8, Issue 6 - "Grooved Axles"
As a refresher, the apparatus consists of a machined steel ring which
is sized to fit snugly over a machined BSA wheel. The ring weighs two
ounces, which is essentially the load on a rear wheel of a pinewood
derby car.
Figure 1 - Weighted Wheel Spin Jig
After sliding the ring over the lubricated wheel-axle assembly, the
axle is mounted onto the apparatus. A length of fishing line with a
weight on one end is wound around the ring (there is a small pin on
the ring not seen in Figure 1, to which the non-weighted end of the
string is attached). On each test, the string is wound until the
weight touches the eye hook. The weight is then released and a
stopwatch is used to measure the spin time. The string is sized such
that it is released from the ring before the weight reaches the
ground.
In order to avoid lubricant contamination, two wheels were used for
each of the five lubes (ten wheels total), and one axle was used for
each of the five lubes. The reason for two wheels for each lube was
to ensure that the performance of a lube was not exaggerated or
degraded due to a "fluke" wheel. The wheels were Ultralight Speed
Wheels, which are machined inside and out. To further minimize
variance, a single mold number was used for all of the wheels.
Each wheel/axle was lubricated in the same manner (lube applied,
allowed to flow over the axle, and then blotted off). Then the
assembly was placed onto the spin jig. To break-in the lube, five
spins were given to each wheel.(2) Then five timed spins were
performed and recorded.
EXPERIMENT RESULTS
Somewhat to my surprise Methyl Silicon 20 and XOil performed quite
well in the spin tests. In fact, they both tested slightly better
than NyOil II.
Figure 2 - Spin Test Results
So, some track testing was called for. As the Methyl Silicone 20 is
rather expensive, further testing was focused on XOil. That testing
showed similar results to the spin tests.
As a result of this testing, Maximum Velocity is now offering XOil in
lieu of NyOil II.
(1) cSt stands for "centistokes", the standard for the viscosity of a
liquid. As a comparison, Krytox 100 is 4.0 cSt.
(2) Except for the Methyl Silicone 5 - in this case the fastest spin
was the first; each subsequent spin was slower.
Read More at: Pinewood Derby Times Volume 9, Issue 4
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