AWD handcycle.

I've just spent a day exploring with a friend on her off-road handcycle (proadaptive XCR). This is a front wheel drive delta trike using a BBS02.
The chassis (and rider) are extremely capable but a few issues really limit her ability to tackle harder terrain solo. The first is that they supply the BBS02 with a standard chainring running to an 8spd IGH and the gearing is simply too high, she's rarely out of 2nd and usually in 1st running very inefficiently. This is fortunately easily solved.

The other issue is traction. A front tire upgrade will likely help but it's hard to beat physics. So I'm thinking some sort of AWD system specifically designed as a slow speed boost for short hills (<1 minute). The ability to reverse or even run each wheel would be great but not essential since she can wheel it backward from the seat.

My first though is hub motors but that does complicate transportation (it's huge with the wheels on) plus not the best for starting on a hill. I wouldn't be opposed to them if the weight and other issues could be solved. There is at least one XCR running rear hubs.
An independent rear mid-drive would be great except the frame is not conducive (continuous axle tube) and she's definitely not willing to break out a grinder.

My last thought is dual friction drives using E-skate components. Benefit could be modularity, wireless control and a bolt on solution that still allows the wheels to be removed.

Any thoughts greatly appreciated. I've run searches but haven't seen this specific trike being discussed and most focused on a primary drive sized to run continuously.

https://proadaptivesports.com/wp-content/uploads/2017/09/1-1.jpg

Friction drive would work but its still friction, wearing out the tire.
Take a look at https://alienpowersystem.com/product-category/brushless-motors/ for powerful motors.
You could ease up on the friction, still use the RC motor idea, but use a gear on the rear wheels.
Gearing would be easy to configure.
You dont want more power, because if you did then I would suggest the BBSHD or the Cyclone 3kw, but its still up front.
I like the idea of using small rc motors to run the rear.

edit: Looking at the bicycle more closely, you maybe able to get away with putting the rear gear on the inside of the wheel, placing the motors behind the seat. A way cleaner look overall. There is the matter of having 2 motors running each rear wheel, at the same speed.

The disc brake rotor will get in the way of a traditional gear installation. Might have to go by way of a V-belt system, placing a ring on the spokes and finding a way to have the belt attach to the motor axle. That would be your hill climbing motor, small drive gear to a large driven gear/small crank to large cassette/fw. Defeats the purpose of the mid drive being the hill climbing beast right.

Moving back to friction drive, be a way cleaner look, but its friction drive.... good for cruising along. I dont think friction drive has really been implemented solidly, wearing out tires, mud, rain etc.

Friction has been done on mountain bikes without too much tire wear:
https://endless-sphere.com/forums/viewtopic.php?f=28&t=96581
Thus is simpler since it would be rarely used and there is no suspension.


The hubs definitely don't have the room for any gearing unfortunately. The intent is for a person in a wheelchair to easily install or remove the rear wheels for transport.

A very small geared up might work with quick release wiring but I don't know how to implement them with a through axle. Any ideas?

Since it would be for intermittent use, a small geared hubmotor, running a lot of volts with low speed windings (if that actually helps) should be able to do the job with small size and modest weight. The only real issue would be torque from a dead stop on a hill, and it would have help with that anyway.

I hooked my son who is a Quad and can't transfer easily into a Delta type like the XCR with a Da Vinci Mobility attachment for his Ti Lite chair that normally is assisted by electric hub wheels.



I was able to try out the concept at Interbike the year before we ordered it and talk with the founder about my son's needs, as all disabilities are not created equal there is a lot to work out. The one I tested had a hub motor and a cadence sensing PAS and it felt great and so we decided to go for the system.

However Da Vinci seems to be always in a state of experimentation with their system and they made the decision to go with a BBS01 and an 8 spd IGH so very similar to the OP's setup. Which leads me to the same complaint we have with his system being front wheel traction. It goes ok on level ground but will start to spin out on steeper grades. He can't do anything about transferring his weight forward due to his condition and the fact that the controls are already very close to his chest.

While I wish is that they had stuck with the hub motor the need for different gear ratio's that are more easily attained by the IGH for his condition was the reasoning to go with the BBS01. I feel that the additional weight of a hub motor would do a lot for traction but still not be the end all by any means. What I want to try is the TDCM motor available from Grin https://www.ebikes.ca/shop/electric-bicycle-kits/direct-drive/tdcm-igh-kit-advanced-pas.html as it has a 5 spd IGH and should give him enough gearing for his needs which granted are restricted primarily to harder surface use.

Cool



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Grantmac said:

Any thoughts greatly appreciated. I've run searches but haven't seen this specific trike being discussed and most focused on a primary drive sized to run continuously.

Click to expand...

My idea would be to use an electric handcycle that is normally used at the front of a normal wheelchair and hang it in the middle of the frame/rear axle tube at the back of her XCR. With a thumb throttle she can then use the assist she needs. When she is going downhill the geared hubmotor will just freewheel. As it would be easily detachable she can mount the extra rear assist only when riding terrain that needs it. So this is my bad attempt in Paint to show you what I mean:

View attachment 2

It would require a detachable electric front handcycle (with a knobbly tire) like this:


View attachment 1


And mount it like this:





Try to get the contact of the assist on the ground as far forward as possible so it won't hinder steering. A dedicated handcycle like her XCR doesn't have a very tight turning circle so I don't see a problem with only hinging the assist without the possibility of it steering left to right.

Post a link to exactly what you have now. We can search, and find something different, and then give bad advice.

https://proadaptivesports.com/xcr-cross-country-handcycle/


Keeping it light is extremely important, if she can't flip it back over solo then she's quite limited in possible uses. So adding an extra wheel likely isn't going to fly. Reducing ground clearance also won't work since it's already "gliding" over obstacles (I'm thinking some Teflon rails to save the frame).
Likewise heavy hubs which are a challenge to mount and dismount aren't going to work.

This has to be a weight optimized system with only burst capability and <10mph as a top assisted speed. A single button for a throttle is likely the only control needed.

THen the best bet is small friction drives on the tires, or the rims. Would only require adding a stiff mounting bracket to the frame near the back of the seat/ front edge of tires, so the friction drive has sufficient support to strongly press on the tire. The drive itself could be removable either at the bracket end or the entire bracket and drive could be removable.

You could probably use a pair of Kepler drives of any generation.

Currently thinking of using an Eskate VESC and motors running an independent battery. Unsure if they can do reverse or indepentent control if heach motor however, further research needed.

Probably use a continuous torque tube to connect both motors with "cranks" off each end to mount the motors. This should allow the user to engage or disengage them from the wheels from the seat. Possibly also capable of rotating the "cranks" 180 for reverse. Some sort of over center spring arrangement could lock them in either orientation.

Wet/muddy conditions are less of a concern compared to lose dusty dirt.

Thanks,
Grant

FWIW, the kepler drives automatically engage and disengage from motor spinup/down, AFAIK.

So you could try a mount that works like those, so the rider doesn't have to do the engaging/disengaging--just use the throttle (or button) to spin up the motors.

I'm thinking about having them disengage like the kepler, more for tire wear than anything else. The over center spring could be tuned to do that.
It might also make for better sensorless hill starts (when it's most likely to get used). Perhaps even run them both off one controller?

I'm thinking the throttle will just be a button and the power in reverse tuned quite low. I do think being able to run the wheels independently in reverse would make for a tighter U-turn.

Grantmac said:

Perhaps even run them both off one controller?

Click to expand...

Only safe to do that if they're brushed, or rotors are locked together.

Brushless motors require position sensing. If you use one controller for two of them, it can't read the position of more than one, so the currents it sends to the one it's not measuring won't be correct for it's actual position (unless the rotors are physically locked together). This won't correctly drive that motor, and it may be possible to damage the controller, or cause problems driving the first motor.

I do think being able to run the wheels independently in reverse would make for a tighter U-turn.

Click to expand...

You can link it to the steering if you like, so that when straight both get the same power, and the more the steering is turned, the more one motor gets power vs the other to help with the turn. If this needs to be different during reverse, you can link this with the reverse button.

It's possible to do with discrete electronics, which is how I'm probably going to eventually do it on the SB Cruiser trike, but it can also be done with an MCU (lke Arduino, etc).

Yeah I did a little digging and it'll be dual controllers. Possibly RC car.

I could see tying forward into the PAS when a switch is made. I don't think I want to try for some sort of electronic torque splitting unless it's required. Trying to keep things simple after all and I'm more of a mechanical person than electronic.