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[Phys-L] Re: Momentum Agina



Ah ye of little faith! You KNOW that couplers must be dissipative,
but you cannot see it in the buckeye, which has a narrow range of approach
velocity for a clean closure. Actually new coupler designs of draw bars
are also stiff in US practise
<http://www.railwayage.com/mar01/drawbars.html>

The buckeye (Janney) is a massive sprung coupler.
Hit it at the right speed, and it can couple quietly.
Hit it slow and it won't couple. Hit it fast and it bangs hard.

But its strength (and therefore weight) holds off those destructive
peak stresses rather well.

Brian Whatcott

At 11:00 PM 12/6/2005, BC, you wrote:
I think Dan has the answer -- I'll add one more obvious item.

Very simply KE is dissipated until both are moving at the same speed
whether it's thru gross inelasticity (one ball is sticky putty) or it's
plastic (or not) deformation of a steel railroad car coupling, or
whether it's completed slowly or quickly.

The "maths" is so transparent I don't see anything more to it.

Because it's done so slowly and even then w/ a resulting jerk, I suspect
there isn't a "soft" dissipater.

Here's a page that may answer the soft dissipation question.


"In contrast[,] the Janney couplers (see below) encourage violent
encounters in order to engage the coupling fully."


Brian Whatcott Altus OK Eureka!
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