Next
I had to figure out a way to mount the motors onto the side walls. here
I had to put a lot of faith into the strength of the honey comb
fiberglass. I chose to drill out one side just large enough to slip the
gear box into the depth of the honey comb and attach the drive unit to
the outer wall of the fiberglass. I started by drilling out the top
layer of fiberglass with a wood boring bit.
I
then continued to work the opening and "bore" it out using a grinding
stone on my dremel tool that just happened to be ~ 16mm. I had to be
careful to only remove the internal honeycomb and not damage the sheet
of 1/32" fiberglass on the other side.
After
much tinkering to get this process down I decided to add a little bit of
reinforcement to the motor mount. I cut out circles of fiberglass cloth
the same size as the motor mount hole and after liberally applying
standard plastics epoxy to the area I dropped the cloth in and moved it
around with a q-tip till it was well saturated and positioned evenly to
center..
After
letting all the holes cure I drilled out a Large hole for the shaft and
two smaller holes for the motor mount hardware. I had to add SS Washers
to the mounting screws, but with them the end result was surprisingly
strong and when you factor in that the two motors together weigh in at
~2.3 oz that means the entire side wall in the photo to the right
weighed in at only .4 oz. later on when I end up shortening the length
of these side walls by nearly 2 inches its even less.
At
this point I turned my attention to the front and back walls of the
build. these two walls where made from the cutting board plastic. I cut
them down and drilled them out for the aluminum center posts, and then I
drilled out even more materiel just to bring down weight. I also
measured out the width of my robot and made slots for the motor mount
side walls to slide into once these walls where attached to a base.
After
trimming down the motor shafts and cutting a rough aluminum base plate
to mount the front and side walls onto, this build started to look a bit
like a combat robot.
However at this point I started to notice a few issues I was going to have to deal with sooner or later. My weight was already getting fairly close to 16 oz and I didn't even have the second set of motors yet. I knew that the rough cut aluminum base plate was to thick and thus far to heavy and would be swapped out later for a lighter material but I also noticed that I was wasting a lot of space and could shave off quite a bit of build material if I shortened the whole robot a bit. at this point I stopped and pondered for a few days. I didn't want to make a rash decision and cut down my materials but I also knew I had to do something.
It
took me a bit and several drafts, but I decided that not only would I
shave off the access, but that I would also remove the lifting arm servo
from the build and shorten the whole robot by nearly 2 inches. Around
this same time I also decided that I was not going to have the weight
for two separate experimental wedges so I came up with the spring wedge
idea that would allow a single wedge to have "give" in all directions
from hard impacts.
At
this point I also started work on some of the electronics. First thing
was to chose a gage of wire that was capable of carrying 4 amps for the
motor leads, and 8 amps for the battery to ESC connection, but I also
had to chose the lightest that could carry that load so I set off
weighing in 18" of all the different wires I had at my disposal. I ended
up using a heavy duty servo wire for the motor connections, and a bit of
high quality braided 20 AWG Silicone wire for the battery connection.
The silicone wire was a hair heavier than I would have liked but I was
only using a single inch of it so decided it was worth the extra
potential current to the ESC.
You
would think that an ESC designed for ant robotics would take weight
seriously. but the stock Ant 150 ESC had over .15 oz of wasted materials
that had to be de-soldered from the board. I cut out everything that was
not needed, bringing the 9 wires that lead from the ESC to the Rx down
to just the 5 that where actually needed to carry power and 3 signals.
Unfortunately I think I may have toasted the flip control during my
de-soldering job.
Tip to ESC developers,.. feel free to provide the Rx wires,.. just don't pre solder them on, that way the builder can chose length without having to deal with de-soldering and trying to get wires back into holes filled with old solder.
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