Steerable (Radial) Locomotive Trucks

[Anonymous]

Someone just told me on another forum that the engineer has a lever to control the steering on radial trucks. Is this true? What happens if the engineer steers the wrong way, does it make the locomotive harder to turn?

just keep asking, just keep learning

[Anonymous]

I thought each axle steers independently, on its own.....

[csxengineer98]

no...engineers dont steer anything....the steerable trucks are self steering...and what is ment by that is...they will ajust in a curve to help eliminate rail and wheel ware...
csx engineer

[Paul Milenkovic]

Browsing the patent database, EMD has a 3-axle "radial truck." The radial refers to the axles being adjusted to being spokes on a wheel whose radius is that of the curve and whose center is the center of the curve.

Wheels connected by a solid axle and with the wheels having a coned taper (see the recent truck hunting thread) are self steering -- they in fact oversteer. One of the things accomplished by putting them in a truck with a rigid side frame is to have them all pointed the same way -- this suppresses hunting at the expense of increase rail and wheel wear. The radial truck allows the wheels to steer themselves into a curve instead of being forced into a straight that has to track a curve -- it has somewhat reduced wear with (one hopes) no degradation in hunting. While the wheels can assume the radius of a curve, they are still interconnected with links so that each wheel is not permitted to steer on its own.

GE has by now come up with its own radial truck -- these things are heavily protected by patents so you have to come up with a different design.

I had asked about the two-axle truck on the Genesis Diesel on another thread. I was wondering 1) who makes that truck (the guesses were Deutz or someone German) and 2) whether that design is radial steer. I talked to some folks in town who were of the opinion that it wasn't.

The interesting thing about the Genesis truck is that it has these long bell crank-like pieces connecting the axle bearings to the bolster, and it looks like it could be a steering truck.

There are also two kinds of steering trucks -- self-steer and forced-steer. The self-steer truck has links to force the axles to either go straight or assume equal and opposite angles relative to the truck side frame, but the main steering force is the self-steer of the coned wheels -- the steering of a pair of axles is coordinated in an effort to prevent hunting. The forced-steer truck uses the pivot angle of the truck with the bolster to provide the steering input. The forced-steer design is more common for high-speed passenger equipment (I believe the Swiss company SIG has such a truck along with their being a Japanese design) while self-steer is more common for freight (the EMD radial truck, the self-steer freight truck of the South African Railway).