(Tim Warris at Fast Tracks developed these a couple of years ago to help me with a problem. He’s now offering them for sale. Click on the image to visit the page on these trucks at the Fast Tracks online store)
A couple of years ago I was unhappy with the six-wheel trucks under my heavyweight passenger cars. They looked fine, but they did not track reliably. Longtime readers will know that to solve the problem, I talked to my friend Tim Warris and – for the cost of a couple of meals at a very nice local sushi restaurant – he developed and manufactured a laser-cut subframe that incorporated rigid beam compensation.
Fast forward to last week, when the tracking qualities of American Models six-wheel passenger car trucks generated much discussion on the forum run by the S Scale SIG. I mentioned how I solved the problem on my layout – and it seems that enough forum members contacted Tim about these that he’s now added them to his online catalogue. Click on the image, above, to visit the store.
Since Tim is now offering these, here’s some additional information that any other users should find helpful:
Before you buy:
1 – The subframes are sold without wheels, and without the American Models side frames.
2 – I use 36″ P:64 (Code 88) wheels on 1.265″ shouldered axles from Northwest Short Line. I believe these are NWSL part 57708-4: Mine were ordered a while ago, and I think the part number has changed.
3 – I do not know if other 36″ wheels will work in these, so buyer beware!
Assembling the side frames:
4 – Read all instructions before attempting assembly!
5 – Paint the outside face of the wheels before assembly.
6 – There are no instructions supplied with the Tim Trucks, that I know of. Look at the photos below for general arrangement. Do not assemble yet.
7 – In the photo above, note that the threaded rod has four nuts on it. There’s a nut inside each rigid beam, and a nut to either side of the centre pivot. We found these two central nuts prevented the rod from travelling too far to the left or the right, and jamming in the side frame. The prototype (shown in the first two photos) did not have these nuts.
Preparing to mount the Tim Truck:
8 – In the photos above, note that there are three screw holes in the top plate. This is because a centre-mount screw will be directly above the centre axle, which would make it impossible to install or remove the finished trucks. To address this, I cut a bolster plate from styrene. If I recall, I used .020″ thick sheet for this. It should be big enough to cover the three holes, but not huge. Look closely at the photo of the truck mounted on a passenger car and you can see the plate.
9 – With this arrangement, the styrene bolster plate can be screwed to the body bolster on the passenger car, and then the truck can be screwed to the styrene bolster plate.
10 – Use a sanding stick to round the edges of this plate so there are no sharp corners. Sand off any flash from scoring/snapping the plate.
11 – I drilled three holes in this styrene plate:
– I drilled the centre hole to clear my truck-mounting screw.
– I drilled and tapped the two outer holes to accept screws to secure the truck to the bolster plate. I used Nylon 2-56 screws from Kadee, so that after I mounted the truck to the bolster plate, I could simply snip these off and file them flush with the top of the plate.
12 – Check the head of the screw you plan to use to mount the styrene plate to the passenger car, to make sure it clears the larger centre hole in the wooden plate that forms the bolster on the Tim Truck. Use a reamer to enlarge the hole if necessary.
Assembling the Tim Truck:
13 – Dry fit the parts and figure out how they go together. Note that the wheels will be trapped in the frame once assembled. Plan your assembly and then start gluing up the pieces.
14 – I used Thick CA for my initial glue-up, then added a thin bead of Weld-Bond along every seam.
15 – In some places, I added small lengths of square strip wood (not supplied) to increase the gluing surface.
16 – Paint the sides of the Tim Truck flat black.
Prepping and mounting the American Models side frames:
17 – I like to paint and weather the side frames before removing them from the stock American Models truck, since the truck provides a handy way to hold them.
18 – Snip off any protrusions on the backs of the American Models side frames, including the pins that hold the frames to the truck bolster. File the backs smooth.
19 – The recesses for the axle ends (I won’t call them “bearings”) need to be reshaped into slots so the compensated axles can move freely up and down. The axles don’t need to move far for the compensation to work: Only about +/- 1mm.
20 – I use a ball-shaped high-speed cutter in a drill press. This is a process of removing a bit of material, testing the the side frame against the Tim Truck, then removing a bit more material. Do it a bit at a time so you don’t remove too much, but you want the axles to move freely inside the slots.
21 – On the Tim Truck, use a tooth pick to carefully apply a small amount of white grease (e.g.: Labelle 106) to the axles where they contact the wooden compensation beams. A very tiny dot on each axle will be sufficient. Be sure to do the trapped axle, too.
22 – Line up the cosmetic side frames and glue in place on the sides of the Tim Truck. The journal boxes should be centred over the axles. Use Thick CA – sparingly! Be sure it doesn’t squeeze out and into the axles.
Passenger car modifications:
23 – The Tim Truck bolster is higher than the stock bolster on the American Models trucks, so the passenger car will have to be modified before the new trucks can be mounted. Modifications will depend upon the passenger car, so I will not offer specifics here, but I will provide two examples:
24 – On an MLW Services combine, the model had a small brass post soldered to the floor as a body bolster. I unsoldered this. I then determined the height by stacking strips of styrene on the Tim Truck and setting the car body in place until the couplers were at the NMRA standard. I noted this height, and built up replacement bolsters from styrene strip.
25 – On an American Models RPO, the body bolster was a square plastic block, injection moulded as part of the floor. I drilled a series of holes around this block, then cut from hole to hole with a cutter in a Dremel Tool, until I could remove the body bolster. I then cut a large piece of styrene sheet to cover the hole. Before installing it on the car, I added a block of styrene to the top of the sheet, sized to fit inside the opening of the car floor and centred on the truck pivot point. I then drilled through the centre of this assembly and tapped it for a 2-56 screw. The added styrene block goes inside the car, and provides extra depth for the truck screw. I glued this plate in place, then fashioned a body bolster on it.
26 – In both cases, once the modifications were made and the new body bolsters fabricated, I screwed the styrene plate to each body bolster and left it loose enough to swivel. To this plate, I then screwed the compensation unit (see notes 8-12). This allows me to remove the trucks without having to access the screw that’s directly above the centre axle.
Why is it derailing?
The new trucks will better support a passenger car. My passenger cars no longer wobble, and they ride level – which was a challenge before due to the sloppy engineering of the American Models trucks. However, while they reduced derailments considerably – they did not eliminate derailments.
When I started running a train with these new trucks, I still experienced a few derailments. I had far fewer derailments than before, but some of the derailments I experienced were new – they were in places that the old trucks had negotiated without any problems.
I spent a fair bit of time troubleshooting the new trucks and learned several things:
A) – With the axles now held perpendicular to the side frames, instead of being able to wobble in loosely moulded holes in the backs of the side frames, I no longer experienced derailments caused by a wobbly wheel set picking a rail joint or a turnout frog.
B) – I initially mounted the trucks with the trapped axles closest to the ends of the car. I had a fair number of derailments. I rotated the trucks 180 degrees – putting the trapped axles towards the centre of the car, and letting the car lead with compensated axles. That solved 90% of the problems.
C) – The ride is a lot smoother and quieter with these new trucks, as all six wheels on each truck are in contact with the rail at all times. The compensation unit takes up minor variations in rail height.
New derailments were in three spots:
D) – One trouble spot was due to the track gauge being slightly too wide. This allowed one wheel to drop enough that it would send the wheel at the other end of the axle up and over the rail. The non-compensated factory trucks probably rode over this spot with each wheel doing a bit of “hang time”, but the new compensated trucks will ride all the ups and downs. Once I determined the problem, a couple of spikes fixed it.
E) – One trouble spot was due to the track gauge being slightly too tight. Since two axles in each truck are compensated, they’re quite happy to ride up and over the rail at a tight spot. Again, once the problem was identified I was able to fix it with a couple of spikes. I’m not sure how the factory trucks made it through this spot. As an aside, the train slowed significantly at this spot as the tight gauge created enough additional drag to slip the drivers on the mogul. Fixing the tight spot fixed that problem, too.
F) – One trouble spot was due to a slight misalignment between two adjacent pieces of rail on the outside of a curve. The lead wheel would hit the end of the misaligned rail, and the compensated axle would deal with the issue by riding up and over the railhead. The factory trucks probably hit the misaligned rail and bounced away from it, instead of riding over it. Again, a few spikes fixed the issue.
Are they worth it?
Are the Tim Trucks worth the extra trouble of assembly, and the time to tune the layout afterwards? I certainly think so. The stock trucks from American Models are wildcards – the axles can wobble about in the side frames, and when a derailment occurs it’s impossible to determine whether it was caused by the track, by the wobbling axles, or by a combination of the two. Often, when I had a derailment in a particular spot I could not repeat the derailment. How can one even begin to fix that?
What the Tim Trucks do – and do very well – is eliminate the truck from the derailment equation. If there’s a derailment, I know I must check and adjust the track work.
Of course, if there are any questions, use the comments feature to ask and I’ll try to answer them. I’d also like to hear from anybody who buys some of these trucks and experiments with them.
Thanks, again, to Tim Warris for solving my passenger car truck problem – and now, for making this solution available to others!