E-bike gurus please step in, building a wheelchairiot thing
 

OK, school me boys:)
I want to use two hub motors to power a conveyance that I can roll my in-laws chair into. I have plenty of creative juices going, but no experience with hub motors.
1) I don't want high speeds.
2) Do want high torque to get it started in soft stuff.
3) plan on controlling with differential steering, but may augment it with some sort of front steering.
What say you?

I recently saw a free power scooter on Craigslist. Would something like that work, or provide guts that would work?

I'm thinking regular steering would be smooth and positive control vs diff steering and casters.

http://www.1800wheelchair.com/media/...ca2e52fe3f.jpg

I need to use big wheels to keep it from getting stuck. If I could figure that out it could work.

Differential steering might help in tight corners, like those skidsteer tractors, but I still believe you'd be better off retaining conventional steering too.

Consider direct drive motors rather than geared, because when throttled-off the direct drive will acf as a brake, which is good for a wheel chair. Geared moted will clutch out when you throttle-off, and then you coast. For a wheelchair the free automatic braking seems safer. I liked my experience with ebikes.ca... here is their motors page: Motors - Ebike Parts - Shop

Good for research for you mostly... their smallest wheel is probably the 16" one.

To control speed and torque the motor controller is your key. Also go for a 36v or 24v system... lower speeds...

What kind of range does it need to have?

10 miles? I think he'd like to go down the beach with his grandkids.
I want to put as fat a tire on there as I can for flotation, and probably go with 4 wheels for stability.
The design in mind is a pair of channels that he rolls his conventional chair up onto, that then lift up for ground clearance. Transfers are the enemy.
Now I transfer him into a 4wd rig and then back into his chair and each time we risk an injury that might lay him up for months. Like 6 months.
This only happens once a year or so, but he lives out in farm country and he'd use it quite often if I made it.
I would prefer only differential steering but that is all on the controller we can cobble up, and how to calibrate it for fine control. An e-bike typically has so much speed to it that the controller is not good for the fine stuff. An electric wheelchair controller is, but at high speed it might get dicey :)

I would think you'd want more than 10 ahr in the battery, minimum. More if you can get it. But the system you want to build is kinda alien to me. I have only built this one ebike that I ride. I like Frank's idea of getting some of the guts out of one of those little elderly person scooters. Or maybe check specs and hardware for a few electric wheel chairs. I would think you could learn a lot by studying websites like this: Electric Wheelchair SuperStore - Power Wheelchairs, Pride, Jazzy, Golden

Batec Mobility - Add-on handbikes for wheelchair: manual and power handbikes easy to attach to the wheelchair. Revolutionary anchoring system - Batec Mobility - Handbikes acoplables para silla de ruedas: acoples para silla de ruedas, propulsores para
For once a year this would be overkill, but my buddy has one of these.... actually thats him on the lake pulling his kids. He uses a studded tire in the winter. May help with the creative juices!

sand is the hard part.

I was also thinking of a K.I.S.S. system, depending on how much traction is needed and if the steering effort vs upper body strength of the operator are compatible:

http://i146.photobucket.com/albums/r...pszqnonc58.jpg

Put ATV tires on it and voila! I mean, not that mower but a cart with fwd and 360 deg steering. Your controller could be a contactor switch.

P.S. As you can see the steering on this rig is geared down for low effort. Plus the lack of caster and the fact it's the drive wheel should make it low effort as well.

the once a year is the beach, he would use it now and then all summer if it worked.

Yes it is. That is why I was thinking a pair of rear drives on 26" fat wheels, and some larger and wide front casters. I can fab all that up in aluminium to keep weight down.
I think the batec would spin out trying to drag conventional wheels through anything dicey.

The hubmotor on my Songi has zero braking action unless the regen circuit is activated. I'd think the geared motors would have the power-off braking action.

Ha, I have one of those.

:)


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Love the necker's knob

How easy is the steering? And traction, stability, etc.

Torque on a motor is a function of current and speed is a function of voltage. Dynamic braking comes from connecting the armature leads to one another with no power applied. I like the ATV tires and chain drive.

Steering effort is moderate, suicide knob helps. Poor traction on soft ground and not very stable are probably the reasons it never caught on.



Something like this would be best. Although it doesn't meet your non transfer needs and is expensive,

TracFab - All Terrain Tracked Wheelchair



A electric wheel chair with the wheel base stretched out and widened would work.

Harbor freight has cheap castors with air tires. Mini ATV wheels could be used to replace the drive wheels on the donor electric wheelchair to provide more traction.






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Things are percolating now. Initially I had him rolling into it from the back. Now I see that is not as good as backing into it.
I could find a donor one of these, they break all the time I am sure something could be had.
Pride Jazzy 614 HD Heavy Duty/High Weight Capacity Power Wheelchair - Pride Heavy Duty/High Weight Capacity Power Wheelchairs
Mount better wheels at the drive motors, install them on my frame. Make my own front big casters. Re-use the power chair controller and battery system. Big wheels will give it some decent go.

Maybe it depends a on the manufacturer, but the direct drive motors I inquired about put constant drag on the wheel. The geared motors are the ones that free wheel. That's why regen is not available with the geared bike motors and is with the direct drive motors.

Respoked to motorcycle
 

How about a Cyistalite
G-30
Specks :
I've run a crystalite 503 3kw @72vdc on Attachment 19905
The hub drive motor was re spoked with DOT motorcycle rim. This was way to fast for your app. 45-50mph sustained @1500w load it yealded 157wh/mi and 50mi+ range on a 20ah 72v bat
The reason for a geared hub is ,no drag from the windings while pedaling.
My regen/ebraking was a fixed value,on or off, ming was set to 800w with a push button, and would cut out @~5 mph
the G-30 is specked at 15mph with a 26"bike tires @24v and accepts standerd bike disk brakes.
---
Sensored or sensorless?
Sensored no cogging more failure points.
Sensorless cogging,simpler construction , cheeper controllers.
motor will start moving to figure out which way it is moving, switch back and forth between forward and reverse to figure out which way it's supposed to be going. Normaly 1/2" or less. Cogging is normaly on take off only and gone by .25-.5mph.

that looks interesting, and I think that geared might work OK since brakes are going to be mandatory anyway.

1 small problem with gearhub .on reverse it has a 1 way cluch to allow free-wheeling. You said[QUOTE I think he'd like to go down the beach with his grandkids.][/QUOTE] my impression is that would involve a requirement for a reverse capable rig. As well as a more capable farm tool. Not my build, your choice.
Gumby stay flexible.

Yeah, about that :D

Lol, I read "gumby stay flexible" in the Mongo voice.
https://www.youtube.com/watch?v=SKRma7PDW10

Some sort of auxiliary electric braking might help, much like a Jake Brake does in a Diesel, but neglecting a regular service brake would be too dangerous.

Consider a 'rhomboid'.

http://www.fordgtforum.com/forums/at...6&d=1321064949
http://www.fordgtforum.com/forums/showthread.php/23626-Frank-Lloyd-Wright-s-car

http://www.carbodydesign.com/media/2...30-720x540.jpg
http://www.carbodydesign.com/2013/11/toyota-fv2-concept/

It could have 5ft high side wheels and (with a swing-away front wheel) kneel to the front for loading/unloading.

An electric motor with a torque converter and implement tires might work at the beach.