With respect to capacity of caters, if you want to be very conservative, work from gross weight. Otherwise go with the empty weight of the truck. The carrying capacity of the truck (30 cwt) isn't very relevant to the casters as there won't be cargo in the truck while on casters.
If you have 4 dolly stands (one at each corner) and each one has 4 casters, and if you assume that all corners of the truck weigh the same (probably a bad assumption), each caster should carry 1/16th of the weight of the truck.
Perhaps this will strike you as picky but 30 cwt is exactly 1.5 Imperial/long tons (since a long ton is 20 cwt, and each cwt = 112 pounds). 30 cwt in any other system will be the result of conversions to that system. 30 cwt = 1.524 tonne = 1.68 ton (short).
The diagram on the right in Hanno's post shows both single and dual wheels (each setup on one side of the truck) which suggests there may have been a choice (unless they were using a generic diagram).
|