Brake Cylinder Dimensions

This topic has 3 replies, 2 voices, and was last updated 3 February 2012 at 07:32 by Chris Randall.

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2 February 2012 at 03:17 #83676
Chris Randall
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@chrisrandall69004
I am fitting a steam brake to the loco but I have overdone the size of the brake cylinder! Can anyone devise a formula for the cylinder diameter? I am not sure of the axle load and calculated it from a guess, making the pressure on the brake blocks equal to the weight carried by the driving wheels.
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2 February 2012 at 03:17 #5914
Chris Randall
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@chrisrandall69004
formula sought
2 February 2012 at 13:47 #83696
MICHAEL WILLIAMS
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@michaelwilliams41215
Hi Chris ,

I could show you how to do the calculation that full sized designers used but in truth for a model there are so many indeterminates that the result would not be very accurate .

I suggest that you do two things instead of calculations :

(1) Get information about steam brake cylinders on successful model designs and adapt and modify to suit your specific needs .

(2) Copy the principles and general dimensions of full size steam brake systems .

Notes :

Typical full size steam brake cylinders usually had bores in the range 4 inches to 9 inches .

Taking the larger size that becomes 9/16 to 5/8 inches for a 3 1/2 inch gauge engine and

3/4 to 7/8 inches for a 5 inch gauge engine .

Some full size engines had two steam brake cylinders – one each side and these were usually smaller .

The success of steam brakes in a model depends very much on the design of the brake valve .

MW

Edited By MICHAEL WILLIAMS on 02/02/2012 13:56:03
3 February 2012 at 07:32 #83735
Chris Randall
Participant
@chrisrandall69004
Hello Mike

Thanks for your helpful post.

Scaling down your suggested dimensions for 7.25 inch gauge I see that max size would be about 1.125 inches based on full size practise. I think mine is 1.5 inches. The ratio of all the linkages must be about 4 times increase in pressure.

It will be interesteg to see what happens when loco is fully assembled and running and I might have to sleeve the cylinder and make a new piston or else end up with square wheels!
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Brake Cylinder Dimensions

Brake Cylinder Dimensions

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