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What’s the Correct Dimension for a Helix?

Regular contributor Kevin has helped so many others with their model railroading problems, and now he is hoping someone can help him out:

“I usually model in HO but I have been given an N gauge layout with 2 engines, 3 passenger cars, and 9 freight cars, about 30 meters of new track, plus some set track curves. Now having never had anything to do with N gauge, so I am asking N scalers what is the best diameter for a Helix? I want two and I have a meter at each side of the doorway into a rook 3m X 4.2m. I was thinking about a 2% rise? Also, the cars have Rapido couplers and the engines have knuckle couplers. It looks like I will have to change the couplers on the various cars? If so what are the best knuckle couplers to use? Thanks.”

If you can advise Kevin, please use the COMMENTS link below to add your comment or answer. If you just want to view the comments and answers as they roll in, you can see them by using the same link.

5 Responses to What’s the Correct Dimension for a Helix?

  • Graemesays:

    Hi Kevin I model in N scale and have built several helixes my latest one is outside diameter 750mm with a track bed of 150mm to accomodate three tracks with a 2% elevation up to a height of 450mm disguised as a mountain. It works very well and three diesel locos can pull 30 coal wagons with little effort. The only downside is not a lot of clearance for locos and not much room to work if something goes wrong. So what I did was us Kato track and sanded the joints so the wagons glided over very smoothly a lot of work to get right but so worth it the helix has been down for 8 months now and touch wood no derailments or conductivity problems . Hope this helps Graeme.

  • Bill Dittussays:

    Hi Kevin, I model in HO, but a helix design is basically the same for either scale. To begin with find out the tightest curve 3 passenger cars can negotiate then add a little more radius. Why you may ask, well simply, so you can run any and all cars on it. next determine the overall height you must climb and remember you MUST have enough room to reach in and re-rail or remove cars which have derailed. In other words enough room for your finger or hand., I chose to lay cork road bed as well, some do not. My helix is supported by all thread (2) 1/4-20 rods and nylon 1 inch spacers which allow the rod to easily slide through, then I drilled and threaded a hole so I could drive a screw into the nylon and snug it to the threaded rod, I the placed a 1 inch wide by 3/8 thick and length was determined by the width of the helix deck plus about an 1.5 longer on either side of the helix deck I will also include a really good website reference http://www.modelbuildings.org/free-helix-design-calculator.html

  • Graemesays:

    Hi Kevin I model N scale and have built several helixes over the years. My latest is outside diameter is 750 mm with a 150mm wide track base to enable 3 individual tracks to use it at the same time. It has a height of 450 mm, the grade is just under 2% and 81/2 complete circles from bottom to top. I made it from 6 mm MDF cut in half circles with 2 lugs on each side to fit threaded rod through very fiddley but makes it easy to fine tune the grade. Downside is not a lot of clearance and even less room to work on if you encounter a problem like a derailment ,to overcome this I use Kato track which are fitted together and then the joints are sanded for extra smooth running it’s a lot of work but totally worth it,I get no derailments and no conductivity problems hope that helps good luck Graeme

  • David Stokessays:

    Bill is right Kevin, regardless of scale, unfortunately your hands stay the same size, so leave room for them. Use the Helix design link and try out some different dimensions and layer numbers, but always remember, the smaller percentage climb, matched with the largest possible diameter is the optimum helix design. His build advice is also spot on.

  • Sheldon Clarksays:

    The tighter the curve (i.e. the shorter the radius), the steeper the incline must be. Bearing in mind that, even on the level, tighter radius curves give a higher rolling resistance than those with a larger radius, your ideal radius is going to be governed by the pulling ability of your locomotive(s) on an incline and the total weight it/they are going to have to pull up the grade. In short, there is no “ideal” or “best” diameter for a helix, only the most suitable you can achieve in the space you have available.

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