Large Scale Central

Pilot truck question

Modeling
#1

This may seem a bit basic but I’m a bit confused. I’ve been looking at lot of pics of scratchbuilds and major mods to locomotives and I’m wondering if the pilot truck on 2-x-x’s should have a pivoting pilot truck or a fixed truck where the wheels/axles can slide back and forth. From my HO days I know I always had a pivoting truck, albeit with the associated tune up work needed to get it to track correctly.
I’m thinking about making the old Bachmann 0-4-0 I have modified into a non-tank loco into a 2-4-0. I’m just not sure what to do with the pilot truck. Inspiration (and confusion) comes from the mod proposals for a Ruby-
http://www.nmia.com/~vrbass/steam/ruby/rubythings.htm

Any advice will be greatly appreciated.
Dave

#2

Dave,
The pilot truck should pivot.
As in the prototype, It’s job is to lead the rest of the locomotive into curves and thru turnouts, besides carrying a little of the forward weight of the locomotive.
jb

#3

A prototypical 2-wheeled pilot truck pivotted around an axis directly above the wheels. That’s why you’ll see on the pilot deck of most 2-8-0s a round bearing-like fixture directly in the center of the deck above the pilot wheel. There was a very limited amout of rotation around this axis–the degree of which limited by the suspension linkage. In addition to pivoting around this axis, the wheels had limited side-to-side play through a swing-motion kind of arangement. This allowed the wheels to slide laterally just a bit as the loco went down the tracks, but was limited enough to where it would still pull the locomotive one way or the other, “leading” the locomotive through the curves.

On our models, that’s not exactly practical, as our curves are significantly sharper than the prototype’s. Thats why most model leading axles swing on a longer arm pivotted back behind the cylinders. In terms of geometry, the “ideal” pivot point for this truck would be the center of the fixed wheelbase of the drivers. “Ideal” and “practical” are rare bedfellows, so most swing arms are considerably shorter.

Later,

K

#4

Kevin,

Just wait until some “innovator” comes out with an “articulated swing arm for prototypical performance”. :confused: :stuck_out_tongue: