pack 335 pinewood derby 2013
TRANSCRIPT
Pack 335 Pinewood Derby 2013Rev up!
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 tracksTypically 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 resultsEach car races in each of the lane – to neutralize lane instability
The CarsBSA certified kits onlyAdd-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 positionsTop 3 in each pack race at Council level (April)and beyond…
And losingScout must be present at the time of racingGetting disqualified at inspection on impound night
The Science Behind ItMomentum, 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 = momentumReduced friction = speedSleek smooth shape = aerodynamicsBalanced wheels = stabilityThat is why you add weights, make all moving parts smooth
and sand and sand and sand…
Car weight = momentum Maximum weight of fully assembled car can be 5 oz. Weight types:
Low density metals = need more, takes lot of spaceHigh 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
storesTungsten – highest density, very costly, buy in hobby stores or online
Even the paint adds some weight! (0.01 oz. to 0.08 oz.)
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 measurementTake 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)
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) headUse the same file to remove the crimp marks Then use a sand paper/cloth to even outRecommend using steel polish for the extra speed
Test your workInsert the wheel onto the axle, add some graphite
(only dry lubricant is permitted)Hold the axle horizontally and give it a few spinsThe wheel should spin freely for a few seconds
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 surfaceFill the gaps and uneven areas with wood putty/filler – let it drySand the car body with coarse and fine sand paper before applying the paint
AccessoriesChoose accessories (cabin/cockpit, drivers, engines, etc.) that are rounded
Front of carDo not make the front too pointy A-shaped or V-shaped as this will be a problem with the
starting device on the track
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 beyond starting line
Car body cannot exceed starting line
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 downWobbly wheels can even brush against the car body itselfMaintain width of 1 ¾“ at axle slots where wheels are to be mounted
How to avoid thisMake sure the axles are straightMake 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
hammerGlue is not really needed, although it does secure the axles in placeDo NOT put glue until you are satisfied with the car and its alignment
Keep the car weight balanced just in front on the rear wheelsMake sure it is easy to tell the front side of the car If the design is even – mark the front using a permanent marker
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
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 soulsDremel has a range of tools and accessories useful for this and many hobby
projectSanding belt
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)
