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Author Topic: grades and clearance  (Read 2771 times)
garyklein

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« on: October 28, 2009, 07:44:46 PM »

How much vertical clearance should I build into a tunnel?

Also, what is the steepest grade you would recommend?  Is there a grade standard?

Thanks

Gary
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Kevin Strong


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« Reply #1 on: October 28, 2009, 08:19:26 PM »

Inside the tunnel, I'd go with as much vertical clearance as you can get away with by however you're constructing the tunnel. That way you can reach in and around to pull stuff out that gets stuck. I'd go with 12" or more.



I used 2' wide cement patio pavers to form the tunnel on my old railroad. They're buried around 10" into the ground, so there's around 14" give or take above the rails.

You can use the portal to hide the fact that the interior of the tunnel is that wide open. I wish I had a photo of the stone portal I built  for this tunnel. You probably don't need more than 10" above the rails for the portal itself, and I'd go 7" wide.

As for grades, the usual recommended maximum grade is 4% (4" rise over 100" of track). Of course, the less steep the grade, the better.

Later,

K
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Loco Bill

Model Railroading since 1947


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« Reply #2 on: October 29, 2009, 10:33:46 AM »

If your tunnel will be fairly long, I would be sure to lay the track very solidly and use the longest possible track sections to minimize the number of track joints in the tunnel and use rail clamps as well.  It is no fun fishing a derailment out of a seven foot long tunnel.  Even with great care some critter might bring in some debris that will cause a derailment no matter how careful you are.    I use covers over my tunnel portals to keep the critters out as much as possible.
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Loco Bill,
Roundhouse Foreman
Missouri Western Railway

Unnofficial Historian of Bachmann Large Scale Products
garyklein

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« Reply #3 on: October 29, 2009, 01:21:30 PM »

I am planning a small tunnel on an indoor track, so it will be easy to lift it off for service.  I would like to keep it as low as possible in order to run another  track over the top.  What do you think the steepest grade would be that will work with four cars on?  I don't have a lot of length to make my elevation.   I don't think I can keep it under 4%

Gary
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MikeD95

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« Reply #4 on: October 29, 2009, 02:13:04 PM »

I am planning a small tunnel on an indoor track, so it will be easy to lift it off for service.  I would like to keep it as low as possible in order to run another  track over the top.  What do you think the steepest grade would be that will work with four cars on?  I don't have a lot of length to make my elevation.   I don't think I can keep it under 4%

Gary

Im working on a similar project (xmas display) with similar space constraints.

I found it useful to do a couple actual setups to ensure my design would even be possible.

Being an uber-novice my first trial had upwards of a 13% grade!  Cheesy

But I massaged the gradient down to about 7 or 8 and its runs pretty smoothly even pulling 5 cars.

Consider that even though the 4% suggestion is not the mechanical limit....more work will be required by your loco to cover the increased load. Still being a beginner myself i'm not sure this is a long term solution with regards to its effect on the loco's motor.
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garyklein

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« Reply #5 on: October 29, 2009, 04:52:56 PM »

Thank you for the guidance.  I think 7 or 8% will work.  Mine will also be going around the xmas tree.  The grandkids are coming from thanksgiving to January.  Since this is a temporary setup, I am not overly concerned with the extra load on the engines. 

Grampa Gary
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Loco Bill

Model Railroading since 1947


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« Reply #6 on: October 29, 2009, 10:16:31 PM »

Have a great time with the grand kids!!  If the loco starts slipping or smells funny just reduce the number of cars!
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Loco Bill,
Roundhouse Foreman
Missouri Western Railway

Unnofficial Historian of Bachmann Large Scale Products
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