Generally the cranks attached to the motor on ebikes are on a freewheel the cranks operate independently of the chainring that drives the chain. This is because when you stop pedalling the motor do not stop immediately (i.e. it can over-run). Whereas the cranks and chainring that are not at the motor b/b are usually linked to the chainring driven by the motor by the timing chain and can not run independently of it. If both pilot and stoker start with the cranks synchronised then they will stay in synch until the person and the motor end stops pedalling then they will go out of synch. If the motor is at the rear bottom bracket it is relatively easy for the stocker to re-synch while riding as they can see the rotation of the pilot's cranks and start pedalling again at the correct point of rotation. Not so easy with the motor at the front as the pilot can't see the stokers pedals without looking behind. Ultimately we have found that it doesn't really seem to make much difference but does take a bit of getting used to the feel of the bike if you are used to being in synch.

The is no reason why either pilot or stoker cannot have shorter (or longer) cranks. Obviously the normal build (and price) will be with cranks the same length but they can be changed. Whether there is a charge for this will be up to the supplier.

Hope that helps...

 

Can I just say that as the stoker of our tandem, I absolutely love the fact that I can carry on pedalling when my hubby decides he'd like to coast a while. 

Having ridden a Dawes Galaxy Twin for 30 years we upgraded to our Orbit Velocity last year and are over the moon with it. 

Sorry there's no technical information in this reply, I'm not in the least mechanically minded, I just love to tandem ride 😁

The Orbit has the motor - and hence a crank freewheel - at the front bottom bracket so whilst the timing chainrings are in sync, the captains cranks are not. For some this is no problem at all but for others, like us, this was absolutely horrible and ruled out the Orbit as an option. We found that it completely removed the wordless communication between us which we so much enjoy and has become second nature over the decades. 

We decided on a Moustache after a couple of extended, tough, test rides and haven't regretted that decision at all. The motor is in the rear bottom bracket and the cranks are in sync, making out-of-the-saddle climbing a doddle as well as fostering that wordless communication - we always know what each other is doing or intends to do. The Moustache, despite being more MTB focussed, makes a fantastic road/trail tandem and rides really well.

It's all down to personal preference of course, and I can't recommend a visit to JD Tandems highly enough. The chance to try different tandems and motor systems back-to-back is invaluable and really brings each systems characteristics to the fore. 

Hello, we tried both synchronised and non synchronised cranks and found the Gepida non synchronised version significantly better than the Moustache (fixed) . Every task is significantly easier on the Gepida from starting off to coming to a halt. Getting my foot in the starting position is easy , just back pedal, without resistance until I get the perfect spot every time. When it's time to slow down I ease off pedaling and there is no pressure from the stocker, just the freewheel noise letting them know to slow down, all much smoother than is possible with a fixed crank setup.  By having the pedals in offset positions actually smooths out the power flow without the dead spots at the top and bottom of rotation.  We had a fixed crank on our old Tandem and were sceptical of the freewheel crank but found it a revelation!

Good job we're all different otherwise what fun would that be!

Sylvia and I are so attuned I never need to say when to ease off, or when to put some power down, and she always places the cranks in the correct position for starting. The only time I need to say anything is when we get out of the saddle on a climb and then it's just "3, 2, 1" and we both stand on the downward stroke of the right pedal.

It's noticeable - to us both - if the timing chain gets a little slack and we start to lose that 'silent communication' between us, so I keep on top of little jobs like that.

Before we started tandem riding it was the cause of some amusement in the club that Sylvia and I always seemed to be riding our solos at exactly the same cadence and always changed gear at exactly the same time. I'm 6'3" and she's 5'2" so the effect was somewhat heightened!

My regular Stoker has had brain surgery, and 90% of the time we don't need to speak, on a few occasions I have to say to keep pedalling up to a junction or traffic lights so that I can change down gears ready to pull away. Luckily we are both spinners and 85rpm+ our preferred cadence. I have recently started piloting for a blind girl and sometimes forget to tell her to stop pedalling through tight corners, it makes for interesting rides. 

Thanks for all the comments.  I obviously hadn't realised about the motor freewheel. My stoker has severe hearing loss so we also have silent communication most of the time therefore I think a rear mounted motor would be the best option.  However that probably restricts the type of rear crank that she could use (probably being limited to the manufacturers supplied fitting, she's 5'1" and rides on 160 cranks normally) and gearing choices. The crank limitation rules out Pendix.

I see Orbit do a rear mounted Bafang option with crossover drive and 1x11 gearing - is this possible as a retrofit option I wonder?

Perhaps we could pay a return visit to JD on the way up to Alnwick.

 

R&R

You can shorten the cranks on the Moustache to 155mm. Highpath Engineering have a very good reputation for this sort of thing. 

They do, but only as a minimum of 20mm shorter.

For Bafang motors, Lekkie make some nice replacement cranks and chainrings which help to sort out chairing and crank offsets somewhat.

That chap on the Moustache Facebook link I referred to above had them shortened from 170mm to 155mm, so there must be enough meat in the cranks to allow that. 

Can't access Facebook, asking my daughter if she can help.  I got the 20mm minimum from the Highpath page which I assumed was to do with not being able to drill too close to the existing hole. I remember hearing about Lekkie from Chris Juden