Templot Club Archive 2007-2020
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posted: 27 Oct 2014 11:59 from: LSWRArt
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How much 'slop' should be allowed between the wheels and the chassis? For example, I model using 0-MF track. If I have an 0-6-0 loco with a certain wheelbase (85mm) running on curves with a certain maximum radius (1200mm), how much movement should I allow on each axle? Is there a simple formula into which you can enter dimensions? This would allow me to decide how much movement to allow on the loco and also whether to gauge widen the track on the tightest curves. If so, can you easily extend this formula to something like an 0-4-4? Assuming minimal sideways movement on each of the axles, how much sideways movement should be allowed on the bogie for a certain wheelbase? I know this is not a track question, but it seems that the two are closely connected. Thanks, Arthur |
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posted: 27 Oct 2014 13:09 from: Nigel Brown click the date to link to this post click member name to view archived images |
The simplistic way of looking at this is this. Suppose that the gauge is sufficiently tight on the wheels that the wheels cannot move sideways on the track. Suppose that your 0-6-0 has equally spaced drivers, say L + L. On a curve of radius R then the central axle will need to move sideways relative to the other wheels by an amount S given by: S = R -SQRT(R*R -L*L) From the figures you give that's about 3mm. However..., the above is too simplistic. For a start, there is a certain amount of slop between track and wheels ie the amount a wheelset can move sideways on the track. This can easily be worked out from your standards. It may well be more than 3mm; if so, in theory, you don't need slop in the chassis. On the other hand, on a curve the wheels aren't parallel to the track, which effectively reduces the amount of slop you have. And if you work too close to the limits then you're liable to get binding anyway. As an illustration, I work in 3mm/ft using finescale 14.2mm track. I have a GWR pannier with virtually no slop in the chassis. The theoretical minimum radius it can go around is about 27". The practical minimum which it can reliably go around is 32" ie that's the absolute minimum radius I stick to. I don't use gauge widening; in practice I keep to 36" minimum or more, except on one siding where I stuck in 32" to test stock on. I'd suggest rather than use formulae that you knock up a bit of track at your proposed minimum and see how stock performs on it; you can quickly test if it's tight, or has room to spare. |
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posted: 27 Oct 2014 13:23 from: Jim Guthrie
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Another simple way of giving you an idea of what sideplay may be required is to use a CAD program, draw a circle of your required minimum radius, draw a chord on that circle the length of your wheelbase, then mark off on that chord your intermediate axle position(s) then measure perpendicular from the chord to the circle to give you half the movement required. This method assumes that the outer axles have little or no sideplay and all the sideplay will be on the intermediate axle(s). Jim. |
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posted: 27 Oct 2014 13:43 from: David Catton
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The table below is for 4mm=1ft vehicles but I'm sure a bit of work would produce a 7mm=1ft version. I confess I do not recall where I got this from but I suspect it was the CLAG website so I trust reproduction here is OK Table of theoretical minimum radius P4 curves Figures in the main columns (shown in inches) are the radii that a six wheeled vehicle will traverse. The figures in the top row represent the end float in the middle axle in millimetres, while those in the left hand column are the centre - outer axle distance (half the wheelbase) in scale feet.0.00 0.25 0.50 0.75 1.00 6 29.83 17.99 12.87 10.01 8.19 6.5 35.01 21.11 15.10 11.75 9.62 7 40.61 24.48 17.52 13.64 11.16 7.5 46.61 28.11 20.12 15.66 12.81 8 53.04 31.98 22.89 17.82 14.58 8.5 59.88 36.11 25.84 20.12 16.46 9 67.13 40.48 28.97 22.55 18.46 9.5 74.80 45.11 32.28 25.13 20.57 10 82.88 49.98 35.77 27.85 22.80 10.5 91.37 55.11 39.44 30.71 25.14 11 100.28 60.48 43.29 33.70 27.59 11.5 109.61 66.10 47.32 36.84 30.16 12 119.35 71.98 51.52 40.11 32.84 12.5 129.50 78.10 55.91 43.53 35.63 David Cundefined |
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posted: 27 Oct 2014 14:53 from: Martin Wynne
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Hi Arthur, For those who find calculating versines a bit of a challenge, you can measure sideplay by mouse action directly in Templot.  Go to: message 11596 Scroll down and begin reading at: "This mouse action can also be used to measure the centre axle sideplay needed on 6-wheel vehicles at different radii..." regards, Martin. |
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posted: 28 Oct 2014 15:16 from: LSWRArt
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Thanks everyone. Lots of different routes to achieve the same ends and all useful. Regards Arthur |
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