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Hello everyone , I hope you can help me out with this. This there a formula for which if track 0 wants to curve off the mainline but the rest of the tracks keep straight? Lets say im traveling on track 0 and track 0 goes off to the left leaving the mainline. I would like to have those tracks keep straight while i turn off, Is their any proper formula to do this? Thanks

Adam

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RE: Question?, Stooopid_person, Nov-25-03, 11:33 PM, (1) RE: Question?, seaview69au, Nov-26-03, 02:11 AM, (2) RE: Question?, ferrovipathe, Nov-26-03, 06:50 AM, (3) RE: Question?, Stooopid_person, Nov-26-03, 08:13 AM, (4) RE: Question?, ferrovipathe, Nov-26-03, 08:39 AM, (5) RE: Question?, Stooopid_person, Nov-26-03, 08:44 AM, (6) RE: Question?, ferrovipathe, Nov-26-03, 10:01 AM, (7) RE: Question?, call2, Nov-26-03, 10:37 AM, (8) RE: Question?, Stooopid_person, Nov-26-03, 10:39 AM, (9)

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Look here
http://www.train-sim.com/dcforum/DCForumID17/284.html

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Hi All my first post, have been lurking for a while!!I use 2 formulas when calculating this sort of thing, to do what
your asking the formula is DX=Lsquared/(2*R)
Where DX = the offset at 25metre increments
L = the distance along the track in 25metre increments
R = is the radius of the 0 or "drive track". Use this one for
calculating the offset when you have a known radius.The second one is when you know how far you want to offset and need
to work out the radius to do it;
R=3.908*(Lsquared+4*Dsquared)/(8*D)
Where R = the radius required
L = the distance along the track-(usually 25 metre increments)
D = the offsetIt is very easy to setup excel worksheets to automatically
calculate these Hope this helps
John

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>DX=Lsquared/(2*R)
>Where DX = the offset at 25metre increments
> L = the distance along the track in 25metre increments
> R = is the radius of the 0 or "drive track". Use this one for calculating the offset when you have a known radius. Yes, your formulae is simple, useful, and have a smaller error than using sinus (because you are using arc of circle and not a straight line).>The second one is when you know how far you want to offset and need to work out the radius to do it;
>R=3.908*(Lsquared+4*Dsquared)/(8*D)
>Where R = the radius required
> L = the distance along the track-(usually 25 metre increments)
> D = the offset But, I don't understand your second formulae.It is very more simple to reverse your first one:
R = Lsquared / (2*Dx)For example,
Radius = 156.25 meters
So Dx = (25*25)/(2*156.25) = 2 metersand R = (25*25) / (2*2) = 156.25With your second formula, we got:
R = 3.908 * (625 + 4*4)/(8*2) = 156.56425With sinus formulae, we got:
Dx = 25 * sin (25/(2*R) {in radian} = 1.99786735 mand it is not simple to reverse formulae.Well done indeed. All the best.

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>With your second formula, we got:
>R = 3.908 * (625 + 4*4)/(8*2) = 156.56425
>
>With sinus formulae, we got:
>Dx = 25 * sin (25/(2*R) {in radian} = 1.99786735 m But 1.99786735 isn't far from 2.0!

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>But 1.99786735 isn't far from 2.0! Yes, it's nearly the same!But I think it is more simple to compute:
Dx = Lsquared / 2 * R and R = Lsquared / 2* Dx than Dx = L * sin (L / (2 * R)) (in radian).
You can do that by hand with pen and paper.And error is smaller, because that formulae use circle's arc and not tangente. (I didn't think about that )If I got some time, I'll rewrite my little explain and put it on my website.For a first post, a very good one.Congratulations and all the best.

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LAST EDITED ON Nov-26-03 AT 08:44 AM (EST)

>And error is smaller, because that formulae use circle's arc
>and not tangente. (I didn't think about that ) No, it doesn't use tangent, it uses sine!

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>No, it doesn't use tangent, it uses sine! I am sorry, it's sometime difficult for me to explain, because I am still thinking in french with maths, then translating.I mean: not tangent ( tan = sin/cos ), but circle's tangent. In reality, it is the string of the arc.When we are using sinus formulae, we take :
sinus of angle of deviation = offset / string of circle's arc.The formulae of John use directly circle'arc. There is a little difference between arc and string of arc's length, difference going smaller when radius increase.It is not really a problem with BVE, as that one put each 25m rail in a curve as if they are string of arc. (Remember, if you don't create curved rails, tracks' curves are broken in small strait sections.)The John formulae is more simple to use, and also more mathematical correct, because the train in reality follow a curve (here a circle).
Basis of compute is the same in the begining (how compute deviation's angle with trigonometry), but John go one step more than usualy, using directly arc's circle. And I didn't go so far, because I didn't think about that.(I am not a maths's professional) . And the result is a very simple and powerfull formulae, easy to use for every one, as a receipe if the explain is not understood.I'll explain more with graphics soon, it's only a little step more than usualy ( a line of explain, I think ). Give me the time of writing and posting.All the best.

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LAST EDITED ON Nov-26-03 AT 10:38 AM (EST)

There you go...I'll bet you didn't know that you would need a degree in applied mathematics when you started to design a route in BVE!Whew guys - you lost me at the first sentence, but maths was never a good subject for me. I do it the easy way (for me) and put down a 25m piece of track and see if it looks ok with respect to where the straight ones run. If it does, I put down the next piece adding a bit more to the deviance. If it doesn't look ok then I change the deviance distance.It's a good question though because when I need to try out some of these formuae I know that I can find the answer in this forum.

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LAST EDITED ON Nov-26-03 AT 10:39 AM (EST)

>When we are using sinus formulae, we take :
>sinus of angle of deviation = offset / string of circle's
>arc. Angle of "deviation"? Deviation means something like "different(not the same)"! You mean "elevation" or "depression"?
I'm too lazy to "think" anymore now!

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