Torque-RequiredStair-Climbing Device

[Saladsamurai]

I am trying to figure out how to design a stair-climbing device similar to a hand-cart that climbs stairs.

I know that the loading will be ~500 lb.

It uses a 3-wheel climbing design design like http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200381541_200381541" except motorized.

I am trying to figure out how much torque I will need at the output of the gear box. I am assuming that this is simply a function of the distance from the climbing-wheel to the loading.

I also would like to figure out what size motor would work in that it should be relatively small and run off of a reasonably small portable power source.

I have no real design experience, so I was hoping for some input/advice.

What kind of small portable motors are out there and where can I see their specs?

What kind of power sources are out there?If my questions are not that clear, let me know and I will try to elaborate.

Thanks,
Casey

EDIT to help put this into better perspective, the motor is to power a 3-wheeled design like the one shown above, but it is to be used on an Ambulance Gurney (stretcher) to assist in moving 'larger' people up and down stairs.

 

[Saladsamurai]

Anyone know of any good sites for motors of this sort? Google is ok, but I would like some recommended sites.

Searching "motors" is a little painstaking.

EDIT: Ok, I am http://www.baldor.com/products/product.asp?1=1&page=1&orderBy=HpDecimal&product=DC+Motors&family=General+Purpose|vw_DCMotors_GeneralPurpose" right now.

Can someone explain what armature vs field voltage? Do I need to consider these?

I googled around and found that armature voltage is the occurs on the coils, but I am not sure why I need to know this

 

[Saladsamurai]

Any thoughts on motors/power sources? I am looking at something like http://www.baldor.com/products/deta...l+Purpose|vw_DCMotors_GeneralPurpose&hp=2.00", but I am not sure if there is a lightweight portable rechargeable power source to go with.

I figured that the torque I need to deliver is ~4000 lb-in

Can I go with a smaller motor without getting to crazy with the gear box? Is 2 HP at 2500 rpm considered a "big" motor.

I know this is a broad question that is design particular, but I am in need of some help/advice as a strarting point/

Thanks

 

[Mech_Engineer]

You'll be able to find a motor that fits your specifications on www.globalspec.com.

As for size of the motor and how much power will be required, I would look into how high you're looking to lift the patient/gurney. By doing this, you can calculate the required potential energy change which can give you an idea on battery sizing.

Also I have to ask- why the heck would you want to carry a patient up stairs on a gurney? What about elevators?