Helix question

[SpaceMouse]

Just out of curiousity, I have seen pictures of helixes and we have one at the club, and they are pretty much true to form.

Now if you make a helix with a '52 inch diameter you raise the elevation 3" every revolution on a 2% grade. Easy enough to do. However, you can only get one revolution out of a piece of plywood.

Has anyone used a spiral. If you started a little wider, say 60-72" and worked your way to the center, you'd have much more control over your grade (could go less thatn 2%) and with several revolutions still maintain a 22" radius. In addition you could get more turns out of your plywood.

Why do you hear nothing of this technique?

Or for that matter oval helixes that fit under a rectangular table?

[Anonymous]

A spiral helix, like you described, could work but I think it's a matter of saving space using a full circle. Same for an oval helix.
Try this link to download a Helix Calclator. http://www.railroaddata.com/rrlinks/Detailed/3941.html

The book "How to Build Model Railroad Benchwork" (Model Railroader) has a section on making a helix by laminating 1/8 hardboard. That method saves a lot of material by making curved sections instead of a big dough nut from plywood (Yumm, dough nuts).

[SpaceMouse]

Okay, on a 52" diameter Helix the grade would be 1.87% and the height would be 2.999 inches.

As for space, I submit that if you have a 4 foot wide peninsula and you want to drop to a staging yard. a 4x6 oval helix takes up less space thatn a 52" round one.

[dwRavenstar]

SpaceMouse,

I've just completed a 44 inch radius helix and I used quarter circles. Actually, I cut arcs of roughly 95 degrees and overlapped at each juncture. The supports were simple enough, just a pair of uprights and 1/8 inch dowels across at each level.

Good luck with yours

Dave (dwRavenstar)

[SpaceMouse]

The spiral Idea actually came as a way to minimize space. I needed to get to a second level. HogWarts was at the end of the layout and was built on a mountain or hill, so I decided to put the helix under Hogwarts.

The spiral idea came when I thought it would be cool if the train popped out of the helix on the mountain for a quarter turn every revolution.

[Anonymous]

Space mouse,

If you cut out 1/4 turns and glue them together you can get a whole helix out f a couple of sheets of plywood. I did exactly that when building mine. My radius is 32". There was an article in RMC last fall using 1/8 circles and cutting them out as straight strips and angling the cuts, ended up like a large octagon.

Having tracks pop out is harder than it looks, but it can be done. The problem with tracks out every revoulution is that usually there is not enough vertical seperation and they have that old bane of realistic scenery, the "Stacked track look"....

[rrinker]

The oval helix would be great for that. Expose the track on the straight sections AND some of the curved sections - and not every level because, as stated, helix levels are a bit too close together. Maybe every other, or every third - maybe one straight side and two of the curved sides. Or a straight on one side, a lower curve on one, and a higher curve on the other. Lot of things you can do.

--Randy

[gvdobler]

If I read your question right.
If you are talking about a spiral much like if you were to cut an orange peal in one continuous piece. It seems like you would go from a 24" radius to a 12" radius in 3 turns and that would only give you a rise of 9"..

The idea of a helix is to rise as high as you can in the least amount of square footage, while maintaining reliablility. A constantly tightening curve sounds like you might have trouble. Once a train gets into the helix, I would think keeping the pull and the turn constant would be better than changing anything. This could also be possible with an oval design, again not constant turns.

Let us know whaat you end up doing.

Jon - Las Vegas [:D]

[Bob Hayes]

Obviously, none of you read Railroad Model Craftsman. In the last 6 months there have been 2 articles on building curved sections of a layout using straight pices of wood. Check out the latest one on page 66 of the April 2005 RMC.

Bob Hayes

[SpaceMouse]

QUOTE: Originally posted by gvdobler

If I read your question right.
If you are talking about a spiral much like if you were to cut an orange peal in one continuous piece. It seems like you would go from a 24" radius to a 12" radius in 3 turns and that would only give you a rise of 9"..

The idea of a helix is to rise as high as you can in the least amount of square footage, while maintaining reliablility. A constantly tightening curve sounds like you might have trouble. Once a train gets into the helix, I would think keeping the pull and the turn constant would be better than changing anything. This could also be possible with an oval design, again not constant turns.

Let us know whaat you end up doing.

Jon - Las Vegas [:D]

You have the concept right, but I was thinking more of starting at a 30" radius and ending at 24 or so. I may run another "loop" on the outside of the mountain at the top to gain another 3" for a total of 15. Also I may not stay true to the constant turn idea, inserting straights in place where appropriate to the terrain like Randy said.

[Big_Boy_4005]

Spacemouse, the way to maximize the use of a sheet of plywood when building a helix is to make your curve in segments. There are 2 ways to do this. One is to cut curved segments, this leaves you with crescent shaped scraps. The other way is to rip the plywood into straight strips wider than the actual roadbed area, then cut trapazoidal segments, splice them together, then trim.

I used the second method, combined with overlapping 2 thinner sheets to create this 10' diameter O gauge helix.



By the way, with your spiral idea you would the grade would be rather messy. As the diameter decreased, the amount of rise would also have to decrease just to remain at a constant rate of climb. Diameter, grade and headspace are all related. It is much better practice, and much easier to pick a diameter, and a headspace that yield a practical grade, and stick to it.

OK, so you waste a little wood. If you are really clever, you'll find a use for it, if not, have a small campfire and roast hot dogs and marshmallows in the back yard.[swg]

[SpaceMouse]

I understand that as the diameter gets bigger or smaller the grade changes unless you adjust. However couldn't you measure risers by linear length toget your spacing like any grade. Since they aren't stacked unifirmity is not an issue.

Also because it is a spiral headspace is not an issue.

BTW: The spiral is about looks on Hogwart's mountain, not about saving lumber. It's also about hiding the spiral to create the time illusion.

Keep these objections coming. Keeps me on my toes.

[bogp40]

The smaller the radius the less distance traveled. Once eased into the helix radius you really shouldn't change the radius or grade, I believe that you would design trouble into the helix, especially w/ long trains or mixed rolling stock having varying lengths and weights.

[Big_Boy_4005]

QUOTE: Originally posted by SpaceMouse

I understand that as the diameter gets bigger or smaller the grade changes unless you adjust. However couldn't you measure risers by linear length toget your spacing like any grade. Since they aren't stacked unifirmity is not an issue.

Also because it is a spiral headspace is not an issue.

BTW: The spiral is about looks on Hogwart's mountain, not about saving lumber. It's also about hiding the spiral to create the time illusion.

Keep these objections coming. Keeps me on my toes.

OK, I see where you're going with this, but there is a limit. It goes back to the headspace issue. It doesn't matter if you make it with the small radius at the top or the bottom, there is no escape without interfering with last turn of the small radius. Think about it, you can enter on the wide radius, no problem. The only way out is for the last turn to have headspace with respect to the previous turn. This is the absolute limit of the spiral scenario.

I guess if you started out large enough, you could do it. The minimum radius to get a 3" clearence at 2% grade is 24". 48" x 3.14 =~150" and 3:150 =2:100 =2%. Of course if you were to start at 36" radius, you would still have to use more than one sheet of plywood. Actually it would be very close, because you could use the 24" drop to make up most of the of the 72" square, then use the cutoff corners to do the last bit of fill for a 72" circle.

Each full circle would be 4" smaller than the previous. 72, 68, 64, 60, 56, 52, 48. To maintain 2%, the first turn will be about 4.25" height gain, with each successive turn being .25" less than the previous. Total gain for the spiral, about 21.25".

It's a little goofy, but I guess it's doable. How high do you need to go?

[SpaceMouse]

QUOTE: Originally posted by Big_Boy_4005


Each full circle would be 4" smaller than the previous. 72, 68, 64, 60, 56, 52, 48. To maintain 2%, the first turn will be about 4.25" height gain, with each successive turn being .25" less than the previous. Total gain for the spiral, about 21.25".

It's a little goofy, but I guess it's doable. How high do you need to go?

I was planning on about 16". Thanks for your work.

Actually with all this talk about it, I'm thinking I'm even going to get goofier. I'm now thinking of using the 1/8' masonite method and cutting standard 90 degree curves and combiining them with varying lenghts of straight sections. That way I can stack the modified helix against the wall and give a more gentle slope to the outside of Hogwarts mountain. I'll have to condsider that a little further.