Weights and wires for 622

There are two things that I didn’t design well when I built #10  (okay, there are more than two, but I’m going to write about two tonight) — weights and wires.  Weight, even on the first iteration, was largely composed of scraps of lead that I squeezed into nooks and crannies wherever I could.  On the other hand, #10 effectively had no room for wires at all, and the result was no working headlight.

For 622, I’m going to improve the design, especially since I’m now in a phase where I’m mostly waiting for parts.  So, it is that I’ve been thinking about out how the model will be weighted.  3D printing offers me some new opportunities.  For example, the image above shows the front boiler weight, which I think I will get printed in steel.

The weight is hollow so that I can fill it up with Cerrobend, which is about 20% denser than Shapeways steel (or maybe even lead for 40% more!).  Incidentally, that neat hollow shape is a doddle to make with OnShape’s shell tool: simply select the faces to remove, and specify the wall thickness.

There are two wire runs on either side of the weight to allow 4 30-gauge Silicon wires to pass up to the front of the locomotive for the markers and headlight.  That should save me some foil-based aggravation in about a year’s time.

Screenshot from 2016-08-25 23:38:11.png

There will in fact be three weights in the boiler.  The front one above, and two in the rear section of the boiler.  The upper (grey) one will be sandwiched between layers of the boiler used to make the wagon top.  The lower (light blue) weight will be glued to the top of the boiler.  To make the rear weights, my plan is to create either a master for molds to cast them from metal, or to get the molds 3D printed themselves.

The grey ring in the middle of the boiler will be printed in “Elasto Plastic.”  The intent is to stop the motor from trying to jump around inside the boiler, while allowing it to move with the wheels.  In this view you can’t see them, but there are holes through this part for the wires too.

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13 thoughts on “Weights and wires for 622

  1. Hi Rene…not sure I quite understand the ” Elasto Plastic” part but will it be a sleeve around the motor? If so, and if the boiler and motor are connected as well in a more conventional manner like a bracket, how will you assure the motor and drive are not over constrained?

    Md

    1. Hi Mark, yes the Elasto Plastic part is a sleeve around the motor. However, this is the only connection between the motor and the boiler. The motor is fixed at only two points: the torque arm on the gearbox and this ring. Thanks, Rene

      1. Is the boiler connected to the drive somehow? I.e. will the elastic sleeve create a redundant connection between the drive and the motor in addition to the torque arm? I worry about the elastic sleeve influencing motor/drive alignment.

        Md

      2. Nope, there is no connection. However, I do have a concern as well that the sleeve could impart some torque around the vertical axis of the drive. This will increase the friction between the wheel axle bearings and the frame pedestals, and interfere with equalization again. Maybe I should shape the sleeve so the motor can move laterally and longitudinally, but not vertically.

        I’m reluctant to add an axle at the axis of wheel equalization, but fixing the drive there might be the right thing to do.

  2. Hi Rene,

    Have you considered Tungsten fishing weights?
    The price of Tungsten is high right now but it’s 60% heavier than lead.
    For small special projects it might be justified.

    1. Thanks, I wasn’t aware it was available for fishing. I’ve bought some in the past from Woodland Scenics Pinecar over on Amazon. Not cheap, but definitely heavy.

      There are all sorts of interesting things in fishing shops. They probably don’t sell it any more, but I once picked up some lead wire about .5 mm in diameter.

  3. Rolling sheet lead around wire (for air lines) makes heavy reservoirs.
    Just hide the seam on the side facing the model.
    Tapering the sheet makes for convex or concave with(out) lip (burnish with a drill bit) tank ends.

  4. René
    Thanks for posting the link to this blog in our exchange on MRH. There is some fascinating reading here!
    Can I offer a slightly different suggestion, if you are still trying to get more weight on the driving wheels of a 4-4-0? Build the tender as a semi-trailer, so that the weight of the back half rests on the bogie, but the weight of the front half rests on the rear of the loco. The front bogie needs to have just enough weight to stay on the track, while the weight from the front of the tender adds to the adhesion of the loco. This is not an original suggestion, as it almost certainly originates from Mike Sharman, who had a taste for “stern wheeler”, single driver Cramptons. Some are illustrated in the video at the link below.

    Also don’t miss out on the model of Albion, which is featured at about the 15 minute point.
    Best wishes
    Eric

    1. Thanks Eric. I have come across the half-trailer tender idea in the past, though I’ve never seen it in practice.
      With #10, I found that the engine truck really needed to bear its part of the weight, otherwise it would find any excuse to wander off-piste. So working equalization is as important as weight on the drivers.

  5. A friend of mine bought a box of steel (maybe tungsten?) filings at Princess Auto. The box is barely a cubic foot in size and it’s heavy. Of course, being metal filings, it’s quite dense. We had a vision of pouring this metal filings (powder-like) into tight crevices in models, such as along a centre sill. I would imagine it could be locked into place by wicking some thin CA glue into the area.

    Might be useful for cramming a bit of weight into all the right places on this model.

    /chris

    1. Thanks for the idea, Chris.

      Wow, a cubic foot of tungsten would be 545 kg! That would be some serious weight in a little engine.

      Actually, you’ve reminded me that Eileen’s Emporium used to sell something called “liquid lead” which was essentially lead shot. I have a bag of it in my nasty chemical supply.

      My plan for the weights is to create molds for them, pack them with as much tungsten as I can fit, and pour Cerrobend or lead around the tungsten.

      1. Yup. That would be heavy. I was so wrapped up in trying to describe the product…sorry.

        I had a vision of a homebrew version of JB Weld based on this material which sounds a lot like the Eileen’s Emporium product you’re describing.

        /chris

      2. No need to apologize, Chris. The approach sounds reasonable to me, and thanks for reminding me of that bag of lead! I wonder what is in that box your friend bought?

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