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View Full Version : [Question(s)] replacing wheelchair motors for Mutant Shopping Cart Project



LUCKY13
05-18-2010, 09:05 PM
I am costing out the design/build of a fleet of electric shopping carts for Burning Man (google it if you don't know as the answer is a 42 page essay on fun). These will be manned vehicles. My first robot project will be financed by this project for my clients.

I have decided to use electric wheelchairs as a donor vehicle for a number of reasons. I have a good source for them used/cheap, I like to recycle as much as possible, 2 motors enables me to skip any steering mechanizm, I don't need to go more than 10 mph, the lower frame of most of the chairs can be quickly/easily bolted to the shopping carts. Did I mention cheap?

I am unaware of the RPMs of the 2 drive motors in my Pride Quantum 610 wheelchair. The manufacturer doesn't offer any specs on them either. I called their tech support & the guy would not divulge the info. Are they are data hording for corporate greed? Most of the repair techs I spoke with have no use for the info either.

By my calculations if I double or triple my RPMs with a higher torgue motor, I can double or triple my top speed. It sounds simple, right, am I missing something? I know that the gear box might not be rated for that but they are cheap for me & easy to replace if I bust one to pieces.

Questions:

1. what type of equipment do I need to check the max RPM of a motor? Dyno?
2. who has the best selection/prices on 12v/24v motors? I can fabricate an adapter plate to match up with my existing gear boxes.
3. does anyone have any online calculators to figure out max rpm based on wheel size, top speed & gear reduction. I have all of that info at my fingertips.
4. how about calculators that help you figure the right motor for desired top speed, & range with the known factors being total weight, battery capacity, voltage, RPM, gear reduction (gonna have that number manana), & torque.

The stock motors are rated for 4 mph, 300lbs & a wee range of 15 miles. OK for your grandma, but not good enough for this kid. I can get heavy duty wheelchairs up to 750 lb capacity but the range & top end are about the same.

Desired range is 25 miles using (2) 12v 100aH deep cycle AGM's either in series or parallel (12v - 200aH/24v - 100aH), 5 mph cruising with occasion sprints of 8-10 mph, mostly flat terrain, 500-800 lb capacity.

Please chime in my machine loving brothers!

LUCKY13
05-18-2010, 09:27 PM
OK, I solved my first problem. I am buying a simple, digital, lazer tachometer to get my RPM's.

LUCKY13
05-25-2010, 02:22 AM
well, I see I touched on a very sensitive subject from all of the heated feedback I am getting.

SteamAutomaton
06-21-2010, 07:47 PM
well, I see I touched on a very sensitive subject from all of the heated feedback I am getting.
I think the headed feedback is because the project is for Burning Man.:tongue: j/k

On a more serious note, I believe what you are planing on doing may not be possible 'on the cheap' As much as I am for re-purposing stuff. You seem to be asking your wheelchairs to fry themselves at the speeds you want.

Do do believe that there is a tutorial about wheel sizes here at Trossen Introductory Tutorials in the left panels.

Anybody else want to chime in?

Sincerely,
SA:)

darkback2
06-21-2010, 08:30 PM
Seams like the sort of deal where you just have to build it and see. If the motors were from a powered wheel chair then I would expect they should be reasonably powerful. Try to find the specs on the chair itself...What weight capacity does it have?...that sort of stuff.

As for 800 pounds going 25 miles at 5 miles an hour...I would probably test the number of amps being drawn under full load. That will tell you how much battery you need. You can use a lab top power supply to do this...or an amp meter. :)

Have fun at burning man.

DB