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Wheel Bore Reaming
The
wheel bore, simply put, is the inside of the wheel where
the axle goes. Molded
Pinewood Derby car wheel hubs can vary in size by as
much as .01" and you must resolve this situation
to have the smoothest fit of the axle into the wheel.
The Pro-Hub Tool allows you to ream the wheel bore to
the same size or to at least select wheels from your
assortment that have a similarly sized bore radius.
This is a very important alignment tip as it allows the
car to sit evenly on all 4 wheels with equal distances
from the axle and wheel hub to the track. You will need
the Pro-Hub Tool to complete this speed tip. To perform
this procedure:
1)
Test fit
each wheel by sliding it onto the tool pin of the
Pro-Hub Tool as shown in figure 1. If the wheel bore
is too small for the tool, use steady hand pressure and
a twisting motion to work the wheel on to the tool.
Remove the wheel and repeat 3 times.
Figure 1
2)
Once
completed, choose another wheel and repeat step 1.
Wheel Hub Squaring
In
order to make precise adjustments to the wheel, one must
ensure that the wheel can be mounted on the mandrel
correctly. The Pro-Hub Tool will square the hub to the
centerline of the wheel which allows for the most
accurate tread face finishing.
(The
Pro-Hub Tool as shown in figures 2 and 3 , has a square
end to improve wheel hub accuracy and a coned end to
reduce hub friction).
 
Figure
2
Figure 3
To square the wheel hub,
which should be done before any other wheel preparation
step, perform the following procedure:
1)
Remove the protective cap
from the square end of the Pro-Hub Tool, pierce a piece
of 400 grit sandpaper (grit facing outwards) and slide
the sandpaper until it contacts the body of the tool as
shown in figure 4. To minimize the risk of a hand
injury, leave the protective cap on the coned end of the
tool.
Figure 4
2)
Place a
wheel onto the square end of the tool, hub side first as
shown in figure 5.
Figure 5
3)
With one
hand hold the tool and the sandpaper, and with the other
hand press the wheel against the sandpaper. Rotate the
wheel back and forth for about 10 seconds.
4)
Repeat
steps 2-4 for the other wheels. Use a new area of the
sandpaper for each wheel.
5)
If the hubs will not be
coned, repeat steps 2 to 4 with successively higher grit
sandpaper (600, 1000 and 1500).
Coning and Sanding the Wheel Hub
As
you can see, the wheel hub is now true to the wheel
itself, but still presents a significant friction point
by rubbing against the car body. We can increase the
overall speed of the car by reducing the hub surface
area and polishing the remaining portion of the wheel
hub. We will reduce the area by tapering, or coning,
the wheel hub. This process can be performed with the
coned end of the Pro-Hub Tool as shown in figure 6, and
sandpaper in the following grits: 200, 400, 600, 800,
1200, 1500.
Figure 6
With the Pro-Hub Tool, perform the
following steps:
1.
Pierce a
small piece of 200 grit sandpaper (grit facing outwards)
with the coned end of the Pro-Hub Tool as shown in
figure 7 and slide the sandpaper until it contacts the
tool. Leave the protected cap on the other end of the
tool to reduce the risk of injury.
Figure 7
2.
Place a
wheel onto the Pro-Hub Tool with the wheel hub facing
the sandpaper as shown in figure 8. With one hand,
hold the tool and sandpaper and rotate the wheel with
the other hand firmly against the sandpaper back and
forth for about 10 seconds.
Figure 8
3.
Perform
step 2 with the remaining wheels, moving the sandpaper
on the tool as needed once an area has been worn.
The wheel hub should look similar to the one shown in
figure 9 when the initial coning has been completed.
Figure 9
4.
Once you
have completed the initial coning procedure and then
applied the finishing steps as described in the
pinewood derby
speed tips manual, the hub should look similar
to the one shown in figure 10.
Figure 10
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