Tunnel problem

[pwjohnson]

I'm having trouble using AJS tunnel M and portal type M.

I'll call the track which comes with the tunnel the primary track, and the one which you have to lay yourself the secondary track. The tracks run roughly east-west, so I'll call one the northern track and the other the southern track. To start with the northern track is the primary one (it's eastbound, as I'm in the UK). The southern, secondary track is westbound. I'll call the short length of track inside the portal itself the portal track.

AI Trains on the northern (primary) track pass through with no trouble. On the southern (westbound, secondary) track they slow down to 11 mph (from 40 mph or 70 mph, depending on what the speed limit was) as they approach the tunnel exit, then at a point which seems to be exactly when the front of the loco is at the start of the portal track, they start to accelerate again.

At first I thought this was because of a slight break in the track at that point (which I could see using Alt-Y), so after some heavy excavations (the tunnel's now at the bottom of a spectacular gorge!) I relaid the southern track (trying this in both directions), with the same result. I then tried deleting and replacing the portal, joining the in-tunnel track before the external track, so that the portal track was generated from the in-tunnel track, again with the same result. Now there is no perceptible join in the rails, and still the AI train slows there. I've stared at the track from all angles using Alt-Y, and it seems perfect.

The above were done with the AI train told to drive via a trackmark some distance beyond the tunnel.

Other things I've tried:
- tell the AI to drive to some distant portal instead of a trackmark. This time it didn't slow at all!
- try the same tunnel/track configuration on a test baseboard. No problem; didn't slow on either track.
- manually drive a train along the southern track - no problem.
- send the AI train the "wrong" direction along the southern track. This time the AI train passed over the portal which has been giving the problems without slowing, but now slowed as it neared the other portal! In other words, the problem's always at the portal where it's just about to leave the tunnel. There's absolutely nothing visibly wrong with this track. One thing though, the point where it started to accelerate again was a few metres *before* the start of the portal track.
- relay the tunnel, so that the primary track is now the westbound track. Still the AI trains going either way along the southern track slow as the reach the exit portal.

In summary, AI trains driven either way along the southern track slow as they reach the exit portal. This happens whether the southern track is the primary or the secondary track. AI trains running either way on the northern track are OK.

I've tried adding and moving signals to no effect. The signals are always clear (including distants). There is one spline midway through the tunnel; all rail splines are yellow.

In desperation I also tried deleting the tunnel and portals, and just having track going through the gorge. This time the train went through the gorge at max speed - no slowing. I take this to show that there's nothing wrong with anything outside the tunnel gorge.

I'd appreciate any suggestions as to what else I could try!

Thanks, Peter

 

[stagecoach]

I had used those portals and had a problem on something I was playing around with. I placed the portals and attached invisible track and then removed it so the portal only used the invisible track. Then I just placed the main line track through the portal to join the tunnel track and not the portal track.

 

[pwjohnson]

Thanks, Stagecoach - I'll give that a try. The other thing I'd wondered was to change the in-tunnel track to be the same as the track used by the portal (if I can find out what it is - another one of Andi's I suspect). I'll try both later and report back.

Thanks again for the suggestion.

Peter

 

[stagecoach]

Think you will find that the portal track changes to match the track that joins it. Tunnel track wont work in that way, you have to actualy change the track kuid in the config file.

 

[cascaderailroad]

Oftentimes with problematic tunnels, that snap to grid, I change the config file track height to -1 ... add my own Dighole 1x1 the terrain ... and ignore the tunnels built in track, by covering it up with another track of my choice, at a height 0.20 above the original tunnels built in track.

To here are several Static asset Tunnel Portals, that you can apply a Dighole 1x1 t to the terrain.

Short segments of Stone Arch Bridge's can be used as a tunnel portal, also.

The Hold/Don't Hold-KB Shift key is a highly usefull tool to stop tracks from joining like mag gen nets'.

 

[pwjohnson]

With ref to Stagecoach's replies:

 I placed the portals and attached invisible track and then removed it so the portal only used the invisible track.

OK.

Then I just placed the main line track through the portal to join the tunnel track and not the portal track.

When I do that (either from inside or outside the tunnel), the portal track changes to the track I'm using. If from outside the tunnel I can then see two lots of rails for the one track. I'm obviously not understanding what you mean.

Think you will find that the portal track changes to match the track that joins it.

Yes, of course, you're right. It's just that it doesn't look exactly the same - the sleeper spacing is different, and sometimes the rail X-section does seem to be slightly different. I'm using Andi's track
JK Track A01-00-02 Default 2m

Re Cascaderailroad's reply:

Oftentimes with problematic tunnels, that snap to grid, I change the  config file track height to -1 ... add my own Dighole 1x1 the terrain  ... and ignore the tunnels built in track, by covering it up with  another track of my choice, at a height 0.20 above the original tunnels  built in track.

If you mean snap to the baseboard grid, these tunnels don't; you can have them at any angle.

But what you say sounds like it might be a solution - a bit kludgey (if that's how you spell it) - but it will nevertheless work, since I've already found that dispensing with the portals altogether and just using ordinary track all the way does work. You only need to dighole where the portals (or whatever you use instead of them) are don't you? You don't need to dighole all along the tunnel?

In the portal I'm using there isn't a track height in the config file. But couldn't I just lower the portal objects a bit? There is an "istrack 1" in the config - if I change that to 0 will it stop behaving (snapping) like a track? And then, as you say, I just use normal track over the whole shebang...

If this works (I'll try it) the only problem is having to excavate along the entire tunnel in order to add the track - or do you know how I can do it without having to do that? It's not just the excavating, it's putting it all back again... (though I suppose I can do it roughly by laying a temporary track with fixed spline heights along the top of the gorge, and then using the smooth spline tool). I have this distinct feeling that in future my engineers are going to find innovative ways round any hills that lay ahead, rather than tunneling through them.

Many thanks to both of you for your help.

Peter

 

[pwjohnson]

For the record, I've finally managed to get this right, based on cascaderailroad's suggestion (thanks again!). Briefly, this is what I did:
1. Position the portals. Lower them a bit (say 0.2m).
2. Lay the tunnel (I used AJS Tunnel M (no track)), with ends near the internal portal ends, then join it to each portal (snaps).
3. Lay each track from a point 20m or so outside one portal to the corresponding point at the other end. Fix all spline heights. (If the tunnel has one or more spline points along its length, the track must of course have corresponding spline points.)
4. Check that the grey portal stuff is beneath the track and not visible. If it is, lower the portal a bit more (not too much, or the loco chimney will disappear into the tunnel roof!).
5. For each track/portal, add a spline point near the interior of the portal and move it to be over the portal's interior spline point as accurately as possible.
6. Use the straighten tool for the track between this spline point and the corresponding end spline.
7. Move the end spline point so that the track is parallel to the portal, and follows the tunnel nicely. (Having the end point some distance from the front of the portal (point 3 above) makes this adjustment easier.) It may be necessary to iterate between the ends of each track to get this right.

 

[stagecoach]

Thats a hard way to do it. The portals already use the invisible track (The grey area is invisible) so wont show in driver. All you needed was to connect the outside track directly with the tunnel track then move the connecting spline to line up with the portal. The tunnel will not snap to the portal in this way nor will any track be attached to the portal.

 

[pwjohnson]

OK, I see that it's not necessary to lower the portal.

But I don't understand "The tunnel will not snap to the portal" - don't you want the tunnel to snap to the portal so that the tunnel walls appear continuous from the inside? When you say "to line up with the portal", where exactly do you mean the connecting spline should be moved to? Do you still need the straighten tool to get the angles right?

Sorry, obviously I don't fully understand what you mean - could you elaborate a bit please?

Thanks, Peter

 

[stagecoach]

Once you have joined the track to the tunnel you can move the tunnel into position and lined up with the portal spline points in the same way you lined up your track spline points. This gives you the same look as if the tunnel was connected to the portal. There are two types of tunnel, one snaps to the grid squares the other is flexible and is laid the same way as track would be. You might need to place a spline point 10m inside the tunnel to get it straight with the portal.

 

[JCitron]

There are some tunnel portals that are actually trackside objects like signals and switchstands. They look really nice, and may work for what you want to do.

John

 

[pwjohnson]

OK, thanks Stagecoach, I see what you mean now. I'll have a play next time I do a tunnel (this one's OK now).

Thanks also John, I'll take a look at them next time.

Peter