Tim Trucks

Regular readers know I’m unhappy with the six-wheel trucks under my passenger cars. They look fine, but they do not track reliably. Earlier this month, I wrote about how I would love to modify these trucks with a subframe to provide rigid beam compensation on the axles.

Well, my friend – the very talented Tim Warris at Fast Tracksvisited last week and he was intrigued by the problem. Tim went home with a set of wheels and a pair of stock American Models passenger trucks, and over the weekend he drew up, then laser cut and assembled, a solution:
Tim Trucks photo Trucks-Warris-01_zpsa20935c7.jpg

 photo Trucks-Warris-02_zps6f913395.jpg

As Tim writes on the Fast Tracks Facebook page,

Took a break from trackwork designs this past weekend and designed this set of S scale equalized 6 wheel trucks for Trevor Marshall’s Port Rowan layout. While custom projects such as this aren’t something Fast Tracks typically does, we made an exception as this seemed like an interesting quick project. The entire assembly is laser cut from plywood, the same wood we use for our QuickSticks. This is a sub-assembly that will have cast sideframes added to it when installed onto the passenger cars they are designed for. While it’s kind of hard to see in the image, two of the three wheelsets are able to rock and twist within the side frame, allowing for very smooth operation over uneven track. These should go a long way to eliminating some operational issues Trevor was having with the poorly designed trucks available in S scale. There is no limit to what can be done with a laser cutter and some imagination!

Tim has posted a video to YouTube showing the trucks smoothly navigating an uneven surface. The two floating axles rise, fall and twist as needed to keep all six wheels in contact with the surface at all times. The threaded rod and trapped nuts make for a very smooth pivot, and the wood construction means there’s no need to insulate the wheel sets from the subframe:

I wondered about the choice of wood, but Tim reassured me: “Wood will outlast almost any other material,” he reports. “Hydro electric dams installed wood bearings 100+ years ago and are still using them, very durable, won’t cause any issues.” That’s good enough for me.

Tim is going to cut a few more sets of these for me so I can retrofit my three passenger cars. We compared schedules and as he notes, trying to find a time when we can get together in the next week or two turned out to be more difficult than designing the trucks, so he’ll pop them in the mail. I’m already standing by the mailbox…

Thanks for this, Tim. I feel like a kid in the days before Christmas – waiting to open my presents. I’m looking forward to putting side frames on these, slipping them under my passenger cars, and saying goodbye to bad running!

UPDATE (JUNE 22, 2015): Tim now offers these on his web site. Having had them in use on my layout for about 18 months now, I’ve written up some construction and operation notes on these to help others decide whether they want to try them.

23 thoughts on “Tim Trucks

  1. Looking good:)

    I wonder if the ‘rigid’ axle should always be toward the center of the car? Like as the trimount locomotive trucks had to be a certain end toward center.

    TCC:}

    • Dear TCC,
      Unlike the proto, where individual axles have their own mass and springing, a model “compensation” rig needs the moving-axles to be right next to each other. Trying to put the moving axles at either end means the “beam” has to navigate it’s way around the (now firmly mounted) centre axle without interferrence under any conditions, which makes the design and deployment that extra-level-of-difficulty. As long as the outside frame members/assembly is rigid enough, having one of the end-axles as the “reference” should work fine…

      Happy Modelling,
      Aim to Improve,
      Prof Klyzlr

  2. Dear Trevor,
    I’ll take Tim’s word for it that the plywood will work as a bearing-surface,
    (maybe a touch of powdered graphite for lube?)

    but my question would be, how will the pivot hole work with threaded-rod (which effectively will work as a very coarse woodworking file)? Anyone who has chewed out a hole in almost any material with a screw thread will know what I’m taking about, and anyone who has used captive screws thru holes in the end of modules as alignment systems will attest to the fact that the holes became elongated/”sloppy” over only a few “dis/connect” cycles. Admitedly, the threaded rod is not pulling in/out fo the hole, but if it’s “worming it’s way around” it could be an interesting test…

    As always, great post, and a fantastic example of modellers helping each other out… 🙂

    Happy Modelling,
    Aim to Improve,
    Prof Klyzlr

    • Prof, I think the embedded nuts take care of the bearing surface between the thread rod and the wood (see 2nd photo). As long as the nuts don’t bind on the thread rod…

  3. Dear Trevor,

    Side thought, with these under the passenger cars, will you still need to screw-them to the bolster in the time-honoured 3-point “one truck is just loose enough to swivel, the other can rock a little” method a la typical “solid trucks”,
    OR
    with both trucks now “fully compensated” will they both need to be “just loose enough to swivel” at the bolster?

    Intrigued…

    Happy Modelling,
    Aim to Improve,
    Prof Klyzlr

  4. I hope that they work for you Trevor, but I have my concerns about the end axle being rigidly mounted to the frame.

    Any problem with the plywood “bearings” wearing can be addressed by bushing with a piece of brass inserted into the worn hole.

    Tim’s trucks are not “fully equalised” by my understanding of equalisation.

    Terry

  5. Hi Trevor,

    I’ve just realised that most of my concerns about the end axle being rigid can be overcome by making sure that only one truck per car provides “sideways” support, ie controls the roll of the car body.

    This can easily be arranged on Tim’s truck by ACC’ing 2 pieces of wire, inline, across the central truck pivot hole. A neat touch would be to do similar but arranged longitudinally along the truck for the second truck of the car.

    I use a version of this technique on my On2 cars and bolsters,

    Terry

  6. Hi everyone:

    Concerns noted – but this is all being done in the spirit of experimentation.

    There’s not enough of that in the hobby, in general: many people prefer to do nothing while waiting for the ideal solution to appear – an attitude often summed up as, “When I build my layout…”

    If these work, I’m laughing. If they don’t, Tim and I have learned something we can apply to the next version.

    Cheers!

  7. Thinking about the surface finish on much laser-cut plywood that I’ve seen and the finish on the axle journals in Tim’s video, the two should wear very little as long as both are smooth. The wood will be worn smooth in time anyhow, the smooth journal eventually wearing down any rough wood edge to provide a smooth running surface for the journal and then wearing negligibly (if at all) as the weight of each axle is distributed along the smoothed arched bearing surface of each axle slot . And all without any need for lubrication–a wet lube would soil the wood anyhow. Proving what Tim says about wood bearings lasting for many years. Maybe a little P-B-L Neolube painted on the wood and journal ends–if you want to get fancy?

    There MAY be a bit of rolling resistance causing the combine to be dragged down the track–but the slack should be kept stretched on the train anyhow! The passengers on The Daily Effort should not be standing up and ready to get off at St. Williams from the slack running in violently when they are planning to travel through to Port Rowan.

    As for the equalisation of the trucks, what Tim devised is a proven and working technique on modelled UK six-wheel steam loco tenders. For a couple of examples, see Scalefour Digest 41.0, sec. 12.2 “Weighted tender”–

    http://www.clag.org.uk/41-0rev.html#section12.2

  8. Your idea of two bits of wire, one on each truck bolster, will work fine. I have used this technique on brass tender trucks, soldering the 10 thou wire right across the hole in the bolster and then clipping the wire to clear the mounting screw. As you said, one wire along the axis of the car and the second at 90 degrees to the axis. PROTO 87 stores sells formed washers with a ridge just for this purpose. A completely proven technique that throws the old idea of one tight and one loose screw right into the dust bin.

    Tim is a clever fellow, and the confirmation from the chap from CLAG is a ringing endorsement.

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