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Re: Question about train wheel construction for class
Re: Question about train wheel construction for class -- Cal3Student	Post Reply	Top of thread	Forum

Posted by: Mylo42 ® 09/14/2005, 22:25:34 Author Profile Mail author Edit

Actually Cal. When a train is travelling down the tracks at speed on a tangent (straight), it rides on the evenly flat portion of the wheels. Both the left and right sides are travelling at the same speed and the train goes straight. When a train enters a curve (say left hand curve in this eg.), the forward momentum of the train causes it to shift over, albiet very slightly, in the opposite direction of the curve. Basically, the train wants to keep going straight...basic physics. When this happens, the train is now running on the inner most part of the right side wheels. The inner flange on train wheels prevents the train from going too far and derailing. You will notice if you look, there is no outer flange on train wheels. If there was, it wouldn't allow for the shifting over that I mentioned as an inner and an outer flange would hold the wheel on the flat portion at all times, even in the curve. The inner most part of train wheels are bevelled in such a way so that it actually makes the diameter of the wheel at that portion, larger than the normal flat travelled on portion. As a result of the right side wheels now being, in effect, larger than the left side wheels, the train turns to the left because the right side is actually covering more distance due to it's larger size. While moving slowly, yes, you are correct, the entire truck (train wheel and suspension assembly) of the locomotive is turned hydraulically from controls inside the cab (steering the loco). I'm not sure if this explains what you need it to but....that's how a train turns. Mylo Modified by Mylo42 at Wed, Sep 14, 2005, 22:36:17

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Re: Re: Question about train wheel construction for class
Re: Re: Question about train wheel construction for class -- Mylo42	Post Reply	Top of thread	Forum

Posted by: Cal3Student ® 09/15/2005, 09:11:33 Author Profile Mail author Edit

Thanks so much for your response Mylo. I had done more research and did find mention that flanges kept the wheels from sliding during turning but it gave no further info as to why they kept the wheels from sliding. I'm not sure yet what my Cal professor was looking for but we'll get the test back tonight. It was actually a bonus on the test and I really feel better now to know that the flange plays an integral part. Thanks again for the info.

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Re: Re: Re: Question about train wheel construction for class
Re: Re: Re: Question about train wheel construction for class -- Cal3Student	Post Reply	Top of thread	Forum

Posted by: Mylo42 ® 09/22/2005, 09:42:36 Author Profile Mail author Edit

Cal, Glad I could help. I'm not an engineer (smart person who designs stuff OR the guy that drives a train), I'm just a model railroad enthusiast. I researched all this stuff when I built my model railroad as I wanted it to be as close to prototypical (model railroad talk for "the real thing") as I could. Yes, the flange is integral. Without it, the train would derail on a curve. Plus, as I mentioned, the taper near the flange is what actually causes the train to turn. Another component of rail design that I didn't mention is superelevation. This is where the outer rail on a curve is actually higher (not by much) than the inner rail which results in a bank. Superelevation will be designed into the curve after the train has started turning. The banking allows the train to take the curve at higher speed as it actually takes the stress off the inner flange. Much the same effect as a bank on a roadway allows a veh to travel it at a faster speed. ....oh ya...did I mention the geometric formula known as a cubic spiral ? This is the formula used to determine how many degrees the rail will turn given a certain length. It is a crucial part in designing, in particular, the switches (where the rails diverge to make another line). This formula comes into play when designing easements as well, which is the "curve before a curve". The easement, basically, "eases" the train into a curve as opposed to just instantly turning it a certain raduis. Make no mistake, the guys/gals that design railways are no dummies. Funny thing is, all these principles are used when model railroaders design their own scale empires. I learned a lot about geometry and engineering design just from having a "toy train". Hope you scored well on the test. I would actually be interested on how your prof scored your answer. Mylo

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