Remember that the goal of this is to get the child
involved in wood working and create something own their own in addition
to working together as a son<->father/son<->mother team.
If your child hands you a choppy non-symmetical unsanded creation, and
beams "Ready for paint!!!", cherish the moment. They are only this
young for so long and some day they can look back at how their own cars
have evolved over the years and feel proud of what they accomplished.
Step 1) Choose your body design.
This is both the most difficult and the most fun.
This may take a while so starting now will allow the child to mull over
ideas while the hard part is taken care of. Note that aerodynamics are
a very minor factor when compared to friction control, weight
placement, and alighment so feel free to have fun with the design.
Step 2) Axles
Get the hard part out of the way first. The axles
and wheels take time and patience so get it out of the way first.
Putting an untreated axle into a wheel will damage the wheel bore (the
inside of the wheel that turns on the axle) so please try to treat the
axles first.
Step 2A) File the axle high spots
First file the high parts on the axle down by hand
using a small file. There are three sections that need treatment; The
burrs on the nail head, the crimp marks on the axle itself, and
sometimes there are burrs right near the pointy tip of the nail. Those
burrs at the tip of the axle can scratch and scar the wheel bore too so
they should be filed down. This might be a team effort.
Step 2B) Polish the axles
Your very best friend here is the Dremel tool. It's
safe and quiet enough for a child to use and allows quick and slick
polishing. Start with a very quick treatment with fine sandpaper over
the areas that were filed. Follow with a metal
polish such as Brasso and a paper towel. If no dremel tool is
available a drill or good old fashioned elbow grease will work.
Step 3) Wheels
Use the small metal file to rub down the bump on the
tread from where the plastic was injected into the mold. Lightly sand
it down just enough so that it is no longer a bump. Too much will
create a flat spot which will be bad. Lightly sand any burrs on the
edges of the tread and the wheel hub by hand using the foam sanding
block.
Step 4) Car Body
Use a framing square to check the axle slots on the
bottom of the car. Please be sure they are square with the car body. If
they are not, the car will be more difficult to align and go straight.
If they are really bad, one can drill axle holes using a #44 drill
bit. Note that accurately drilling an axle hole using a #44 bit is very
difficult and could be more innacurate than the axle slot. Plenty of
cars were very fast using just the provided axle slots.
Step 4A) Car Body Front/Back
If you are using the axle slots, the axle slot that
is closest to the end of the car is the one that should be in the back.
This allows the car to be more stable when the weight is placed
further back. Marking the front and back on the bottom of the car will
help your child when they cut the car.
Step 4B) Car Body Weighting
It is recommended to use weights to make the car
weight just under the 5 ounce limit. Once the body is cut, one can put
the body, weights, axles, and wheels on a food scale to get things
close. Another option is to leave space for more weights and add them
at weigh-in on race day. There are many things people use for weight.
Some of the die-hard Dads will melt lead into pockets in the car for
their kids. Others will spring for Tungsten. Others use lead fishing
weights or the lead weights used to balance automotive wheels. If using
lead, the adult should handle the lead In a pinch, one could use a
3/4" Forstner drill bit and then fill the pocket with pennies.
The weight should be placed as far back and low on
the car as possible without affecting stability. The reason that this
works is that the track starts on an incline and then goes flat. When
it transitions to flat from the incline, the weight that started
further back has further to fall to overcome friction thus making the
car faster. If the track was a straight incline, then the weight would
be better in the middle for stability. Note that a forstner bit is a
great way to drill accurate holes to place weight in. One might need to
add weight both into the car body as well as add a plate or two of
weight to the outside of the car. An adult's help is likely necessary
to drill the holes.
Step 4C) Cutting the Car Body
The most fun part of this for the child might be
cutting their own car body. Either that or painting. Some who are not
mechanically inclined may have their child trace out their design and
bring it to somebody with decent power tools. In our home, the kids
used a small saw as well as a coping saw. There is one power tool,
however, that a child could use to cut their own car however. An
Oscillating tool. It can only make straight cuts but the Dremel
Oscillating tool basically just vibrates a little blade at the end. A
Scout recently used one to cut his car and was beaming with pride. He
spent over 4 hours cutting his car last year and this year it took him
30 minutes. The result was choppy looking and he nearly cut right
through the wood block but it worked out great in the end.
Step 4D) Sanding
Some children do not want to sand much while others
do. It's their car so let them do what they wish. A foam sanding block
makes it real easy for them to sand their own car in whatever way they
wish. The Dremel Oscillating tool also has a sanding attachment that is
safe to use and works great. The Dremel sanding drums for the regular
dremel tool can also be quite useful and empowering for the child to
shape and round their car. Adult supervision is necessary there.
Step 5) Painting
Pinewood Derby cars usually show up in a wide range
of fun styles and finishes. Spray painting is the easiest way to get a
good looking finish that dries really fast. Krylon seems to work well.
One could also use a can of spray primer beforehand allowing for fewer
coats of the Krylon paint and less of the woodgrain to show through.
Step 5A) Painting Prep
If the paint gets into the axle slots or axle holes,
it will most likely throw off the car's alignment and keep the car
from going straight. A good trick is to put round
toothpicks into the axle slots or axle holes before painting the car.
This only needs to be done tight enough to block the paint from getting
into the hole.
Step 5B) Painting The Car
If the child spray paints the car, please suggest
they use a mask of some sort for protection. Once the car has been
painted, allow it to dry a bit and check it out. Several coats are
likely necessary and should be done within two hours of each other. If
more painting is desired after the two hours have passed, wait several
days for the paint to cure before painting over or the paint might
ripple up and be destroyed.
Step 6) Final Assembly
The child is now ready to put his axles through his
wheels and put them on his car. The child should take care to put them
in straight the first time.
Step 7) Lubrication
Apply dry graphite powder to the wheel hubs and spin
it in. This lubricates the wheels and the axles allowing for a fast
car. Last year's fast car used Hob-E-Lube.
Step 8) Alignment
Ensure that the car goes straight. If it does not,
one can see which axle is not straight. A twist of the nail using some
pliers on the nail head is usually enough to get the car going straight
as the axles are usually slightly bent from the factory. Once the car
seems to roll straight enough, glue the nails in the axle slots. Avoid
using superglue as it can run down and into the wheel destroying all
that hard work. Hot glue works as does Titebond wood glue.
Step 9) Insure The Car
What?!? We're not kidding. If your car crashes and
loses an axle, it is very likely that it will be put on differently
than before and the car will get slower with an alignment that is off.
To ensure that the car is put back correctly, put a dab of marker such
as a sharpie at the top of each nail head so that the
child or person manning the repair stand can make the car good as new
if they lose an axle. The repair folks will be instructed to look for
the marking dots on the axle heads on race day.
That's it. Have a blast! |
|
|
|
Event Details >
Pinewood Derby Tips |