Turntable Quirk

[ricksan]

There's an interesting discussion about turntable behavior over at TS.com having to do with the fact that the turntable bridge track sometimes doesn't align with the radial exit tracks. Otto Wipfel posted a few shots of the Hagen-Siegen turntable illustrating the problem. Another one of the posters suggested that this might be a new bug arising from the recent release of RailWorks2.

Actually this is a real bug, but it has been around for a while, perhaps even from the beginning. I believe the issue has come up some time ago on the UKTrainsim forum as well. The problem manifests itself as follows. When the turntable bridge is at its natural starting position and you drive a locomotive onto it, everything works as advertised except if you rotate the turntable 180 degrees. When the rotation is complete, the tracks are clearly misaligned. Interestingly, if you look closely the locomotive itself, it's aligned with the exit track, but not with the track on the turntable bridge. Despite the apparent misalignment, you can run the locomotive off the turntable with no problem. The misalignment is purely a visual phenomenon.

Not all turntables exhibit the problem. For example, the small one at Bath seems to work fine. I can only speculate that the problem might have something to do with the number of connection points, as this seems to be the only difference between the ones that work and the ones that don't. Having built a 40-connection turntable, and having encountered the same problem, I can tell you it has nothing to do with the turntable geometry. In my case, I have checked multiple times and I'm satisfied that everything is perfectly centered and aligned. I'm sure that's also the case with the Hagen-Siegen turntable.

Another possible cause of the problem may be the animation protocol. For the technically inclined, I'm using 20 key frames for the full 360-degree rotation and a Relative-Repeat Out-of-Range Controller. I've tried using 40 key frames as well (again, it's a 40-connection turntable), but with the same results.

If you're building a route and having this problem, here's a workaround. Position the turntable such that the bridge is aligned with a track you don't expect to use much, or where there will be no track at all. Then attach all the tracks where you need them. As a locomotive approaches the turntable, just hit the G key and the bridge will align to your track.


Default turntable position -- utility track.


Default turntable position, 180 rotation. Note apparent misalignment.


Alternate turntable position -- aligned to a primary yard track.


Alternate turntable position, 180 rotation. Properly aligned!

[ozinoz]

Rick...
Cant offer anything on the turntable issue, but your mention of a 40 connection turntable you have created piqued interest

Is this for a new GTrax release or something for yourself?? GTrax has been particularly quiet of late and a new steam project or route would be just the thing for the winter hours (summer here, but it is still not too much fun outside)

Hoping there is good news on the horizon

Thanks for all your hard work on past releases, it was great to see the level funds raised

Cheers from Down Under

G

ps: if for general release, is it likely to be big enough to get some steam on?? Maybe not 128' Big Boy steam, but GS4's, Berkshires etc Cheers

[g_nash]

Actually this is a real bug, but it has been around for a while, perhaps even from the beginning.

The problem existed pre-release , it was first noted at the demo presented by Kuju at the CG in Leipzig in 2006 .

[ricksan]

Since 2006? I don't know whether to laugh or cry!

Interesting question about the steam engines. This turntable is a 100-footer. The one at the Brooklyn yard in Portland is also that long, and the preservation guys there tell me the SP&S 700 wheelbase just fits on it, with parts of the tender and locomotive overhanging at both ends. So for fun, I ran the virtual 700 onto the virtual turntable. Sure enough, it just fits...



Unfortunately, the turntable doesn't turn! I would guess it has something to do with the bounding box, a property our virtual models have, but not one that the real-world engineers have to worry about. The Berkshire is only a little shorter than the 700, and it also overhangs. No, I didn't try the Big Boy!

You may have noticed the turntable's unusual through-girder structure. I had never seen one of those before -- most turntables are built with deck girders -- but I suppose this design was used in other places as well.

As for the route, these are of course blatant teaser shots. I'll make a more formal announcement in another few weeks.

[ozinoz]

You tease

Look forward to the details, but I am guessing a modern route seeing as you hadnt tried your steam

Cheers