How to solve chain derailment on BBSHD and BBS02

[edllorca]

Retrorockit and Ncrkd Looking at a front mount indeed. Have to think through what the stoker will feel clipped in when the motor kicks hard. I do not have E-bike experience (except for 1 ride on a bbs01/250 that I built for my stokers single bike). Agreed that the bbs02/750 or even a pair of 01/350 is closer to doable than the bbshd. So much to consider. Ground clearnce has to be checked too before I venture in that direction. The genesis of this project when I bought the bike was to mount the mid drive 'vertical' on it's own BB clamped or welded in the middle so the motor is not hanging under.. Still can go that way with an 02/750.

As for where this bike will go the answer is, everywhere. Will build a second set of wheels with road rims/tires so one bike does it all with simple wheel changes.

[ncmired]

... mount the mid drive 'vertical' on it's own BB clamped or welded in the middle so the motor is not hanging under.. Still can go that way with an 02/750.

You mean, via a kid-back or child-stoker mount, maybe on the diagonal between the seat tubes? If so, you could probably use the bottle mount screws to help stabilize it. I'd then be concerned about clearing the chain through the shock/rear triangle gap - hard to visualize second-hand.

I considered using one of the stoker mounts to slow down the sky-high BBSHD cadence (2:1 chain rings) on one of my builds, but it just seemed like a mechanical mess especially if the motor broke down on the road.

[Retrorockit]

They're going to be mechanically connnected anyway AFAIK. The driver is steering and should have the throttle . Simplifies the wiring. No photo of the front BB so I can't say. But the BB can probably be adapted. The rear suspension looks like there's no good solution there. I don't think offset 40t will help because the diameter will keep it from moving the chainline in anyway.

Oh I see no one way clutch between the stoker and the motor. The opposite of ghost pedaling I suppose.

[Retrorockit]

I came across this which may offer a way forward. It looks like they used just the BB portion of a BBS including the pawl clutch. Without the gear case the chainrings can be smaller and sit in more. I could see this in the stoker position with 2 chainrings on it.
Another way if making your own parts is an option is to put a simple roller clutch in there. They look like and function as needle bearings but lock up in one direction. TSDZ2 uses one inside the drive pinion of the motor. With 2 riders and a BBSHD it would have to be a much higher torque capacity part than that one.
Actually the only torque through the roller clutch would be the 2nd riders out put. I have no experience with tandems so it takes me a while to get it straight in my head.

[Ken Reich]

Currently i an running a 44 tooth 9 mm negative offset on my BBSHD trek caliber 7- would like to tidy up the chainline in lowest gear, are there any 12-14 mm negative offset rings out there? In 44 tooth?

[73Eldo]

Lekkie has a 42 or 46 with 18.3 so you would have to use spacers which I would think 4mm is pushing the limits. The Lekkie 40 can be 20.8, 18.3, or 15.8 depending on how you use the included spacer, not sure if you could us another spacer with the included one or not. How much threads you have left ? If you have 4mm there maybe sticking a BB spacer in and going with the Lekkie 42/46 would be the way to go?