tight fit for our drive belt.
It all came together without requiring us to contort our
hands too much to reach inaccessible screws.
Swapping out the drive motors didn’t require any
additional design work. We pulled out our simple test bed
for identifying good Maxons and put in ones that didn’t
draw extra current and felt nice and smooth. We have
boxes full of these Maxons, but they all have about 2,000
miles of racing on them, so it’s understandable that some
of them are as run down as aging Rocky after 10 rounds in
There were still plenty of good ones in our boxes, so
we selected some new drive motors and some spares and
checked that item off the to-do list.
One of the most labor-intensive repairs was to the body
panels. Every outer body panel needed to be replaced.
Troublemaker is clad in 1/8”
thick 7075-T6 aluminum which is
not the easiest thing to machine,
but was a welcome change of
pace from the titanium that
covered Double Jeopardy. We
picked up the hole placement on
our structural posts using one of
favorite tools in the garage:
Threading them into the
mounting hole, positioning the
panel on the bot, and giving it a
light tap with the hammer takes
all the guesswork and
measurement out of the process.
For the front panel, we opted to
go with a thicker 1/4” thick
plate of 2024 aluminum — some
of the same material that went into
frame components for Double Jeopardy.
These panels were straightforward,
but one was as difficult to work with as
the timeline in Terminator: Genisys.
Troublemaker’s back panel is an 1/8”
thick piece of 7065-T6 with four 45
degree bends in it. Generally, when you
bend 7075, it will fracture. We didn’t
quite remember how we had gotten
such nice bends in the original 2001
back panel. After RoboGames, it had
yet a few more bends in it. Our first
instinct was to try and bend it back into
place, but even after a careful
application of brute force the original
back panel fractured.
We knew we would have no hope
of bending the panel without the
proper tools, so we popped over to
trusty Harbor Freight for an affordable sheet metal brake.
The minor assembly of the brake was simple, and we were
ready to bend the rules of metalworking.
To test out the brake, we put some bends in 6061
aluminum, which is not as brittle as 7075. We successfully
put one bend into it. And then another. On the third bend,
we didn’t quite get to 45 degrees, so we gave it another go
in the press and promptly fractured the panel. We tried
another 6061 panel and fractured it too. Despite these
discouraging results, we went ahead and tried 7075, which
we also fractured.
We knew getting the bends into the 7075 was possible
— we had done it back in 2001. Maybe all we needed to do
was heat things up. We used the propane torch to heat up
the areas we wanted to bend, and swiftly used the press on
the hot metal. It bent nicely and did not fracture. We got
70 SERVO 07/08.2018
TRANSFER SCREWS ARE AMAZING TOOLS.
UPGRADING FROM A SOLENOID TO A RAGEBRIDGE.