1. Pack 335 Pinewood Derby 2013
Rev up!

2. What is Pinewood Derby
 The Race
For cub scouts and their parents & siblings too!
 The Track
Most packs have their own set of wooden or aluminum racing tracks
Typically 3 or 4 cars run on each track lane at a time – called a “heat”
The electronic scoreboard at the finish line displays the heat results
Each car races in each of the lane – to neutralize lane instability
 The Cars
BSA certified kits only
Add-ons can include weights, paint, decals, accessories within the BSA
guidelines
 Winning (levels)
Top 3 in each Rank (Tigers, Wolf, Bears, Webelos I, II) get a trophy!!
Top 3 of each rank race for top 3 Pack positions
Top 3 in each pack race at Council level (April)
and beyond…
 And losing
Scout must be present at the time of racing
Getting disqualified at inspection on impound night
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3. The Science Behind It
Momentum, gravity, slope/angle of the tracks, weight of the
car, friction, aerodynamics, balance.
 What you start with:
A 7” x 1 ¾” pinewood block, 4 wheels, 4 axles
 What you CANNOT change:
Slope of the tracks…its pre-built!
Gravity…sorry can’t do much about it on our planet (yet)
 What you CAN change:
Car weight = momentum
Reduced friction = speed
Sleek smooth shape = aerodynamics
Balanced wheels = stability
That is why you add weights, make all moving parts smooth
and sand and sand and sand…
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4. Car weight = momentum
 Maximum weight of fully assembled car can be 5 oz.
 Weight types:
Low density metals = need more, takes lot of space
High density metals = need less, takes less space
 Options:
Zinc – low density = need more, easily available (Michaels)
Steel – more density, cost effective, easily available (check your garage!)
Lead – higher density, poisonous (use gloves), cost effective, buy in hobby
stores
Tungsten – highest density, very costly, buy in hobby stores or online
 Even the paint adds some weight! (0.01 oz. to 0.08 oz.)
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5. Car weight = momentum
 What to weigh
Weigh all parts (car body, wheels, axles, accessories, additional weight)
before putting it together) – get it to 4.9 or 4.95 oz.
Even the paint adds some weight!
 Where to weigh
Use a kitchen weigh scale that has ounce measurement
Take everything to a post office OR grocery store OR check with neighbors
OR get in touch with me
 Where to put the weight
You can add/attach weights anywhere on or in the car body
Ensure the finished car does not exceed:
2 ¾” in width; 7” in length; about 5” in height
and bottom clearance is at least 3/8”
Some zinc weights are designed to fit under the car
(like ones in Michaels)
Weights must be firmly attached (no tape)
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6. Reduced friction = speed
 The most friction comes from the wheels brushing against the axles
and the tracks
 Nothing much can be done for the friction with the track
 The axles have burr and crimp marks
Use a thin file to remove the burr under the axle (nail) head
Use the same file to remove the crimp marks
Then use a sand paper/cloth to even out
Recommend using steel polish for the extra speed
 Test your work
Insert the wheel onto the axle, add some graphite
(only dry lubricant is permitted)
Hold the axle horizontally and give it a few spins
The wheel should spin freely for a few seconds
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7. Sleek, smooth shape = aerodynamics
 Some friction comes from the car brushing against the air
 Shape of the car
Go for designs that allow the air to disperse
 Smoothness of the car surface
Fill the gaps and uneven areas with wood putty/filler – let it dry
Sand the car body with coarse and fine sand paper before applying the paint
 Accessories
Choose accessories (cabin/cockpit, drivers, engines, etc.) that are rounded
 Front of car
Do not make the front too pointy A-shaped or V-shaped as this will be a problem
with the starting device on the track
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8. Sleek, smooth shape = aerodynamics
 Cross section (graph & chart) paper with inch markings works best –
plain and ruled paper are fine too
 Mark the outline of the car’s wooden block and the axle positions on
the paper
 Draw your design - side and top view
 Front of car
Do not make the front too pointy A-shaped or V-shaped as this will be a
problem with the starting device on the track
Sharp tip can slip
Car body cannot
beyond starting line
exceed starting line
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9. Balanced wheels = stability
 The track has a ridge in the middle – the guide strip
 This keeps the cars from running off the track or into each other!
 But if the wheels brush against this guide strip then it will slow the car down
 Wobbly wheels can even brush against the car body itself
 Maintain width of 1 ¾“ at axle slots where wheels are to be mounted
 How to avoid this
 Make sure the axles are straight
 Make sure the axles are inserted at a perfect right angle (90 deg.)
 After putting the wheels on, tap the axles in and close to the car body using a screw driver
and light hammer
 Glue is not really needed, although it does secure the axles in place
 Do NOT put glue until you are satisfied with the car and its alignment
 Keep the car weight balanced just in front on the rear wheels
 Make sure it is easy to tell the front side of the car
 If the design is even – mark the front using a permanent marker
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10. Safety First or Last or Somewhere
 Use safety glasses/googles during most of the work
 Use dust mask when cutting, sanding, spray painting, etc.
 Use gloves while handling lead weights and as appropriate
 Ask older scouts about “the blood circle” from their whittling chip
experience
 Get a parent to help with all power tools
whether running on mains supply and battery
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11. Tools
 Use a clamping vise – to hold car body, drill, etc.
 Use a rasp – for quick shaping
 Use a file – for finer finishes to the shape
 Use a T-square – for perfect right angles
 Other tools: chisel, hammer, screw driver, coarse and fine sand paper
 For the more enthusiast souls
Dremel has a range of tools and accessories useful for this and many
hobby project
Sanding belt
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12. Impound night & inspection
 Test your car before impound night pack meeting (21st February)
 The box to check the cars – max. width 2 ¾“; max length 7”
 The weighing scale – max. 5 oz.
 Clearance – At least 3/8”
 Starting devices, washers, wheel bearings, bushings, change in axle
positions, loose parts, springs, oil lubricants are strictly prohibited
 Official pinewood BSA wheels, axles, pinewood cars
(accessories can be of any solid material, plastic, metal, fiber glass,
other types of wood)
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13. See you at the finish line…
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