I require some input from members regarding the length of trains that they operate on a helix that has a radius of 24 inches. It would be good to know how long of a train and the type of equipment used to pull it. Here is the reason why:
I am in the process of planning a new layout in HO in a 24 foot by 24 foot space above a garage. The theme is that CP had a huge increase of business in the 90’s, so they had to rebuild their main line that contained a spiral tunnel. After completing the work, the government forced CP to sell the spiral tunnel to a competitor-competition law-political reasoning beyond the understanding of the average human.
The result is that the old spiral tunnel line is operated by a shortline operator, using old SD40’s, Alco C630’s, MLW 424’s and other old equipment while CP uses the large AC’s to operate their main line. The spiral tunnel -which is 24 inch radius- is to be inside the loop from CP-36 inch radius-which follows the edges of the layout. From this point the main lines are to enter their own respective helix to climb to the upper level. The CP main line will be in a 36 inch radius helix, while the shortline is to be in a 24 inch helix.
I have had a layout that had 3 levels connected by a 30 inch helix and was able to pull 30 car freight trains with 3 diesels, without issues. Will it be possible to pull a 15 car freight with three diesels up a 24 inch helix? This would make a great contrast to pulling a 24 car freight up the 36 inch helix with just two diesel engines.
What are your experiences with a 24 inch helix and 36 inch helix?
I think you’ll have problems with the big six axle units on 24" radius, even if it’s not on a grade. The problem with a smaller helix is it’s a double whammy - as the radius decreases, the grade has to increase, making things even worse.
Any mention of the “H-word” will bring a lot of responses. Most telling you that it will only work with a large radius because of either the “effective grade” or the potential for stringlining.
My last layout had a 24" radius helix. I was only running 4-axle diesels at the time, but I had no trouble pulling 10-12 cars up the helix with a pair of the old yellow box Atlas RS-11’s. I was very concerned about making sure that it was going to work so I was very careful with the trackwork and it was tested to death. The only problems I had was pushing a train up the helix. This resulted in a derailment about half the time. I don’t recall the exact grade, but I used 1/2" plywood and met the NMRA minimum clearance standard.
Grade is another religous arguement. I asked a few grade questions a while back and the concensous opinion seemed to be that I can’t know what would work without testing it with my equipment. As a result I built the lower level benchwork and subroadbed of my new layout without risers so I could experiment (it was a real pain to go back and install risers afterward, btw). This portion of the layout is a 9.5’ x 13’ U shape with 24" curves at the corners. I pulled 22 Broadway Limited hoppers up a 5% grade with a pair of new Athern SD45’s without problem. The cars were frest out of the box so slightly under NMRA weight. These 2 locomotives could have done more, but due to a lader type riser I already had in place for the track above, I couldn’t test with more than 5%.
I have also tested several 6-axle diesels on the 24" curves without problem. Tested were BLI and Athearn SD40-2’s, Athearn SD45’s, and Bowser C628’s. The C628’s would do better with a longer shank coupler, but they all worked.
This of course represents my experience only and is not a recommendation of how you should proceed. I do guaran
I have more Helixes on my layout than I would like but needed them to accomplish the project.
Most are only a 1 or 2 turn Helix.
One I made purposely at 3% and most single unit trains require a Pusher!
All radiuses are 24" or slightly larger!
I have never understood the reasoning if having pusher service on the layout IF YOU DON"T REALLT NEED IT!
If I have a 2 unit consist then the trains will pull all of the Grades and Helixs on the layout - We just run some single engines to give the crews a little more to do!
I have a Pusher engine (with its own Throttle) stationed at the bottom of the one Grade/Helix and the crews can easily run the pusher up the hill as the coupler has been modified so it doesn’t couple and once the train come out of the tunnel at the top the Operator just flips the throttlle into reverse and runs the Pusher back down the hill and into the pocket for the next train!
Give the crews some real fun things to do - not pretend that the train needs a pusher when it doesn’t!
I’d go with a radius larger than 24. While long wheelbase equipment that says it runs on a minimum of 24 inch radii won’t always do it. Walthers equipment is well-known for not making the minimum suggested. This means passenger equipment, auto cars, and anything longer will likely have issues. I’d make the helix as large as possible just to ensure you can run most anything.
Due to layout configuration I don’t have any helices on my main line - but I do have one loop-back which turns through 270 degrees of curvature on a sustained 2% grade, 610mm (24") radius. So far it hasn’t caused any problems. There’s another ‘over 180 degree’ curve of the same radius on a visible 2.5% grade scheduled to go in the opposite corner when I build out to that location.
Of course, I run short trains of short cars, most of which have needle-point axles running in steel bearings (read, "What rolling resistance?) I’ve never tried to move a Powder River Special or a BNSF-length train of stacks and racks. My biggest locomotives are 2-C+C-2 catenary motors. (Their protypes are 2-Co+Co-2, but the models have three axles geared to each motor.)
My helices are on my mountain goat route, 350mm (13.78") radius, 3.51% grade, 1 1/2 turns or less. They don’t connect levels, but do serve to help with some vertical mismatches/clearance issues. The usual train is a couple of 4-wheel wagons and a short coach, with a pair of 0-6-0T kettles for motive power. The ‘long’ train is powered by a modified Mantua 2-6-6-2T and is less than a half-turn of the helix long.
The one basic about operation on serious curves and grades - all cars should be of similar weight and the weight should be kept low.
No less an accomplished modeler than Joe Fugate found a 24" radius HO standard gauge multi-turn helix to be too tight for mainline operation and rebuilt it to much broader curves. You can read about it in this older thread, scroll down to the next to the last post to read of the problems he experienced and how much better things are with the broader helix.
thank you for the replies. They are greatly appreciated. It is good to read that also six axle units have made it up a 24 inch radius helix. The reason for the difference in diameter as mentioned before is to convey the reason for creating a new main line while at the same time introducing interesting operating challenges.
I model a narrow gauge prototype in 1:80 scale on 16.5mm (HO) gauge track.
My helices are laid in dodecagons of steel stud material, about 3.25 inches (82mm) railhead to railhead height.
When I said, “Keep the weight low,” I was referring to a low center of gravity. My preferred method for adding weight to TTT cars is to wrap wire solder around the axles. Of course, my short wagons actually weigh out at (barely) NMRA RP for HO stock.
Chuck (Modeling the vertical scenery of Central Japan in September, 1964)
I checked Joe’s comments in the other helix discussion. When I read the comments on bigger radius I assumed ok, 30, 32, even 36. But no, he replaced the 24-inch helix with a whopping 40-inch radius helix!!! That is absolutely gi-normous! They made it fit, but what a beast!!! It would be interesting to know what is the happy medium between too tight and huge. Bigger is always better of course, but like most things in the hobby, compromise is usually a big part of the game.
I considered a 450 degee helix with 30 or 32 inch radius in my 10 x 18’ room, but have instead decided on going with a 3% grade an a “no-lix” design. The helix would have fit, but the benefits would have been minimal for the trouble it would have been to construct it. The 3% grade is considerably steeper than I wanted but it’s been complicated enough to shoe-horn in the amount of running I want with generous curves and an around the wall design, after so long of not having a layout.
You knew it was coming… It depends on what you want to run. [:D]
24" worked fine for me with 4 axle diesels and 12 freight cars of 50’ or less. It would have sucked with a 20 car SP Daylight at NMRA recommended weight.
Having moved, I had a chance to start my layout over. The layout in my old house had a 24 inch Helix. While I had not problem pulling at 24 car coal train up the helix it was a bit nerve racking. The helix limited the type of equipment I could run on the layout. I was not able to run any passenger trains at all and had to put longer couplers on my six axle Diesels.
The new layout has a 28.5" and 31.5" radii double track helix. The larger passenger cars have no issues navigating the 28.5" inside helix. This lets me run all my passenger equipment (BLI Zephyr and Walthers cars) without issue. I have 4 return loops on the outside of the helix as well that are 34.5" radius as well.
From my perspective I am glad I did not go with another 24" radius helix. It was just too tight for the eqiupment that I run.
Sorry I was less than clear. I was not talking about 24" curves, but a 24" radius helix that “worked” for me on a previous layout. And as you guessed, the theme was mid to late 1950’s.
You are of course correct that a helix is not (exactly) the same as a standard curve, but what works on a helix, like a standard curve/grade, is still dependant on what equipment you plan to run and how long/heavy your trains are.
It is still the same grade on a curve problem - it’s just that the curve is more than 360 degrees. Your 40 years of experience still applies. The only extra consideration is that because the loops are stacked on top of each other the choice of radius effects your minimum grade.
My layout has two 24" radius helixes of 3 and 4 turns. A two unit lashup of 6 axle diesels will pull 20 two bay hoppers with loads without a problem. I use Atlas U30c and SD35/SDP35 units for coal drags. General freights of 15 cars are also possible. Four axle diesels are limited to about 10-12 cars (very realistic). Helpers should be on the front end, as pushing up a steep grade with tight curves is asking for derailments. The helix is on 1/2" sanded plywood with 3 1/2" spacers (1x4 blocks laid on their sides). Great care was spent on insuring a constant grade and near perfect trackwork. Be sure to use grade easements at the top and bottom so couplers do not have a chance to mismatch. Yes, I was concerned about operational integrity when I built it, but after learning the limitations of grade and curvature, I do not have any issues after 2 years of usage.
In HO, I’ve built helices on my layout and for a friend. (Most of mine are double track with 30" radius on the inside and 32-1/2 radius on the outside.) They work fine and are the best track on the layout. (The above grades worked out to about 1.7% and 1.9% respectively.) Your 24" radius helices will work with shorter trains and a limit on the wheel base of locos. But most commercial steam locos will hardly pull anything if at all on a grade and curve like this unless they have traction tires. Brass steam locos are the worst. (Be aware that even if a model steam loco can do the job on such a steep grade with traction tires, you could burn up the motor.)
IMHO, there are two important factors on a helix to make sure things work right. The first is to make sure things are level across the top of the two rails. I used threaded rods to support my helices and during construction the helices want to twist, so I use a line level mounted on a small block of wood to check things across the top of the roadbed and the two rails. With threaded rods and nuts and washers, I can adjust anytime but preferably before the track is down!
An equally important factor is to make a consistent grade. I did this by using a small tool made from a small, rectangular block of wood with an adjustable wood screw on the end on the underside and the line level on top. When I build the first level (lowest) I adjust the grade until I get to where the next level just starts to cross over the bottom level. If the overhead clearance is too high, I back in the screw and try it again. If the overhead clearance is too low, I back out the screw and try it again. It might take severa