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"HONGZ" stands for HO scale, N scale, G scale, and Z scale.

Post your non-O scale stuff here!

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Not to belabor this or embarrass my high school geometry teacher, but in my world diameter is defined as the straight line through the center of a full circle so, by definition, a semi-circle cannot have a diameter. The straight edge of a semi-circle is simply the diameter of the full circle from which it came but it cannot, itself, have a diameter.  

That's my story and …….


Boy this sounds like beating a dead horse.     Simply measure across the half circle with a yard stick in inches, and then divide the result in half (ie by 2).    If  you come up with 36, your raidus is 18, if you come up with 30, your radius is 15.     It is not necessary to take the track  up, why make work?

PLCProf posted:


All you need is 1 piece of curved track and a straightedge and a ruler as shown in the photo. Radius of this piece is about 18, it is O-36. 

No good - Too simple.......

Not that I am disagreeing, but you have to admit for the general trig class they don't assume the width of the line defining the circle would be wide enough to know which direction to point the ruler and straight edge to end up in the center.

Without the width of the track to guide us in how to hold the ruler roughly perpendicular at the ends of the piece of track, it would be easy to measure incorrectly with that method.


Last edited by Dave45681

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