When using the cookie cutter method on plywood, does it make its own vertical curves? Do the grades have their own easments? Or do I have to manually/consiously add these effects?
I was originally planning on cutting these features into faom on top of plywood but it seems I have plenty of plywood and bits that can be used as risers so I’m thinking of doing cookie cutter instead.
3/4" plywood, which is what you should use, is pretty stiff. You’ll have to form your own easements into the vertical curves. Except for extreme cases I really try to limit the grade to no more than 1 3/4 to 2 percent. This means roughly a 1 3/4" to 2" rise every 8 feet (or 100 inches to be exact).
When setting the risers, just install the ones on each end of the hill to set the grade. When that is done bring the middle ones up from the bottom until they just touch the bottom of the ply.
At the bottom of the grade you’ll have an angle where the hill meets the straight/level run. Gently set your flex track so it spans this section and let the natural sag of the track form the vertical curve. Backfill the gap under the sag with ballast.
At the top of the grade you can sand a slight roundness to knock the corner off. Hope this helps.
Lance Mindheim
Visit Miami’s Downtown Spur at www.lancemindheim.com
I understand what you’re saying but, I was thinking of doing the grade all in one sheet of plywood, not multiple pieces. Said differently, the entire grade and verticle curves would be one continuous strip, like spline roadbed turned sideways.
This avoids any sharp angles at either end of the grade, just not sure if the curves would be too tight.
As long as the grade isn’t extreme, say 2% or less, the plywood should form its own easements top and bottom if it’s continuous into the flat areas at the top and bottom.
Here is a link to an on-line Google book by Jeff Wilson showing some benchwork construction. There is a section on cookie-cutter including an up hill curve using a contiuous piece of plywood. The captions also show how he recommends setting the risers.
Also, if you have an overpass, be sure that your supports are firmly secured, before cutting out where your bridge(s) will be placed.
Unless you can find sheets of plywood longer than 10 feet, you’re going to have to do it using more than once piece. I ripped a sheet of 4x8’ 1/2" plywood into strips 3 1/2" wide. I used joiners made of the same plywood that were 6" long, instead of the 4" I usually used. I knew what clearance I wanted at the top, so I screwed the sub-roadbed to a riser at that point. I CLAMPED the riser to the benchwork at that point. Then, using a 4’ beam level, I adjusted the risers between the bottom and the top so there was NO gap between the level and the strips. I then laid the roadbed and track before permanently attached the risers. Using a train made up of my longest cars (passenger cars), I checked to make sure there were no coupler issues at the transition points at the top and bottom. Once everything was fine, I then attached the risers to the benchwork using screws with NO glue. It’s worked for me.
Yes, the plywood will form its own vertical curves naturally. In my smaller spaces, and modeling lumbering and narrow gauge lines with 4%+ grades, I find 3/4" plywood way too thick to bend into the curves I want and need. But note that I have short engines and cars - I use 50ft passenger cars - in HO and HOn3 that can negotiate tighter vertical curves. I have successfully used 1/2" plywood in the past, and will use either 1/4" or 1/2" on the current layout.
Putting bends into plywood actually makes it more rigid - a level piece of 1/4" plywood that would sag between supports will not sag if bent into an arc at the same support spacing.
As suggested by others, lock the ends of the plywood into the desired grade (usually flat areas) with at least 2 risers. The plywood will assume its own natural vertical curve between the two pinned areas. Just support the natural curve at reasonable intervals. On a long grade, you also may want to pin the midpoint(s) to form the curves on either side.
Final note: if the grade is on a curve, you will have to force some twist into the plywood with the risers to keep the track level across-ways going up or down the curve. The unwanted superelevation and negative superelevation occurs naturally and has to be removed. The tighter the curves and the steeper the grade, the more the plywood will have to have the twist induced. Don’t ask me how I know this - I had 4% grades with 18" radius curves with 1/2" plywood, and the unwanted tilt was quite visible. It would be very difficult to twist 3/4" ply in this situation.
Fred W
The only issue I had with Jeff Wilson’s method was how he attached the subroadbed to the risers. I learned the hard way. I modified mine to use Linn Westcott’s method to attach the strips to the risers from underneath. If you attach it from the top, then you have dig through track and roadbed to find the screws should you have to modify it.
Hi, to make the bending of your plywood a bit easier, just cut a series of crosswise grooves on the underside, but not more than about 1/2 way through. Don’t forget to do the same at the top of your grade as well.
3/4" ply is rather stiff. If you are building a 4x8’ layout, 1/2" ply might be a consideration. Mine is 11x14’, using a 2-layer sandwich of 1/4" plys, cookie-cutter style with the layers glued together. Use lotsa clamps! I set the bottom layer on its risers and then glued on the top layer. If you go larger than 4x8, just be sure to stagger the joints by at least 6" for strength.
Have fun, George
Agreed. But he does address that. He has a paragraph that states that if you are thinking of making changes, maybe you should use risers with cleats “as shown in chapter 7”. Maybe they added this if they revised the book?
The plywood will form its own vertical easements when properly installed. Fasten the roadbed in place at the bottom of the grade at the point beyond which you need it to be level. Raise the section which will form the grade (it can be multiple sections joined together with plywood splice plates - I have one which is over 45’ long and includes an “S” bend) and fasten the top end at the point beyond which it must be level. The roadbed thus attached has now already formed its rough vertical easements. Find the mid-point of the grade, attach a riser to its underside, and raise or lower it until the top of the roadbed is at an elevation one-half that of the entire grade. Fasten the riser to the layout’s framework or, if you want to add eased superelevation to a curving grade, simply clamp it in place. On a fairly short grade, using 3/4" plywood and with no superelevation required, you can probably just add all of the other risers, attaching them to both the roadbed and the layout without further adjustment. The vertical easements will have formed themselves. For longer grades with no superelevation, it’s probably best to further subdivide each half of the grade into halves again, repeating the riser installation as necessary. Don’t, however make any vertical adjustments as you near the top and bottom of the grade, as the self-formed vertical easements will be disturbed.
To add superelevation to a curve, on a grade or not, is very simple using cookie-cutter plywood subroadbed. Attach risers to the underside of the roadbed at all points where there’s a layout framework member to which they can be attached. Next, raise the ends of the curve to the proper elevation and, if not already done, attach the roadbed to the tangent track. Now, raise the curved roadbed at the riser closest to the mid-point of the curve and clamp it in place. If the curve is a long one, repeat this
OK, I kind of thought the ply would make its own vertical curves, just wasn’t sure.
Thanks for the tips on superelevation, I hadn’t considered that as a problem but the solution sounds way easier than fixing it later.
So now to finish cleaning out the mess from tearing down the old layout and making an inventroy of what is still useable. Then reconstruction can begin…
If I am understanding correctly what you want to do you would be better served by using spline subroadbed cut form 3/4" x8’ clear pine shelving into 1/4" thick strips. pine has some natural flexibility to it you will actually need to keep the 8’ long pieces from whipping their so flexible.
You have two options spline subroadbed a la Howard Zane using pine strips cut into 1/4" thick strips from 8’ long pieces of pine shelving using pivot blocks and homasote roadbed or Homasote cut into strips and stood on end and glued together using lots of clamps and lots of white glue. Same method used by Allen McClelland on his famous V&O layout. In my O/p Howard Zane’s variant is easier to achieve vertical curves and easements as your working with thinner pieces which are more flexible.
You can most likely achieve some what the same effect using cookie cutter and 3/4" plywood but it will entail doing a lot more work.
I’ve done both in the past and have had good luck with them both, I think I prefer the cc better though. as far as material goes you can probably get away with 1/2 ply its cheaper, I use it on my layout (soon to be dismantled) with 1x4 framework and it is very sturdy, I can stand on any section of my layout and I have. I am no lightweight either, last time I looked at the scale in my bathroom it said 240!