Tim Truck Testing

There’s something very different about this passenger car:
Compensated Trucks - Installed - Normal View photo Trucks-Warris-05_zpsa3d21a78.jpg

It’s not at all obvious in the photo, but the car is staying on the rails, consistently – and it no longer leans to one side. That’s because over the weekend I upgraded the running gear on this car (and the adjacent combine) with Tim Trucks.

I visited Tim Warris last week at Fast Tracks World Headquarters, and collected three pairs of the rigid beam compensation units that he designed and laser cut for me:
 photo Trucks-Warris-07_zpscc1d9e98.jpg
Compensated truck components being cut from very thin plywood by the Fast Tracks laser

The two photos below show the compensation units in place:
Compensated  Trucks - Combine photo Trucks-Warris-03_zps39ee3131.jpg
(Under an MLW Services combine)

Compensated Trucks - Baggage-Mail photo Trucks-Warris-04_zps876e1685.jpg
(Under an American Models baggage-mail car)

The combine was the easier of the two to convert. The model has a small brass post soldered to the floor as a body bolster. I unsoldered this, then built up a replacement bolster from styrene strip.

On the baggage-mail car, 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 couple of blocks of styrene to the top side of the sheet, and drilled through all three layers and tapped them for a 2-56 screw. The added styrene blocks go inside the car, and provide extra depth for the truck screw. I glued this plate in place, then fashioned a body bolster on it.

In both cases, once the modifications were made and the new body bolsters fabricated, I screwed a styrene plate to each bolster and left it loose enough to swivel. To this plate, I then screwed the compensation unit. This allows me to remove the trucks without having to access the screw that’s directly above the centre axle.

The side frames from the American Models trucks are now cosmetic. I pulled the side frames from the AM truck bolsters, then cut away the mounting posts and filed/sanded the backs of the side frames smooth. I then used a cutting tool in my drill press to grind away some of the plastic inside the journals to create a vertical slot. This cavity allows the ends of the axles to move freely behind the plastic side frames. I then secured the modified side frames to the sides of the compensation units with CA. Tim cleverly designed the units to be exactly the same width as the space between the side frames on the stock trucks, so no spacers were needed.

I received some questions about the appearance of the cars with the compensation units installed. As the lead photo for this post demonstrates, during an operating session one can barely see the trucks – let alone the compensation frames. But in the interests of full disclosure, here’s a photo taken from track level:
Compensated Trucks - Installed - Closeup photo Trucks-Warris-06_zps24572241.jpg

In this photo, I have not painted the wooden sub frames. Even so, they’re barely visible. I will brush-paint them black and then dry-brush some more weathering onto the plastic side frames of the trucks, and the sub frames should completely disappear. In any case, I’m pleased with the appearance – and very pleased with the improved performance of the trucks. As a bonus, they better support the cars: the cars do not wobble, and they ride level – which was a challenge before due to the sloppy engineering of the American Models trucks.

They also reduced derailments considerably. Yes – reduced: not eliminated.

When I started running the mixed 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 on the weekend troubleshooting the new trucks and learned several things:

1 – With the axles now held perpendicular to the side frames, instead of being able to wobble in loosely drilled 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.

2 – 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.

3 – 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. (Actually, when Tim demonstrated the units to me he said “You can go offroading with these things” – and he’s right!)

The new derailments were in three spots:

4 – 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.

5 – 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.

6 – 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.

I’ll continue to do my testing. I’m running the mixed train the length of the layout – forwards and backwards, while facing both directions – and at top speed (which isn’t all that fast since I have put custom speed curves into my DCC decoders). But early indications are this has been a great success for me. Thanks again, Tim!

8 thoughts on “Tim Truck Testing

  1. Hi Trevor,

    I think you discovered a few “disadvantages” of using fully balanced trucks, that It can ride over the rail for any reasons. I noticed it many years ago but completely forgot out it.

    It proves something, the closer to scale you want to be, the less tolerance you can have on the trackwork. Great posting as always.


    • Salut, Simon:

      Thanks – although I wouldn’t call them “disadvantages”. Overall, my derailments have reduced and after tuning my trackwork, I had them at zero yesterday afternoon.

      The problem with the trucks, as delivered from American Models, is this: If there’s a derailment, what caused it? Was it the track, or the truck? Maybe it was the track one time, and the truck the next time? What I’ve done is eliminate the truck from the equation. If there’s a derailment now, I know – absolutely – that the track is at fault. That makes it easier to eliminate the problem.

      For the same reason, I also decided very early on – even before the layout was started – to use one manufacturer’s wheel sets exclusively. I opted for NWSL wheels, but the specific manufacturer doesn’t matter. They could just as easily have been the factory wheels from S Helper Service. What does matter is that every wheel on the layout has the same profile. This eliminates a variable from trouble-shooting. Otherwise, when I had a derailment I would have to ask, “Is it the track? Is it the wheel set on this specific car? Is it the truck or the way it’s mounted to the body? Is it a combination of two or three of these things?” By eliminating the wheel set as a variable, I can better investigate and solve the problem.


    • Thanks Terry. Now, to keep the layout “in tune”!

      I have to admit that while adjusting the track, I thought how great it would be to model a prototype without trees, so I wouldn’t have to reach around them to do stuff like this. Yes, one of the problems was behind a stand of wire armatures…

  2. Hi, just found your web site and I really love the level of detail you have achieved. I’m an N scale guy who is looking to build a small switching layout in S scale but have very little knowledge about which products to use. I would like to hand lay the track and I’m looking to get one of the Fast Track jigs but I’m not sure on which rail size would look best. Just wondering what size of rail you are using and/or what you might recommend. What do you recommend for wheel sets?



    • Hi Don:
      Welcome aboard!
      S scale is challenging, but also rewarding. I certainly recommend the Fast Tracks system as I’ve used it myself, but the rail size and jig size that’s best for you is really dependent on what you’re trying to model. I’ve used Code 70 on my layout, which represents an obscure, lightly trafficked branch line at the end of its life.
      As for wheel sets, I’m relatively new to S scale so I standardized on Northwest Shortline’s wheels, because I had good experiences with them way back when I was building a home layout in HO.
      Since you’re new to the scale, you might want to join (at no cost!) the S Scale SIG. The SIG has lots of information online, and runs a very useful forum. There are many knowledgeable people on the forum and there’s not a lot of banter, so it won’t swamp your inbox, either.

      • Thanks. I am looking to do a more dilapidated layout that’s seen better times. In N scale I just have several modules that I take to local shows so the scenery and modeling detail are of a lower quality in order to stand up to the constant transporting. My main reason for getting into S scale is to try and take my modeling skills up a notch or two. I have looked at the other scales but for some reason I can’t put my finger on I keep coming back to S scale as the most appealing. I will check out the Northwest Shortline wheel sets and the S Scale Sig.


Leave a Reply

Your email address will not be published. Required fields are marked *

Please prove you're not a nasty spamming robot thingy * Time limit is exhausted. Please reload CAPTCHA.

This site uses Akismet to reduce spam. Learn how your comment data is processed.