Track Gauge Widening, All You’ll Ever Need to Know

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Will L
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Re: Track Gauge Widening, All You’ll Ever Need to Know

Postby Will L » Fri Apr 07, 2017 9:05 am

In a post elsewhere(click here to go back there)
andrew jukes wrote: The vertical loads in our 1/76 scale models are indeed roughly (1/76)^3 of those on the prototype - but so are forces that result from the model’s weight. The lateral forces on a wheelset running round a curve are a function of the vehicle’s weight, the radius of the curve and (the vehicle’s speed)^2. This means that for a vehicle running at a scale speed on a curve of an appropriate scale radius for that speed, the lateral forces on a wheelset are proportionately 1/76 lower than simple scaling would suggest. We take advantage of this by running trains relatively too fast on curves of modest radius (100mph on 1.4m radius in my case).


In this thread we discussed (at length!!) the need for Gauge Widening, and went on to discuss the related topic of under what circumstance the flange on the leading wheel into a curve will try to climb the outer rail. In that discussion we were never able to explain the observable fact that model trains happily go round curves at far greater scale speed than the prototype. Thank you Andrew for pointing out what we missed.

If you have just read the preceding few post on the performance of 6 wheel coaches and would like additional information, you will also find further relevant material by following the link to Andrews original post at the top of this and then reading forward.

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Noel
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Re: Track Gauge Widening, All You’ll Ever Need to Know

Postby Noel » Fri Apr 07, 2017 10:37 am

Guy Rixon wrote:* Models moved fast over very-irregular plain line. Seems to apply to all scales and standards, but especially to 00.


BR also had this problem, and on plain track in acceptable condition, too. Initially with Palvans in 1962, the problem spread to other types of SWB vans as well, and led to progressively lower speed limits being applied to such vehicles. Various experiments were tried with different types of springs, with only limited success, I believe. The problem went away when LWB vehicles with modern suspensions became the norm in the 1970s.
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Noel

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Martin Wynne
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Re: Track Gauge Widening, All You’ll Ever Need to Know

Postby Martin Wynne » Fri Apr 07, 2017 10:45 am

Noel wrote:BR also had this problem, and on plain track in acceptable condition, too. Initially with Palvans in 1962, the problem spread to other types of SWB vans as well, and led to progressively lower speed limits being applied to such vehicles. Various experiments were tried with different types of springs, with only limited success, I believe. The problem went away when LWB vehicles with modern suspensions became the norm in the 1970s.

The problem was thought to be caused by the change from flexible bullhead track to much stiffer flat-bottom track. After a lot of testing and experimental work, no real solution was ever found, other than not to use short-wheelbase vehicles at speed. There was general amazement that such vehicles had ever been run at express passenger speeds in bullhead days.

Martin.
40 years developing Templot. And counting ...


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