Going around the Bend !

[Keith1500]

I hope some who is good at maths can check this theory... !

My milk tank was a bit resistant to traveling though some pointwork when tested by Alan the other day.

So today i dropped the end wheels off and removed the washers I had put there to control end float. These measured in at 50 thou and so have now been replaced with 40 thou giving another 20thou end float.

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I placed a straight edge across the backs of the wheels and measured the difference when the end two were down and the middle one up.

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This gap measured 100 thou or 2.5mm.

Now in theory... using the cord / circle geometry...

R = h/2 + cxc/8xh
where R = raduis of the track
h = the height measured in the photo
c= the cord which is the distance between the outside two wheels

Run the calculation and I get...

R = 2.5/2 + 355 x 355 / 8 x 2.5
R = 1.25 + 126025/20
R = 1.25 + 6301
R = 6303mm or 6.3m / 20' 8"

So this wagon should be good for a 25 foot radius. I say that because I haven't allowed any calculation for the flanges though these may have no effect at all in which a 22 foot radius could be negotiated with out a problem.

Keith

[Dave Noble]

Keith,
I use a slightly different equasion, but it of course gives the same result, yes, your tanker should have no problem on 21 foot curves.
In fact, it should go round significantly tighter ones as you have not allowed for flange clearance, the gap between a flange and rail when the other flange is hard against the other rail. This clearance varies depending upon the radius of the rail head, but should be in the order of 70 thou on our tracks.
This theoretically allows your tanker to go round 12 foot radius curves as the centre axle has effectively 4.25mm of sideways movement.
There should have been no need to reduce the thickness of the spacers unless Alan was trying to negotiate very tight curves, he wasn't trying to go round one of the new "35 foot" radius turnouts was he?

[Alan Wood]

Yes we were trying on one of the mew points ,when we tried my 6 wheel brake van it was fine but Keith's milk tank became tight at the blade area , when we checked it had very little side play on any of it's wheel sets and no movement on its centre axel boxes . Where as my 6 wheel brake van has plenty of side play and had no tightening up on the points. In all our standards there is not any mention of how much side play there should be on any wagon let alone a 6 wheel wagon.