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Thread: Question for TurboBill

  1. #1

    Default Question for TurboBill

    Hi Bill !

    A UK trainset vendor made me aware of this, using the rear cab of his HST the cars start to separate slightly as speed increases and there is severe jerking and juddering of the cars in the consist:





    My DASH-9 + 31 US2Freight + GP38 does the same when driving from the GP-38's imaginary rear cab, the rigid couplers moving but stopping short of separating !

    Can you check one of your trains which has a helper at the rear to see whether it's wagons have the same jerking problems when driving it from the helper's cab, using your couplers ?

    O t t o

  2. #2
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    Default RE: Question for TurboBill

    This issue has been addressed and will be greatly reduced in the next coupler release. I've been waiting for more testing results. Thanks to Joe Morris for his guidance on this one. Stay tuned. The problem is the train is now one big spring with little segments of the spring having stiff and no stiffness areas. With Joe's addition, the big spring is broken up into little springs, one for each car and the compound jerking effect is greatly reduced. You may still see a little with really big heavy trains and big power but the shudder is very minimal and a fair trade off for the realistic physics and slack.

    Also MSTS like uniformity, that has been discussed and confirmed. If you create enough uniformity, MSTS will be more forgiving in other areas as testing has shown.

    One area that has massive nonuniformity and actually laughable values is in the .sd file of many cars. In investigating these files, I have seen cars that sit way off to one side of the rail, their bounding boxes dragging on the rail and couplers completely enveloped by the bounding box.

    here's the formula I am using on the C&NW fleet and when you look at them in the sim with the Contol/number pad "+" buttons activated, are a thing of beauty bounding box wise.

    Bounding Box value (-1.5 (regardless of models width) 0.9 (makes sure the cars collidable object bottom does not strike the rail head on severe elevation changes) -xx.xx (one half the modes size length minus 0.3) 1.5 (plus width for the other side of the wagone) xx.xx (leave this hight number whatever the developr used) xx.xx (the same length value as the third one calculated the same but without the negative symbol))

    Use this formula and things seem to work much better in the sim. At least you know th ecouplers will uncouple and couple and the cars are uniform in width and height off the rail. With MSTS every little bit helps.

  3. #3
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    Default RE: Question for TurboBill

    Bill,

    Yuri Sos and Mike Simpson (Route Riter) spent considerable effort on bounding box and .sd file values. See http://steam4me.railpage.org.au/trai...ing_stock.html

    Recommend you co-ordinate with them and see if their values work better than yours or if yours work better, look into getting theirs updated.

    FWIW.

  4. #4

    Default RE: Question for TurboBill

    Hi Bill !

    These trains run perfectly when driven from their front units but not when driven from the rear cabs of trailing ones, units in the consists jerking and shuddering backward and forward.

    "Rigid" couplers should not move or jerk one way or the other when driven in any way and can't see that them doing it has anything to do with the other coupler settings ?

    O t t o

  5. #5

    Default RE: Question for TurboBill

    You might also want to consult this:
    http://www.trainsim.com/howto/boundbox.htm

    The rolling stock contained in my [/b]mp3kcons.zip[/b] has taken all this into account, as well as advise from other experts on the subject and it's Bounding Boxes are as perfect as can be ! ;-)

    O t t o

  6. #6
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    Default RE: Question for TurboBill

    A bounding box width of 1.5 is too wide for Otto's HST.

    For British stock it should be no more than 1.36 ( 9ft )otherwise it will crash on finescale track.

  7. #7

    Default RE: Question for TurboBill

    Hi Ian !

    Which HST are you referring too ? The HST-OTTO one on my web site is Bruce Bryant's Virgin HST which has these problems he asked to to look into and it's BB width is 2.79m, just covering the sides of the cars as it should.

    My HST's BB is 2.94m wide and again just covers it's sides.

    The issue here is the severe forward and backward jerking of carriages in a consist when being driven from their rear locos cabs.

    Try one of your trainsets like the JT-Intercity 125, JT-Eurostar, ICE-3 STP_DB_403, default ACELA or similar and you will find that the faster you drive from the rear cab the worse the jerking of carriages gets.

    I reported it to George and wanted to make sure that Bruce and I are not the only ones having this problem !

    O t t o

  8. #8
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    Default RE: Question for TurboBill

    Otto,

    As an experiment, try significantly reducing your stiffness and r0 values when using double coupler sections that both have the "rigid" line set to 1. You can even try setting both r0 values to 0 and both stiffness values to 1e5N or even less.
    Joe Morris, OVSRails Vice President
    OVSRails Engineer #2
    OVSRails
    OVSRails Forums

  9. #9
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    Default RE: Question for TurboBill

    Unfortunetly I never run European items. I know American Railroading cause that is what I ran. Ihave never checked these coupelr values for running the kind of operations you are describing. They work so far as desired in RW American Railroading situations. We don't go very fast with our freight trains over here. We also don't do cab swapping and run from a trailing unit unless it's a very rare situation. The bounding box width I use are obviously for American train widths. The point I was making is that MSTS like uniformity, I have found this to be true, but more so if you really look at all the rollingstock in your fleet you will be amazed at what you will fine and then understand why MSTS has problems. You look down an American train, all the cars and engines are the same width within a couple of inches. So I figured, follow that example. I found some rollingstock that was so close to the rail that if there was even a slight hump or aggressive drop off in elevation, the vehicle would actually strike the railhead and at speed derail. By raising to 0.9, the problem cleared so I have taken that to be a safe number. BTW most if not all the numbers and theories I have taken from past postings from experts who are here now and gone and test those theories with hours and hours of running. I have assembled the vr's fleet with the best performing theories and so far every single engine, and railcar has worked perfectly out of the box. I want to thank every single contributor to these forums and I have a long list of special people who have assisted me with this massive project. I will post that listing at C&NW when the project is completed and announced.

  10. #10
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    Default RE: Question for TurboBill

    Bill,

    I totally agree with as much "uniformity" as possible. However, I do tend to set the BB width's to match the rolling stock as closely as possible. One other thing I have found is that it seems to help to limit the number of "significant" digits. A BB width of 1.5 is much better than 1.48997, even if that is what exactly matches the model. And the .9 lower BB may be "overkill", but it was chosen as the approximate height for RW couplers. The lower BB must be at least .3 or higher, and a single standard does seem to work best. That is why my team chose the .9 when working on couplers long ago. There is some equipment out there that actually has a negative lower BB number, placing the BB below the track, which is sure to cause some problems in some routes.
    Joe Morris, OVSRails Vice President
    OVSRails Engineer #2
    OVSRails
    OVSRails Forums

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