Propeller Car Evolution

By Randy Davis

(The third in a series of articles originally published November 26, 2003 and December 1, 2010)

Many organizations sponsor open competition races, some of which allow the use of powered cars. Whether your organization holds this type of race, or you are looking for a “crowd pleaser”, the propeller car is a fairly simple way to get awesome speed from a pinewood derby car.

Propeller cars have come a long way since the first “Erector Set” version I built in 2001.



Figures 1 and 2 – Original Propeller Car

The Erector Set car is indestructible, but it carried too much weight to be fast.

Through various iterations, the propeller car was optimized with the version we sold from 2008 to 2012.


Figure 3 – Production Propeller Car

This car had fewer parts, was light-weight, and used a compact ducted fan to produce crowd-pleasing speed.

CAPACITOR CAR
But in the spirit of continuous improvement, more speed had to be found. This was accomplished in a novel way by Rod Shampine, and documented in Volume 10, Issue 5. Instead of feeding the motor directly with a 9 volt battery, Rod used capacitors to feed power to the motor. This allowed the motor to run at a higher RPM (the battery limited the amps available to the motor), thus producing more speed.

My first version of the capacitor car is shown in Figures 4 and 5.



Figures 4 and 5 – Original Capacitor Car

The car is similar to Rod’s design (but a bit more robust).(1) When the front switch is not in contact with the track’s starting pin, the capacitors discharge to the fan and the battery is disconnected. After the capacitors are fully discharged, the car is fully inactive. When the car is placed on the track and the switch is depressed, the capacitors are disconnected from the fan, and the battery is connected to the capacitors. As long as the car sits at the starting gate for long enough, the capacitors will be fully charged for the run.

PROPELLER CAR II
After some consideration, a few improvements to the capacitor car become obvious. First, removing the battery from the car reduces weight and increases the speed.(2) Next, the wiring and capacitors could be mounted under the car for a cleaner look. Finally, the ducted fan was mounted at the back (more for looks than speed). This
upgraded capacitor car design is now available as a kit from Maximum Velocity in our “Propeller Car II” kit (see Figure 6 – now version III).(3)


Figure 6 – Propeller Car III

The new Propeller Car is much faster than the previous version, is lighter weight, and has a sleeker design. The car is charged with a 9 volt battery using a power jack and plug (provided with the kit). The kit requires just a few common tools to assemble – no soldering is required.

PROPELLER CAR II PERFORMANCE
On a 32 foot track, the standard propeller car crosses the finish line in about 1.9 seconds. The Propeller Car II crosses the same distance in about 1.6 seconds. Not only is the capacitor version faster, but an added benefit is that it turns itself off, since the fan quits turning after the capacitors fully discharge. The links below have videos of the Propeller Car II racing against the original Propeller Car and a standard pinewood derby car. I think you will be able to figure out which is which!

Propeller Car vs. Propeller Car II
(propcar2vs1.avi, 3.4MB)

Propeller Car vs. Standard Car
(propcar2.avi, 4.4MB)

CONCLUSION
So, if you want to blow away the competition in a real race, or just have a fun car to demonstrate at your event, consider the Propeller Car II from Maximum Velocity.

(1) For more information on the design of a capacitor propeller car, please
Click Here

(2) On a gravity powered car, more weight generally provides more speed. But on a powered car, lighter weight is better as this allows faster acceleration.

(3) The Propeller Car II is available Here

From Pinewood Derby Times Volume 12, Issue 7

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(C)2012, Maximum Velocity, Inc. All rights reserved.

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Pinewood Derby Car Showcase – December 21, 2012

PINEWOOD DERBY CAR SHOWCASE

F-15 – Philip & Joshua Huffman

Our family made four cars this year, three of which were entered in the outlaw division and came in the top 10. My son Joshua’s F-15 car was the only one entered in the scout race. His car was our test bed for using the full range of Pro-Tools and other supplies. The results? Joshua won first in pack, first in district, and first in council! Moreover, on every run he set a new track record. We’re making plans now for our 2006 entries. Wish us luck!


The Iguana – Brenda & Alex Wight

Alex wanted his car to stand out this year; and it certainly did! First, he did as he’s done the past few years; he looked on your web site for some inspiration. Alex said he wanted to go in a different direction from the usual, when he spotted a car that resembled a reptile. With a bit of brainstorming, he began his drawings of what was to become “The Iguana.”

Alex presented his rough drawings to his pack leader – a lady that has taken on 12 active boys, and is married to a guy that’s as handy with power tools as she is in handling her pack of scouts. He chiseled the block of wood under the careful scrutiny of my son, into the stream lined drawing Alex had sketched onto paper.

With his iguana in the rough, Alex sanded, sanded and then sanded some more. He brush painted layers of just the right green, layered some darker greens to give it the illusion of reptile skin, and decided to go with bright yellow feet, legs and tail. The jagged back was formed out of modeling clay, snipped with scissors, and glued into place.

The Iguana Car, although sleek in design, wasn’t much of a racer. One could say it was built for looks, not for speed. It traveled well down the track – even when placed backwards – and came in second during a three race heat, but just didn’t make the cut. Not placing in the race didn’t seem to bother Alex in the least. After all, it’s the excitement of the design that thrills him. I can’t wait to see what he’ll come up with this year!

From Pinewood Derby Times Volume 5, Issue 7

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Pinewood Derby Car Showcase – December 18, 2012

Today’s showcase cars are from Maynard Hinton.

Batmobile & Dick Dastardly – Samantha Hinton


My daughter Samantha’s Batmobile took first in design and speed. The
next year her second car, Dick Dastardly, took first in design and
second in speed (by only 1 thousandth of a second).

Hershey Bar – Terie Hinton

Out of all the cars my wife Terie has made, the Hershey bar had the
best results. It took both second in speed and design in the adult
division at our Awana Grand Prix.

The Mythbuster – Maynard Hinton

I made this car from a design I saw at a derby car building class. I
went the next step further after watching MythBusters when they showed
how a golf ball would fly farther and faster because of the dimples
that are on the ball. So I used my Dremel tool to make dimples all
over the car to test that theory. Unfortunately, I had to shave the
inside of the fenders because they were rubbing on the rails. Long
story short, the car was pretty quick, but not as fast as I had hoped
because I got sawdust in the front axles from the late modification.

From Pinewood Derby Times Volume 12, Issue 6

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Weigh-in Problems and How to Avoid Them

By Randy Davis

(An update of an article originally published February 23, 2005)

I have been the head race official for many pinewood derby races. One
of the tasks is to manage the check-in process (which really means
“do everything you can’t find someone else to do!”). As I have helped
kids and parents check-in I repeatedly see the same major mistakes. It
doesn’t seem to matter whether we have workshops, pass out detailed
instructions, or pass out simple instructions; the same mistakes
appear each year.

In today’s article, I will identify the main issues that arise at
weigh-ins, and suggest some ways to remedy these problems. My intent
is to provide race officials with some ideas as to how to deal with
these issues, and to help pinewood derby “freshmen” to ensure these
problems don’t occur with their car.

NOTE TO RACE OFFICIALS
If at all possible coach the car owners to make their own adjustments
(after all, it’s their car). If at all possible, don’t put yourself in
the position of working on the car yourself, as damage can easily
occur. When it is apparent that you will need to work on the car, ask
the car owner if they will permit you to work on the car. Then tell
the owner that you will do your best, but that the car may be damaged.

CAR IS SIGNIFICANTLY UNDER WEIGHT
This is the most common problem that occurs. Oftentimes, new car
builders do not understand that weight must be added to the car in
order to make the target weight.

The only reasonable way (i.e., without risk of damage to the car) to
add 2 or 3 ounces of weight to a car after it is painted and assembled
is to attach a zinc plate weight under the car (available from most
hobby shops). If this type of weight is used, make sure that the
bottom clearance specification is met.(1)

Officials – These plates typically sell for about $3.95.(2) So
consider purchasing a few and then selling them to the folks that
bring in light-weight cars.

Owners – Before doing any work on the car, decide how weight will be
added to the car, and then create any needed weight holes/pockets
first. This will eliminate lots of grief at the weigh-in.

CAR IS NOT LUBRICATED
This is the second most common problem I have seen. I used to be very
concerned about this and would work with folks to get some lube on
their car. But it is very difficult (and messy) to effectively
lubricate after the car is assembled. So, in recent years, I just ask
them if they want to add lubricant, and then loan them a tube of
graphite if they say yes.

Officials – Have a few tubes of graphite on hand, and identify a
location where the race owners can use graphite (typically outside the
building).

Owners – Lubricate the wheels and axles before putting them on the
car.

CAR IS SIGNIFICANTLY OVER WEIGHT
I’ll never forget the Bus. The family glued another block of wood on
top of the original block and then carved and painted the body to look
like a school bus. The only problem was that the second block of wood
was not pine, but was instead fir, a much denser type of wood. The Bus
weighed over 7 ounces! To make the car legal, the dad had to hollow
out a large portion of the vehicle.

The point is that depending on what is used for weight, removing more
than a few tenths of an ounce can be a difficult problem.

Officials – The method to remove weight depends on the type of weight:

– Lead – Remove lead with a drill and drill bit. Lay the car on a
clean rag, and slowly drill into the weight area. Collect and properly
dispose of the lead fragments.

– Hard metals embedded in body (steel, tungsten, zinc) – Avoid
drilling into hard metals. The amount of pressure required to remove
material will likely damage the car. Instead, try to drill around the
weight and then use a small chisel to pry out individual weights.

– Zinc plates – Remove the zinc plate, and snap off pieces of the
weight with pliers. Weigh the material before reattaching.

Owners – Weigh the car body along with the weight, wheels, axles, and
any accessories early in the process. This will allow time to make any
needed weight corrections.

WEIGHT HANGS TOO FAR BELOW THE CAR

Typically clearance problems occur due to weights attached to the
bottom of the car. In one recent case at our weigh-in, a zinc plate
was screwed onto the bottom of the car with the wrong type of screws
(the original screws were lost). The weight itself cleared, but the
screws didn’t.

Officials – Make sure to check for car clearance. If the car just
barely does meet the specification, and you know that there is plenty
of clearance on the track, you can choose to let the car race.(1) But
if the car clearance is far from the specification, make sure the
problem is fixed. Otherwise, the car may drag, scratching the track
and performing poorly.

Owners – Make sure your car meets the specification before coming to
the weigh-in.

CAR IS OVERSIZED
At one of our races, a family came to the weigh-in that had not
previously registered (so they had not been given a copy of the
rules). Their car (actually a boat) was really neat! It was nicely
detailed, but had a mast and a bowsprit (a spar projecting from the
bow of a vessel) that caused the car to be too tall and too long. We
decided to allow the parts to stay on for the design judging, as long
as the parts could be easily removed by the race officials prior to
the racing. We have also done this for a few other cars with tails and
other accessories.

Officials – Make sure that the rules clearly define what is allowed,
and provide the rules to all participants. Then enforce the rules.
You may want to clarify in the rules whether accessories can be added
for the design judging that cause the vehicle to exceed the size
limit.

Owners – Make sure your car meets the specifications before coming to
the weigh-in.

GORILLA GLUE
Gorilla glue is a relatively new type of construction cement. It is
activated by moisture in the air or on the surface to be glued. When
it is activated, it foams and expands. This probably works well for
construction, but is generally a disaster for pinewood derby cars.

At a recent weigh-in a family brought in three completed cars, all of
which had Gorilla glue foam on the wheels. Apparently, they used it to
glue the axles in the slots, but then later found that the glue
essentially took over the car! I gave them some replacement wheels and
axles, and they did their best to repair the cars.

Unfortunately, the family brought along the bottle of glue, and
someone else used it to glue tungsten cylinders into holes drilled in
the bottom of the car. They turned in the car, and we left if lying on
its back for the glue to dry. As the evening progressed, the tungsten
cylinders slowly rose out of the holes. I shoved them back in a few
times, and finally they stayed in. But if I had not been watching the
car, the glue would have cured with the cylinders extending out about
a 1/2 inch, and the car would not have been able to run.

Officials – Ban Gorilla Glue from the weigh-in.

Owners – Don’t use Gorilla Glue on your car.

CONCLUSION
The issues that can arise at weigh-ins are certainly many, and not all
of them can be anticipated. But as an official or owner, preparing for
these common issues will facilitate a smooth and (relatively) painless
weigh-in.

(1) For our race, we allow zinc plates to be attached to the bottom of
the car, even though the clearance specification is not quite met. I
know that cars with zinc plates run fine on our track. These plates
are very convenient for correcting weight issues at the weigh-in, and
banning them would be like shooting yourself in the foot.

(2) Maximum Velocity offers zinc-plates for considerably less than
hobby shops. You can find them
Here.

From Pinewood Derby Times Volume 12, Issue 6

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Is it Cheating?

This past year I received several e-mails relating situations where car builders were accused of cheating. In some cases the writer of the e-mail was certain that another parent had cheated, and in other cases the writer was accused of cheating.

In several of these cases, I disagreed with the accusation. I am certainly against cheating, but before an accusation of cheating can stand, there must be an understanding of the definition. According to the dictionary, to cheat is “To violate rules deliberately, as in a game”. Thus, for cheating to occur, the following must occur:

1. Breaking a clearly documented rule,
2. Deliberate act.

To put this into pinewood derby terms, for cheating to occur:

1. There must be a clear, written set of rules governing the construction of the car,
2. The car owner must knowingly violate a particular rule.

This may seem like a narrow view to some, but let me share some situations that will (hopefully) make this more clear.

LACK OF RULES OR RULE CLARITY

The rules that come with the BSA Car kit and with the Awana Kit are notoriously vague. Many packs, districts, and councils have annotated these rules for their own use, but many others still use the rules in the box alone. This can lead to accusations of cheating when the interpretation of the rules in the box varies. Here is a case in point from a newsletter subscriber:

“Our pack had no printed rules other than those in the BSA kit. In addition, I was told by the pack leaders that the only rules were 7 inches long, 5 ounces maximum weight, and 3/8 inch ground clearance minimum. So, we put the car together and complied with these rules. We did use axle holes (instead of slots) and had a three wheel on the ground setup.

When the car was inspected at the race, the inspector said we should have used the slots on the bottom of the car so that the axles could be seen. This was the first we had heard of this rule. After a brief discussion with the officials we were allowed to race (our car, built in 2 days, was one of the shabbiest looking entered in the derby).

Well, the car won every heat in the den by at least 2 car lengths. Suddenly everyone was protesting our axle holes. One family in my son’s den had won the den and the overall pack race three years in a row and they were irate! The race officials conferred and we were told that we would have to cut axle slots in the car to be able to compete in the overall pack race. If we didn’t cut the slots we would be disqualified as the den champion! Knowing we were legal, we consented and pulled the wheels and cut the slots in the car. All of this was done with no alignment tools other than a credit card for wheel spacing. We were pressed for time and pushed the axles into the original holes that had been drilled into the body. The axles could now be seen, but the axles were only held in by friction, as we didn’t have any way to glue them in place … “(1)
(Edited and names removed to maintain anonymity)

What happened here? Did the car owner cheat? Did the previous champion have a valid issue? Were the race officials justified in their actions? In my opinion, the car owner followed the rules (there is no mention of axle holes or slots in the ‘Rules’ section of the paper in the BSA kit), the previous champion had no valid issue, and the officials should be ashamed of themselves for changing their previous ruling during the middle of the race.

Is this an isolated incident? I wish it were so. I receive numerous e-mails every year with a similar theme. Here is another one:

“My boy and I have been lucky enough to win three 1st Place trophies. I do own a very good drill press, and I built our own test track. But, my biggest challenges have been working with my son to understand all of it, patience to do it all, and, most of all, dealing with the aftermath of winning because he gets accused of cheating. After our first win he was not allowed to enjoy the good feelings that should have accompanied the 1st Place trophy. The judge – who actually inspected his car and approved it for racing – threatened to disqualify it after it won the first three heats (two of them were against his son). After the trophies were passed out, he informed both of us (loudly, and in front of all) that when we went to District that we would be disqualified if we left the graphite on the outside of our wheels. We weren’t, but most of the Moms and Dads who heard what he said told their boys that my son and I had cheated … ”
(Edited)

Did cheating occur in this situation? The car evidently met the rules and was allowed to race with no issue. The victory was not due to a rule violation, but was due to the amount of time and effort put in by the parent/child team.(2) Clearly, the accusations had no merit and were just due to ‘sour grapes’ on the part of the race official. What a display of childishness.

I could go on, but I believe the point is made. A different interpretation of a vague rule does not constitute cheating.

DELIBERATE ACT

While the major source of cheating accusations is due to vague rules, it can also occur when people are unaware of the rules. This oftentimes happens to people who are new to pinewood derby racing, or have previously participated in the event in a different organization. The following can happen:

“We built a car for my Cub Scout’s pinewood derby race. We had previously raced in the Awana Grand Prix and had done quite well. So, we built a car using the same techniques (long wheelbase, three wheels on the ground, et al). At the pack we took 1st Place. But when we went to the district race, our car was disqualified because of the long wheelbase. Of course there was nothing we could do. Another member of the pack was at the district race and witnessed the disqualification. The boy told my son that we had cheated at the pack race …” (Edited)

Was this cheating? Apparently the long wheelbase car was acceptable at the pack race so there was no cheating at that event. Since the car violated the district rules, it was rightfully disqualified. Since the car never raced at the district, the car owner certainly couldn’t be accused of cheating. Too bad that the district and pack rules were not synched up.

A slightly different scenario can also occur: a car violates the rules, but the violation is not caught at inspection. Later – usually when the car does well in the heats – the violation is detected and the owner is accused of cheating. This is a more difficult situation that can take on two flavors:

1. The rule violation was obvious, but for some reason was missed.
2. The rule violation was hidden, but somehow became known during the race.

Let me provide an example for each. These situations do arise, so officials should be prepared with a response.

1. The rules specify that the car must ride on all 4 wheels. A car is entered with only three wheels on the ground (a very easy thing to unintentionally do). The violation is not detected. Later, while the car is being staged, the starter notices the violation. Should the car be disqualified? Is it cheating?

2. The rules specify that no moving parts are allowed except for the wheels. During a heat, a car crashes and mercury comes spilling out (this actually occurred in early 2004 at a BSA race in Kansas). Was this cheating?

In case 1, in the highest likelihood the violation was unintentional. The owners would have had every reason to believe that the violation would be detected at the inspection, so to intentionally attempt the illegal technique would have been pure foolishness. What should be done when the illegality was detected in the race? In my opinion, since the car passed inspection and was allowed to race, no action should be taken. The car should be allowed to continue racing. The pack should make sure to improve their car inspection check list before the next derby event.

In case 2, cheating may or may not have occurred. It is possible that the parent did not consider mercury a ‘moving part’, and equally as possible that the parent knew, but gambled that it would not be detected (of course in either case, the parent showed highly questionable thinking by using a highly toxic substance in the car). Since the rules specified no moving parts, and since the detection of the mercury would have been difficult at inspection, I recommend disqualifying the car. The situation would be the same if during the race a wheel came off and it was found that a hidden bearing or bushing was used, or that illegal axles were used.

Clearly, this is a gray area, so to avoid problems and legislating from the bench, set a policy ahead of time as to how to respond to illegalities found after inspection.

CONCLUSION

Certainly, cheating does occur. But to avoid false accusations make sure there are clear rules in place, and there is clear intent to violate a rule. Remember also that pinewood derby racing is a child-oriented activity. Parents, keep it fun by avoiding unnecessary conflict.

(1)The car ended up taking 2nd Place in the pack.

(2) Consistent winners are oftentimes accused of cheating, especially if their car is significantly faster than other cars. While it is possible that some illegal technique is being used, more likely they know all the speed techniques, are taking every possible advantage offered by the rules, and put a lot of time into constructing the car. Working smart and working hard generally pay off.

From Pinewood Derby Times Volume 5, Issue 7

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The Wrong Lube

Last year was a poor year for pinewood derby performance for my sons. From the scout store we had purchased the pinewood derby speed kit that included: sandpaper, extra nails, a white powder (that I thought was Teflon lube), wheel mandrel, etc. Then we went to work.

The cars were the boy’s designs. One was a limo, and the other a cross between a submarine and a shark. We used a drill press to get straight axle holes, then we sanded the wheels and nails. We painted the cars, and even bought two plastic models to get decals to use on our cars. We then lubricated with the white powder. The wheels just didn’t spin for very long, but we were in the middle of a move so I couldn’t put any more time into the cars.

Our cars performed marginally well – we won a few heats and lost a few heats. But they were a lot slower than our prior year cars. My boys were disappointed in not winning as many heats as in previous years.

After the race when we had more time I decided to find out what was wrong. Oh, you probably know already. The white powder wasn’t lubricant, but instead it was axle polish (powdered pumice). When I cleaned out the powder and replaced it with graphite, the wheels spun like crazy. We learned how to really polish axles, and what not to use as a lubricant on race day!

Michael Law

From Pinewood Derby Times Volume 5, Issue 6

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Pinewood Derby Car Showcase – December 12, 2012

Here are the last two cars that I built for our Outlaw Race …


Pharodox – Randy Davis


Pharodox was modeled after a Hot Wheels car by the same name, and was raced in April of 2012. It is equipped with Super Stock Needle Axle wheels that had the sidewalls customized on a CNC machine. The car was quite fast, taking 2nd behind a car with X-Lite Needle Axle wheels.

Lightning Bolt – Randy Davis

In 2012 we moved our local race from spring to the fall (two races this year), so I didn’t have much time to work on a second car. Instead I used the photo model for the Lightning Bolt, which was a kit we sold for several years. I equipped the body with Needle Axle Wheels (white – a special order item), and our Needle Axle Upgrade Kit. The pattern on the sidewalls was cut out of sticky-back vinyl with a Cricut machine by my wife (thanks honey!). I’m sure the vinyl added a touch of weight, but it didn’t matter as the car handily won the Outlaw race.

… and two cars from another entrant in the race.

Finn McMissile – Richard Larson

In spring of 2012, Richard modeled Finn McMissile from the movie “Cars”. The only non-wood parts are the dual mirrors, which came from a model car kit. Finn took first place in design.

Red – Richard Larson

In the fall of 2012, Richard modeled the fire engine known as “Red” from the movie “Cars”. Red weighs exactly 5 ounces, and actually has a small amount of ballast weight. The blue tubing represents a stream of water as Red is watering the flowers. It detaches for the actual race. Not surprisingly, Red took first place in design.

In 2011 Richard modeled ‘Mater. You can see it in the Car Showcase at:

From Pinewood Derby Times Volume 12, Issue 5

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