Eccentric bottom bracket housing

[Shannock]

Hi All,
Thinking about fitting a crank drive to my Thorn tandem. It would go into the front eccentric housing.
If anyone has done it has there been a problem with twisting the whole assembly under load.
I have a front wheel drive at the moment but a crank drive would be easier when splitting the frame.
Pete

 

[anotherkiwi]

All documentation for BB motors I have seen say "don't fit in eccentric BB"

 

[Shannock]

Thanks 'anotherkiwi'. I will have a word with Woosh nearer the time, I may use it in my tourer.

 

[RobF]

I wonder if you could dump the front eccentric bottom bracket on the Thorn.

Probably not, because when you adjust the rear eccentric BB to tension the secondary chain to the Rohloff hub, you probably need to adjust the front one to maintain the correct tension on the primary chain.

But the primary chain tension is presumably not as critical, provided it doesn't jump.

Or there might be another way of tensioning the primary chain, although nothing springs immediately to mind.

 

[RobF]

A chain tensioner on the rear drop out might do it.

That would tension the secondary chain - a lot of Rohloff bikes tension the chain that way, so there's no need for an eccentric BB.

In your case the secondary eccentric BB could be left in place and could be used to tension the primary chain, leaving you free to use an ordinary bottom bracket at the front.

 

[Shannock]

Yes it's a Rohloff hub, I suppose I could really screw in the two setscrews to pierce the eccentric whether the motor would still rip it out. I(we) only use the front hub to give some assist up hills or into hard headwinds and when touring pulling a 'bob' trailer which is no problem. I suppose the bb motor could still cause problems with this sort of loading. Any way thanks for your thoughts, it seems we will keep the Ezee on the tandem.

 

[Cyclezee]

Plan B.
Change to an eZee DT battery... if there is room for it.
e.g.

 

[RobF]

I didn't realise the OP's tandem was already electrified.

Pointless trying to engineer a crank kit when he's got a well-regarded hub kit fitted.

 

[Shannock]

Thanks John, that's an idea, I would have to move the controller forward as well so it looks like I will be in the market for a battery plus some connectors as the wiring will need to be shortened and I hope Monica will willingly give up the throttle.

 

[Cyclezee]

Thanks John, that's an idea, I would have to move the controller forward as well so it looks like I will be in the market for a battery plus some connectors as the wiring will need to be shortened and I hope Monica will willingly give up the throttle.

Actually it's not that simple, the The DT battery has the controller integrated with the battery mounting bracket and is only compatible with the Mk2 eZee kits. Also the phase wire and Hall sensor connectors are different from the Mk1.

 

[Cyclezee]

Plan C.
Keep the existing kit but move the controller to the front section of the tandem.
You would need a longer power lead from the battery to the controller but all the others coming from the controller could be shortened.

That would mean you only have one lead to disconnect when splitting the tandem.

 

[Shannock]

Thanks John