About a year ago SGMA members collected extensive data on the underhang and overhang of Standard Gauge engines and cars on curved track. At several shows menbers had noticed that some locomotives and cars with significant overhang and/or underhang made contact with each other on our corner modules when passing each other on our then standard 72 and 84 mainlines.
Obviously, a change was needed as contact is not something you want to happen between your expensive Standard Gauge trains. However, we didn't know how much change was needed to correct the problem. To determine this, SGMA members collected overhang and underhang data on our Standard Gauge trains going around our then standard 42, 72, and 84 mainlines and on a proposed replacement for the 84 mainline, i.e., an 87 diameter curved track mainline. Fortunately, the data collected indicated that replacing the 84 mainline with an 87 mainlne would solve the contact problem at least for the trains on which the data was collected. Based on this research, SGMA members voted to change our outside mainline standard from 84 to 87.
However, I should note that there may still be a contact problems between trains passing each other on SGMA's current 72 and 87 mainlines for those trains on which overhang/underhang data wasn't collected. For example, I don't belive data was collected on the Brute's new supersized passenger cars.
A table containing the overhang/undehang data for a lengthy list of Standard Gauge trains was developed but to date I don't believe it has been posted on the SGMA website. I will try and make that happen.
Bob
