[PRCo] B-3 truck development

[Boris Cefer]

The B-3 truck story is very interesting and there was far more hanky-panky than we realized before. And of course, there are also some facts still hidden to us.

The company built two prototypes, one in 1940 (truck "A" for future reference) and the other in 1941 (truck "B"). The dates given by Jim Holland are probably correct, but it is not clear when they were installed if these are dates of shipping.

Truck A was the one which copied upper frame design of B-1 truck and had conical rubber ssprings, superresilient wheels and tread brakes.
Truck B had separate motor transoms, bolster with swinging double spring pots, standard wheels and gear-mounted drum brakes. The suspension was made by means of concentric coil springs, the outer ones being right-hand wound.

On truck A, the rubber springs probably did not work satisfactorily and were soon replaced by steel coil and rubber combination (car 1225 photographed in August 1941). It is not clear, but perhaps at the same time the motors were removed from the upper frame and suspended from independed (resilient) transoms similarly to truck B. Diffucult to say how long this version was in service.

Truck B was probably more satisfactory, but the swinging bolster pots caused problems with riding quality. A new, solid bolster was created and substituted for the original. At the same time or shortly after, four Houdaille shock absorbers were attached to the bolster to dampen vertical motions. It appears that trucks of this type were tested under car 1230.

Now we are getting back to the A truck. The design with upper frame was not considered good or satisfactory and it was perhaps too complicated. It was sent to the company for rebuilding. The upper frame and steel coil and rubber combination springs were removed. The original swinging bolster from truck B was installed together with coil springs wound left-hand (bottom photo page 132 PCC Fought Back). Tread brakes were replaced by gear-mounted drum brakes. At the same time or later NACO wheels were substituted for superresilient wheels and two Houdaille shock absorbers added to the bolster.

Now there were two very similar trucks (pairs of trucks), but one with a swinging bolster pots. There was probably certain testing which showed the solid bolster design better, but still a very complicated design. A decision was made to simplify the trucks and the new bolsters had single spring pots, like all mass-production units. Some parts were salvaged and other parts newly built, but after rebuilding, the trucks from 1230 went under 1614 (with standard wheels) and the other pair under 1613 (with superresilient wheels and three Houdaille shock absorbers on the bolster - one for horizontal and two for vertical dampening). There are photos showing the trucks for 1614 nearly ready for fitting in August 1945.

It is not know whether the superresilient wheels under 1613 did not work satisfactorily, but they were replaced with NACO wheels later. Also the bolster safety links were removed and two automotive shock absorbers installed (two Houdaille shock absorbers removed).

B