How to Identify track size

[Anonymous]

Paul,

Thanks that helped, it is 11 inches.

 

Mike

[pbjwilson]

I Just measured the straight section of my O42 MTH switches and they are 11" long. I think the O54 and O72 switches are much longer. Hope that helps.

[jimhaleyscomet]

If you are a regular customer at a friendly hobby store you could compare to the switches they have.  Or if you have a friend that has the longer curve MTH track, check it against theirs.

 

Jim H 

[IRONROOSTER]

If the math above looks a little overly involved you could draw each of the possible MTH curve radii on a sheet of paper using a straight piece of wood as a trammel.  Then see which one your switch center rail matches.

Enjoy

Paul 

[lionelsoni]

If you can figure out how many of the curved sections make up a complete circle, you can calculate the radius.

Measure the chord length between the ends of the center rail of the curved section. Then divide half of this by the sine of half the angle that that piece would occupy in a circle, to get the radius to the center rail. For example, with 8 pieces to a circle, divide half the chord by the sine of half of 45 degrees, which is 22.5 degrees, or .382683. With 12 pieces to a circle, divide by the sine of half of 30 degrees, which is 15 degrees, or .258819. With 16 pieces to a circle, divide by the sine of half of 22.5 degrees, which is 11.25 degrees, or .19509. Be sure to measure the chord exactly between the centers of the ends of the railheads (excluding any track pins, of course). This method is not very sensitive to whether the track has been bent a little to another curvature, especially for the gentler curves--it will tell you the original or intended radius. But, if you have any worry about that, pretend that you have divided the piece into two equal parts and measure each part separately, using the sign of half the halved angle, then average those two results. Here's an example: Suppose we have a piece of ordinary O27 curve. We measure the chord and find that it is 9 9/16 inches, or 9.57625. We divide that by 2 to get 4.78125, then by .382683 to get 12.494, which we round to 12 1/2 inches, the actual radius of the track, to the center rail. If we want the nominal diameter, we double that radius to 25 inches and add the length of a tie, 2 inches, to get 27 inches.  Or:

Measure the chord and multiply it by the magic number. The magic number is 1.306563 for 8 pieces to a circle, 1.931852 for 12 pieces to a circle, and 2.562915 for 16 pieces to a circle.

[Anonymous]

I was at a grage sale and bought 2 MTH swithces a left and a right.  There is no size on the back all it says is Patent pending.  I have O31 and the curve is not the same.

 

Thanks

 

Mike