I’m sure that this has been brought up before but what is the minimum Radius and ideal grade of a helix if i’m using modern cars some being: 89’ flats, autos, stacks, and ribs? I will have a helper grade so that my helix won’t be so high.
You want it to be as wide as you can possibly make it, because the curvature will add resistance, making the grade effectively even steeper. I don’t run anything that’s 89’ long, but my guess would be you want a pretty serious radius, like 30" or more.
Personally, I was thinking about having a radius of 36 inches. I’m sure that this is okay, but can I go smaller.
WOW a 6 FOOT diameter helix !!! That would leave me enough for a 3’ x 3’ layout in my train room.
I hate a helix, really, it steals operating time. I like the idea of a visible helix, one that curves the line over observable scenery even if you cheat a little bit scenick wise.
elsewise, long cars need wide radius and I wouldnt go under 24 inch radius.
For my shelf modulars I compromised curve radius, I like 36" but thats impractical for what I am doing. 26" minimum for my South Shore and 24" for all else, except for industrial trackage where I could get down to 15" on occasion.
I would go as wide as you dare, or have room for, just a matter of deciding what seems best for the situation.
To be honest with all of you, I too hate the Helix system but I really want the feel of a big layout (I have so many ideas), so I need to have a double deck layout. My trains won’t be much longer than 30 cars but like I said, I want to have a train of all auto carriers. That would mean that I would have to use a big helix, but what can I get away with? Again, like I said, my visible part of my layout will be mainly a grade so that my helix will be something like two loops, but I need to know maxes on helix grade and radius.
Take a look at the NMRA RP-11 for curvature and rolling stock. A 89" passenger car is in class P. In N scale the recommended minimum radius is 21.5 “. The grade will depend on the total rise and number of turns. Using the Helix Calculator, A 21.5” radius, two turns and a 5" raise will give you a grade of 1.852%.
An alternative that is often overlooked is to use two decks that are not physically connected but are linked by operations and staging. Each deck has its own staging and visible scenes.
An example might be a mainline and a (virtually connected) branchline. The train leaves the mainline for the branch by running into staging. On the other deck, a similar consist leaves staging representing the mainline to run on the visible branchline tracking.
I’m using this concept on my own layout and it’s worked on a couple of clients’ layouts as well.
I wrote about the concept in the Layout Design Special Interest Group’s Layout Design Journal # 28 (Spring 2003). Back Issues info:
http://www.ldsig.org/pages/journal.html
Regards,
Byron
Gary brings up a good point.
Are we talking HO, N, what?
It makes a difference not only in the radius, but the height necessary to clear the next level.
No matter the scale, a helix takes a lot of space! I wouldn’t go go any smaller than 24" radius on it. On my last layout, I used a train lift that I scratch-built. It’s basically an elevator for trains. When I wanted a train to go from the bottom level to the top, I ran it onto a siding that was just long enough for the train. It would then lift the entire train, track and all, to the top level where I’d drive it off onto a siding to the mainline. Did the same thing to get back down. Just make sure the lift is on the level your operating on when you go onto the siding. It’s a long way to the floor! (Been there, done that!)
sounds like some serious engineering, Jeff! An indexed hydrolic lift, to boot? Or just blocks & ropes?
My under-construction,four-track helix in HO uses 36, 38, 40 & 42 inch radii.
Here’s a couple of shots:
My train lift was like an elavator. it used 4 nails on the bottom to line up the tracks when the lift came down. There were 4 more nails to line up the lift when it went to the top level. The lift itself was operated by a hand turned crank that was attached to 2 thick strings supported from the ceiling. These connected to two metal arches, one at each end of the lift. It really worked rather well. Regrettably, I don’t have any pics of it.
Guys, sorry that I didn’t disclose this at first but I’m running HO, and I’m pretty sure that I want to use the helix system.
In that case, class P rolling stock has a recommended minimum radius of 40" for HO scale. Two turns that raises the track 8" has a grade of just over 1.5 %. It would have a verticle spacing of about 4".
I have a HO helix with 36 and 33.5" radius curves. I run 80+ foot long passneger cars on it with no problems but I dont think I would go much tighter with the passenger cars. The auto racks your taking about are even longer so I’d say 36" min should assure acceptable results. If it is multi track make sure the spacing is large enough to prevent side swipes. Grade can also have an effect. My grades are about 1.6%.
That’s a lot of cars to hull up grade. If a coupler breaks or pulls out of the box, they’ll take off like a roller coaster and hopefully they don’t fly off the layout hit the floor. Lets say each car cost $25. That’s a $750 train. Do you want to risk breaking them?
Did you mean to say big helix? It’s tempting to cheat, but you would be compromising reliability. The smaller the radius, the steeper the grade unless you add more turns. I believe Walthers recommends a minimum radius of 24" for their auto racks. However you add a grade and the dynamic forces start to change, especially if you try to hull thirty cars up a long grade.
You didn’t say how much of a raise you need, so I’ll use 8 " which would give you 4" vertical spacing. A 24" radius, 2 turns raising the track 8" would have a grade of 2.654%.
I had the same dilema last year, after taking months to plan my layout in a 11 x 14 foot area. The darn helix was just taking up too much room even if I used a smallish radius like 24" minimum. So I opened a discussion on this topic with others and the concensus was to go with the nolix (just wrap the mainline around the room a few times). I can do this at 1.5% grade and add/subtract 7" per revolution. One drawback is that the tracks need to be behind by lower level backdrop since I am not modeling the mountains–Chicago area for me. The other drawback is that I need to bridge my entrance with many more tracks.
But you may want to sketch this format on paper to see what you think. It is very good not dealing with a helix. Good luck with this.
Mike
Go for the bigest radius possible but whatever you choose, don’t build a helix to the minimum radius on your layout. My minimum helix radius is 2" larger than my minimum mainline radius in exposed areas. It works! I have all my problems in easy-to-reach locations. My test track is an “S” curve with a radius of 1" less than the minimum on the layout. Thus most problems never reach the layout.
Typically in HO 32" of radius equals one percent grade in terms of increased pulling resistance. I’d recomend that after using this formula on your helix and non helix track that the compensated grade in the helix be about at least 0.5% less than compensated grade outside the helix.
I have run helpers up my helix, just to see if there are any operatiional problems, even though it’s not the ruling grade and have found there is no problem, even on 40 car trains but I still dont recomend doing this/