Hello,
Is one of these https://www.sparkfun.com/products/9836 hooked to an Uno good enough for detecting impacts with billy carts?
Is the G rating sufficient for even heavy impacts?
Cheers
I would have thought that this is sutiable for your application.
Hi, they have a comparison chart link at the sparkfun site, so it might be worth looking at.
Its range is to 16G, what you must find out is what is the decell, accell, G that you would consider as impact limits on a billy cart.
The specification of the system will have to be considered first before matching a unit.
Tom...... 
Normal acceleration sensor are not ment to measure impact g-forces.
A 'hit' with the metal (not the rubber wheels) to a concrete wall could peak at 100 or 200g.
This sensor is in a version up to 250g, but it is only single axis!