Usually two axles but in certain cases there may be three.
some have 2 and some have 3 depending on the length and weight.
Normally just two. The front and the rear axle. It just has the frame streched. I have seen one around town that has three axles. It has 2 rear axles. I haven't seen it in a while, so I don't know if it is still in service or not.
