Helix Thoughts

[rockislandmike]

Friday night I will begin construction of the benchwork for my helix. I am planning at least two tracks - one at 26", and one at 28.5". The mainline will climb 1.83 revolutions; there will also be a fully scenicked level above the helix; and there is a branchline below the mainline of the helix that travels the opposite direction.

Here's my questions for you veterans (this will be my first helix).

(1) I still haven't decided whether to use wood supports on the outside; or threaded rods. Favorites? If I do go with threaded rods, what thickness would you recommend?

(2) How is it best to cut the subroadbed (plywood) to make optimal use out of it. I.e., I can't obviously cut a full circle from a 4' x 8'.

(3) I'm still considering another track, at 23.5". I know this would be pretty tight, but I'm modeling 1980, so there are considerable 4-axle and 40'/50' cars, where a smaller train of these units could use that third track.

Thoughts ????

 

[shaygetz]

December '04 Railroad Model Craftsman page 88 has an excellent article on helix construction. I plan to use it with the only change being that I will use 3/8" All-thread rod instead of wood blocks.

 

[Gary Pfeil]

Hi Mike, When I built mine I had access to 16" wide 3/4" plywood shelves. I made a template to mark each shelf with cut lines and cut them with a sabre saw. My radius's are 23 7/8 and 26 1/8, clearance is fine for 80' passenger cars. I kept my grade minimal by making my vertical clearance low, you would want more clearance for your more modern era. Turned out each shelf made 1/4 of a circle. I then used a router to remove half the thickness on each end, top on one end, bottom on the other. This way they overlapped without splice plates, further reducing grade by keeping clearance minimal. I then ripped 2x4 to get something approaching 2x2, then marked them with my 2 5/8 clearance (again, you'll want more) and 3/4" (for the part to be removed to fit over the roadbed) I set my tablesaw blade 1/2" high and ran the 3/4" sections over it repeatedly, then used a chisel to remove the debris. Then I was able to hammer them over the roadbed edges. I'm no carpenter and it ain't pretty, but its been in faultless operation for 5 years now.

Here is a link to my Rail Images page, you'll find a pic of the helix there.

Good luck with it, be sure to lay the track very carefully, will be next to impossible to work on later!

Gary

http://www.railimages.com/gallery/garypfeil

 

[Lehigh Valley]

Good luck on the helix. Take your time and build it right the first time. Make sure you have a good transition from your flat level to the completion of the first turn (ie, make a constant grade over the whole length of the first turn). That way your next turns will be at a constant grade also and will reduce the chance or your trains surging at they climb or decend the helix. If you don't have a constant grade (what ever % you choose) your train will surge forward on the easier grade and slow on the steeper grade and increase the chance of derailment.

Put you feeders on and track down as you build the helix. Don't try and go back later get it done. It will be much harder and you will not do as good a job.

Here is a picture of mine. I am in the process of building a second helix on top of the first. The constant grade on the lower heix makes it easy to build the upper one.

http://webpages.charter.net/dmnolan/P1140188.JPG

 

[shaygetz]

Great work on that helix, Mark. Sometimes the woodwork can look so good it seems a shame to cover it up with scenery.