FIGURE 6
FIGURE 7
Freight models so it could not be
used as a spare for them. The first
stage gears are plastic (Figure 6)
but the second stage are metal. The
different motor and gears give a
higher output speed of 900 RPM.
The casing is very similar to the
old drills, but the Double D nose is
just slightly larger so will require
gearbox mountings to be modified.
The output shaft is 0.3” longer
(Figure 7).
To sum up, this drill should be
good for combat use in a 12lber
with 3” wheels.
The plastic first stage is a
drawback, but most impacts will be
on the second stage metal gears.
The longer shaft, increased RPM,
and slightly larger case means they
are not a direct replacement but
could be fitted to most existing bots
with a little modification of the
mounts and the wheel hubs.
The Bad FIGURE 8
The “Boston Industrial” drill
purchased through Amazon looked
at first glance to be nearly identical
to the old Harbor Freight models,
and I had hoped that they would be
simply the same drill repackaged for
a different vendor (none of the drills
here are actually made by the
companies selling them). However,
this quickly seemed to not be the
case since the batteries were not
interchangeable.
Closer examination of the drill
revealed all was not as it should be.
The drill packaging and casing is
labeled 18V (Figure 8) but curiously
the charger was only rated at
FIGURE 9
FIGURE 10
FIGURE 11
9V (Figure 9).
The final answer came when
opening up the battery pack to find
only six cells, i.e., 7.2V (Figure 10)
and the motor on the drill had a
7.2V sticker on it (Figure 11). Yes,
it was a 7.2V drill, mislabelled and
being sold as a 18V model! They
say you only get what you pay for
but it seems sometimes you don’t
even get that.
Amazon and the vendor have
been contacted, and the drill had
been removed from sale at the time
of this writing.
The Ugly
The Power Smith isn’t really
ugly. It’s as good a drill as the
Harbor Freight model and it has
the same 550 RPM. It also has
plastic — but chunky — first stage
gears (Figure 12) and a press fit
gear. What makes it ugly for our
purposes is that the gearbox case is
quite different, with a rounded
triangular nose (Figure 13). It
would not fit any existing bot
designed to fit the old designs. I’ve
seen this triangular nose before but
its not a common design, so future
replacements may be even harder
to locate.
Conclusion
The new Harbor Freight
68239 drill is usable as a drive
train for 12 lb bots. Its first stage
plastic gears are not as good as the
metal ones we are used to, but
these are not particularly likely to
fail. The higher RPM should give
FIGURE 12
36 SERVO 12.2011
