Motor and Wheel Combination

Don't see anything that cheap....

http://www.uumotor.com/shop/electric-tricycle-motor?zenid=8ueek2vjm7vt4ih2cp3p08oa93

http://www.uumotor.com/shop/electric-tricycle-motor/electric-trike-kit-with-differential-gear-bridge-800w-to-2000w

What kind of surface? Smooth concrete? Asphalt? Lawn?

Mostly smooth surfaces. Occasionally cutting through the grass.

Well considering the limited 1000' range, and targeting lowest possible cost, you could adapt a cordless drill to drive your vehicle....possibly even 2, one on each rear wheel, with independent control to aid steering....they can be had cheap second hand...and then some small mountain bikes from surplus police impound auction....attach 2 bikes side by side for a 4 wheeler, seems the simple solution.....2 mountain bikes could support 300 lbs no problem....

http://www.publicsurplus.com/sms/auction/view?auc=793034

http://www.ebay.com/sch/Cordless-Drills-/71302/i.html

You are cheap, overweight, get lost very easy, yet have electronics and mechanical fabrication skills good enough to build a off road mobility device that can find its way home?

Sorry I just had to ask.

On a more serious note your best options are going to be to use the drive systems for such units given your payload and terrain conditions.

Unless you have very hard ground you will need a moderately large footprint type tire system and a lot of driving torque to make it go and to turn given the swivel caster type third wheel design. Given the payload plus the units own weight you may need to consider the two drive wheels being similar to the back tires used on a typical riding lawn mower.

From that assuming a total weight of sya 450 pounds trying to turn full around by driving one wheel and having the other drive wheel locked it may very well need to be able to produce upward of 200+ ft/lbs of torque at either drive wheel on a worst case situation.

More info on your part would still be useful here.

To answer your first question, of course not. A certain amount of misdirection is necessary to protect the concept long enough to come up with a prototype that makes it tough to copy. The products that survive in the marketplace tend to be the designs that start out at the lowest cost or the highest level of technology.

You are exactly right about the requirements for the footprint, load, and assumptions about going across the lawn. I am trying to avoid full blown tires because the market seems to be all about maintenance free solid wheels.

I need this to be robust, yet inexpensive. There are several companies out there that would love to steal my concept. New product concepts are very tough to protect long enough to make a profit. And, while a patient may be in the works, I'm not too enthusiastic about making the information public at this point.

That being said, I don't think that 200 ft-lbs would be required unless I was dragging the thing without the help of wheels. The thing is that a geared down high RPM motor can produce plenty of torque. Speed reduction through gearing may be the most expensive way.

Perhaps I should just start by obtaining some used motor powered wheel chairs. I have never seen anyone who use motor a powered wheelchair driving across the lawn but I have no doubt that the capacity is there for that terrain.

Imagine what the neighbors will think when they see running tests in a used wheelchair...

A lot of wheelbarrows are now using solid rubber tires instead of pneumatic. They are on the order of 10" diameter. You might look into your local Tractor Supply, Home Depot, or Ace Hardware for those.

Not sure how you could connect to drive them, though. Generally they just freewheel on a smooth spindle axle.

Go to this page; it's free but you have to register. Select "AGV" (Automated Guided Vehicle) motor sizing on the bottom.

http://www.orientalmotor.com/support/motor-sizing.html

But be aware, AGVs are generally expected to be run on smooth factory / warehouse floors, not 'occasional grass". Sinking in the grass is a new challenge that I don't think any canned software can account for, but you will want as wide a profile as possible, and as high of a clearance as possible, both of which will increase your torque requirements significantly. But at least with this selection tool, you can get a starting point.

Thank you all for your help. I really don't get to work with motors as much as I would like. I shudder a little bit when I think about dusting off my motors textbook, but not because of what is in the text. Instead, it takes me down memory lane to the class, taught by a Professor Crim. He was very knowledgible on the subject and he expected his students to match his years of experience in a single semester. No one ever accused him of seeking a job in acadamics to avoid the real world. He brought the real world to class, every day. We called his class "Criminology".

you should be able to pick up a used elect. chair for 3-500$. Most motors are gear reduction sized for the tire, you should be able to go to a larger tire depending on loading. Encoders are not used on these as the controllers use a joystick operating a PWM driver for the L/R motor. If you are using encoders on the motors you need computer control and servoamps with software, with PWM control you can use line following sensors, or possibly GPS. Check out 'instructables.com' for similar projects.