looking for platform for outdoor robot

[4by4]

I'm looking for an off-the-shelf 4-wheel electric-powered platform for an outdoor robot with the following characteristics:

About the size of a standard push lawnmower
Wheels around 8 to 10 inches in diameter for good ground clearance
4 wheels equal in size
Speed around 3 to 5 mph
Costs less than $500

I suspect that no such thing is available on the market, but I thought I'd ask. The closest thing I've found is a kids Power Wheels type car, but these require so much modification, it's probably easier to build one from scratch. Other than that there are the R/C trucks, but these are either too small (the 1:8 scale category) or cost $1K-$2K and up (1:6 to 1:4 scale). There is the Superdroids All Terrain Platform, but it's too small and too expensive. There is the Machine Labs line of platforms but they are in the $4K price range.

[airman00]

Use 4 wheelchair motors mounted to a wooden or plastic or metal frame

search the forum for wheelchair motors for more info

[dunk]

seen this:
http://www.lynxmotion.com/Category.aspx?CategoryID=111
?

dunk.

[airman00]

dunk i think thats too small

wheels are 4.75" and platform looks small also...

also, 4by4 why do you need such a big robot for anyways?

[Del]

How about starting with the Vex kit and expanding it?

http://www.vexlabs.com/vex-metal-chassis-kits.shtml

Something like this maybe:

[4by4]

Why such a big robot? It's all-terrain. I've found that for all-terrain you need big wheels, a lot of ground clearance, and powerful motors. Big wheels means at least 8 inches diam. The Lynxmotion is too small.

Wheelchair motors are fine if you can get them for cheap. However, I think Power Wheels motors will be sufficient, and they are very cheap even brand new. That is my current plan, but I just wanted to check if anyone had come across something off-the-shelf.

[Mega]

I used an RC truck as the platform for my robot that I also plan to use outdoors:



Advantages: big wheels, good ground clearance. Disadvantage: difficult to control the speed (ie. difficult to drive slowly).
For more info, see: http://megabotblog.blogspot.com/2007/12/hummbot-basic-object-avoidance.html

[Rebelgium]

4by4, you want a difficult size for your robot, it's a size that's not very common...
I see two choices:
easy: go for something smaller. Then the best choice is to go for an RC offroad truck (buy a quality one!!)
hard: custom build your own big robot. But building your own suspension system etc, is NOT easy.

If there are no very important reasons you want to go so big, I recommend the easy choice.

[4by4]

Thanks for the pointers, all. I know I'm dealing with a difficult size. I agree there's probably not anything available in that size out there, but it doesn't hurt to ask.

Just for general interest, there's a large all-terrain modular robot available commercially, called Volksbot:

www.volksbot.de

Their RT-4 model is exactly what I want. Only problem is it costs >5,000 euros! The high cost for this sort of thing is due to the fact that they have to amortize the engineering cost over a small numbers of unit sales. Same goes for the Machine Labs products.

[airman00]

Just use the idea I previously mentioned. Wheelchair motors with pneumatic tires are fine.

[SmAsH]

are you intending to have it climb over medium rocks and other obsticals? if so have you considered suspension?


~smash