Howto Builda Pinewood Derby Car by 1pSSX0M


									       How to Build a Pinewood
              Derby Car
               Pinewood Derby Model Car Racing Rules and Hints
                          for Building a Better Car

The Pinewood Derby is one of the most popular events in Cub Scouting. Every year more than a
million boys and parents team up to carve, decorate, weigh, adjust, fret over, and finally race a
Pinewood Derby car. Welcome to the club!

                                 COMPETITION MAKES LIFE FUN

It is the intent of this “Survival Guide” to see that all of the Cub Scouts have access to the same
knowledge. With the care and goodwill of all the members they will also have access to the same
equipment needed to ensure fair competition. Simply put, the Cub Scout and his helper who use the
knowledge and equipment to their best abilities will win.

The Pinewood Derby is a race and Cub Scouts are supposed to compete with each other. There will
be “winners” and “losers” that is the nature of competition. However, the Pinewood Derby is not all
about winning. It’s about spending time with your son building something. The memories you build
with your son helping him to create his Pinewood Derby car will last his lifetime.

                           GOOD LUCK and HAPPY RACING!


 Read all of the steps completely before you start building your car. That
  way you will have a clear understanding of the purpose for each step.

1)    Check your car body for square axle grooves
      Square axle grooves will make the car run straight and stay off the sides of the track.
      You can check the squareness of the axle groove with a good carpenter's square. You
      need a 90-degree angle on the axle groove to the car body.


      You may move the axle groove location on the car, as you please, providing the
      following criteria are met:
      1) The wheels do not protrude beyond the front or rear of the car
      2) The car does not exceed the maximum allowed length
      3) The car maintains the minimum clearance
2)   Pre-fit the axles in the car body
     Method No. 1: Using a hammer, pound an axle 3/8ths of an inch into the car body at
                      the exact spot where it will eventually be mounted. Then carefully
                      remove the axles with a pair of pliers. By doing this first you ensure
                      that the wheels can be mounted to the finished car without damaging
                      either the car or the wheels. This also helps to see that the wheels will
                      be mounted at a 90-degree angle to the car. Insert and remove the
                      nails very carefully so you do not damage the nail heads.

     Method No. 2:    Use a numbered drill bit and a drill press. The axles will vary slightly in
                      diameter. However, by using an accurate measuring device, e.g.
                      calipers, you will find that a #43 (0.089”) or a #44 (0.086”) drill bit will
                      provide a very snug fit for the axle.

3)   Design the car body shape
     It has been found that the shape of the car body has very little effect on speed.
     Therefore, every Cub Scout should design as much of his car body as he can.

4)   Choose a color scheme and any decals
     The Boy Scout Shop and local hobby stores carry decals and paint. Let your Cub Scout
     pick out his favorite decals. Use of decals can add a lot to the appearance of the car
     and it gives the Cub the opportunity to add his personal touch to his car.

5)   Cut out the car body
     Once the Cub has designed his car shape, the helper needs to supervise the Cub’s use
     of the saw. IT’S ALWAYS SAFETY FIRST! Everyone wants a safe and accident-free
     derby project.

6)   Properly sand the car body
     The secret to a shiny car body finish is to do the proper sanding, use sanding sealer,
     and use a good paint designed for wood models. Sand the car in 3 or 4 stages. Use a
     finer grit sandpaper for each stage with the last stage being a very fine grit. You may
     wish to add weight to your car at this time to minimize the amount of refinishing work
     you will have to do later. Be aware that a good paint job with primer and two to three
     coats of paint will add as much as five grams of weight to your car.

7)   Apply sanding sealer
     The car should be coated several times with sanding sealer and allowed to dry between
     each coat. Between each coat of sanding sealer use a very fine grit sandpaper and
     lightly sand the car.

8)   Paint the car body
     Your official Boy Scout shop and local hobby stores will carry the paints needed to paint
     your car. Whether you choose brush or spray paints several light coats are better than a
     few heavy ones. Once you are satisfied with your paint job its time to add those special
     decals that give your car that personal touch. If you choose to wax your car after
     painting please be careful not to get to much wax in the area where the wheel hubs will
     contact the car. The graphite used to lubricate the axles and wheels may react with the

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9)   Remove burrs and polish axles
     The single most important parts of a pinewood car when it comes to speed are the
     axles. Most of the drag generated during the race is caused by friction between the
     wheels and axles so pay very close attention here. The car with the fastest axles should
     always win the race. The axles that come with the kit will need a lot of finishing work to
     run fast. At the very least, they need to have the burrs removed and then polished
     mirror bright. The axles can be mounted in a drill or Dremel tool and a metal file used to
     remove all burrs. After removing the burrs polish the axle as smooth as possible.
     Everyone in the race will try to remove burrs and polish axles so it takes a lot of extra
     work to have the fastest axles. Polish your axles till they are mirror bright and make
     doubly sure all burrs are removed.

10) Remove burrs and polish wheels
    Using very fine sandpaper remove all burrs on the wheels’ outside surface. Visually
    check the inside of the hub where the axle fits through the wheel, if you see any burrs
    they can usually be removed with a small nail. Next make sure the bottoms of the
    wheels are flat and the wheels are perfectly round in shape. If they are not you will need
    to use a wheel mandrel mounted in a drill or Dremel Tool and sand off any uneven
    wheel material. After you are satisfied with the shape of your wheels it is time to polish
    the wheels with very fine emery cloth or sandpaper while the wheel is spinning. The
    ideal wheel is as smooth and burr-free as possible to reduce drag between the wheel
    and the track. BE CAREFUL! Altering the wheel shape is not allowed.

11) Pre-lube the wheel hubs with graphite
    Use only fine-grain graphite powder. Lubricant is a very important and often overlooked
    part of pinewood car racing. The only lubricant you should use for a pinewood car is
    graphite powder because oils and Vaseline will react to the plastic wheels and actually
    melt them. You need to ‘BURN’ graphite on the axles and insides of the wheel hubs
    before you permanently mount them on the car. Place each wheel on an axle and then
    mount the axle in a drill motor. Next, put some graphite inside the hub and run the drill.
    The spinning axle will rub or ‘burn’ the graphite onto the surface of the plastic inside the
    wheel hub. After the burning-in process the wheel and axle should be kept together as
    a pair. Also, try to spin the wheels in the direction they will be turning after they are
    mounted on the car. Next, use your finger to rub some graphite on the car body where
    the wheel hub touches the side of the car. During the race the car body and the wheel
    hub come in contact with each other. Placing graphite here reduces this friction.

12) Install proper amount of weight
    Maximum weight is five ounces or 141.75 grams - this rule will be strictly enforced. All
    members are encouraged to have their cars weighed before the actual race day. If you
    wait till race day to have your car weighed you risk having your car damaged at the last
    moment and not being able to be an effective competitor. Where do you place the
    weight? The general consensus is to have the weight towards the rear of the car
    because it falls a longer distance. This will give it a little longer boost and help to
    increase car speed. Actual car design will usually have an influence on weight
    placement and you may wish to keep this in mind when designing your car. Never place
    weights directly on the bottom of the cars. You must maintain a minimum clearance
    of 3/8” or it will drag on the track.

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13) Install axles and wheels
    Great care must be taken to install each wheel and axle as straight as possible.
    Carefully place your car on a soft surface so you don’t mar your paint job. Then, attach
    your paired axles and wheels onto the car. Leave approximately 1/32nd of an inch
    between the wheel hub and the car body so the wheel will not drag on the car body.
    The wheels need to be mounted so they point straight ahead which will make the car roll
    straight and not rub the sides of the track.

14) Check for straight wheel alignment, and that all wheels turn freely
    This step is the final one before the axles are glued in place. This will be your last
    chance to make any wheel changes you deem necessary. If it is at all possible you
    should trial run your car on a flat surface to see if it runs straight, any corrections that
    are needed can be made at this time.

15) Glue the axles in the car body axle grooves
    This step is an option that many people choose not to do. If your car has very tight
    fitting axle grooves, use of little or no glue would allow you to make adjustments or
    emergency repairs on race day. If you have any play at all in the axle grooves the axles
    must be glued in or the wheels will not stay in position. The rougher your racetrack is,
    the harder it is to keep the axles in place without gluing.

16) Re-check the car's weight
    If it is at all possible, have your car's weight checked again after final assembly. While
    we want our cars to weigh as close to five ounces as possible coming to the race with a
    car that is too heavy could spoil all of your hard work.

17) Lubricate again with graphite
    After you are fully satisfied with your race car's appearance, weight, and tracking it is
    time to graphite your wheels again. Remember, a little graphite goes a long way so
    apply it sparingly or your perfect paint job will end up being a dull gray color.

18) Remember the BIG SEVEN:

     1.   HAVE FUN!

     2.   Make sure that the axle grooves are square in the car block

     3.   Properly finish axles and wheels

     4.   Mount wheels and axles at a 90-degree angle for straight wheel alignment

     5.   Make sure your car weights as close to five ounces (141.75g) as possible

     6.   Lubricate your wheels with graphite powder

     7.   HAVE FUN!

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