# Tunnel & Portal Clearance



## Matt Vogt (Jan 2, 2008)

I'm sure the info is out there somewhere, but I've tried a few searches in the new and archived forums with no results. Can someone give me advice on vertical and horizontal clearances for tunnels / portals for 1:20.3 with a 10' radius curve? 
I'm wanting to try my hand at modelling a stone portal./DesktopModules/NTForums/themes/mls/emoticons/shocked.gif
Thank you much,
Matt


----------



## altterrain (Jan 2, 2008)

Hey Matt,

A minimum of 7 inches wide and 9 inches tall will clear most rolling stock.

-Brian


----------



## Tom T (Jan 2, 2008)

*RE: Tunnel & Portal Clearance*

Hi Matt, 

Good question, and I'm looking forward to seeing what you accomplish in the way of a stone portal, as I have toyed with the same possibility myself. To date I only have one tunnel (on a straight) which presently has wooden portals. I model 1:20.3, and run Shays, Moguls, a Connie, and more recently a K-27. Here's what I have done: Tunnel portals (remember, on a straight) 7 3/4"W X 9 3/4"H. Comfortable on width without being overly wide. 9 3/4"H, which is probably just a little generous. Despite the 'K' the tallest piece of rolling stock I own is an AMS caboose which just clears a bridge which is 9" above the rail head. The 'K' is a little less than this. 

Like you, I have sort of standardized with 10' dia. corners. I do however have a helix at 8 1/2', and other hand bent corners at 11' -13' dia.. The 'K' while being about as fat as a Connie, has a longer wheelbase, and hence has a greater swing on the pilot. My tunnel is not on a curve, but the areas of my R.R. which have curves often have rocks either side. When the 'K' arrived, out came the angle grinder! I found the 'K' needed about 3 1/4" clear from the outside of the railhead on the outside of the corner in order to have clearance. This has not as yet taken into account expansion of rails in summer, and the resulting relocation of track, so use this figure as a guide, rather than gospel. 

I love the old narrow gauge look, of tight clearances, and narrow paths. Incumbent upon this thinking is the requirement to be responsible for variances in tight tolerances due to things like track expansion, which will literally 'Move' your track around. Lastly, curved tunnels can be done, but can also be a recipe for disaster if they are not big enough, or you don't provide access to remove a derailed train. They can be a real pain in the butt to re-engineer! Good luck with your portals, and make sure that you post some pictures! Inquiring minds need to know! 

Regards,


----------



## Dougald (Jan 2, 2008)

*RE: Tunnel & Portal Clearance*

Matt 

I too have 10 foot radius curves and model in Fn3. 

My experience is similar to Tom's though I do not have a K to test with. I found the overhang with a Connie even on these curves to be wide enough that I use 4.5 inches (11 cm) clearance from track centreline. My track is fastened to prevent movement and the expansion is taken up at railjoints so I do not worry about heat related movement. 

This clearance is more than is really required on straight sections. Brian quoted 7 inches which I believe is sufficient for all F scale equipment even standard gauge, but it is a bare minimum as it corresponds to just under 12 feet in prototypical width. 

As for height ... the standard of the day (early 20th century) for real railroads was 15 feet from the railhead. A height of 9 inches from the railhead will just clear the tallest F scale equipment from that era. Keep in mind that west of the Mississippi where railroads mostly predated settlement, bigger equipment was used. Even in ng, that crane or other specialized gear may be higher than 15 feet in the prototype. For that reason I use 10 inches as the minimum clearance. As Tom has pointed out, reengineering later is usually awkward so be a bit generous with your dims to start with. 

Regards ... Doug


----------



## Dan Pierce (Jan 2, 2008)

*RE: Tunnel & Portal Clearance*

I used 10 inches above the rail head for my tunnel. With my RR being on the ground (not raised) you can not tell that it is a little too big, but everything goes through with no problem. 

The width is around 7 inches. 

Widest rolling stock for me is the Aristo plow. Tallest is the C&S beartrap and a Bachmann 10 wheeler.


----------



## Guest (Jan 20, 2008)

*RE: Tunnel & Portal Clearance*

i agree more or less with tom. 
my tunnels were 235mm =/= 9" and 2/3 above the base of the sleepers. (highest LGB loco i measured was 225mm) 
and 150mm wide =/= 6" when in straights. in curves plus 1" on the inside, 1/2 on the outside. 

korm 
.


----------



## imrnjr (Jan 2, 2008)

The answers above are good for straight entrance portals and  tunnels, but I have two tunnels with decreasing radius curves in them.  After asking the same question that you have and getting similar answers that left me somewhat more confused,/DesktopModules/NTForums/themes/mls/emoticons/unsure.gif  I actually laid the curve out on the barn floor,  took the largest piece of rolling stock I had and measure the deflection from the centerline of the track at both the mid-line of the car on the inside and the ends of the cars and engines.

Once I had the greatest point of deflection I then I added 1 3/4"  on both sides to deal with equipment that might appear magically in the future.  This gave me a tunnel interior of 14"  with the track roughly centered thoughout the curved tunnel and portal entrances that are 12"H by 10" wide where the train is entering or exiting on the beginning of end of the curves.  

I run Big Haulers, a Three truck Shay, and a LGB Forney and various 22.5 (Bachmann)/24 (Delton-Aristo Classic)/20.3 (AMS and Bachmann) cars and have had no problems with any contact  into or out of the tunnels in either direction./DesktopModules/NTForums/themes/mls/emoticons/satisfied.gif

Good luck with the portal.

Mark


----------



## Matt Vogt (Jan 2, 2008)

Thanks for your thoughts, gents. I don't want to regret going to small, considering I plan to someday add a crane, etc. It sounds like 10"Hx9"W will be enough for the future.It may even be larger than a 10' rad curve.
I started cutting stone last night. Wow! It takes a lot of stone!/DesktopModules/NTForums/themes/mls/emoticons/tongue2.gif
I'll post my progress as it comes along.
I invested in a table top wet saw. I wonder if there would be a market for real stone portals at enough money to be worth building. Might help justify the saw to the wife.I am enjoying it so far.

Thanks again!
Matt


----------



## stanman (Jan 4, 2008)

Although my tallest loco is a Shay at 8 inches above the track, I made my portals 10.5 inches high in case I ever wanted to equip the tunnels with catenary.


----------



## JerryB (Jan 2, 2008)

*RE: Tunnel & Portal Clearance*

Matt: 

I have a clearance gauge based on RGS practice that I bought from Jonathan Bliese at Electric Model Works. It's 7 1/8" (12' in scale) wide x 10 3/32" (17' in scale) from the railhead to the top. These dimensions are designed to be used on tangent track. It does have various slopes at the top and at platform height, but I consider this the absolute minimum for my RR even though I wont be using large motive power. 

I also worked out a formula for added clearance for curved track based on the NMRA recommended clearances for the smaller scales, but can't locate it right now. If you are thinking big motive power, you will need all of the clearance you can get! 

Happy RRing, 

Jerry


----------



## Guest (Jan 21, 2008)

have a look:

(it is the only portal, i got a foto of)
five sleepers in the tunnel begins a home-made curve that has 1" less radius, than LGB R1 has.


----------



## coolhand (Jan 7, 2008)

*RE: Tunnel & Portal Clearance*

I have two tunnels, one above and behind he other, passing under a waterfall. I built the support structure from concrete block and pavers. I set the track 
(6' radius) in and ran a 1:20.3 accucraft box car though each level before putting the top on. 
My portal openings high. are either 9 1/2 or 10 inches


----------



## Richard Weatherby (Jan 3, 2008)

*RE: Tunnel & Portal Clearance*

I just measured the width of my K-36 and the running boards or each side of the boiler are 6-1/2 inches BUT the awnings over the cab windows hang out farther. The stack is 9 inches above the surface the track sits on. The metal carry case that comes with the loco is 9 inches wide by 10 inches high. It is dark and cold outside, so I can't measure my portals but I am betting 9 inches wide by 11 or 12 inches high. None of these dimensions account for curved situations. Engine and tender are 41 inches long, 26 inches are loco with almosts 9 inches from cow catcher to first drive wheel.


----------



## NTCGRR (Jan 2, 2008)

*RE: Tunnel & Portal Clearance*

I vote 9" X 10.5" and its a boy ,due in July.


----------



## N.S. Rob (Jan 2, 2008)

I would agree with Marty. I made mine 9x11. I cast my portals out of concrete. I used mortar and added Portland to make it stronger. I know a lot of people are working with plastic cement. I just used what I had laying around. I then  reinforced it with a coat hanger. It took a couple of pours to get it right. I made my forms out of wood. I found using grease on the wood acted as a good releasing agent. I had a problem with the arch always cracking. So I used some metal flashing around the arch. Before I took the form apart I made sure I could  pull out all the flashing. I will look for a pic of the portal.


----------



## Matt Vogt (Jan 2, 2008)

Oh, sure. Everybody says 9 x 11, now that it's too late!/DesktopModules/NTForums/themes/mls/emoticons/crazy.gif

Well, I made them 8 x 12. We'll have to see if that's enough. I really doubt that they will be on much of a curve, and I can always make sure they are on a straight away if they are not wide enough.
Marty - a boy in July?  Sorry if I'm issing the joke, or is this an announcement for a new railhand?


----------



## NTCGRR (Jan 2, 2008)

*RE: Tunnel & Portal Clearance*

folks usually say 9 pds , 10.5" long at birth,,, forget it, bad joke.


----------



## Matt Vogt (Jan 2, 2008)

Sorry Marty. Just speak slowly, and use smaller words. I'll catch on eventually./DesktopModules/NTForums/themes/mls/emoticons/blush.gif


----------



## jbwilcox (Jan 2, 2008)

I just built a new tunnel using Pressure Treated 2 X 12's,  This gives me an opening of about 8 1/2 wide by about10 high. Then I bought two Aristocraft foam tunnel portals.  I was worried they might be too small since they are 1:22 I think. 



However, when they arrived, they fit the opening of my tunnel perfectly.  I am very happy with the appearance.

John


----------



## Jerry Barnes (Jan 2, 2008)

*RE: Tunnel & Portal Clearance*

What would be the width of a tunnel with two tracks? Space in between? I have to redo my waterfall, the tunnel goes underneath, so I will make it a two track tunnel so I can have two separate loops. Jerry


----------



## Matt Vogt (Jan 2, 2008)

Posted By jbwilcox on 02/25/2008 9:32 PM


... I bought two Aristocraft foam tunnel portals.  
John



May I ask what dimensions the opeing is, John?

Thanks,
Matt


----------

