Pipe Cart Wheel Span

[paulberrylively]

I need to design carts that carry 3000#, 10" dia, 15' long steel cylinders. Imagine a structure made from 4"x4"x1/4" structural steel welded together in the shape of the letter "I" (lame pic below). The long body of the "I" is 9' long and the legs are a width of 20". Two vertical 4"x4" pieces of structural steel are welded on the ends to carry the pipe. The cart has 4 swivel caster wheels. I need to design this cart in such a way that when it is pushed sideways it will not tip over when it hits a bump. I need to determine a safe wheel span for this cart. We are replacing similar carts that have 17" center to center wheel spans with this new design. I believe 17" ctc is unsafe but I can't prove it. I recall seeing standardized equations for determining how wide a wheel span should be for a high COG cart like this but I am not able to find them. The question is - how do I determine what a safe wheel span is for a cart like this?


side view
_____ _____
| | | |
| | | |
| |42" tall | |
| | | |
| | | |
_________________________________
|_______________9'________________|
O O


top view

--- ---
|+| |+|
| | | |
| | 9' long | |
| ---------------------------------- | ~20" wide
| ---------------------------------- |
| | | |
| | | |
|+| |+|
--- ---
casters are located where the + signs are.

Hope that the question I have is clear enough to answer. thanks for any help.

 

[GregLocock]

It might be wise to use a 'trip' loadcase of 3g for one axle. Your cg height is around 20", so you'd need a 30" track.

3g is a typical wheel meets curb sort of an impact.

Cheers

Greg Locock