Hi folks, got a cargo trike with coaster brakes and hub gears - mechanical disc brakes on the front wheels

It has a Pendix edrive motor kit. But it's not very powerful, from the internet 50nm torque. And the battery is tiny, about 7ah, and about 7years old so the range is pathetic.

 

From looking, about the only motor I've seen suitable for coaster brakes is the Tonsheng tsdz2 ? Apparently 80nm torque? Is there anything better?

 

Ideally I would run it off a 48v 20ah battery as I use them on other bikes.

 

I don't want to go fast, the trike isn't suitable for speed - but want to be able to climb hills!

Edited January 17Jan 17 by scbk

Pics of the dream machine, I'm hoping a tsdz2 will fit in front of the tube, in the "step through" part of the frame

If the bottom bracket is a standard size then it stands a chance. Check weatherproofing of cable entries and so on given the unintended mounting angle.

 

Assuming UK, check that the 250W versions include 48V option. Running a 36V version on 48V might affect its happy pedal speed range, forcing you to pedal faster than you want to.

Yes, I don't think it's a good idea to run a mid motor that's designed for a 36v battery with a 48v battery. There is a 48v tsdz2 I think, and also a very powerful tsdz8 (Woosh sell one that has been rated and marked as 250w)

Yes I've got a tsdz8 on another cargo bike, they're good motors, never seen a coaster brake version.

 

On the tsdz2 coaster brake, PSW power do the 36v for only £199.

But to get the 48v version, best price I've found is about £330 (elsewhere) which is a fair jump!

I'd stick with the Pendix. Hub gears don't last well with high torque and 50Nm is as good as most geared hub motors up to 500W. It could be a tired battery holding the bike back and current Pendix motors run at 48V so you might be in luck.

 

If you do go for a mid-drive some 3 speed hubs are tougher than the rest and there may be some IGHs designed for ebikes out now.

If it were my bike, I'd investigate whether the motor can work with an an independent controller. If it can, you could use any battery you want and whatever current you want.

 

It would be worth finding out what output voltage and connections the torque sensor has for compatibility, otherwise, it looks like it's possible to fit a cadence sensor on the right side, so you could use a KT controller, which would be a good solution. The speed sensor looks like a standard 5v pulsing one, but worth checking.

Bit of a faff? The Pendix controller's current is probably matched to the hub's torque limit so as not to trade off longevity. "Pathetic" range says the battery's had it so voltage sag will restrict the torque.

I'd stick with the Pendix. Hub gears don't last well with high torque and 50Nm is as good as most geared hub motors up to 500W. It could be a tired battery holding the bike back and current Pendix motors run at 48V so you might be in luck.

 

If you do go for a mid-drive some 3 speed hubs are tougher than the rest and there may be some IGHs designed for ebikes out now.

 

I had some experience of pedalling a Sturmey Archer srf 3 for over 4000 miles a little while back - well probably 15 years ago. I have one on a 16 inch Brompton copy, called a 'Merc', made in Taiwan. I stopped using it when I bought a proper Brompton. It is buried in the back of a garage, but it still works fine although the frame broke at the seat tube clamp from hammering by the swinging arm back end, and I had to drill through the frame and seat tube, and put a bolt through to allow the bike to continue to function without the seat tube clamp. It was the only way to secure the seat post after the clamp part snapped off.

 

I stripped that hub a couple of times to inspect, clean, and lubricate it while the bike was in use and it looked a very sturdy bit of kit. There isn't a lot to go wrong in there. I suppose the pawls might break, but the odd burst of 500 watts from a 250 watt Bafang crank motor would not be that much more than what a strong, young, athletic cyclist might put out, and stuff like that has a solid margin of safety in its design. They are also as cheap as chips so I wouldn't scruple at trying one with a 250 watt crank motor. You would need to be careful about gear changes I think, they won't change under power anyway, but I wouldn't want to try it powered by a Bafang.

 

Maybe there is an archive somewhere of terrible failures on these hubs. I'm just not aware of it.

 

There was a member here who was using one like that a year or two back. I think it was working for him OK. Can't remember his name.

Maybe there is an archive somewhere of terrible failures on these hubs. I'm just not aware of it.

 

There was a member here who was using one like that a year or two back. I think it was working for him OK. Can't remember his name.

 

That was [mention=39361]Brik[/mention].

 

https://www.pedelecs.co.uk/forum/threads/giant-hybrid-with-bafang-middrive.47407/

Ah - Briks was his name. Here is a post of his:

 

https://www.pedelecs.co.uk/forum/threads/bbs-motor-with-gates-belt.46915/#post-725901

 

Edit :

 

We doubled there Guerney . Yes - you found him before me. He says he had done 1100 miles and six months with no issues. I think he also bought a new e-bike so that expriment may never have been taken further.

 

And it wasn't a 250 watt bafang either, it was the BBS02, so likely about 500 watts (I'm guessing the wattage).

Edited January 18Jan 18 by Tony1951

Bit of a faff? The Pendix controller's current is probably matched to the hub's torque limit so as not to trade off longevity. "Pathetic" range says the battery's had it so voltage sag will restrict the torque.

People used to say that about the average 250w hub-motors until we found that 1200w was no problem. I'd be very surprised if it can't handle at least 50% more current, which would satisfy OP.

 

What's easier and cheaper - install a cadence sensor, KT controller and standard battery, or rip the motor out, and replace it with a complete crank-drive motor and battery?

 

If nobody experiments, we never find out how stuff works.