clearence for helix

[airwolf crazy]

Greetings,

I am adding a Helix (1 1/4 turns) to a staging yard onto my layout.  It passes and clears all but one section of existing benchwork.  The vertical space is less than recommended due to a piece of plywood that is a splice for a joint.  I have placed a piece of track in the area and a box car does clear the splice block of wood.  The area is small so I am not concerend with getting my hand in to remove a derailed car.  The car can be moved up or down the helix to a better access point.  I am willing to live with that.

I will be running rolling stock that is from the late 40's early 50's.  So, here is the question: What is the tallest typ. height for engines and rolling stock for this time period?  Real heights will be fine, I can do the math to get it to HO but if you happen to know the HO scale size that would be good too.

Thanks
Christopher

[tomikawaTT]

The clearance for the highest thing that I recall having been moved by rail during your period (the 200 inch mirror for the Hale telescope on Mount Palomar) would have been about one scale gnat short of 2.5" in HO.  However, it would be better to measure your own rolling stock.  IIRC, Crandell (Selector) learned the hard way that the Athearn 200-ton crane, and the smokejack on one caboose, were taller than he had allowed for.

My own helix has 3" overhead clearance, arranged by using a steel stud cut into segments and screwed together.  Total roadbed plus flex track thickness is about 1/4 inch.

Chuck (Modeling Central Japan in September, 1964)

[ollevon]

I am planing to put a helix in my layout, but I never built one before, and have no idea of how to start. what would the radius be I have about 8" to drop down to,so how many turns or full loops would it take?

Thanks for any info.

Sam

[Allegheny2-6-6-6]

I've built two helix's one for the club layout and one for a friend and I had 4-1/2" clearance on both of them and I flelt that was tight. If it were me I would remove that piece of wood and replace it with possibly a piece of thinner plywood say 3/8" maybe or perhaps a piece of flat aluminum stock. Something thin but strong cause if your luck is anything like mine any derailment problems you have will happen right where your clearance is the least. If you are determined to keep that in place simply measure the tallest piece of rolling stock you have and ad as much clearance to it as possible.

[fwright]

A good read on prototype and model clearances is at http://www.nmra.org/standards/sandrp/gauge.html.  Note the equipment that the different clearance plates apply to.  Also note our models don't necessarily comply with the appropriate AAR plate dimensions, due to being mounted higher on their trucks than their prototype, much greater side overhang on curves, and so on.

You don't say what your clearance actually is, nor have you checked for extra clearance for changes caused by rolling down the track and track imperfections.

my thoughts, your choices

Fred W

[hon30critter]

Make sure you check all your rolling stock for proper clearance. While most of your era's rolling stock may be fine, like Crandell, I discovered the hard way that caboose smoke jacks are a lot taller than the rest of my cars. I am building a model of the East Broad Top paint shop. I had it looking pretty good until I checked a caboose for clearance. OOPS! Now I have to figure out how to hide an addition to the foundation which doesn't look all that great.

Dave

[airwolf crazy]

Greetings folks,

Thanks for the responces.  I have the NMRA information but thanks for the link Fred.  The more that link gets posted the better.  :-)

The current space is 2.75" from the base to the bottom of the splice.  Allegheny2-6-6-6 said to replace the splice block.  I would but, it got screwed in from the top instead of from the bottom.  The cork roadbed, track, and ballast now all cover the screw heads.  Yes, I know bad choice.  It is possible I could get a belt sander or angle grinder in there and remove some of the wood.

I too did not concider things like the stove pipes and other small items sticking up.  I will double check what rolling stock I have.  It is future purchases that will have to be watched.

Sam, a good place for you to start may be this article: http://mrr.trains.com/How%20To/Articles/Layout%20Planning%20and%20Operation/2010/09/Construct%20a%20%20simple%20and%20reliable%20helix.aspx and get this book: http://www.kalmbachstore.com/mrpdf032.html  Good luck to you Sam there are a lot of good people here willing to help.

Thanks,
Christopher

[Jeff Sarsons]

Good Afternoon Christopher

I am new to MR building so am on line always looking for good info when I read your note.  I do have a question.  Can you reduce the size of the block of wood that you have used as a splice by replacing it with a strip of metal?  There are a lot of metal splicing pieces using in construction that can be easily screwed into place.  They are not heavy nor obvious.

 

Just a thought

 

Jeff Sarsons

[fwright]

airwolf crazy

The current space is 2.75" from the base to the bottom of the splice. 

Thanks,
Christopher

According to the link I gave you, the NS version of the double stack clearance works out to 2.85" (20ft 8") when scaled down.  So everything from earlier periods should work pretty easily, provided they are accurately scaled in height.

Fred W

[rrinker]

FOr calculation purposes, the length of track in one loop of track is 2 x pi x radius, or about 6.28 x the radius of your track. With a 24: radius, one loop would contain 150.7 inches of track, at a 2% grade that would be 3" of clearance, railhead to railhead - so subtract out the thickness of the benchwork and roadbed. Expand to 30" radius and 2.5% grade and you have 4.7" railhead to railhead - even with 3/4" material you still have more than 3" railhead to railhead, so anythign should run.

 Numbers are per turn. I thought I saw 8" thrown out, you're not going to do that in 1 1/4 turns unless you make the grade excessive or use a much larger radius. 36" radius at 2.8% grade would get you 8" in 1 1/4 turns. Smaller radius with 2% gets you enough clearance between levels but requires mor turns. Stick with the smaller grade.

                    --Randy

 

[Jeff Sarsons]

tomikawaTT

Good note.  Can I ask what the ambient sound was like using the steel stud?  What type of road bed did you use?  What did you use for your vertical structure?

Thanks

JEff Sarsons