SERVO 05.2017 27
wedge in my angle
vise and used a
carbide end mill to
carry out this task
proved easier than I
expected. However, it
is hard on tooling and
you need a big slow
mill to do it.
block’s profile had
been water cut with
zero draft edges, but
I still needed to add
the tapped mounting
First, I drilled the
pattern (Figure 6),
then hand-tapped the 10-24 threads.
With 10 threads per block, this took
quite a while!
I then machined off a large
section of each block to create right
and left hand mounts (Figure 7).
With that complete, I could do a test
build-up of the wedge onto the bot
This let me see what needed to
be done to limit its travel, so that it
would lie flat against the ground if
the bot was inverted, and not go so
far down and under that it could
result in lifting the front wheels off
To stop the former, I machined a
little off the front of the side rails so
that these acted as the stop for the
wedge, but allowed just enough
travel when inverted (Figure 8
To prevent the latter problem, I
added a couple of UHMW blocks
(Figure 9) that stop the wedge
swinging much below what is
necessary to keep it in contact with
the floor. The completed wedge on
the bot can be seen in Figure 10.
The new wedge had its first test
at Motorama 2017. So, how did it
do? Well, better than at last year’s
event, but we still haven’t found the
answer to the new generation of
The wedge shrugged off the
horizontal blade of “Susan,” but it
only took one hit from “Minor Threat
3” to knock us out.
The hit took a neat chunk out of
the front edge of the wedge and
curled a little bit of UHMW which
high-sided the drive on one side. We
tapped out promptly!
Isotelus went on to have a
winning record before going out to
another vertical disk when we got
hung up on a wall after a hit.
The new wedge stayed more or
less straight, and the bot is otherwise
undamaged after some hard fights.
Unfortunately, it failed to get reliably
under the wedges on the vertical
The new wedge only weighed 2
lb/13 oz as mentioned earlier, so I
still have one pound left to play with.
I will be experimenting a bit
more with designs to try to gain a
completive edge before the next
event at Franklin Institute 2017. SV
Figure 9. Wedge limiting
Figure 8. Test-fitting the
Figure 10. Ready
Figure 11. Damaged