5KidsRacing

Pinewood Derby Racing

 

"EASY Pinewood Derby Car WINS using Science!!!" Video Review

   -RjJtO51ykY 

This video has been hitting the derby sites and has been shared a lot on FaceBook....  It has a lot of great information about the science behind your pinewood derby build and it shows an awesome representation of Potential vs. Kinetic energy and the associated friction loses....  great job and well done on that part!

 
 
BUT.......  there is some wrong information told and some bad techniques
techniques shown on this video that I will point out below....
 
 
 
#1  Non-Grooved vs. Grooved Axles
 
What he got right:  
 
Scientifically spot on, making a groove in your axle does not decrease the friction, the friction is the same in either case.
 
What he got wrong:  
 
In reality, every axle and every bore has imperfections.....  if you assumed that there were no imperfections then you would come to the result that grooves do not help in a pwd race... by having grooved axles you minimize your chances of riding on a bad part of the wheel bore or axle.  Quite simply you are riding on less bore/axle area so you increase your odds of having a faster car by eliminating possible bad spots.  Additionally having a center grooved axle makes the wheel ride on the two ends of the bore stabilizing the wheel.  Imagine a high spot in the middle of the bore either on the axle or the wheel bore, the wheel would wobble back and forth creating a teeter-tooter effect making for an unstable wiggly car..... bad, bad, bad...  BSA axles are horrible, they aren't round and they aren't concentric from end to end.  Adding a groove removes all of the bad material in the middle and forces your wheel to ride on the two outer points, stabilizing the car.  If legal in your race buy quality grooved axles.....  not multi-grooved either, single center groove.
 
 
#2  Graphite
 
What he got right:  
 
If you are limited to graphite then you should use it.....
 
What he got wrong:  
 
All graphite is NOT created equal... NOT even close....  I don't know what "professional" said this, but this is totally untrue.  In fact I don't know of one pwd racer that has spent any time racing with graphite cars that would make that statement. There are fast graphites out there and there have been many tests done and not one of those tests say all graphite is created equal.  Derbydad4hire, Hob-E-Lube & Maximum Velocity graphite's are some of the fastest out there...  MV graphite is good for burnishing, but not as effective for running.  DD4H & Hob-E-Lube are great running graphite's.
 
 
#3  Canting the wheels
 
What he got right:  
 
Canted wheels are faster because it reduces friction.
 
What he got wrong:  
 
Bending the rear axles makes alignment 100 times easier?  I think he is 180 degrees off here, bent axles makes alignment 100 times harder....  You have to spend a lot of time rotating the rear axle to get zero toe in or toe out and even if it looks right it probably won't perform on the track.  Bending axles is NOT the way to go for a fast car.  Drilling canted holes and using straight axles will beat a bent axle car every day of the week.  None of the fastest racers use rear bent axles and you shouldn't either.
 
  
 #4  RailRiding is fast
 
What he got right:  
 
Using rear negative canted wheels and a positive canted front (steer) wheel and steering you car to run down the rail is fast....  yes...  He has the correct language using an incorrect technique.
 
What he got wrong:  
 
Railriding is a term associated with bending the rear axles to achieve cant.
 
RailRunning is a term associated with drilling canted holes to cant the rear wheels.
 
RUN my friends!  Don't RIDE!! 
 

 #5  RailRunning Set-Up
 
What he got right:  
 
You should adjust your DFW (steer wheel) so you get a drift (turn) so your car runs the rail.
 
What he got wrong:  
 
Adjusting the steer on a car so that you have 1" of drift over 4-6 foot will not make for a fast car?  Wrong!  On a standard BSA type pwd car build you need at least 3-4" of drift in 4 foot for a car that will run the rail.  Less than that will make for a car that wiggles which scrubs off speed.  Even the best racers on the best set-up tracks have more drift than 1" in 4-6 foot.
 
 
 
 
Overall, the other information (the stuff that I didn't mention above) in this video is helpful for the average scout pwd build.  
 
The good news is that the people that read my site will still be ahead at the finish line over the scout Dad's that watch and base their build off of this video.
 
 
 
 
Want to really know how to go fast?  
 
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