Friday, December 19, 2014

Runoffs - When and Why to Run Them
By Randy Davis


Years ago, virtually every pinewood derby race used an elimination method (usually double elimination) for running a pinewood derby race. This method was relatively easy to implement and easy to understand, but did have issues including:

1. Slowest racers ran a few heats and were then eliminated (and likely lost interest in the event.

2. Possible unfair trophy assignment (third fastest car is eliminated early due to repeated pairing with the fastest two cars).

3. Cars did not always run on all lanes, so some cars had an advantage if they were assigned to a fast lane.

With the advent of Race Management software, many events have transitioned to a chart-based racing method, whereby all cars run the same number of heats, race in all lanes and are paired against a broad selection of other cars. These methods are much fairer, and are more accurate in assigning trophies.

But when using a chart-based method, the scoring method must be selected: time or points. I won't get into a full comparison of time vs. points in this article.(1) Time-based scoring is certainly popular and is really the best choice for large events. But for smaller events, I prefer point-based scoring. I believe this method keeps the audience more engaged, keeps each heat exciting, and makes the finish order of each heat important.

But with point scoring, the final trophy assignment may not be accurate after the heats are complete. Like elimination methods, random heat assignments can result in the third fastest car being relegated to fourth place.(2) So, to ensure that trophies are assigned properly, another round for the fastest cars may be needed. Let's look at when a second round is needed, and how many cars to select for the second round.

WHEN IS A SECOND ROUND REQUIRED?
To answer this question, we must first understand the terms "Perfect-N" and "Partial Perfect-N" (PPN) as they apply to race charts.

A Perfect-N race chart is one in which every car races the same number of times in each lane, and races against every other car the same number of times.

The simplest case is 4 cars on a four lane track, racing one time per lane. Each car races one time in each lane, and in each heat races against the other 3 cars. Other cases of Perfect-N charts will be described below.

A PPN chart is one in which each car races the same number of times in each lane, and heat assignment is optimized so that no one car races against any other car more or less than one time greater than the average.

An example of a PPN chart is one with 8 cars on a four lane track, racing one time per lane. Since the example car will need to race against 12 other cars (3 per heat), and since seven (the original 8 cars minus the example car) doesn't divide into 12 evenly, the example car will race against 7 cars one time and 5 cars a second time.

For a four lane track, Perfect-N charts exist for the following numbers of cars(3):

4 - Yes
5 - Yes
6 - Yes - Bye required(4)
7 - Yes
8 - No
9 - No
10 - No
11 - No
12 - Yes - Bye required
13 - Yes

For all car counts greater than 13, only PPN charts exist.

When a race has a Perfect-N chart the race is perfectly fair and a run-off is not needed (except in the case of tie). But if the race has a PPN chart, it is possible that a trophy may be incorrectly assigned. In this case, a run-off race is required.

HOW MANY CARS SHOULD BE IN THE SECOND ROUND?
From the above discussion, the answer is clearly that a number must be selected that has a Perfect-N chart. In no case should a second round use a PPN chart.

Typically, we select the top seven cars, except when there are ties that would drive the number beyond seven. Then we select the top five or six cars.

IMPLEMENTATION / CONCLUSION
I grant that a time-based race is easier to implement, as the need for a second round is not necessary. But with a modern race management application, such as Grand Prix Race Manager, creating a second round is quite easy. In our race, we typically have the second round ready to go in two minutes from the completion of the final heat of round 1. Our emcee fills the time with a few kid-friendly jokes, so the excitement of the event continues during this slight delay. Then during the second round (seven cars typically take less than ten minutes), the excitement level (and sound level) reaches its peak.

If you are currently using a time-based method for your small race, consider switching to a point-based method. I believe you will generate greater interest and excitement, for just a few extra minutes of event time.

(1) For a comparison of these two methods, please refer to:
Points or Times: Which Method Should I Use?

(2) For example, if the third fastest car races the two fastest cars resulting in two second place finishes, and the fourth fastest car only races against one of the top three cars resulting in one second place finish, then the fourth fastest car would be incorrectly assigned the third place trophy.

(3) If you have a track with more or less than four lanes, you can use Grand Prix Race Manager (GPRM) to determine the Perfect-N charts.

(4) A phantom car is inserted into the schedule. When it races, the lane is left empty. GPRM automatically takes care of byes.

From Pinewood Derby Times Volume 14, Issue 6

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Friday, December 12, 2014

Pinewood Derby Car Showcase

Related to the previous post, here are a few more of James White's frame and skin cars.







From Pinewood Derby Times Volume 14, Issue 5

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Friday, December 05, 2014

Shop Talk: "Frame and Skin" Car Construction
By James White


I would like to share the "Frame and Skin" car construction method used by my grandson (Aaron Shain) and myself for pinewood derby car building.

We start with a normal pinewood derby block with drilled axle holes. After cutting out the profile we want, we remove all material except the frame of our car, and then we apply a rock hard varnish to the areas where the wheel hubs will rub the frame.


Figure 1 - Frame of Car
(An additional support piece was added over the front axle holes)

Next we build side extenders to be glued to the frame sides.


Figure 2 - Side Extenders

We then add a carbon fiber rod for stiffness down the car center and glue a 1/64 inch thick model plywood bottom skin onto the frame.


Figure 3 - Carbon Fiber Rod, and Bottom Skin

Tungsten weight is then added into the two rear pockets (not shown in photos). We target 4.85 ounces with all parts included. Tungsten putty is used as trim weight after the car is complete. The putty is placed into 1/8 inch holes drilled into the bottom of the car between the two rear axles.

Next, a 1/64 inch thick top body skin is cut out and glued to the frame.


Figure 4 - Top Skin


Figure 5 - Top Skin Installed

Fender tops are placed over the wheel wells (if desired). At this point, we install the prepped wheels and axles to do some tuning and testing.


Figure 6 - Fender Tops

After a paint job is applied, we are ready to race!


Figure 7 - Finished Car
(Photo is of a sister car, so the wheels are different)

From Pinewood Derby Times Volume 14, Issue 5

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Friday, November 28, 2014

PINEWOOD DERBY CAR SHOWCASE

Iron Man - Randy Davis

I built this car as a prototype for a CNC machined car, but the shop I was going to use closed down. Oh well. I still had the prototype, so I entered it in our local Outlaw race and it took 1st Place in speed and 3rd Place in design. I used some X-Lite Outlaw wheels that were machined from Turcite-X. The wheel color doesn't really match the car color, but the wheels certainly draw attention to the car.

Olaf - Richard Larson

Olaf ran in our local race as well, and took 2nd Place in design and speed. Every year, Richard builds great looking cars. Here are links to a few of his previous cars:

'Mater


Red


Finn McMissile


From Pinewood Derby Times Volume 14, Issue 4

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Friday, November 21, 2014

Rail-Riding - Getting that Extra Speed
By Randy Davis


If you have spent any time on the Internet researching pinewood derby racing, you will have ran across the term "rail-riding". This alignment technique had been used for many years by a select few, but became popular around 2008.(1) The Pro-Rail Rider Tool, the Pro-Axle Bender and other tools were introduced soon after to facilitate the implementation of this technique.

But with all of the tools, videos, and documentation available, I still get many calls from confused car builders about rail-riding. Therefore, the intent of today's article is to organize the many facets of rail-riding in such a way that clarity can be attained.

WHAT IS RAIL RIDING
When a pinewood derby car rolls down the track, it will contact the center guide rail.(2) Each time a wheel contacts the rail, some performance will be lost. Moreover, when a rear wheel contacts the rail, even more performance is lost since the rear wheels carry the majority of the car's weight.

So, the fastest car (all other factors being equal) is one that never touches a guide rail. It would seem then that setting the cars alignment to go straight would be the best bet. This might work if the track was perfectly smooth and level, but we all know that is a pipe dream. All tracks will lean one way or another (and some lean both ways alternately by track section). So, a car that is set to run straight will follow the lean of the track, resulting in contact with one or both wheels on one side of the car.(3) In addition, if the car is a three-wheeler (with a raised, non-spinning wheel) and the raised wheel contacts the rail, the advantage of the raised wheel is lost.

How can we compensate for this? Recognizing that the least amount of loss occurs when the lightest loaded wheel (a front wheel) contacts a rail, if we could set the car's alignment so that a dominant front wheel is the only wheel that contacts the rail (the non-raised wheel for three-wheel cars; your choice of wheels for a four-wheel car), we would achieve the least guide rail losses. This is the basis of rail-riding.

Read the entire article on Rail-Riding Here

From Pinewood Derby Times Volume 14, Issue 4

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Friday, November 14, 2014

PINEWOOD DERBY CAR SHOWCASE

Speed Racer - Nick Fish

This Bear pinewood derby car was built by Nick Fish and his Dad. We love Speed Racer, so we did our interpretation of Speed's Mach 5. It won the den and took first place in the pack without losing a race. District competition was a lot tougher with a 5th place finish. The car is a modified Wing design using a 3.5 oz. tungsten canopy, tungsten putty for the final weight adjustment, raised front wheel, polished/grooved axles, aero underbody, and custom graphics.

The Reaper - Jason Otis




My pack's Pinewood Derby Bandit/Open Class is pretty competitive every year, to the point where we had to create a class just for the parents. I got tired of coming in second, so I put this thing together a couple of years ago.

The main body is from an original BSA Pinewood Derby Kit, and the fan shroud was carved from three pieces of glued-together 2 X 4s.

Specs & Info:
Propulsion: 55mm 8-Blade 60K RPM ducted fan (19oz thrust)
Power: 3-Cell 11.1 Li-Po Battery
Best Track Times: 32-Foot Track-1.111 sec, 38-Foot track: 1.267 sec

From Pinewood Derby Times Volume 14, Issue 3

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Friday, November 07, 2014

Pinewood Derby Awards
By Randy Davis


Should every child entering a pinewood derby race get an award? Or should only the top cars for design and speed be given a trophy? How about a compromise? The answer to these questions will likely vary from person to person, and depends a lot on your philosophy of raising children.

I am not a child psychologist, so I can't argue the theory that underlies awarding children. But I am a parent that cares about my children. Before they leave our home, I want to give them a solid understanding of how they should behave and what they should expect to encounter in the world.

I do not believe that every child should be equally rewarded, that is, no winners and no losers. This is certainly not the way the world operates, and teaching a child this perspective will not prepare them for reality. In my opinion children need to understand that sometimes you win, and sometimes you lose, and greater effort leads to greater opportunities for winning. Learning how to deal with losing (and winning) builds character and maturity. So I believe that trophies for the fastest cars and best designs are certainly appropriate.

NON-TROPHY AWARDS
But on the other hand, I think providing a larger variety of awards can be a great encouragement for kids. These can be certificates for: "Best Paint Job", "Car Most Likely Built By a Kid", "Silliest", "Funniest", "Most Aerodynamic", etc. If you are interested in providing these types of certificates, many free downloads are available on the web. Just search for "pinewood derby certificates".

Be careful with these type of awards. If you decide that every participant will get one, then it will be a big challenge to make sure that the number of certificates match the number of entrants, and that the awards are given out appropriately. Again, I don't believe it is necessary for every entrant to receive an award of this type. But
that leads to...

PARTICIPATION AWARDS
Providing all entrants with a ribbon (or alternate) for participating is certainly appropriate. I am still amazed how much my kids like those ribbons. Even when they won a trophy, they would drape the participation ribbon over the trophy.

Participation awards can be more elaborate. Stan Pope has provided a neat idea for providing a mounting plaque for every car. The plaque has the date of the race and group name/number.

Certainly other participation awards such as pins, patches, etc. can also be used. In recent years we have gotten away from ribbons and have been giving each participant a "Hot Wheels" car. My wife watches the ads and picks them up for less than $1.00 each. These are a bit more expensive than ribbons or patches, but the kids really like them (a lot of trading goes on after the race).

CONCLUSION
I realize this article is a bit short, but of course my experience is limited to the races sponsored by our organization. So, I would like to get your input on this topic. If your group has a method of providing awards that works well or is unique in some way, please send me a description. I will try to include your comments in a future newsletter. You can send your comments to:
info@maximum-velocity.com.

From Pinewood Derby Times Volume 14, Issue 3
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