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Pinewood Derby time again - after 25 years

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  • Pinewood Derby time again - after 25 years

    Ah, the grandkids are in cub scouts and its pinewood derby time again.
    My son in law asked me to help him and them with the cars.
    First thing I did was dig out the boxes of stuff we did when my son Jeff was in cubscouts. Click image for larger version  Name:	20200112_235802_resized.jpg Views:	14 Size:	138.7 KB ID:	838339 This was 25 years ago, My car and my son's car and a couple of experimental spares on a test track I built.

    If you don't know, they give or sell you a kit with a block of pine and two axle slots, four plastic wheels and four nails.
    Then you compete on Derby day with the other scouts. THey have an inclined plane that launches the cars downhill onto a straight flat altogether about 25 feet long and then crown a winner after a mutti level side by side competition. They also give various prizes for beauty and artsy style, humor and cleverness. So design counts.
    You have to use the block and wheels, it has to weigh or be weighted to no more than 5 Oz. and a host of other rules.

    These kids are only 8 and 9 and can't really handle full out woodworking tools so we let them make a couple of cuts but I set up the bandsaw and router and drill press. I mean my grandson was too scared to really push the wood through the bandsaw by himself but I held his hand. Cutting curves on a 2" thick block with a bandsaw is not an easy thing for an inexperienced adult!

    I kind of got into woodworking as the den co-leader when my son was in cub scouts. He didn't finish all the way through high scool with boy scouts but I picked up a hobby for 25 years.

    I wish I had I had my current set of tools and I wish I had me to guide myself back then, I kinda think I did some good work today. I'll post pictures the naked cars less the wings and fins and stuff the boys need to add.

    I showed them how to polish the nails chucking them up in a slow drill and filing off the burrs under the head that drag on the wheel, and polishing the axle using a strip of fine sandpaper.

    And we raced the cars I made back in 1995 on the short track I made to test rolling friction and straightness.
    And I even have a small scale that weighs oz. to .001 resolution.
    Last edited by LCHIEN; 01-16-2020, 05:42 PM.
    Loring in Katy, TX USA
    If your only tool is a hammer, you tend to treat all problems as if they were nails.
    BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

  • #2
    Nice! Great fun!
    Bill

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    • #3
      Click image for larger version  Name:	20200116_032308.jpg Views:	0 Size:	213.3 KB ID:	838343
      Here's the kids new cars, to be. A shark and a hedgehog.
      I did some of the roughing sanding for them, then let them do the fine finish sanding and the wheel tuneups.
      Don't say anything about that wheel.
      Last edited by LCHIEN; 01-16-2020, 05:33 AM.
      Loring in Katy, TX USA
      If your only tool is a hammer, you tend to treat all problems as if they were nails.
      BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

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      • #4
        I like the names of the latest two. Hedgehog and Shark.

        Do you shoot for a target of as close to the 5 oz as possible? If you are over weight by 1/4 oz, how do bring it down to below the max weight?
        Do they allow adding a washer or two for weight if the finished weight w/o washers is - say 4 or 4.5 oz?

        Maybe I am overthinking this.

        Hank Lee

        Experience is what you get when you don't get what you wanted!

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        • #5
          You almost always have to add weight. Since the heaviest car is the most advantage, you want to be at the full 5 Oz. The full uncut block probably weighs just under 5 Oz. The thing is that no matter how good your scale is, they go by whatever they declare the "official" scale to be at the time of weighin.

          So I make the car a bit overweight with the last few weights to be a row of countersunk wood screws in the bottom. I take out as many as I need to until the weight is below 5 Ounces. I weigh the screws beforehand so I pretty much know exactly how many to take out to be right on if I am over the official scale weight by some amount.

          The two bodies + wheels weighed 3.098 and 3.97 ounces - I told my SIL to get a couple of flat round fishing disc lead weights for the coarse adjustment - I drill a hole in the center and them drill a Forstner cavity in the bottom of the car to fit the weight in.

          If nothing else you can always drill holes in the bottom removing wood where no one will (not) see it.
          Last edited by LCHIEN; 01-16-2020, 05:44 PM.
          Loring in Katy, TX USA
          If your only tool is a hammer, you tend to treat all problems as if they were nails.
          BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

          Comment


          • #6
            Do the axle/nail holes come pre-drilled? I know drilling 4 holes for axles doesn’t sound hard, but try it sometimes. When the kids were younger we built trucks, Cars and trains our of scrap wood and invariably one of the wheels would not be on the ground.

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            • #7
              Originally posted by capncarl View Post
              Do the axle/nail holes come pre-drilled? I know drilling 4 holes for axles doesn’t sound hard, but try it sometimes. When the kids were younger we built trucks, Cars and trains our of scrap wood and invariably one of the wheels would not be on the ground.
              The official blocks come with 3/16" deep slots across the width of the bottom, one in front and one in back.
              The kerf is just a hair smaller than the official nails so someone without a drill can use these; the 3/16 depth is just the right height for the axle position for proper clearance.
              I always figured a drill press and a fence go a long way to drilling axle holes at the right height and perfectly square to the chassis so the wheels run flat and parallel in all respects. Which should give lowest rolling resistance and least rubbing against the guide rail.

              OTOH, there are some who advocate putting one wheel on the light corner a bit high so that the car runs on three wheels making less friction (4 wheels is a requirement but nowhere does it say all have to touch). As an experiment I also drilled an alternate set of holes at a slant of 2 degrees so that the wheels run on the edge instead of the flat... less friction?

              Another PITA is that if you do a lot of on and off for the wheels (polishing and lubricating them), the holes get looser and the wheels fall off. The nails are crap with molding flash under the head and rough shanks. The diameter back then as now is actually not round, its an oval of roughly .088 x .100 inches. I found that a 5/64 bit was too tight and 3/32 is too loose. And that a #44 (0.086") bit was just right in ease of getting it in and out without too much wear and tear. Who has those (besides tool nerds like me) lying around?


              Loring in Katy, TX USA
              If your only tool is a hammer, you tend to treat all problems as if they were nails.
              BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

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