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Forces DerailBuffer and DerailRail

Started by Yankee15 7 posts 4 min read

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Yankee15Member since Sep-26-04 · 12 posts

I'd like to know how the sim treats these two, so I can have it respond the way it should. I'm assuming DerailBufferForce is for coupling events and DerailRailForce is for non-straight track, ie:curves and turnouts.4 MPH is the accepted standard coupling speed before damage to the lading begins, not when the car derails, like in the sim.Overturning speed on curves is generally more than twice the speed of a curve's posted limit.There are four general speeds associated with curves.1)Equilibrium speed -- A theoretical ideal speed2)Comfortable speed -- The maximum speed at which no unpleasant sensation of unballance is felt within the vehicle3)Maximum Safe Speed --the speed at which the resultant of vehicle weight and centrifugal force falls at the extremity of middle third of the track gage, ie: 9.417 inches outside the center line of the track for standard gage 4'8-1/2".4)Overturning speed -- The speed at which the resultant falls at the point of contact of the wheel with the outer rail, when any further displacement of the of the resultant woud effect an overturning moment.Those speeds for a curve of 6 degrees (955' radius) with 3 inches of superelevation, such as the actual curves on Cajon Pass are:Equilibrium--27
Comfort--36
Safe--47
Overturning--72The speed limit on the actual Cajon Pass track is 30, which you can see is set between the equilibrium and comfort speeds.One thing is for sure, real trains will not derail at 1-3 MPH above the speed limit as the Sim models (out of the box) do.I see where NERR has established a standard for DerailRailForce of 2.5 times the Mass figure for a particular vehicle, but they are fudgy on the figure for DerailBufferForce." ( d ) DerailRailForce is set to 2.5 x Mass "
" ( e ) DerailBufferForce is adjusted to take into account the type of car and the mass."

(technical data obtained from "The Steam Locomotive" by Ralph P. Johnson, M.E. - Chief Engineer - Baldwin Locomotive Works - Copyright 1942

Regards,
Nick

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RE: Forces DerailBuffer and DerailRail, plainsman, Oct-10-04, 04:25 PM, (1) RE: Forces DerailBuffer and DerailRail, ctillier, Oct-10-04, 10:01 PM, (2) RE: Forces DerailBuffer and DerailRail, Yankee15, Oct-11-04, 01:27 AM, (4) RE: Forces DerailBuffer and DerailRail, Yankee15, Oct-11-04, 01:21 AM, (3) RE: Forces DerailBuffer and DerailRail, GaryG, Oct-11-04, 07:25 PM, (5) RE: Forces DerailBuffer and DerailRail, steam4me, Oct-12-04, 05:25 AM, (6)

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ctillierCharter Member · 430 posts

RE: Forces DerailBuffer and DerailRail

Hello,The DerailRailForce is a centripetal force threshold, arbitrarily set at some value. If you hit it, bang you derail.I've found the most intuitive way to enter it is like this, using explicit SI units:"3.5m/(s^2)*68t" In this case 3.5 m/s2 is the centripetal acceleration, or velocity squared divided by curve radius. (velocity in m/s and radius in m).As a somewhat unrelated aside, AI trains respond strongly to this parameter at very high speeds... evidently the AI physics take into account the mass of the entire train in figuring the force and comparing it to the threshold, resulting in heavy slowing for curves. Fudging the values upwards is the only way to get AI trains to behave correctly near 200 mph.cheers

--
Clem
Forces DerailBuffer and DerailRail – image 1
http://www.tillier.net/speedworks/index.html

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Yankee15Member since Sep-26-04 · 12 posts

RE: Forces DerailBuffer and DerailRail

LAST EDITED ON Oct-11-04 AT 01:28 AM (EDT)

Thanks Clem.I don't do a whole bunch of activities, so I don't worry much about AI trains. And my trains don't get anywhere near those speeds on the routes that I normally run. I like heavy freights on heavy grades.Speed kills!

Regards,
Nick

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GaryGCharter Member · 300 posts

RE: Forces DerailBuffer and DerailRail

Hi Bob, clarification please:>Try:
>DerailRailForce is set to 2.7 x Mass
>DerailBufferForce is set to 2.86 x Mass
>Bob For a Mass ( 100t ) piece of equipmentAre the following what you're saying?
DerailRailForce ( 270t )
DerailBufferForce ( 286t )I want to confirm you're using 't' rather than 'kN'.Thanks,
GaryG

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steam4meCharter Member · 317 posts

RE: Forces DerailBuffer and DerailRail

I'd suspect Bob means 2.7 times mass in tonnes expressed as kN, so using your example above...For a Mass ( 100t ) piece of equipmentDerailRailForce ( 270kN )
DerailBufferForce ( 286kN )RegardsYuri.
(steam4me)
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