On Jun 6, 9:55*am, dpb wrote:
DerbyDad03 wrote:

...

The project I need these bolts for has some very strict rules about
manufacturing your own parts or modifying readily available parts. My
options for this bolt are pretty limited - carriage or elevator, by
rule. Due to air-flow issues over the surface where the bolts will be
installed, the carriage bolts would be a distant second choice.

These bolts are for a Soap Box Derby car ...

I have hard time believing there's high enough speeds involved the drag
differential would show up...

--

Drag differential showing up.

Our timers measure the differential between the cars crossing the
finish line to the thousandth of the second. I have seen dead heats
where the timers read 0.000. Average speeds for most tracks are 24 -
28 MPH but races are determined by the time differential between the 2
cars in a heat, not by top speed. Races are run in a 2-phase lane-
swap, wheel-swap format to ensure that the only factors are car and
driver, not a faster lane or faster wheels. The total differential
between the 2 phases is what determines the winner of the heat.

While a single bolt head might not make a full 1/1000 of a difference,
2 bolt heads might. Or maybe 1 bolt head and an axle spindle out of
alignment. Every little bit matters, and it's the sum of all the
little things that you have to be concerned with. Trust me, if you
know what you are looking for, you can see the differences between a
well built car and one that was put together per the plans but without
the attention to detail required.

Let me give you another example: When the cars are inspected prior to
the World Championship races in Akron OH, you will either get a fancy
VIP sticker on the nose of your car (meaning your car was 100% legal)
or a repair sticker that tells you what is wrong and how long you have
to fix it. These repair stickers are your standard 1" x 3" mailing
labels. Years ago, after you repaired the car, they removed the repair
sticker while VIP stickers were left on as a "badge of honor".

One team took their VIP'd car to a wind tunnel and ran a test, at
average speeds, and proved that the VIP sticker caused air turbulance
at the front of the car. In essence, Akron was causing *harm* to the
cars that were sent to Akron ready to race. Based on that test, they
now leave the repair stickers on the cars also. Like I said, every
little bit matters.