Just wondering what experiences people have with helixes out there. I need to build two. One from the upper deck to lower deck and one from lower deck into staging below. I was looking at 18R with a 2" drop per loop. I have the space to go bigger (about 24") but obivously that takes away space along a wall for the sceniced portion of the layout. Believe 18" will give me a 1.76 degree slope. I know on a straight line run this is not bad. Most of my trains run 2-3 locomotives. Will have a couple of shorter ones (1 engine with 12 cars) and am worried if I go 18'R the combination of curvature and slope will be prohibitive.
Best thing I found out while building my helix was; before installing the helix on the layout is to first set up a couple of loops of helix on a workbench or table then run a train of length and weight (motive power and number of cars) that you think you will run typically up your helix. I found out I was limited to about 8 cars with one loco with my radius and grade that I had chosen. You will find out that the curvature of the track limits your ability to pull more cars, just like the prototypes. That is why some of the prototypes put in "compensated" grades, meaning if the track were to go up a steep incline, they would try to not put a curve in the design also (a double whammy!). Bottom Line, experiment before you try! Hansel
Largest radius you can fit is the answer. Towing a 50 car consist up a helix is very problematic what with friction and all. Smaller radius equals smaller trains. Jim
I agree. The larger you can go, the less chance of trouble. And your trains will pull up that grade with greater ease.
Something else to consider is access. Your answer to this will influence the other big question, size. Let's face it, there is an immutable law of nature that says that trains will always derail in the most inaccessible spot. For many of us that's a helix. When I had a layout with a partial lower level, the last thing I wanted was for viewers to see the helix, I've always thought that that was a part of the behind the scenes workings that were never to be seen as it draws attention away from the thin veneer of realism we all have tried so hard to get. So, make the radius sufficient that you can stand up inside the helix. As I found on several not so fun occasions, you will need to sooner or later.
I would split the difference...go 21-22" and then doubletrack it....so keep a 19-20" radius loop as well and use that for downhill.
Tony, I have had a 20" radius helix in the past,, worked well. Now I am going with kato unitrack 18 7/8 and 17 5/8 radius. I did a test,, I can run the 86' auto parts cars both ways without any interference. I know on my past helix,,, 20-25 cars plus two kato 6 axle units worked,, 3-4 atlas units for the same size trains. I am curious to see what is going to happen on the kato super elevated track. I have the track on order with FRT,, I need to start cutting my sub roadbed. I plan on using all thread with pvc spacers to provide the proper clearance. I need to traverse a 18 1/2" difference in elevation. I would say 20" is a good number,, the bigger radius,,, the less of a grade. Adios, Wyatt
Doug, great idea. Did not think of that. The helix will decend to the lower level (about 16" to 18") and represent the line from Forbay (outside of Lewiston) to Kooskia. It would also allow me to use helix as a passing siding.
My double track helix has a 24" and 22" radius. It climbs 3" for every revolution. That gives me a grade of 2.17% on the outside and 2.38% grade on the inside. My helix also has 14 revolutions. My layout has three levels. The outer track on the helix goes from the bottom level to the middle level and then middle to the top level. The inner helix track goes from the top level all the way to the bottom level. Think one giant loop. The biggest train I will run is 4 locos and 20-22 cars. I have no problem going up or down with that size of train. When I was building it, I took my time. I put together a couple of the radius pieces together, laid cork and track. I then would put in another piece, lay cork and track. It was easier to approach the build this way then trying to lay track in a three inch space. Hope this helps. Check out N Scale Railroading May-June 2003 Issue 017. I got a lot of good ideas on how to build my helix from that article. Steve
Mike Fifer built a really nice one using Unitrack.... <a href="https://www.youtube.com/watch?feature=player_embedded&v=HlCc4R-ql8U" target="_blank">[video=youtube;HlCc4R-ql8U]https://www.youtube.com/watch?feature=player_embedded&v=HlCc4R-ql8U[/video] <a href="https://www.youtube.com/watch?feature=player_embedded&v=3hwNdd0X31A" target="_blank">[video=youtube;3hwNdd0X31A]https://www.youtube.com/watch?feature=player_embedded&v=3hwNdd0X31A[/video]
If it doesn't bother you, using the Kato double track will be about the best track solution. I forgot who made the helix kit that works with the Kato track. It is probably in the youtube, I just didn't have the time to view it. Just that it the taller rail will hold the wheelsets better.
Tony, as far as helices go, go big or don't go at all. Tight curves will leave you frustrated. Access is everything, as well. I built one heavily relying on Ppuinn's guidance (http://www.trainboard.com/grapevine/blog.php?4195) and design for a bowl-shaped helix that continuously increased radius (and thus was not stacked, for near 100% easy vertical access). The one I built was custom-designed for my application; it started at about 15.5" radius and opened to about 21" radius at the top. I no issues with the helix at all. It was dismantled with the layout I built it for when I moved from MT to Germany in 2010. http://www.trainboard.com/grapevine/entry.php?394-Helix-engineering-101
Wyatt, One problem with a helix is that it curves while it is rising (duh!). That increases the chance for string lining. If you put in super elevated track, you are increasing the possibility of string lining. Super elevated track is all about show. Since a helix is hidden trackage, it just doesn't seem to make sense to use superelevated track. Just my 2 cents worth.
"a 2" drop per loop." Not sure if that means what I think, but 2" doesn't give you much clearance between the top of the rail on one level and the underside of the deck above it. I optimized with a formica deck and flex on slightly less than 2 inch pitch, but 1/4" ply or unit track might not work out so well.
One more hint, if you need a turnout in your helix, either match the radius to the turnout radius or make it a race track oval with straights.
My helix is 4.5 turns, 18.5" radius, 3" clearance, 2.6% grade. My mainline in general is limited to 18" radius and 2.65%. It's also hella curvy, with S bends being the norm. The helix is located about a train-length into the climb, and with the way my trains run (3-4 units on 15-30 cars) trains will stringline on the superelevated curves before they stall out in the helix, which is not superelevated. 3" deck to deck gives me just the right amount of room to grab cars in the event of a derailment - The helix is made out of 1/2" plywood, so it doesn't get in the way much, and it's sheathed in 1/8" hardboard, giving it a goodly amount of strength. Yeah! I think I may run out of problems when I start running manned helpers, but that is a ways away yet.
