Klaynos Posted June 2, 2008 Share Posted June 2, 2008 Let me state it clearly, metal over metal in case of metal wheels of a locomotive over metal rails never produce friction! --------------- eric This is just wrong. It's pretty trivial to show it's wrong even the fact that you can have collapsible aerials hold them upright and they DON'T collapse straight back down show that this is just crazy talk.... Friction being reduced is why there's always problems in the UK in the autumn with leaves on the line.... they reduce the friction and stop the trains breaking ability... or accelerating ability... Link to comment Share on other sites More sharing options...
John Cuthber Posted June 2, 2008 Share Posted June 2, 2008 If metal on metal friction wasn't significant car engines wouldn't need oil. Just because you don't like reality doesn't mean reality is wrong. Link to comment Share on other sites More sharing options...
tvp45 Posted June 3, 2008 Share Posted June 3, 2008 I have been thinking too much about generalised concepts! Equations in physics might be solving every querry. But ask yourself a huge metal wheels of a locomotive if turned by the axil of an engine, then the force might have been produced with accumulating weight which combines with the momentum of the locomotive! Then when it comes to stopping the train, might be that the axils were applied pressure for lowering down the speed! But if not then the locomotive should be going forward on its own weight! Might be that the friction that we are discussing would be even negligible! Then how come the locomotives stop and even start so smoothly! ------------- eric Bellbottom, Were you to look at old movies of the big N&W coal locomotives, you would find your answer. Sometimes the crank (I guess that's the right word) would be near the top dead center position at start and the engineer would give an extra shot of steam to move it off. Often the driver wheels would spin like crazy for a second. The trick was to start and stop slowly. By the same token, the maximum grade was generally under 2%; on steeper grades, there was a sandbox in front of the driver wheels to help. But, the coefficient of friction for steel on steel is fairly high. Rent the DVD Emperor of the North to see how hobos used to slow trains on grade. Link to comment Share on other sites More sharing options...
imp Posted June 3, 2008 Share Posted June 3, 2008 If the contacting surfaces of the wheels and rail did not DEFORM under the imposed load, the AREA of CONTACT would be zero, that is, a a straight tangent (rail) to the curve of the wheel. If contact area were zero, no force could be transmitted. However, in reality, the metal surfaces deform elastically, the amount depending on the load; the finite contact area thus produced allows the transfer of forces from wheel to rail. The same concept is applied in ball bearings- the raceway curvature is slightly LARGER than the bearing balls, which deform under load and lose their shericity to conform to the raceway. Exagerrated, did you know that bearing balls assume an egg-shape under load? imp Link to comment Share on other sites More sharing options...
insane_alien Posted June 3, 2008 Share Posted June 3, 2008 imp, area doesn't come into it. it cancels out because the less area you have then the more pressure. the areas cancel and you are left with the normal force, and, assuming the mass doesn't change considerably, this is a constant. Link to comment Share on other sites More sharing options...
bellbottom25 Posted June 3, 2008 Author Share Posted June 3, 2008 Sorry for interrupting foolish people discussing! But i still say that there is no friction between the rails and the wheels of a locomotive! Imagine the wheels of an boeing of metal, and you all stupids would still be discussing about friction? -------------- eric Link to comment Share on other sites More sharing options...
iNow Posted June 3, 2008 Share Posted June 3, 2008 Sorry for interrupting foolish people discussing! But i still say that there is no friction between the rails and the wheels of a locomotive! -------------- eric And you're still wrong. Why are you the one calling others foolish? Link to comment Share on other sites More sharing options...
bellbottom25 Posted June 3, 2008 Author Share Posted June 3, 2008 I am always absolutely correct! ----------- eric Link to comment Share on other sites More sharing options...
insane_alien Posted June 3, 2008 Share Posted June 3, 2008 bellbottom, we have given you experiments you can try yourself in your own home that show that there is friction between metals. you are the foolish one if you can not see what is right infront of your face. have you even seen a close up of a metal surface? even if it looks mirror smooth it has lots of ridges on it. these cause the friction between metals. no amount of name calling will change the fact that there is friction between metals. I am always absolutely correct! evidently not. a little humility would be good for you. Link to comment Share on other sites More sharing options...
bellbottom25 Posted June 3, 2008 Author Share Posted June 3, 2008 And i say again shut up very nicely you all low caste foreigners! ------------- eric Link to comment Share on other sites More sharing options...
Phi for All Posted June 3, 2008 Share Posted June 3, 2008 I am always absolutely correct!Then please go away, the rest of us are human. I'm not sure why you insist there is no friction between metal when there are so many experiments you can perform with items all around you. As insane_alien says, take a metal tray and put a coin on it, then tilt the tray 15 degrees. If there were no friction the coin would slide to the edge of the tray. Since it doesn't, what's holding it still? Friction. And since you have not responded to any of the questions put forth, and still just keep repeating you're "absolutely correct", even though you can't tell us why, I'm closing this thread as a big waste of time. bellbottom25, next time you ask a question, be prepared to discuss why you reject the answers you receive. Otherwise you're just a troll. The Flaming post above has earned you a 3-day vacation. If you can't be civil, please don't come back. Link to comment Share on other sites More sharing options...
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