Re: Narrow Gauge Truck Size

The earliest California NG trucks were 3'8" wheel base with 24" wheels and outside hung brakes. (The 1874 M&SV cars had body hung brakes while all later cars had outside brakes hung off extensions of the truck side frames, not off the body)

when 15 ton cars were introduced, circa 1885, they used 26" wheels, and had to increase the truck wheel base to 4" to give sufficent room. (California trucks were at the time swing motion with wood transom beams, so the truck bolster assembly was much wider than those used in Colorado.

NPC and SPng later cut the truck extensions off (or substituted new trucks without extensions) on many of the cars and substited body hung brakes. SPng had its home made "theilson" style trucks in several wheel bases, the longer used inside truck hung brakes while the shorter used outside body hung brakes.

Later Hammond built cars including the 2nd order of boxcars for the PVC and the Tonapah RR cars had body hung brakes.

I suspect passenger trucks are longer in part to allow for the equalization system. The Carter/CA third class passenger truck, (used on some cabooses and baggage cars) which does not have equalization is either 3'8" or 4" wheel base.

Generally, it seems that they kept the trucks as short as possible.