the shell and fit the new insert:

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[Karl Rowlands]

wonderful! Thankyou all. Took the old wheel off - I think I can see what happened..the one side of the axle was loose in the frame..and there were no anti-rotation washers in that setup anywhere..so, the sheer motor torque looks to have spun the entire wheel.

Net result is one loosened nut (probably the one that would undo in the direction of wheel rotation), and the rotation of the entire assembly then has torqued up the whole axle so badly that even with the rear cog removed and the roller brake off, the wheel is locked solid, and I can't loosen the bearings or axle up even with spanners!

So, I'm guessing it started that, which self-inititated the terminal tightening of the axle bearings, until they bound so hard that it spun the whole wheel/selector arm round twice..which would explain why the cable was looped round the axle until it snapped.

SO, I'm taking the wheel into work tomorrow, it'll be clamped in a vice and then i'll attempt to loosen it up..then if I can, I'll have the cartridge out, and look over the bearings. If I'm really, really lucky I may be able to re-bearing the wheel and the gears may have survived.

If not, there's one on the way to me anyway in a wheel already..which I will drop into the frame and hopefully, with a new cable and selector the old girl might just roll again.

If that doesn't work..I'd be tempted to go for a new e-bike..it hurts, but the Yamaha is hellishly heavy and very big..not portable at all. I love the quirkiness of it, but it's a very custom machine..no proper bottom bracket etc.

Next time, for the limited cycling I do, the need for portability, and the ability to take 3 bikes in the car (mine and the kids), I could be tempted by an electric assist folder...I already have 2 1970 folder restos in the garage..finding a 20inch e-wheel is seemingly near impossible and certainly financially daft..I can get a bike for not much more than a wheel!