Well, not too strange, I remember seeing a quote about how many square inches actually touch the rail on a 100 car freight train, the answer is phenominally small, I’ve tried evreywhere to find the solution,any answers?
A good approximation is 2 square inches per 100 tons (200,000 lbs) (gross), which is represents steel wheels on steel rails, with the steel having a yield strength of 100,000 psi.
Wow, that is small! It’s just like the time a golf club is in contact with the ball.
Trainboy
Any wonder why a train will take so long to stop, even in full emergency braking. On top of that, there’s the traction of steel wheel to steel rail (or lack thereof).
as far as i can think tom its sheer momentum and after the wheels lock up its basically floating on the rail not really getting alot of traction
I wonder if a train wheel gets a flat spot after locking up and sliding to a stop from full speed?
yes it does
It also may burn the rail after a number of wheels have slid over one spot. The track gets HOT!
wheelslip can cause VERY serious damage to trackwork, beleive me, a diesel railcar weighing only 50 tons or so was driven very hard by its novice (driver) engineer whilst stood still on wet track, result - 2" deep ruts in the track and melted wheels, it litterally welded itself to the spot and had to be removed by a crane onto a semi trailor and taken away by road[:-^]
This question is also closely related to the overall low cost of shipping by rail. No other mode of transportation has the low friction components of round steel-to-flat steel, not even boats in water.
The wheels on trains do compress (they have to or the metallurgy would not withstand the forces and the wheels would shatter…if I understand correctly), but it is many times less than a high pressure bicycle tire would on a road racer…and they don’t compress much!
Flat-spotted tyres can be a real problem in colder climates - brakes can freeze on, and this may not be noticed (if it’s one or two axles in a 5-car train, the drag won’t be that obvious). Some of the Swiss metre gauge lines paint yellow marks onto wheels to allow train crew to check if everything is rolling properly after a station stop - this may be a common technique elsewhere too.
I have not noticed this in Canada, Matt. We run trains 24/7 at -36 deg Celsius in prairie winds, and I have yet to see a train wheel painted with stripes or marks as some airlines paint their engine spools.
Heheh…Had to laugh at the thought of a 100 car train with stripes on all the wheels passing in front of me at a railroad crossing!! Wow!! Talk about psychodelic!![%-)]
Matt I had seen the paint stripes on a few freights before in NW Ohio… didn’t know what they were for until now! Thanks!
underworld
[:D][:D][:D][:D][:D]
I think it might be a case of Canada being too cold for the problem to arise - as I understand it, it’s caused by the brake shoes heating up when applied (melting the ice) then cooling (allowing the ice to reform). Minus 36 is well below winter temperatures in the Alps so it may be that the ice doesn’t get a chance to melt in the first place!
I don’t know about trains, but as a former truck driver, many companies encourage the drivers to paint a white or yellow stripe on the trailer tires as a reference to make sure the brakes do not freeze when applied. I could see the profit of doing that on a train as well. I assume that the ETD would fill that role.
Randy
O.K. Explain to me how painting a stripe on a tire will prevent brakes from freezing, don’t tires and wheels rotate? this one has me really puzzled, maybe the traffic guy who marks tires with chalk doesn’t realize he’s doing them a favor. please explain.
The strip is just to make it easy to tell if the wheel is rolling or being drug from a distance. It is diagnostic not curative.