So I’m halfway through building a helix, and what shows up on my doorstep, but the latest MR mag telling me I’m doing it all wrong!
I’m not going to put the track directly on the plywood, there’s no way that it’ll be flat over the joins. So, instead of cork roadbed (although I’m not sure why it’s evil) would you suggest using masonite instead?
Campers tape.
Just lay the track directly on the plywood. I did when i built my helix. Saves vertical space and the helix works flawlessly. No humps and bumps in the track.
Guy
It’s just the extra thickness that people try to avoid. This reduces the clearance required from turn to turn and thus can result in a lesser grade compared to a helix built with cork or other roadbed. Less grade = good.
I’ve seen many plywood and masonite helixes built and used with no roadbed … if built with reasonable care, there’s no unevenness at the joints.
[:-^]
I just carried on using WS foam roadbed all the way down. 4&1/2 loops. The only trick to it that I can think to mention is >> be sure to split the roadbed and put it down 1/2 at a time. It goes down supper smooth with no buckling. My sub road bed is made of chip board so it wasn’t that smooth to start with. But it works great now.
Johnboy out…
In building a helix, making the vertical thickness as small as possible trumps sound deadening. Mine is sculpted from steel stud material laid trough fashion, and the only thing between the steel and the Atlas flex is a thick layer of latex caulk.
Chuck (Modeling Central Japan in September, 1964)
Sounds like everyone’s making too big a deal out of something small! If you think about it, the cork roadbed’s 1/8" thick, as would be masonite, and my helix is 4 turns…that means not using roadbed saves a whopping 1/2" - That doesn’t give me another turn with lessened grade, that just leaves me half an inch below the next level!
If you do the math, it makes the entire helix a lesser grade because you need to climb less with each turn for the same radius. But if you don’t care, that’s fine. For folks without unlimited room for a broader radius helix, the eighths of an inch add up.
Double post
But it doesn’t…you still need to do the same number of loops in the same space to get up, unless the vertical space saved sums up to another clearance’s worth. If you lessen the grade just because you have more clearance, then you end up short of the desired height.
[:-^]
You are correct, it makes no difference. In this case the clearance is measured from the top of the road bed to the bottom of the sub road bed above it. All has to be accounted for from the starting road bed surface to the road bed level on the next level. Your variables are the space you have for the radii on the helix to accommodate the distance that you have between levels and your entrance and exit points and to make that a reasonable and acceptable incline.
It worked for me…
Johnboy out…
Some people are focusing on the overall height of the helix, which is immaterial: one can just adjust the entrance and exit grades.
The key factor in helix performance is the grade within the helix. Take for example a 16" radius helix in N scale. Personally, I’d probably want to climb at least 2 1/8" per turn for railhead to railhead clearance (1 21/32" NMRA minimum for the rolling stock, 1/4" for the roadbed above, maybe 3/16" for the track and adhesive above, and a little extra for possibly oversized rolling stock.
16" radius equals 32" diameter times Pi for the circumference, rise over run equals 2.12% grade. With the extra resistance of the curve, the effective grade is higher, maybe 3.25% or so.
With the extra height of an additional 1/8" roadbed, the climb is now 2 1/4" per turn, so the pure grade in the helix is now 2.24% and the effective grade with the curve is 3.38% or so. Maybe that difference is significant to you, maybe it’s not. But it’s real.
The OP clearly feels that he already possesses all the knowledge on the topic that he requires, so I won’t waste his time and mine with more replies. Good luck.
Isn’t the point of a helix to get up to a high enough height? If you don’t get high enough, what’s the point? In addition, the grade difference for saving that 1/8" per turn is a whopping 2.55% over 2.65%…so why am I not supposed to use roadbed? Apparently it’s a waste of your time to give a sensible answer, so…
LM&E Hogger: I understand that, but unless we’re reducing it enough to add another turn (or just add another turn and raise the next deck, but I’d rather not do that as it’s another 113 inches for the train to travel, and helixes take up enough time as it is! I love the sig, by the way.
There are two reasons to not use roadbed in a helix.
The main reason is time… It takes more time to install roadbed and it serves no function in a helix. Road bed is a cosmetic addition to track to make it look prototypical., it doesn’t serve a function other than to make the track look more like the real thing. Why take the time to put roadbed in a helix where you won’t see the track?? My helix is double tracked, with two separate parts for a total of over 100 feet of track, not installing road bed shortened the project construction time considerably…
The roadbed reduces the clearance between the track and the next level sub-roadbed. The extra height of the road bed doesn’t make any difference in the stack height (overall helix height) but leaving it out does give more room to reach in and clear derailed cars where space is already very tight.
Your original supposition that laying the track directly on the plywood would cause unacceptable humps and bumps wasn’t borne out by my experience actually building a helix.
There is no reason you cant put roadbed in a helix. I didn’t in mine, but the choice is up to you.
Of course, Your mileage may vary,
Guy
Guy, what did you use to join sections of roadbed? Did you use plywood? I have a very high-clearance method, but it’s not 100% stable.
I used Masonite tabs glued to the bottom of 1/2" cabinet grade plywood. Most of the stability in the helix stacks comes from the quality of the plywood used for the sub road bed and the number of supports that are put in to hold up each level.
Also check your “conversations” tab…I sent you a message.
Guy