Well, for steam, freight could be anywhere from 63" to about 68" for fast freight. For passenger, it could be anywhere from 70" to 85". On branch lines, 44" and 56" drivers found some favor. I’m sorry, I can’t really answer for diesels.
Normal wheel size for first /second generation diesels is 40" , for later locomotives 42 and some 44" is used. Most MU cars these days run on 33 " wheels
Another interesting exercise is the change in acceleration of an automobile doing a head on with a train. Have both vehicles moving in opposite directions say a 18,000 ton coal train at 45mph and a nice shiney new Corvette going 80mph and 45mph almost instantaneously thoug in the opposite directions. The rate of deceleration of the train is calculable but not measurable.
A more interesting project for Mr. Feed: In the age of steam, calculate the optimal reduction in the size of drivers for e.g. a Pacific-type locomotive relegated to mountain service where the ruling grade is e.g. 2 per cent.
U.P. once had just such a problem; its standard Pacifics had 77-inch drivers.
No part of a moving wheel ever travels backward. If you attach a lite to any point on the rim of a moving wheel the lite does not describe a series of circles but an arc. The lite lifts off the rail rising to a height equal to the diameter of the wheel at half its circumference and falls again to the rail at a distance equal to the circumference of the wheel.
A point on the tread does describe an arc rising above and dropping down to the railhead. But a point on the edge of the flange drops below the railhead and describes a little loop (as the tread pivots on the railhead) between each of it’s arcs.
ValorStorm is right. As the point on the tread pivots, the point on the flange moves backward.
Lets try this. Draw a line from the top tread of a wheel to the point it contacts the rail through the center of the axle. The lite on the tread travels up and down this vertical line and the forward movement of the axle gives us the arc. You can draw this same line on the back of the wheel from flange to flange and a lite on a point of the flange will also travel up and down this vertical line, albiet on a slightly larger arc. You can see the same effect on a bicycle when a reflector is fastened to the spokes above the tire tread; it just describes a smaller arc than a lite lower down. Don’t forget the flange and the tread are inexoribly bound together, being a single piece of steel. The tread on a bike does not describe a little loop on the pavement.
ValorStorm was correct in answer to Old Timers question; the part of the tflange near to the point of contact of the tread is always moving backwards relative to the rail and train. The analogy using a bicycle wheel is incorrect as no point of the bicycle wheel is below the point of contact. It is difficult for many to understand as the diameter of the flange is only slightly greater than the diameter of the tread. Try an experiment with a large and small plastic jar lid attached back to back and roll the smaller one along a table edge, then you will see the truth of the maths.
I’m visiting my folks in St George Utah right now, and ya’ got me rifling thru my mom’s cupboards grabbing lids & plates & saucers. “Old Timer,” you started this! WHERE ARE YOU!? THIS IS MY VACATION DARN IT!!!