I'm biginner in ho scale layout. I want to build a helix to my layout. The biggest loco is a Spectrum 2-10--2 USRA Light and I got some passenger cars. My question; 24 " radius is it ok whit a slope of 3 percent ?
Thanks you
chef_de_gareMy question; 24 " radius is it ok whit a slope of 3 percent ?
Probably not. Most people have found that a much broader radius is needed for reliability with large engines and full-length passenger cars. 30" radius and up would be more reliable.
The friction of the relatively tight curve adds to the grade, making the effective grade of what you describe somewhere around 4.3% (nominal grade plus 32/R is one widely used rule of thumb). The grade and friction create the tendency for long heavy trains to "stringline" (derail across the center of the helix).
If you've never built a layout before, a helix is not the easiest beginner's project. But making it broader probably increases your chance of success. A model railroad helix does not abrogate the laws of physics, despite what many hope.
Good luck.
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Here is the story of the LION and his helix.
The helix is much further along now, but I have not made new photographs of it yet It is only one and a half turns. As it was built on a flat table, I constructed several risers each one a 1/4 inch taller than the previous, thus I was able to make the grade as shallow as possible and still clear the level below it. I placed bilder's shims on top of the risers to give the helix a super elevation. From there I just glued some spacers to the first loop, and laid the second loop on top of that. I used 4" bolts to secure the second level to the first. This could go as high as you need it. The table and thus the helix is 5' in diameter, thus the outside track has a radius of about 28" but it is a four track helix. I decorated the inside of the helix before I built the level above it. It is on the table's edge and people can look into it. Since this is a subway layout, a tunnel is a tunnel is a tunnel.
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
The main thing is to make sure you really want one. I'm a relative novice at MR, but I've always been willing to try anything once. On my second layout, I built a helix (HO gauge). It worked fine, but I absolutely hated it. It's impossible to scenic and I never got comfortable with a train being out of sight so long. To me, it was a monstrosity.
Shortly after I finished it, I tore it down. Never again will I build one.
Just my experience. To each his own.
- Harry
My 2-10-0 dose fine on 18" but my trackwork is dead on and I don't have anything longer than a few 65' passenger cars with everything else closer to 40'. You can get by with tighter radius and they will look fine (not talking the helix here) but anything they are pulling looks bad after 50' with 18"
I was going to do a helix and found that I could get more usable scenic and train viewing space by using "partially hidden" grades going around/along the back of the layout or center--we have 3 levels. The poster who showed the effective grade to be 4.3% is absolutely correct about the effective grade being much greater with small radii.
If you're set on doing a helix, try a mock up with a 5% grade and see how your locos and cars do pulling. I suggest 5% just to be safe, since derails and stalls aren't easily fixed in a helix.
Note that a 24" radius will result in a requirement of about 52" diameter structure, maybe more depending on covering/addressing inside and outside overhangs.
Richard
That's part of the killer I'm dealing with in a future HO layout design where folks are tell me based on my roster that I need to think 30" radiii as a minimum and keep the grade under 3% and thus pushes my layout space width to it's limits; and maybe over them...
Darren (BLHS & CRRM Lifetime Member)
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