I was looking thru my cat performance handbook and seeing where a 312 w/ a va boom will reach almost 29' at hinge pin height. Thats more than a 320 std. boom. Do I need a 320's power for wooden structure demo? Is a va boom too weak for demo? Is a 312 too light to pack cans properly?
Not sure what a "VA" boom is but I don't think you need the power of a 320 for wood building demo. I think that the reach advantage of the 320 would be more important. I also think the 312 will pack cans well enough. It might be necessary to "pack" in smaller lifts. I've used both machines but neither for demo work. My 315 will pack a 40 yarder to the point that it will bend out the top rails. I bet the 312 will do the same.
va = variable angle, instead of a fixed curve in the main boom, there is a pin and cylinder there. I've packed cans with a 315cl and found that i had plenty of power as well. I have read on here that a 320 size is prefered for its reach when demoing houses, and a 312 va has the reach in a lighter easier to move package.
A 20 tonne machine like a 320 has a very distinct advantage over a 12 or 13 tonne machine like a 312 and that's the weight of the machine and the power. For an average house you don't necessarily need all that weight but an old multi-storey building with heavy timber frame construction can be a challenge for a lighter machine. The VA boom could be handy with a little more vertical reach but I don't know how robust they are, more moving parts can mean more maintenance and repairs. I have seen special booms made more for demolition work that are more straight than conventional ones and built stronger for the purpose.
VA boom will handle residential demo fine. It is one more joint to maintain, but that won't be a huge increase in operating expense. The trick will be finding one in NA. If you don't need hydraulics a pined boom could be an option. Don't think it will be any eaiser to find one though. I have a seen a couple of 200 series cats with pinned booms, but they were probably gray market machines.
Never used a VA boom. I think a 312 it to light, but it can be done it just takes more time. Your body and the machine are going to take more abuse with that small of hoe, but if your saving the slab a 312 is probably a good choice.