I am considering building a 2 track HO helix, with 30" and 27.5" radii. I want to run 85’ passenger cars, but do not have any rolling stock of that size to test my track clearance. Will 2.5" between track centers be sufficient for the overhang on these long cars?
Thanks, Bill
it be best to build a mockup on a scrap pc a ply or a table ect ,then just tack a little track down @ your radi &spaceing and push the equipment back and forth to see net clearance …but to be honest Id say 21/2 should work but test for yourself,the helix is going to be a tuff pull @ that radi w/85 ’ cars . …Im thinking along the same helix but @ that radi Im going to try an make it oblong ruffly 60x78 +or- to try and reduce the drag…good luck Jerry
Bill
The overhang of a passenger car is not the only consideration when laying out curves. There is more severe overhang in larger mallet type steam locos but not in the center. They overhang at the front and rear to the outside of the curves. You may not have large steamers now but later on you may. When I built my industrial track I laid out the curves and spacings from the freight cars that would be used in the sections. When it was all built and run my 0-6-0 through the area the pilot hit several structures that was close to the track. I never thought about loco pilot overhang.
Two and a half inches at those radius’s should be alright but don’t forget the outside clearances. If you end up widening the track spacing you may be placing the outside track dangerously close to the helix supporting structure.
Pete
You really need to aquire a sample of the equipment you intend to runa dn test it. You might be able to find cheap versions at a train show. Different cars have different types of overhangs, too - the long box cars tend to overhang to the outside of the curve (trucks are more inset than long passenger cars) while the passenger cars tend to overhang to the inside. Worst case usually would be the passenger car on the outer loop with the giant box car ont he inside, but you really need to test all combinations. On my previous layout I had designed 30 and 32 inch radius curves with 2" of clearance - it turned out to not be enough and I had to open up the outer curve to 32 1/2. The track spacing widended at the curve and then came abck together on the straight sections. This worked with everythign I tested it with - but you are proposing 27 1/2 and 30, with the smaller radius smaller, I wouldn;t guarantee anything without testing.
–Randy
First, the good news. 27.5" and 30" radius concentric curves should clear almost anything (except a hyper-long load that would require spacer cars to handle lengthwise overhang.)
Now, the not so good news. One full 360 degree circle of 27.5" radius is just about 14 linear feet - and a 14 foot train isn’t long. Add in that you will probably want five inches between railhead heights (clearance over a double stack, subgrade, roadbed, flex track - plus a little finger room for [oops] events.) That equates to a sustained 3 percent grade.
Now, if your levels are 15 inches apart, you will need three full turns of helix. An upgrade freight, lugging down to a speed appropriate to that grade, will be out of sight for a couple of minutes. Also, Joe Fugate discovered that his original short-radius helix caused operating problems - IIRC, he ended up rebuilding it with something like a 48 inch radius to ease the grade and the drag on his locomotives. This does NOT mean that your planned helix is unworkable. It simply means that there will be operational restraints that you will have to learn and live with.
My own railroad has a couple of one-and-a-little turn helices on much steeper grades (4 percent) and with a MUCH tighter radius than you plan - but I run very short trains of very short cars. At the one place where I will have to deal with a significant height mismatch (about 13 inches) I’ll be installing a train elevator.
Chuck (Modeling Central Japan in September, 1964)
Chuck makes some good points. One comment: It is possible to do a helix with a 3.75" spacing between railheads. No sub-roadbed, using 1/2 inch plywood will get you there. This will cut the grade back to more reasonable terms. There is little finger room, but I haven’t found the need for it as you can pretty much get to everything from the side and I rarely have derailments in the helix. 27.5" radius is tight but I have a 30"/32.25" radius double helix that works just fine.
As far as pulling power issues, I have found that free rolling trucks and high quality wheelsets pretty much make this a non issue for common train lengths found on most layouts. I can pull a 25 car reefer train up my helix (2%+ grade) with one cab forward, no sweat. Yes, the trains are out of sight for a while, but there are drawbacks to every climbing scheme…
I would suggest that the OP purchase a couple of the cars in question and mock it up to be sure of the geometry…even cheapie Athearn or some other inexpensive stand in will give you the clearances and you can use the cars for testing clearances elsewhere as you build the railroad without risking top shelf rolling stock during the chaos that seems to ensue during layout construction.
My two cents,
Guy
A while back I noted a made up test car in MR that was assembled from a pair of trucks and a sheet of plexaglass the size of a box car, but could be made to any size for testing trunouts and radi sizes. If you are planniong on using 85’ passenger cars then make your test body that size and use two pair of 6 wheel trucks. The clear plastic allows you to see the track, roadbed and any problems before you go to a lot of work and expense to build a helix.
Joe
2.5" spacing should be ok for the passenger cars (as noted, other cars and locos may be special), but the 27.5 will be tight for full length cars with touching diaphrams, such as the Walthers or Rapido. I run a set of Walthers on a half circle of 28" going up a 2.3% grade and that is tight. I had to do a little guage & cross level adjusting, making sure the circle was true, to keep the pressure between the cars from popping a truck off the rail. I know Walthers says 24" but I wouldn’t want to try it.
Can you operate with the passenger only on the outside track?
Phil
Bill
I think with those radius curves you should have no problems all you need to do to assure yourself that it will work is solder up a couple sections of flex track and tack them to a piece of plywood or what ever as long as the two track centers are 2.5" apart thats all you need to test your theory.no the grade doesn’t matter what so ever. I have posted a few pics form Easy Helix’s website showing their double track helix and it appears that they are using the same radius’s as your planning on using if not the same pretty darned close. You can always email them and inquire about their product and ask what are the recommended radius track center to center distances etc.
