Tunnel portal dimensions and diesel overhang?

If you run steam, you should be looking at those, as many of them have much more overhang then diesels.

I'll be happy if a Hudson loco like the Polar Express will fit through it without me having to rip out or remake the portals. That's the biggest steamie I run.

A short section of straight track just outside each tunnel entrance will significantly improve things. It eases the clearance requirements substantially.

OGR Webmaster posted:

A short section of straight track just outside each tunnel entrance will significantly improve things. It eases the clearance requirements substantially.

The layout was made using Scarm leaving no room for any modifications. The tracks entering the tunnel on one side are pretty straight, I should have no problem there. It's the other side that are on the curve. 

I made some mock up tunnel portals out of cardboard, the opening is 6 inches tall by 5 or 5.5 inches wide. I'm just having a hard time figuring out how much I have to offset the portals to compensate for overhang. Maybe I should just install them with the track dead center and then Dremel out sides as needed?

If you want maximum clearance, offset the tunnel portal to the outside of the curve, that's where the maximum overhang will be.

gunrunnerjohn posted:

If you want maximum clearance, offset the tunnel portal to the outside of the curve, that's where the maximum overhang will be.

Oh alright, I was guessing it was the inside of the curve where the train hangs over. Good to know.

Just in case I think I will also cut the mountain tunnel at an angle that way the tunnel portals after following the curve, if you know what I mean.

Here's my Vision Line Big Boy on an O72 curve.  Note that it's barely over the inside of the Fastrack roadbed on the inside, but it's WAY outside the roadbed on the outside.

Jim Barrett did a great article in the OGR mag on this subject and even showed how we could make a jig for portal clearance. It would be well worth your effort to look it up.

gunrunnerjohn posted:

Here's my Vision Line Big Boy on an O72 curve.  Note that it's barely over the inside of the Fastrack roadbed on the inside, but it's WAY outside the roadbed on the outside.

Wow that's crazy. I appreciate the pic, it really gives me an idea of the overhang as it's real hard to tell from YouTube videos.

It looks to be about an inch of overhang, maybe an inch and a half to be safe. That'll take a big tunnel portal, looks like I may have to enlarge mine a bit. I don't have any plans of steamers that big but you never know. 

 Although that's a huge steamer and even with bigger tunnel portals I don't think there is any way that would still work on 0-36 track. I will probably just stick with the steamers like the Hudson, lol. Right now I only have a 4-4-2 and I have the 0-4-0 gold mine train on pre order.

gg1man posted:

Jim Barrett did a great article in the OGR mag on this subject and even showed how we could make a jig for portal clearance. It would be well worth your effort to look it up.

Ok I'll search for it. Thanks.

I believe the actual overhang when measured from the center rail was right around 3".  You probably want a tiny bit more to be safe, assuming O72 curves and scale Big Boys.   Obviously, if the VL-BB would run on smaller curves, the overhang would be even more absurd, but it's O72 minimum.

Would there be much difference in overhang between a 4 wheel truck, 14" Lionchief diesel when compared to a Railking 18" diesel with 6 wheel trucks? Or are both diesels relatively short in the front so there should be no issues?

Babajaga posted:

Would there be much difference in overhang between a 4 wheel truck, 14" Lionchief diesel when compared to a Railking 18" diesel with 6 wheel trucks? Or are both diesels relatively short in the front so there should be no issues?

Interesting question. I would guess that there would not be a conflict.  RK engines are mostly all scaled to run on O-31 turns though the overhang on some could be extensive.  

The Lion chief line are aimed at pretty much the same market. But as John stated above it's always better safe then sorry when building a right of way.  

What about passenger cars, is there any particular length I should stick with to avoid problems? I was going to get the 60' or 70' Alaska passenger cars but would they be too long? I'm also not sure if anyone makes a shorter Alaska passenger car, the 60' and 70' is all I have seen.