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| Re: R Train May Run 8 Cars Instead of 10...Re: Is There an Update on the R160's Wheel Wear Problem? (1640033) | |||
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Re: R Train May Run 8 Cars Instead of 10...Re: Is There an Update on the R160's Wheel Wear Problem? |
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Posted by Stephen Bauman on Sat Mar 15 08:50:37 2025, in response to Re: R Train May Run 8 Cars Instead of 10...Re: Is There an Update on the R160's Wheel Wear Problem?, posted by Train Dude on Fri Mar 14 22:50:41 2025. There's a tendency to believe if a system is tested for stability at the extreme values for a certain parameter, then all intermediate points will also be stable. In this instance, braking with no load and maximum load. This assumption isn't necessarily true, when the system includes energy storage elements. There could be resonance points which could be excited at intermediate loading levels. These are usually damped out.One exception was the PCC car. I had plenty of experience riding them during the time I spent in Boston during the early 1960's. Passengers loading and unloading would rock the PCC's from side to side. This was especially evident at Park St for cars going to Scollay Square and beyond. Both sides opened on this track. Many cars would completely unload and load. Operators would have to wait for the rocking to subside before proceeding. One effect that I did not mention is that braking will place more weight on the front truck and reduce the weight on the rear truck. The effect is similar in an automobile. If you brake hard, you will notice that the front end dips. This is due to braking deceleration is applied at the wheels but the car body wants to keep moving. The car body's continued forward motion will make it try to pivot at its connection to the axle. The magnitude of this effect depends on the location of the car body's center of mass. In particular it's proportional to the ratio of the CM's height above the track over its distance from the front axle. I would not think this should be a factor, given car body dimensions. I think it would be greatest when there is no passenger load. Then the weight of the roof mounted AC units would raise the CM's height. Again, just a solution looking for an appropriate problem to solve. |
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