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  • Routing plywood and how many plys?

    Now that I finished my second track, I have some ideas for a third track. But, it needs to be light weight. My first two tracks were routed 1/2" MDF. But, MDF is pretty heavy. So I'm wondering about routing plywood... how clean the slots would be. I have some pieces of 3, 4 and 5 ply 1/2" plywood. 3 ply doesn't look like it would leave a nice clean slot. 4 and 5 ply look pretty good. So, I'm thinking 4 ply, as 5 ply is expensive. Any thoughts?

  • #2
    While you can certainly route plywood (many tracks have been made with plywood) there are some things to consider.

    Depending on the quality, you may find..............

    1/ The slot walls may not be as smooth MDF, and, some tears/splinters etc. may occur.
    2/ There can be some "voids" in the plywood , where the glue has not completely covered both sides of the laminates.........this may show up when routing.

    Both of the above can easily be repaired with some filler and sanding, but, it is another step in the process if it occurs.

    While not a big issue, many folks who do work with plywood, say that the glue used in laminating the various plys' can clog the router bit, and, over time damage the bit.

    While none of these are big issues, the chances of this happening with MDF are virtually zero, so, if you are set on plywood, give it a try, but, overall, I think you will be happier using MDF.
    If you are "weight conscious",.... using 3/8 MDF may be a good solution, .......lots and lots of tracks are constructed of 3/8.......take a bit of care with the routed pieces of track when moving them around, and you will have no issues.

    Cheers
    Chris Walker

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    • #3
      I would never build a routed track from plywood for the reasons that chrisguyw stated. The first commercial track that I raced on was plywood, but there was tempered Masonite on top of that. if you must use plywood there are different grades, one used for cabinet making may have less voids or be less likely to splinter.

      Comment


      • Pappy
        Pappy commented
        Editing a comment
        And a lot more expensive.

    • #4
      You can get what is called light weight MDF. I am a trim carpenter and we use it when it is available. A sheet of 3/4 is approximately 30% lighter than normal sheet of MDF. It does come in different sizes including 1/2.
      Mike
      Clover Leaf Racing 7746 Clyde Road Fenton MI 48430 U.S.A. 313-473-SLOT
      web site: https://cloverleafracing.com Facebook: http://www.facebook.com/cloverleafracing
      YouTube Chanel: http://www.youtube.com/user/CLR132slots?feature=watch

      Comment


      • #5
        I did my second routed track from plywood in the mid 80's. . Back then there was no internet and I didn't know anybody that had ever built a slot track. It actually worked pretty good and 40 years later it is still in operation in another basement. Can't say that I remember any problems associated with using plywood. I think any weight savings would be minimal and MDF is definitely easier to rout cleanly.
        Click image for larger version

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        Matt B
        So. In
        Crashers

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        • Pappy
          Pappy commented
          Editing a comment
          1/2" MDF (not lightweight) 69 pounds.
          1/2" Pine plywood 43 pounds.
          Myself, I wouldn't even consider using plywood.

        • Fast Co.
          Fast Co. commented
          Editing a comment
          I never heard of lightweight mdf, but if a regular sheet of 1/2” mdf weighs 69 lbs, then a regular sheet of 3/8” mdf would weigh about 50 lbs and if you can get the lightweight stuff in 3/8” and it’s 30% lighter then you’re down to about 35 lbs. That’s the direction I would go..

      • #6
        I am looking for light weight and strength because it will be a large track (20 x 8) that will be suspended from my garage ceiling to be raised and lowered. That's only 5 sheets of plywood, so even 5 ply 1/2" is like $400.

        Comment


        • PetesLightKits
          PetesLightKits commented
          Editing a comment
          I just bought 1/2" cabinet/furniture/paint grade birch plywood for $37CAD a sheet. I am using it for a lower shelf and track table surface. The 3/8" MDF track will go on top of that.

      • #7
        Just a question here , but couldn't you use Masonite on top of the plywood , as in glue the masonite to the thinner sheet of plywood ? Just a thought . I know that with out looking a the prices of the materials what would be cost effective . They do glue masonite to what they call particle board for counter tops , wouldn't that be the same thing ?

        Comment


        • Bal r 14
          Bal r 14 commented
          Editing a comment
          Your suggestions are appreciated. This whole idea is in the planning stages, all options are considered.

        • Fathead59
          Fathead59 commented
          Editing a comment
          I am looking at all of the suggestions myself , for when I decide to ever take the plunge and build a track .

        • Bal r 14
          Bal r 14 commented
          Editing a comment
          There is no question, 1/2" MDF is the best material to use for building you own track. It's readily available at most big box stores, it's easy to route, easy to repair, leaves nice clean surfaces and edges, is relatively strong and reasonably priced. It's just heavy. But, for any time weight isn't a concern it is great.

      • #8
        Why not cut out what’s not being used for the track itself?
        That full 20’x8’ surely won’t be the racing surface. Fill in the cut out areas with thin foam, fiberglass screen or anything to keep cars off the floor.

        For the best surface with plywood, you’d want is known as ‘sign board’. It has a paper covering that takes pain very well.

        Comment


        • Billy boy
          Billy boy commented
          Editing a comment
          its called MDO i believe. nice surface

        • Mikeinclover
          Mikeinclover commented
          Editing a comment
          Billy you are correct it is called MDO
          Medium Density Overlay.

      • #9
        You may also want to take a look at "Ultralight MDF". It weighs about a third less than regular MDF of the same thickness, costs a bit more, is not quite as strong but is easier to cut and route. I made a small track out of this and found it good to handle and work with - really noticed the weight difference when moving the sheets around single handed.
        cheers
        Scott

        Edit - Ah, several posts since I opened the initial post and my reply. I see another suggestion for lightweight MDF. A 20' x 8' track will definitely need a supporting framework under it, so the slight decrease in strength of lightweight shouldn't be a factor. Frame design will be important.
        Last edited by GT6; August 9, 2021, 03:14 PM.

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        • #10
          WOW! what kind of lift system have you engineered. thats a long table.
          bill ,framingham ma

          Comment


          • Bal r 14
            Bal r 14 commented
            Editing a comment
            I have two of the electric attic lifts kits that were taken out of a house. They have been used, but still in decent condition. Frame design is definitely a big concern. I am figuring this project will take at least a year to do it right. I will be designing frame work and track layouts many times before I get it right. In the meantime, I have a new track I just finished and used once. I think I like designing and building tracks more than racing on them.

        • #11
          I seen a post somewhere , cant remember if it was on uTube or not , A guy built a track for his garage and used a truck winch to rise and lower it , had PVC pipe for legs . Again not sure where I saw that video

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          • #12
            As you work on the track design think about if you want to include elevation changes and any banking. Both will stress the track material which may constrain choices so you aren't chancing cracking. Overall I like a multi-layer approach. My oval is 1/4" Masonite over a 1x3 frame. I routed bottomless slots that went all the way through the Masonite so I never had to worry about crude building up in the slots - it just falls through. Individual pieces of MDF were glued to the 1x3 pine boards before routing and it's been rock solid for 16 years now. No need to use complete sheets of any material, just cut out the track sections then mount and route them.

            It should say Masonite above instead of MDF.
            Last edited by slothead; August 10, 2021, 07:13 AM.

            Comment


            • Bal r 14
              Bal r 14 commented
              Editing a comment
              Routing all the way through 1/4" Masonite is a definite possibility. Elevation changes and some slight banking is very likely. I expect to use aluminum angle for the frame. I like the PVC leg idea, too.

          • #13
            Here's an update... my garage slot track will have to be put on hold as we just committed to doing a major renovation to the garage. But, I am going to use the things I learned here to start work on designing my next indoor track.

            Comment


            • #14
              Don’t forget if you want a light track that is easy to store there is the option of 1/4” MDF. This is one of our tracks that has an long extension which disassembles into separate segments & hangs on the wall then the main table folds up against the wall. The segments are designed to fold very flat as the main table tilts up strategically against of the track extension segments. The 1/4 MDF is supported by lightweight crossmembers you can see. Each crossmember has a little bit routed out of it to make the slot depth a hair deeper than a 1/4”.

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              • Bal r 14
                Bal r 14 commented
                Editing a comment
                That is quite ingenious! It really opens things up size-wise, too. Thanks for posting images.
                Last edited by Bal r 14; August 20, 2021, 09:09 AM.

            • #15
              I believe there is such a thing as marine grade plywood. I'd look into it, as I would think it would be the highest possible quality. A bad sheet of marine grade plywood could result in a tragic failure in service.

              I also believe any such plywood would be very expensive.

              If I were going to try to make the lightest possible track I would go with CNC routed MDF, but routed on both sides. Rout the slots on the top surface, rout the underside to remove excess material, leaving a lattice of ribs with triangular voids between. Do those underside cuts with a large diameter router bit to keep the machine time down to something less than insane. Of course making sure the underside cuts don't intersect the slots would be very hard to achieve, except that CAD design and CNC routing are the perfect tools for doing that job.

              At a guess I'd think you could reduce the weight by one-half to two-thirds. The reduction in stiffness might not be that much.

              If I wanted to make the whole thing a lot stiffer I would glue-and-screw a thin sheet of Masonite to the underside. May or may not be worth the extra weight. You might do as well or better going to a thicker sheet of MDF to start with. Either way you might need very little framing underneath in the final assembly.

              I once built a track with a lift system in my garage, but it was only a 4 x 8 HO track. Would you believe the lift system was powered by a windshield wiper motor out of an automobile? Seriously. It did work. Very marginal to be sure.

              Doing my duty as a licensed engineer I'd recommend checking the load-bearing capacity of your garage roof. I had to do that once for a rental property when the tenant asked if he could install a waterbed. In that case I discovered it would have been safe to fill the whole room with water a foot deep. I okay'd the waterbed. Never caused a problem.

              Ed Bianchi
              Last edited by HO RacePro; August 20, 2021, 08:50 AM.
              Ed Bianchi
              York Pennsylvania USA

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