I am intrigued by the force/load limitation. I have wondered more than once about the traction afforded by the relatively tiny footprint of a polished steel wheel on a polished steel rail. Is the force/load limitation primarily a matter of overcoming inertia to get the load moving in the first place, or is it a more continual problem of overcoming friction and wind resistance to keep the load moving down the track? Does traction take a big hit from rain-slick track, or is it a marginal degradation? Now where are we going and what's with the handbasket?
Ha! First time I see this expression. What is/does a shade tree engineer?
Is the force/load limitation primarily a matter of overcoming inertia to get the load moving in the first place, or is it a more continual problem of overcoming friction and wind resistance to keep the load moving down the track?
That depends on speed and grade :-)
On high grades, most of the tractive effort (the locomotive's/motor car's/EMU's/DMU's pulling force) is needed to hold part of the train's weight [weight times the grade], at any speed - that is, inertia has primacy.
As for train resistance on flat terrain: until say 160 km/h (depends on the train), rolling resistance (e.g. wheel-on-rail and bearing friction) dominates. For higher speeds, it's wind resistance.
Now, all the above are part of static train resistance. If you subtract them two from the maximum tractive effort at a given speed (the one allowed by adhesion and the train's maximum power), you get the force that can be used to accelerate the train. (You get acceleration by dividing that force with train mass.) This dynamic train resistance can matter, too (e.g. for rapid transit trains).
Does traction take a big hit from rain-slick track, or is it a marginal degradation?
A rather big hit, to the tune of 40%. *Lunatic*, n. One whose delusions are out of fashion.
Shade tree engineer is a play on the term shade tree mechanic, an amateur mechanic who works on his own vehicles in the shade of a tree in the yard. That's a common term in Oklahoma, and I imagine elsewhere. The men in my family tend to take it a bit farther than that. Most of them imagine they could do a better job than the professional engineers who design things. My dad routinely modified his farm implements to make them work better. His brother parlayed a degree in agricultural education and a knack for pragmatic solutions to mechanical problems into a rise from day laborer at a power plant to plant superintendent. Now where are we going and what's with the handbasket?
