I have been kicking around how to add a second level to my small "HO" layout. The first must have is not to move any walls. second is "Maximum" use of the space. It dawned on me that I could use the space beside the closet for a helix, building the town on a slight hill with the helix below. I know that the helix is rather tight but I'm still kicking it around. With a elevation change of 15.5" and a layout thickness of 4.25" that leaves me with 11.25" above the lower level.
But that means moving the yard over to the window side of the room. And gives me the yard and staging on the lower level, also I have been able to work in the turning wye I wanted.
Johnnny_reb Once a word is spoken it can not be unspoken!
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Looks like a plan!
Have you considered making your helix longer in the 63" module dimension? You could probably add fourteen inches (28 inches per lap) and ease the grade accordingly.
Considering the overall dimensions of the layout, I imagine that you will be running fairly short trains of not too long cars. Given that, you should have no problems.
Have you considered a sector plate or super transfer table for your staging? Has the advantage of yielding longer staging tracks while eliminating hidden turnouts.
Chuck (modeling Central Japan in September - with 1-turn spirals)
Johnnny_reb wrote:with a 22"r and a loop spacing of 3.25" the grade becomes 2.351% and is over 749" long with 5.417 loops and 17 19/32" between upper and lower levels.
That's a rail-to-rail spacing and doesn't take into account the thickness of the track, roadbed, supports, and your fingers reaching in there if something goes wrong. In addition, when the whole train is on the curved grade at once, the friction on the rails increases the effective grade substantially.
While it can be possibly be made to work, no less a modeler than Joe Fugate found that his 24" radius helix was problematic, tore it out, and replaced it with a much larger radius. Caveat condor (builder beware).
ByronModel RR Blog
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Johnny,
Something else to keep in mind with a helix is induced drag due to the curvature. Consider that the inner and outer rails have different radii on a curve. To traverse a curve the outer wheels need to travel farther than the inner wheels. On an automobile there are a differentials to allow this to happen. But on trains (full size and model) the wheels are permanently attached to the axles. If one wheel is turning at 20 revs per minute than the one on the other end of the axle is also turning at that speed.
This means that either the inner or the outter wheel is going to be slipping when your train negotiates a curve. The engine has to pull extra hard to get those wheels to slip (and overcome friction). Normally this isn't much of a problem because only part of a train is on a curve at one time. But in a helix the entire train is on the curve all at once.
The need to overcome friction causes what some call induced-gradient. It of course doesn't make the hill any steeper than it really is. But to the engine it appears as if the curve was steeper because the engine has to pull harder. Now add in that fact that at least one side of the engines wheels are going to be slipping due to the curvature of the track it's on and the pulling power of the engine is reduced too.
John Allen wrote about this 40 years ago. It means that your helix grade will appear to be steeper than the 2.3% you computed (how thick did you say the roadbed in the helix would be?). The actual extra drag will depend on the radius with a tight radius such as your 22" being worse than a generous radius (perhaps 40"). It will also depend on the length of your train (because long trains have more wheels that will be slipping on the curve).
If you're planning on an engine and 5 or 6 cars your helix will likely be fine. If you're thinking of a dozen cars, expect it to look like you have a 3.5-4% grade in there. If you're thinking of 20 car trains you are going to have some big time problems in there.
Joe Fugate originally designed his Siskiyou Line layot with a 30" radius helix. It proved to be a complete disaster with his 20+ car trains causing him to tear it out and substitute his current 40" radius helix.
Good luck to you!
Regards,
Charlie Comstock
Charlie, Joe described it as a 24" radius helix in his article in Layout Design Journal #14, Spring 1996 (published by the Layout Design SIG). In the article, he mentions that the nominal 2.65% grade (to maintain a 4" rail-to-rail height) seemed more like a 4% grade after including the effects of the tight curves. He also cautions against having the most difficult grade on the layout in the hidden track.
Temporary LDSIG link is:http://www.macrodyn.com/ldsig/home
Normal LDSIG URL is:www.ldsig.org
Byron
BCSJ wrote: Something else to keep in mind with a helix is induced drag due to the curvature. Consider that the inner and outer rails have different radii on a curve. To traverse a curve the outer wheels need to travel farther than the inner wheels. On an automobile there are a differentials to allow this to happen. But on trains (full size and model) the wheels are permanently attached to the axles. If one wheel is turning at 20 revs per minute than the one on the other end of the axle is also turning at that speed.This means that either the inner or the outter wheel is going to be slipping when your train negotiates a curve. The engine has to pull extra hard to get those wheels to slip (and overcome friction). Normally this isn't much of a problem because only part of a train is on a curve at one time. But in a helix the entire train is on the curve all at once.
cuyama wrote:Charlie, Joe described it as a 24" radius helix in his article in Layout Design Journal #14, Spring 1996 (published by the Layout Design SIG). In the article, he mentions that the nominal 2.65% grade (to maintain a 4" rail-to-rail height) seemed more like a 4% grade after including the effects of the tight curves. He also cautions against having the most difficult grade on the layout in the hidden track.Temporary LDSIG link is:http://www.macrodyn.com/ldsig/homeNormal LDSIG URL is:www.ldsig.orgByron
Byron, I'd second that thought about it being a potential problem having the ruling grade in hidden track! Nothing like having an engine 'fall down' when you can see it happening!
So the 3.5" between levels might seem like enough. But subtract 1/2" for the roadbed thickness. Then subtract another 3/16" for the thickness of the track and you're down to 2 13/16" of clearance between the railhead and the underside of the roadbed above.
This may work with some cars and locomotives, but it violates the NMRA Standard S-7
It allows no room at all under the roadbed for splice plates (how are you going to joing the pieces of the helix together). And I'd expect you could have some real problems with HiCube box cars (not a problem if you're modeling the era before big box cars came into use).
I'm sorry to be a grumpy gus about this. But this helix is sounding (to me) as though it's going to be a problem for you.
There is one thing you could possibly do though, make the helix an oval instead of a circle and expand it to more completely fill your closet. This should allow you to a pair of 12" (mostly) tangent sections to each lap increasing lap length by 24". The increased length, at a 2.5% grade increases the railhead-to-railhead elevation change to 4" instead of the 3.5". I don't know if you can really manage an extra 24" per lap - with 22" radii you'll need easements from the curves onto the straight sections so it might not work at all. Just another free idea (and likely worth what it costs)
I have measured it myself and have a track gauge. My rolling stock stands 2.25" high from the railhead add in the track and roadbed and it goes up to 2.5". So with a raise of 3.5" on 3/8 plywood. Now take out the 1/4" for roadbed and track. Then 2 1/4" for the rolling stock and it leaves 1' between the top of the rolling stock and the plywood over head.
But as always it's my railroad and I'll build it like I want to. I do find that some people just have to go off the deep end of everything no matter what it is. I have done my research on this matter and with the space limits. A helix of 20" to 22" inch radius would be the best for me. You can kick it around forever and get no where or you can go for it.
Note: In a helix there is no need for a roadbed of 1/2 inch. In "HO" scale that would be over 4.5 feet add in the 3/16 for the trackage and it becomes 6 feet in "HO" scale. In a helix there in no need for the roadbed unless you are building a helix around a mountain. In that case there would be no overhead structure for the next loop.
But my calculations are wrong. With a raise of 3.5" ( from the floor of loop one to the floor of loop two ) and a sub-roadbed made of 3/8" plywood, then 3/16" for trackage. You end up with a floor and track thickness of 9/16". Now take 9/16" away from the 3.5" raise and your left with 2 15/16 between each raising loop, then with a rolling stock height of 2 1/4" your left with a space of 11/16" for fingers to rescue any derailment. With that said the NMRA height gauge is only 3" tall in "HO" scale. If you are concerned with staying with in the NMRA standards I wound recommend a raise of 3 3/4" between loop floors.
The space of 44" x 63" is all that I am willing to give up to a helix. But that will be phase two of my current layout if at all. I may build a train elevator of some sort.
Yes, it was a 24" radius and with the extra drag of an entire train of 20+ cars being on a curve, trains would routinely stall in the helix where the trains would run fine on the visible layout. My operating crew hated the 24" radius helix and the moment I showed some weakness when they pleaded with me to replace it -- they had it completely torn out in a couple of hours!
They also helped me mastermind how to get a 40" radius helix to fit in the same end of the room -- and in hindsight, they were exactly right! The 40" radius helix runs wonderfully while the 24" radius helix was a total nightmare.
The moral of the story for me is:
Joe Fugate Modeling the 1980s SP Siskiyou Line in southern Oregon
cuyama wrote:Right, no sense in trying to learn anything from anyone else's experience.
I didn't read it that way. I read it as a necessary compromise, verses total abandonment of the concept.
So here is a little warning and a little inspiration that I think explains this impasse:
You HO people really raise the bar and must overcome much to do so. I considered my hope of a two level room layout as an impossibility even in N-Scale, until I realized I wanted to rebuilt that childhood layout modified to meet my standards. That left me with a peninsula large enough to accommodate a helix.
At age thirteen, I did not wholly grasp the complexities of grades, but felt comfortable since I was following published plans. So it never occurred to me that my father's spur-of-the-moment decision that I would be happier if I used 3/4" ply instead of the 1/2" the plans suggested, and his offer to pay the difference would spell disaster.
That 1/4" raised the grade so nothing could climb without my finger helping, and worse, when entering the hidden level-- or trying to, the top of the engine when "thunk" on the level it was supposed to pass under. There was no salvaging that first attempt-- and the failure after so much work was enough to have me give up trying again for several years.
I am forty-eight now, and I want that disaster to become reconciled for several reasons. I regret having given up on something that promised such joy. I hate what I denied myself out of frustration (and embarrassment). I want to share that promised joy with others. I see it as a necessary means to an end of beginning my “dream layout” with a module that will have an unmatchable personal intrinsic value when finished. I want to slay that demon and satisfy that childhood imagination that still exists with me.
Can we all relate to that?
Crews