One thing that has me perplexed about a helix is this, how do you know what size is needed? Turns??? I am guessing that a 4.5 turn helix has the train going in a circle 4.5 times?? How does one figure out the height, size of curve etc??? I know the amount of space allocated and the radius of the curves I want to use on my layout. I know roughly the height needed for the helix (will not know for sure until I have the benchwork in place and see how everything fits per say). Some of this is greek to me.
Matt, You can try this program: http://www.fortunecity.com/westwood/beautiful/819/HeliCal.htm If this program doesn’t work for you, let me know and I will try and explain how to do it using the math. It is actually a lot easier to do it, than it is to explain how to do it.
And you thought you would never use high school math again! The key elements are separation and grade. Remembering that you need a minimum of 1.5" between rail and bottom of the next level, and probably more for you full scale hands to get in there, you need a combination that gets you around the circle to a differential of at least 2" within your minimum radius and maximum grade. Actually, since there is more drag on a circle, if your max. grade is 2.5% then you should be around 2%, if possible. The distance of the curve is 3.14 X diameter. With 18" radius, that is a total travel of just over 9 feet, or 108 inches. 2" separation gives you a grade of just under 2%. If you are using a double track helix,the inside grade will be a bit more than the outside grade, so use that track to figure and/or arrange it so the inside track is the downhill direction normally. If you have the space, consider an oval helix to gain more travel distance. You probably need to know more, but hope this helps.
I remember seeing online a neat little oval helix featuring double viaduct Unitrack. The guy used a set of threaded rods in the shape of the oval and dropped the viaduct loops on top. I believe one of the tricks was to use rods smaller than the holes in the viaduct and nuts bigger than the holes so the viaduct would rest on the nuts. It looked easy to setup and easy to adjust the grade on the helix. Too bad I can't seem to google it now.
That sounds like a pretty neat idea. I will search for it as well, if I come up with anything I will post here.
This is why I am happy I will be running the Plywood central for a little while and put the actual layout on hold for a bit.....to work out some grey areas in my planning process (and to buy more rolling stock of course.....I cant help it....it is my crack )
Ah. Found it. (?) Unitrack helix Looking at this again, this isn't quite what I remembered. There must be another one out there. [ October 20, 2005, 09:08 AM: Message edited by: David B. ]
It's so much easier to make a long ramp or Nolix. That way you have better control of the trains entering the nolix(ramp) and could scenick it as well. Stay cool and run steam.....
There was a thread dealing with helix math a couple months ago, might want to take a look... Helix Clearance
David B, You might have seen photos I posted on Trainboard previously. I copied this gentleman's idea, except I used threaded rods and nuts instead of brass tubing and plastruct spacers since it was easier to adjust that way. It seems like it would work great...the test loop I set up was successful although I didn't do a lot of hard core testing. From Rossford Yard's comments, the reason I abondoned it had nothing to do with the Unitrack part, but the helix part. I have reverted back to my original plan of using a nolix, which is going to be 1000X harder to build but was the only way I could fit it in the space I had available. Anyway, I highly recommend the Unitrack helix. It will cost around $50/turn for the track, plus around $40 for the hardware, so it's not cheap, but it can be built FAST and works good.
