Tips from the Pits:
Speeding Up a Motor Change
● by Pete Smith
Half the battle in combat robotics is
having your bot repaired
completely in time for the
next fight. This is the first
of a series of short articles
detailing some ways to
make that just a little bit
easier.
FIGURE 1.
My Dave’s
Hub.
FIGURE 2.
Machine flats.
Dave’s Hubs (Figure 1)
are one of the most
popular ways to mount
Lite Flite wheels on
an Ant or
Beetleweight bot.
The hubs are
secured to the axle
with a set screw,
and the tire is held
on by a custom
washer and a
screw. It’s normal
to loctite these
screws to ensure
the wheels do not
come off in
combat. However,
sometimes a little too much loctite makes the screw very hard to loosen up.
This is made worse by the fact there is little to stop the wheel from
simply turning when you want the screw to move. This is the last thing you
want to happen if you need to change a tire or a complete motor between
fights at an event.
In order to stop a wheel from turning, I machine a flat on either side of
the hub (Figure 2) so that a slim wrench can be slid down behind the tire
and onto the hub. I just happened to have a slim 19 mm wrench, so I machined
mine to match that, but 3/4" would probably be an easier size for most in the
US. If you don't have access to a milling machine, you could simply use a file to
add the flats.
A modified hub can be seen fitted to my Antweight Saifu (Figure 3).
Notice the other benefit of the modification ... it’s now possible to get at the
mounting screws for the motor. This is very useful if the set screw on the hub
will not come out.
In Figure 4, you can see how the wrench fits behind the tire, turning what could be a nightmare in
the pits into a quick and easy task. SV
FIGURE 3.
Hub fitted
to a motor.
FIGURE 4. Using
a wrench to hold
the hub.
38 SERVO 06.2013
