Any response?

just my 2 cents

I think people obsess about noise. I think it's a non-problem, and I won't include noise as a consideration in my layout construction at all. So I don't think anything is necessary between cork and plywood, and I only view the cork as something to provide the profile of a ballast mound. Homasote is better than cork if you can cut it into strips outside because it holds track nails better. Whichever you choose, once you've covered it up properly with glued-down ballast it won't matter anymore. 

Also, I don't think tempered hardboard will take track nails at all well. And I think that even if your plan is to stick down your flex you would be well advised to nail down your turnouts instead so you can remove them for maintenance when problems occur. Tempered hardboard used for spline is a different situation, there the nails are going into the edge of the hardboard, not through the tempered/finished side. Save the hardboard for fascia or backdrop.

Best is a variable....

MDF = Bad

MDF excels at being hydroscopic.  When you start doing scenery with glues and wet water, the MDF will suck it up like a sponge and then bubble, deform and break down.

Track will be very quiet on cork, but the moment you lay ballast the noise level will dramatically increase.  There are probably more views on roadbed combinations than there are modellers.  The best suggestion I can make is to do several practice combos and pick the one you like best.

I would not use tempered

I would not use tempered hardboard. As eastwind stated it will be very difficult to penetrate the hardboard. Not just for nailing, but for drilling holes for under-track switch machines, as well. Drilling for wiring may be fine, as the diameter of the hole is much smaller. I would, also, be leery that 1/4" hardboard would sag over time.

I used the cookie cutter style with 1/2" plywood, actually 7/16". On top of that I glued Homasote roadbed. The plywood and Homasote was sealed with latex paint. Until I converted my rolling stock to metal wheels there was not much in the way of realistic sound, from the trains I ran. Once I converted all the wheels my trains sounded more realistic. The sound is not overbearing at all. Just adds a nice clickety-clack of the wheels as they pass over gaps in the track.

There are as many opinions about this subject, as there are model railroaders. This has worked well for me for a very long time. I am about to begin an expansion of my layout and will construct it in the same manner. Good luck with your decision. Glenn

Helix

Skip the Homasote in the helix. Just doing a helix is enough challenge and then adding cork will be plenty. Transition back to your methods when going into or out of the helix to the visible part of the layout. As others have said, once scenery and ballast are down the rail and wheel noise seem to get absorbed. 

just 1/4" luan?

so is luan good enough in a helix?   1/4" luan would certainly be thin enough.  not as hard for nailing as masonite and probably stiffer and easier to cut than MDF

supported with angle brackets on the edges to keep thickness minimal above the tracks?   how far apart should there be support?

track glued over a thin (1/16) layer of cork would probably minimize noise

Plywood and Soundproofing

Hi Tim,

I used 3/8" plywood as my roadbed.  The difference between 1/4" and 3/8" in warpage and sagging is considerable.  I have a traveling module with 1/4" luan top with cross braces every 12".  Over the years it has sagged 1/16" between the supports.

Regarding your helix noise...consider adding foam rubber(carpet pad?) behind the scenery and/or fascia.   It could be easily added after the helix construction and testing has been completed.

I used the cookie cutter

Bad news, Glenn - you're probably wasting your time by painting the homasote and plywood with latex paint, if the main purpose is to seal the wood. Latex paint does NOT seal against moisture. For that you'd need a sealer, like Thompson's Water Seal or something.

A few years ago I spent a couple hundred hours painting all my benchwork with brown latex paint to moisture seal it. Then I learned the truth. All I really got for my trouble was a lot of nice looking brown benchwork.

The sagulator

If you want to find out relative sag of various thicknesses, spans, and materials for roadbed, check out the sagulator:

https://www.woodbin.com/calcs/sagulator/

Roadbed

The MR project railroad was N scale so  the rolling stock and locomotives are very lightweight. That layout used 1/4" tempered hardboard (Masonite) only in the helix, if I recall correctly. Homasote laid flat has very little supporting strength. 1/4" Masonite is best if supported at least every 12" and the combo of Masonite and homasote or Masonite and cork should work OK so long as it is laid flat upon a plywood base or supported at least every 12" for N scale. I would not use that type of roadbed for HO or heavier locomotives and rolling stock.

On my own HO layout I have used Masonite with homabed road bed where I have minimal clearance for about a foot in length, BUT I epoxy glue 1/2 inch brass tube on both sides on top lengthwise the length of the Masonite to act as girders. I needed to do this to reduce the deflection of the Masonite to zero when a train travels over this portion.

John

Helix roadbed

I agree with not worrying about additional sudroadbed on the helix. On my last layout I built a double-track 2-1/2 turn helix and only used plywood. Not even cork. Pinned the track directly to the plywood. I used my trusty Dremel & a #75 drill to drill pilot holes for each of the track pins as I laid the track up the grade. Simply pushed the pins home with a pair of pliers. Since the helix was mainly covered by the layout and front skirting, the noise was nowhere near as noticeable as you would think it would be. A little noise actually was helpful to assure the operators the trains were still running OK in the helix.

Bye for now,

Lyndon Spence

Just a thought!

As I understand this. You want to lay track on a helix. IMHO track on a helix does not need anything. Just lay the track on wood or masonite or whatever and I would just caulk it/use a light coat. The only reason I love caulk so much is that it holds very well and yet can be pried up and moved if necessary. And caulk won't transmit any more noise than roadbed. If you do want it permanent, then nails are OK. (or liquid nails?) But keep in mind that nails can dent the ties or do other damage. And can be noisy as the nail transmits sound. As for noise, I tend to agree with Lindon, a little let's you know the engine is there! Also, there's the "it don't matter much" opinion. Good luck!

Remember the Gator board

Remember the Gator board helix?

https://i.imgur.com/SMwkKxmh.jpg

It's through provoking.  I saw it at the Timonimum Train show but want a larger diameter - more like 32 or 33 inches, which at that time wasn't available.

Helix ballast?

Forgot to mention in my previous post. A major contributing factor to noise is installing ballast. On my last layout, the double-track helix was hidden, so I did not use any ballast. No need. Maybe your helix will be the same. After all, the purpose of ballast on a model railroad is purely cosmetic.

Bye for now,