In answer to Almo's question: Yes, the number of a turnout is the ratio of spread through the frog. As the frog number increases the length of the turnout increases. While I don't deal with long high-speed turnouts, from my experience the published "lead" of a #7 turnot is around 63 feet....that is the distance from the point of switch to point of frog. To figure out how much real estate you need to install a #7 you need to add the lead distance PLUS the distance to the clear point. If it is a diverging industry track you can fudge the alignment to fit what room is available; if the turnout leads to a parallel siding you need a lot more room to bring the curvature past the frog to an acceptable radius (shouldn't be any sharper than the turnout)to go back parallel with the main line.

A # 10 turnout has a lead of somewhere around 78 feet; longer turnouts need a LOT of room and are rarely used except on the mainlines. As a rule of thumb, you are allowed one MPH per turnout number on the diverging track; i.e., 7 mph through a #7; 10 mph for a #10. Mainline turnouts with premium components such as screw spikes, concrete ties, spring frogs, etc. allow higher speeds; self-guarded frogs generally stick to the 1 mph rule. All turnouts with one track tangent are designed with a short piece of tangent track through the frog on the turnout side, although it is hard to see in most of the shorter turnouts

Another factor I failed to mention in my original post deals with super-elevation. If the mainline is curved to the left, say, and the turnout goes to the right or "high side" you will always have reverse super to deal with on the diverging track. Depending on the class of track, this "warp" must be dealt with in order to correct the reverse super change going into the diverging track. Generally it must be several carlengths as the side bearing clearance must be able to acommodate the warp without lifting the wheels off the rail when the couplers limit the twist available.

One last thing; when designing track to handle the longer cars, it is important to have a long enough tangent between reverse curves to allow the cars to "straighten out" through the tangent section. It is also important to design in enough tangent track behind the frog to allow coupling on tangent track rather than in a curve so as not to "bypass" the drawbars which makes for much safer operations for the train crews. We see this as VERY important when operating with the new high-capacity reefers on sharp curves.

Enough for now; time to go put all this BS into practice!!!

Shortline Sammie