Bariatric wheel chair dual drive, advice for what to read

[BigRider]

Hi. I have learned over time that knowing what to search for and where to search seriously reduces the level of research needed to get to the right answer. I'm willing to read, but don't know what to search for exactly.

I'm 750 lbs. Can stand and walk about 15 feet, but that's about it. I'd like to get out and do things like the zoo with my wife. I am pretty good at fabrication and electronics.

In my ideal world, think wheel chair with dual hub motors and floating front casters. I realize this won't work for a variety of reasons. I have done a few hours of preliminary searching and reading

I think two motors, with gears and chains. One per rear wheel. Big common battery. Think twist handle style controls, one per wheel.

I don't care about speed, but a bit faster than walkers would be nice.

Things I know so far:
- Hubs don't do the torque needed and have way more speed than needed
- axle sticking out that's not across the whole chair will probably snap off
- I likely want a long axle with a hub that plugs on the end and has a chain sprocket on it. Axle is stationary, hub on end rotates and is driven. Don't know the right name for this style, but that's what I've found that looks best so far.

Things I don't know
- wheel sizes that's best
- motor power and torque needed to move a solid thousand plus pounds
- how to size the battery

I can design the rest of the chair around it, but what terms do I need to research / threads that's done this. I have read some, but didn't see one just like this but my size. But I did learn some from it.

I don't plan to truly off road, but reading threads makes a good point that it needs to be able to do curbs and inclines.

I look forward to any pointers and advice. Like even "go read this particular motor thread to learn basics" is welcome. I poked around and read a few. But what is the good stuff?

Thank you .

 

[Chalo]

Two wheelbarrow hub motors under the largest fraction of your gross weight would do it. You'll need to get ones that are reversible. They're designed to do what you're trying to do, slow and torquey.

I lost about 36% of my body weight over the course of a year and a half. No drugs, no diet formula, no gratuitous exercising. I just tolerated a modest amount of hunger and used my best judgment about the calories I did take in. It can go fast if you're committed, and staying as active as you can (which is what you're talking about) is a part of that formula.

 

[BigRider]

Two wheelbarrow hub motors under the largest fraction of your gross weight would do it. You'll need to get ones that are reversible. They're designed to do what you're trying to do, slow and torquey.

I lost about 36% of my body weight over the course of a year and a half. No drugs, no diet formula, no gratuitous exercising. I just tolerated a modest amount of hunger and used my best judgment about the calories I did take in. It can go fast if you're committed, and staying as active as you can (which is what you're talking about) is a part of that formula.

Thanks. I'll look into them. And this is what I was talking about. Didn't even know wheelbarrow motors existed. That is a great lead. Thank you.

Weight: yeah I've fought this all my life and what I tell most people is nobody would choose this, and if you get this big things are clearly messed up. That part of the conversation is enough on that though. I am glad that worked for you. Truly.

 

[neptronix]

I lost all my weight on keto. Turns out my problem was carbs all along. Appetite works different for me w/out them. No exercise, because at the time, i was physically disabled.

But we can't optimize the human immediately, only the ride

I left some good info on this thread a while back about building such a vehicle:
Mobility use - 14" wheels and hub motors?

 

[BigRider]

I lost all my weight on keto. Turns out my problem was carbs all along. Appetite works different for me w/out them. No exercise, because at the time, i was physically disabled.

But we can't optimize the human immediately, only the ride

I left some good info on this thread a while back about building such a vehicle:
Mobility use - 14" wheels and hub motors?

That thread is a gold mine. Thank you. That's exactly the sort of pointer I was after.

I don't know enough yet to ask truly intelligent questions. So I'm enjoying reading the other threads with similar questions I haven't thought of yet.

 

[amberwolf]

wheel chair with dual hub motors and floating front casters. I realize this won't work for a variety of reasons.

What reasons? (knowing these may help prevent suggestions that aren't useful for the same reasons).

I think two motors, with gears and chains. One per rear wheel.

I do heavy cargo hauling now and then, hundreds of pounds at a time, so I build my bikes, trikes, etc so they can handle that; been iterating changes to improve things over time.

Given the weight, I would go with some form of that system, probably with as you said elsewhere an axle across the entire chair.. but stub axles *are* possible to handle this weight, if hte frame itself is stiff enough and built correctly to prevent canting inward above the axle from the load on the wheels.

See below **** for one alternative.

In my Schwinn trike conversion thread Amberwolf's Schwinn Trike Rebuild / Conversion to Heavy Cargo Hauler, which will be another heavy cargo hauler build like the SB Cruiser The SB Cruiser : Amberwolf's 2WD Heavy Cargo Trike & Dog Carrier , it will have single-ended stub axles mounted to the frame with "regular" bicycle wheels on them, and be chain driven from a peerless differential that itself is driven from a single motor. If you can steer the chair from the "caster" wheels, or if a trike style chair is an option (there are several chair builds around the forum that do this, though most of those use a front hubmotor) the single motor option could work for you.

Things I know so far:
- Hubs don't do the torque needed and have way more speed than needed

There are some that can--as noted the wheelbarrow types probably could, and some companies (QSmotors, for example) will do custom windings so you could have motors made with the kV / kT you are after. (QS also makes single-sided mounting hubmotors for heavy vehicles (cars, etc) that would be useful for a side-mounted wheel like on a chair (or a trike).



**** There are also hubmotors *for powerchairs* that may do what you want, albeit not with the powerchair *controller*. The invacare version I have one of (wish I had two; I'd've built a trike with them long ago) is probably equivalent to a QS205-50H hubmotor. (and is at least as heavy), but it also has a built in parking brake, and has a great big flat mounting plate that is part of it's side, so you don't have to figure out how to mount it. And it has big bearings and a big axle/motor shaft. I don't know what it's weight rating is, but you coudl probably find out from Invacare.

It's designed for tiny little wheels less than a foot across, but if you have fabrication tools and abilities, you can probably come up with several ways to mount "real" wheels to it.

They are not light, but neither are the similar-capability DD ebike/etc hubmotors out there. They can be cheaper than those motors, or about the same price; this ebay auction has a pair for $450 OBO.
Lot of 2 RT LT INVACARE POWER WHEELCHAIR BRUSHLESS MOTORS TS1113090 & TS1113091 | eBay

They are built for low speed and high torque already, and while going up in voltage (from the 24v the powerchairs usually use) will give a higher *possible* top speed, you don't have to use that; and it doesn't decrease the torque available.

One thread for these motors showing one type of them;

Direct drive brushless motor from powerchair.

First off I'm on a borrowed computer so my response may not be punctual. Second issue is I need to learn photo transfer to ES Forum site. I have got the images from the SD camera card to a computer file. Amberwolf has a topic for the same motor class but a different reason than mine. He has...

endless-sphere.com

I have another that shows some testing with hall sensors installed inside a different version of the motor:

Powerchair Direct Drive Brushless Motor (High-Torque)

A friend dropped by tonight with an interesting motor. It is from a powerchair, and the wheel bolts directly to it. Normally it would run at less than 200RPM, on 24V SLA, for a few MPH on a small-diameter wheel, but the manufacturers have apparently tested it up to 65MPH on the same size...

endless-sphere.com

They don't have common UVW / ABC hall sensors, though, but rather SIN/COS encoders (which are more precise), so you'd either need a controller that can use the encoders they have, or you'd have to add UVW/ABC hall sensors (like ebike motors have) to use the most common ebike controllers.

There are also existing (expensive) mounts for them that include a form of suspension, but you'd probalby have to replace the springs with ones that have a rate more applicable to the total weight your chair will need to support. But you could also build your own based on the pics of this type that are out there. One example Invacare Arrow Gearless Brushless Motor Mounts for Power Wheelchair #E473 | eBay

 

[BigRider]

Thank you. Lots of stuff to process in there. Many things I have no idea about, but that's ok. Having the search terms gives me traction and I have more threads to injest. Going to take a while to get through these replies. Thank you. I'll undoubtedly ask follow up questions.