Anyone try any small diameter helixes? I think an 027 circle helix would be nearly impossible with a 7.4% grade. How about a 42" or 54" helix?
27" would probably be just about worthless. 42" would be the absolute minimum, and you may not even be able to get 5 cars up without some spinning. Each engine will be different, but I think you want something that most engines can reliably climb. I haven’t built any because it takes up a 1/2 of my available space.
Wes
The problem with helixes is the stress put on the couplers and the cars themselves. Anything under O72 would cause too much stress (due to overhang) and could really cause some nasty derailments.
I designed one for use as a display/storage unit under my layout, the problem was it would require building this first and then building the layout, and I’m glad I decided against it because of all the construction dust. If I were going to do this I would modify the design to each ‘leg’ were more like a small yard so you could get access to different cars in the display. A small switcher for getting cars and building the train would also be cool. Then you couple the engines and bring it back up to the layout.
Hi Boyd
There is a vendor, Ashlind designs [?sp? google it] that markets helix kits. principally for HO but they can/will do O. all you need do is put it together. OH and pay for it, the shipping is most of the cost. Another way is to prototype…relatively cheap…Michaels hobby stuff store…flowers and the like…sells circles of foam and mdf-like materials. You can cut and try it with some dowels to see what the slope etc. will be. you can even try a small set of rolling stock. then if it looks like what you want, and it is reasonably stable, power it up for a test drive. THEN build a production model substantively.
I bow to the experts, but if you really want one, think out of the box. Think of a cone or oval. There is no rule that says it has to be a perfect circle where one loop is just above the previous or just under the next with a constant diameter. Mix the diameter of the track and mix short sections between. This will control the slope/grade of the route to keep it manageable for PW locos, Beeps etc to run. If you are thinking big-boys or some of the larger scale MTH stuff, you will have a lot more engineering to figure out - weight is a factor in buiding it. think of an 0-31 diameter and short trains. it will work. Also, if you do invest time/dollars, build a two/three track one.
From my table top to an under table storage yard double track…one up and one down to a freight yard where i store my stock and some engines…unfortunately not up and down the pathway at the same time…i did not allow for passing, even with the small engines. It isn’t a visual, i need sit on the floor to see the operation. I began it after most of the benchwork/tabletop/trackwork was laid. A second undertable yard for my engines [principally] uses an incline to decend/ascend.
Note: in the layout it is located in a far corner and i must hand/knee to get there. While i’m still working on the wiri
I did some quick calculations for grade with the inches climbed per loop.
circle==6" rise===5.5" rise===5"rise
27-------7.07--------6.48----------5.89
42-------4.54--------4.16----------3.78
48-------4.00--------3.64----------3.31
54-------3.57--------3.25----------2.96
60-------3.22--------2.93----------2.66
72-------2.62--------2.43----------2.21
Cheech, the cone design works fine until you get to the smallest loop, whether on the top or on the bottom. Then that smallest loop has to cross over or under itself if the train is going to be able to get anywhere outside the helix.
+I remember a store in Mingo Junction,Ohio that had a window display of a helix with a train going up and down.It did not connect to a layout and was a self contained display.There may have been a second train.This was with tubular track and I think it was Lionel.This was in the late 1940s’ [I think].Could this have been a magnetraction display?
I have vivid recollection of this and saw it for several years and I don/t think I imagined it.
Anybody have any info?
I remember a store in Mingo Junction,Ohio that had a window display of a helix with a train going up and down.It did not connect to a layout and was a self contained display.There may have been a second train.This was with tubular track and I think it was Lionel.This was in the late 1940s’ [I think].Could this have been a magnetraction display?
I have vivid recollection of this and saw it for several years and I don’t think I imagined it.
Anybody have any info?
Hi bob
your correct…
…but its a matter of being creative on the entry/exit.
the goal of the helix and whether its a layout centerpiece or a method for getting items to a different level has a lot to do with it.
ralph
Boyd,
Thanks for providing the helix/grade chart. Based on C = 2 Pi r, I agree with your calcs.
Would you have any idea how many cars could be pulled up which grade with how many engines (a. postwar w magnatraction), (b. modern w/traction tires)?
runtime
I’m afraid Boyd’s numbers are a little optimistic, at least for tubular track. The nominal diameter is to the outside of the ties and sometimes a little more even than that, whereas the actual diameter between the center rails is what counts. For example, for O27 track and a 5-inch rise, the grade is actually 6.37 percent.
The actual radii, as I measure them, for O27-profile track, are 12.5, 15.75, 20.25, 26.375, and 35.25 inches respectively for O27, O34, O42, O54, and O72.
Another disappointment is that the clearance is reduced from the rise per circle by the thickness of the track itself and of any board that supports it, although a clever design could, for example, support the track with crossbars between the ties or inside the ties and dispense with that.
Thanks Bob,
You are precise and acurate as usual.
I still hope someone can answer my question about cars pulled/ engine(s).
runtime
Right now I don’t have the time to build any helix loops so I don’t know how many cars can be pulled up that size loop. Yes my calculations were calculating the grade on the outside edge of the track accept the 48" loop which would be Fastrack. Fastrack circles are measured center rail to center rail. On all the rest of the circles to be perfectly perfect I should have figured out the grade center rail to center rail but don’t have time for that. But I think I was close. On the steepest part of the Lionel graduated trestle set rises 1/2" per section. Straight 027 sections are 8.75". So the grade on the steepest section if just using straights is 5.71%. Its my office layout I’m working on a simple 027 layout. The plans are to run my K-Line Porter on it just pulling 5 or so cars. If it has trouble I could buy a 2nd Porter and run a double header.
Below is a test I ran (from a previous post)
Hello all,
Because of your excellent feedback I decided to do a grade test with my locomotives. I used a K-line 4-6-2 Christmas loco(Cab 115), a few beeps (cabs 204, 274, 1224, and 2005) and a K-line Plymouth switcher (PS). The PS has no traction tire. All the beeps worked best with the traction tire in the rear. Beeps with new traction tires pulled better than ones with old tires.
On the straight grade I could go very steep. Even with a 21% grade my 115 would pull its tender plus a full train. A “full” train consisted of three K-line cars (O27) and a lighted RMT caboose (LC). However, on the down slope in reverse the 115 was very jerky in operation. One of the beeps with a new traction tire could pull the LC and one 027 car up 21% without slipping!
Two beeps pulling together could pull the full train up a 10% grade. However, the duet could only pull one 027 car and LC up a 15% grade.
The Plymouth switcher could only climb a 15% grade and that without any cars.
With a 5.2% grade most beeps could pull 3 cars and the LC. One of the traction tires was bulging though. Double heading the beeps increased the full train grade potential to 10.4%.
Next I wondered what would happen if the rise was on 027 curves. I limited the grade to about 6% (5 inch rise over one circle of 027 track). Again the K-line 462 pulled a full train no problem. Here the Beeps ran into different problems. Because of the fixed 4 wheel frame they tended to “jump” off the track under load. Also, sometimes one of the drive wheels would lift off the track causing the beep to spin. The PS excelled here because of its short wheel base. I think it struggled up spinning with a full train! Because of the above results I decided to go with a helix made with 031 curves.
With 031 curves and a 5” rise (5.2% grade) everything was much easier. The PS could struggle up the grade pulling three cars and
I’m just glad someone finally pushed all the math aside and started testing! Thanks Jim.
Wes
Warning: Post contains math
May I suggest my favorite track, Marx O34, as an alternative to O31? Its diameter to the ends of its shorter ties is not even 3 inches greater. And it’s 1/4-inch lower than O31 since it uses O27-profile rails. For example, the clearance of a 5-inch rise with a 5.63-percent grade in O31 can be duplicated with a 4.80-percent grade in O34. Conversely, the same 5.63-percent grade can achieve an extra .89 inch of clearance when done with O34.
That’s right! Try it!
And use the lightest cars you can find.