How to make Decent Curves in Surveyor

Dreadnought · Posted: Sun Aug 10, 2003 4:03 pm

Folks,
Having had a look at a lot of layouts in Trainz, one thing I noticed was that the curves most had were pretty unrealistic, even on some of the prototype based layouts. With only a ruler to work with, curve building had been awkward.

Since I started looking at doing an accurate version of a branchline using Trainz Surveyor, I've been thinking about a way of doing these so they didn't look like a dog's hind leg....

Having looked at a number of original surveys from the 1880's in Victoria - Buninyong, Waubra, Daylesford (via Creswick), Scarsdale and Port Fairy - I noticed that the surveyors liked to keep things simple.

They always followed a curve with a straight (with one exception at Daylesford where they had to sort out the junction) even if the straight was tiny (one on the Buninyong line was only 10 feet long). So by default, a curve is simply the bit of track that separates two straights that point to the place where they'd intersect (which I'll call the "focus") and the points where the curve starts and ends are equidistant from that hypothetical focus.

Using this theory (which is really just simple trigonometry), I've can work out the start and end points and the intersection point for any curve. Better still, with a bit of calculation via a spreadsheet, only a ruler is needed to set it up. This enables fairly accurate curves to be laid out.

For example, the second curve on the Buninyong line is a 346m long curve with a radius of 402.3m gives means that the start and end points are 335.4m apart and the distance from the start/end point to the focus is 184.5m (there's a bit of rounding there but you get the idea). Beginning with a piece of straight track running up to the start point, you lay out a ruler 184.5m straight ahead from the starting point (which gives you the focus, put down another 184.5m ruler from the focus to around where you think the curve should end and then lay a third ruler 335.4m long from the start point to where the second 184.5m ruler ends. You may need to play around with these final two but when they match up, you have your end point. Lay a piece of track from the focus over and beyond the end point (be careful to be precise), add a spline point right at the end point, hit the track beyond the end point with the "straighten" function, delete the 184.5m of track from the focus to the end point, then lay track from the start point to the end point. If you've done it accurately, you should get a pretty good looking curve.

The same sort of theory can be used for setting up straight track where the bearing line of the track is known. Simple triangle solving does the trick.

Well, I've been waffling about this 'cos it's fairly complicated to explain but I haven't seen anyone using this method or any mention of it elsewhere so I hope this is of use to those railfans wanting to make accurate models of their favourite lines.

I'm currently doing the Buninyong branchline and I'll send it to the download station at Auran when it's ready.

If you're interested to know more about "curve theory", let me know and I'll send you info.

Cheers,
Frank S

Lt-Cdr Dreadnought - Lithgovian Military Attache to South West Victoria and the Tholian Assembly

Five.....
Four....
Three...
Two..
ONE!
Thundergunzels are GO!

Dreadnought · Posted: Sun Aug 10, 2003 8:14 pm

Here's a few screenshots - hope these help explain the system.

The 930 & train are traversing the double curve shown in the second screenshot.

Cheers,
Frank S

[img]a:\1curveb.jpg[/img]
[img]a:\2curveb.jpg[/img]
[img]a:\930_2c.jpg[/img]

Lt-Cdr Dreadnought - Lithgovian Military Attache to South West Victoria and the Tholian Assembly

Five.....
Four....
Three...
Two..
ONE!
Thundergunzels are GO!

K163 · Posted: Sun Aug 10, 2003 8:31 pm

they don't work, you have to upload them to a web site hoster somewhere, and link the pics.

Regards,
Craig Walton
What I say here is my thoughts, and doesn't represent the MRPS or Woolworths ltd... smeg imagine it did!

If you want to loose weight, don't eat anything that comes in a BUCKET!

Dreadnought · Posted: Sun Aug 10, 2003 8:42 pm

Bugger!

Don't have a website I'm afraid I can't post them just yet.
They'll turn up when they turn up.......
Cheers,
Frank S

Lt-Cdr Dreadnought - Lithgovian Military Attache to South West Victoria and the Tholian Assembly

Five.....
Four....
Three...
Two..
ONE!
Thundergunzels are GO!

K163 · Posted: Sun Aug 10, 2003 8:49 pm

well if you want to know how to get pics to bee seen here, look at James's tuturol in the MSTS general section.

Regards,
Craig Walton
What I say here is my thoughts, and doesn't represent the MRPS or Woolworths ltd... smeg imagine it did!

If you want to loose weight, don't eat anything that comes in a BUCKET!