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New oval about to be built

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  • New oval about to be built

    I started posting about building a new version of Shepherd Speedway in March. After getting a lot of feedback on many ideas I finally have a finalized design and appointment with a CNC shop to get the routing done this weekend. This is working out great because even though it's summer I'm still in stay at home mode and can take my time getting it put together, taped, and wired up. The plan is to have it fully working and tested out before deciding to take down my current version of Shepherd Speedway that's been in use since 2005.

    The plan was for the track to be a 3 lane oval (suggested by Harry), but since I've been a solo racer for over 5 years now I didn't want the other lanes going to waste. I designed a 3 lane oval that could be transformed so a single car crossed over to the other lanes to make 3 loops before completing a lap.

    Here's the crossover section I designed.

    Click image for larger version

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    Wobble proposed a longer crossover section that could also be swapped in & out with a normal straight section.

    Click image for larger version

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    I ended up designing 4 foot long interchangeable straight sections that fit into the 8 foot front and back straightaways. I exchanged emails with Brad Bowman (Brad's Tracks) who was creating the CNC program for me and decided to move forward. Brad interpreted my plan differently than I intended and put the crossovers in the corners.

    Click image for larger version

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    The transitions will be much smoother this way but the track will now be a dedicated 1 lane track. I decided to go with this design and this is what's getting CNC routed this weekend. The corners are designed to create around 8 degrees of banking when the straight sections are pulled in to be parallel. The finished track will be 14 feet long by 6 feet wide.

    When I get the track pieces home I'm going to be asking for more input on final assembly. For starters, should I attach the straight section to the corners before pulling the corners in to create the banking? One long (4 foot) section and short (2 foot) straight section will go on each (front & back) side of the track. I also want to flatten out the banking from the corners as quickly as possible rather than maintain the banking all the way around the track.

  • #2
    Just my opinion, but I think you are going to have issues and the crossovers are just going to make it harder. While I like the idea of crossovers in the corner on an oval, I still prefer two distinct lanes. I tried to make an oval with corner crossovers a long time ago. It worked (kind of) I used the crossover points from Scalextric curved crossovers mated into Monogram full size 1/32 track. The original plan for corner crossovers was in a Popular Mechanics back in the early 60's. It was all drawings so I'm sure an actual track was never built.

    I'm sure a simple 3 lane oval will be more enjoyable in the long run. Fiddling with a 3 lane crossover in the main straight will require complicated wiring and probably you will be d-slotting every other lap, which is a quick way to get tired of slot car racing.

    Just my opinion and I was wrong one time. Give it a lot of thought and anybody else have opinions before his wood gets cut? Be a shame to do all this work and not be happy with the result.
    Matt B
    So. In


    • #3
      Well.....I would say it's just wood, and it's just a slot car track. If you don't like it, change it. Easy enough.
      I would also say that it's wise to make sure that the entrance side of the crossovers should be slightly wider than the exit so a slightly sideways guide flag doesn't de-slot you every time like Matt says. I did that on a figure 8 and it worked ok.
      The wiring isn't hard, but it is tedious and very detail oriented. I had to do it one at a time so I didn't mess it up. Theoretically you could run wires to a numbered terminal block, if desired.

      As far as attaching straights....I presume in the CNC cutting they will do the pie angle? If so, then I would attach the straights since the longer lever arm will make it easier to pull in and align. If not, then you can't have the straights on until you bend the curves in to mark and cut the angle.
      If it was me, I would put the crossover back on the straight to make it easier to swap later......but that's just me.
      Come Race at The Trace!
      Timberline Trace International Raceway - SW of Mpls, MN


      • #4
        Thanks for the comments guys. The current design of the track isn't what I decided on but is worth trying because it's how the CNC files were created. I can always have Brad redo them if this design doesn't work. Getting the files done cost me $100, having them redone would cost about the same. It's going to cost me $200 - $300 to have them routed ($45 an hour for the shop operator's time and 25 cents a minute for the CNC machine). $400 is less than I thought it would cost and I'm fine with giving this a try. The money I'm saving by staying in will more than cover the cost of the track.

        Since the track is actually just one long lane all I need to do for wiring is send power to one pair of copper tape rails and add jumpers to the other rails. Yes, I will have to bridge the 2 crossover points by making connections under the track but I expect it to be like putting in a couple of dead strips. And, because it's a single lane track it only needs one dead strip for the lap timer/counter. I will use numbered & color coded terminal blocks under the track to keep things straight.

        Bottom line is, for $500 or so I think it's worth a try. I've already purchased the copper tape and have plenty of wire and connectors on hand. If it doesn't meet expectations I'll probably just hand route a flat oval and slant the corners like Harry did on his track. (The pie angle for the banked corners on this track is in the current CNC file.) That will just cost me 2 more sheets of MDF, time, and more copper tape.
        Last edited by slothead; July 15, 2020, 01:20 AM.


        • mattb
          mattb commented
          Editing a comment
          I'm just trying to make sure you give this a lot of thought. Seems like you could actually just rout a 1 lane oval and have what you want. Just be sure to let us know how it works out.

      • #5
        gee, i liked your first one with one replaceable crossover straight. if one fed the power to the track on that section and connected the driver(s) panels to it then the wiring wouldn't be an issue.
        i did a very similar thing on my test track, which comes apart in three sections. it has plug-in connectors on pigtails underneath for the wiring to cross the joints.

        when i was a kid we raced midgets on an oval where all the lanes were identical size and shape, offset diagonally so that an outside lane would dive to the inner one at one end of the straight entering the corner, and then run straight through the others back to the outside at the other end, etc. it took a little judicious filler at the crossovers sometimes to keep it working, but it wasn't too bad compared to the fun and realistic racing line action that it provided. i've been tempted to recreate it but we don't do a lot of oval stuff around here.

        [how far up in Maine are you? i'm in Merrimack, between Nashua and Manchester (NH).]
        Last edited by SpeedyNH; July 15, 2020, 10:29 AM.


        • #6
          I appreciate your comments. If this track doesn't work out as planned and I end up routing another oval I think I'll make it 2 lanes with a crossover section that can be added if desired as if it was a plastic track. This way it could be raced on with 2 cars or used solo with a single car that will alternate lanes.

          Oval tracks can be so fast once you get into the 'zone' with a car that I want to create longer lap times by making a full lap twice around. It will also make driving more challenging because of the different corner radii. On my current 2 lane routed oval it takes a different driving style for each lane. The outside lane is easier to drive because of the wider turns but the inside lane can be faster due to the shorter lane length if you learn how to enter the tighter corners just right.

          When racing solo I record a lot of lap times to create simulated races. That should be even more interesting to do if there's more variability in lap times.


          • #7
            The build is officially underway with the MDF being CNC routed this past weekend. CNC routing is definitely the way to go, but there were some issues.

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            As seen above (from post #1) the entire track is composed of 6 sections cut from 2 full size sheets of MDF. I got the MDF at Home Depot for $27 each. I'd already paid Brad (Brad's Tracks) $100 for the CNC files - so far so good. I took the materials to the CNC shop yesterday and the 1st sheet of MDF (left one above) only took about 40 minutes to setup and get routed. In the photo below you can see one of the crossovers.

            Click image for larger version  Name:	routed corner front 1&2 crossover1crack1.jpg Views:	0 Size:	1.56 MB ID:	46029

            Here are the 2 short straight pieces. The one on the right has been cleaned up with a sanding block and had the slots vacuumed.

            Click image for larger version  Name:	routed short straights 3.jpg Views:	0 Size:	1.85 MB ID:	46027

            As the 2nd sheet started being routed I thought I noticed an error and the operator shut the machine down and said she'd loaded the same program again (left sheet) rather than the one for the right sheet.

            The operator was very apologetic and said she'd get and run a 2nd sheet of MDF at no cost, but I suggested we flip the sheet over and run the correct program on the other side. The slots were being routed 5/16th inch deep in 1/2 inch MDF and I didn't expect a few voids to matter. However the few slots that were cut before the error was detected ended up being in some compromising places.

            Click image for larger version  Name:	routed long straight 1.jpg Views:	0 Size:	1.39 MB ID:	46030Though hard to see in the above photo, the correct slots on the front of this long straight section are on top of left over slots from the first attempt, and go all the way through for about a foot down. Being a straight section which won't have any major stress on it I can easily patch this with a thin sheet of MDF glued to the back.

            The biggest problem is with the corner section from the salvaged 2nd sheet. Two cuts from the 1st pass are almost directly in the center of the turn as seen below.

            Click image for larger version  Name:	routed corner back4.jpg Views:	0 Size:	1.43 MB ID:	46031
            These 5/16" slots in 1/2" MDF weaken the whole corner section and while moving into the barn it started to crack as seen on the front side below.

            Click image for larger version  Name:	routed corner front crack3.jpg Views:	0 Size:	1.51 MB ID:	46032

            I stabilized the corner section with strips of wood and clamps but now need to fully repair it. Unfortunately, since the corners were designed to be banked about 8 degrees and need to be pulled in to 180 degrees to do that, I don't think I can just glue a backing on like I intend to do with the straight section above. I should be able to get wood glue down into the problematic cuts in the back of this corner section but am not sure that alone will make it strong enough to withstand the warping that needs to take place while banking.

            Click image for larger version  Name:	routed corner front clamps3.jpg Views:	0 Size:	1.31 MB ID:	46033

            Help! Has anyone encountered something like this? What suggestions do you track builders have to offer?
            Attached Files
            Last edited by slothead; July 20, 2020, 04:02 AM.


            • #8
              Luf would know, but my bet is that you need to replace that piece.

              You might be able to get by with filling those slots up with something, like bondo or some other filler (something rock-hard putty I don't recall the name of?). Whatever you do, don't try to get the bank going until that's been taken care of... and expect the failure point to be at those cuts. Fortunately, you're not doing a high bank, but it's still a lot of stress on the wood until you get it secured. Maybe have all your supports good to go, and get it fully secured ASAP after setting up the bank.


              • #9
                No more banking than you are doing, go to HD and get a 4 foot piece of 1/4 mdf and glue and clamp it to your curve. It will still bend the little bit you want.
                Last edited by mattb; July 20, 2020, 06:58 PM.
                Matt B
                So. In


                • #10
                  she did volunteer to get you a new piece of wood an do it over, right?


                  • #11
                    Yup, I would say get another piece of wood. The problem with MDF is that it never bonds well again.......but that's just me.
                    Come Race at The Trace!
                    Timberline Trace International Raceway - SW of Mpls, MN


                    • #12
                      If it's worth doing....and you know the rest.

                      Just cut another.


                      • #13
                        Thanks for all your comments. Yes, she offered to CNC another sheet but it's nearly a 2 hour drive each way to go back to the shop. I will do that if the problematic corner section fails, but thought it was worth trying to repair first. The other 5 sections are fine - 3 perfect and 2 straights that just need a back piece glue on.

                        I'll see if anyone on the Zoom meeting has any additional thoughts before trying anything. If not, I may try JB Weld in the slots on the back of the corner and then glue a thin sheet or pieces over them. I found a quarter sheet of 1/8" MDF in my stash that might work. It also probably makes sense to get the other sections completed before replacing the faulty corner if needed, just in case I have to redo something else or want to alter the design.

                        Problem corner w/ cleaned slots and more clamps for stability. CNC work looks great, the crossover for lanes 1 & 2 is really crisp.

                        Click image for larger version

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                        • dinglebery
                          dinglebery commented
                          Editing a comment
                          Doesn't JB Weld cure to a rock-hard substance? That wouldn't be good. You need something that's flexible like hard rubber. SikaFlex makes a product that's used to fill the gaps of teak decking on boats - it's used on practically every single boat made - the black rubbery fill between the teak boards. That's what you should use to fill the cuts that shouldn't be and use a thin coat (2mm) over the area that's cracking, running about 10cm over on each side. Ohh and don't get it on Anything it shouldn't be on because you won't get it off.

                        • slothead
                          slothead commented
                          Editing a comment
                          That's a great point and suggestion. Something with very good grip that's also flexible is what I need.

                          Thanks very much for your comment.

                        • SlotCat
                          SlotCat commented
                          Editing a comment
                          Was thinking same about JBWeld cures rock hard. ShoeGoo cures very strong and flexible.
                 Second choice maybe bondo as it has some (very little imo) flex when dry.

                      • #14
                        Glad it cleaned up. I have no idea how JB would do, but Bondo works well.

                        I will say I'm a bit confused: if you showed Brad the pic (I assume you did) of the original design...his interpretation or otherwise should have matched. If not, I'd have requested a do-over. It is only a computer program, not wood that may/may not now be what you wanted.

                        Just my thoughts.


                        • #15
                          I sent photos of my sketch to Brad (same as at top) and suggested we arrange a quick call to talk details before he got started. He said he understood what I wanted and to send $ by PayPal for the files. I'd considered putting the crossovers in the corners for smoother transitions so went with what he'd done. This will be built and tested before deciding to replace my current oval, and if I don't like it I can always stay with what I have now.

                          Starting to run the left sheet program a 2nd time is what created the current problem. If it was a flat track, or had slanted corners I'd lock it in place and move ahead, but as is that corner will come apart under banking pressure.

                          Thanks for the bondo suggestion for the back. I may need to recreate the problem on a scrap piece and try out several solutions.

                          I wouldn't have to PM you if not for your participation in the Zoom meeting and mentioning plans to get started on PDR soon.

                          I appreciate your response.