Improving The Rolling Capabilities of Older Accucraft Trucks

[Jim Kottkamp]

Older Accucraft freight trucks have poor rolling characteristics.  A test of 4 different cars on the same test track had the following results:
Cars with unmodified trucks began rolling on a 5 to 5 ½ percent grade
The same cars with modification began rolling on a 2 to 2 ½ percent grade

The trucks use springs on the outboard-only side of the truck side frame (prototype trucks have a second, inboard row of springs to equalize downward pressure, keeping the side frames perpendicular to the bolster).  The outboard-only springs force the truck side frames inward, pinching the axels, and generating friction.  This extra drag is dependent on keeping the side frames perpendicular to the truck bolster.

Once you have taken the trucks apart, gently file all bolster ends/side frame contact areas.  This will provide flat surfaces, enhancing ease of movement. 

The next step is to shorten the truck springs.  Use a high-speed cutting wheel to remove 2 - 3 turns of the coil springs.  The factory springs are too strong to allow proper side frame movement.  Shorter springs significantly improve spring action.   BE SURE TO USE SAFETY GOGGLES, AND DIRECT THE FORCE OF THE CUTTING WHEEL DOWNWARD, NOT UP – TOWARD YOUR FACE!! 

I offer the following three options to solving the inward thrust problem. 

Solution #1:  Install a plastic or brass ¾" long 3/8 X 3/8 inch "L" brace underneath the bolster.  Shape it to fit and drill a #48 hole to accommodate the bolt that holds the bolster ends together.  Re-assemble the truck, putting the 2mm bolt through the "L" brace, side frame tab and fully tighten it into the bolster.  The main drawback to this method is the flat side of the "L" brace can be seen through the truck springs.  Painting the brace the same color as the truck will lessen this effect.

Solution #2:  Fabricate a  5/8" "U" brace and place it over the top of the bolster.  This is a more involved process requiring drilling out the threads in the truck bolster and tap drilling and threading the brace.  You will also need to file away the sides of the bolster slightly so the 5/8 "U" brace will just slide down over the bolster.

Take a piece of 5/8" square brass tubing and place it in a miter box adapted to cut a 20 degree angle.  Cut off the slender bottom side to make a "U" shape.  Shape the brace as shown in Figure # 2 and drill a #53 hole and tap for a 1-72 thread.  The new 1-72 x ¼" bolt passes through both the side frame and bolster and threads into the top of the brace.

Solution #3:  Place a spring inboard on the side frame.  Attach a ¾" long brass 5/16 X 5/16 inch "L" brace on the inside of the bottom of the truck side frame using super glue.  File the paint off the inside of the side frame to obtain a metal-to-metal bond.  Place a short bolt through this brace to hold the bottom end of the spring in place.  It is much easier to reassemble the truck and then glue the brace in place.  If you attach the brace before reassembling the truck, the brace will be in the way when you tighten the bolt.  Also, if you cut off a part of the outboard springs you will need to cut off one less spring coil on the inboard brace, or it will press the truck side frame outward. Press the spring in place between the bolster hex head bolt and the head of the bolt you installed on the "L" brace.  Sorry no photo for this option, I'm out of space...but this is pretty straight forward.

Any one of these three inexpensive solutions will double the rolling capability of your trucks allowing you to pull longer trains.  Keep in mind that if you are interested in installing ball bearings, you will need to modify the trucks first to keep the side frames perpendicular to the bolsters. 

[Ray Dunakin]

Good tips, thanks for posting!