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Weapons
We spent a long time toying around with ideas
for a weapons for Storm II. We could go down the route of putting a
'token' weapon on the robot or we could try to put on something a little
different. It was time to get the meccano out and start playing around
with some ideas. After toying with the idea of a spinner we decided that
the most visually impressive weapon (had to do something to silence our 'no
weapon' critics) was a lifter.... and the design that fitted into the Storm II
was a 4 bar linkage system, similar to Biohazard.
After 9 months of being compared to Tornado, we
now fully expect to be compared to Biohazard (I wish people would make their
minds up !). Anyway, the system is a little different from Biohazard, they
use linear actuators and convert rotary motion, into linear motion and back into
rotary motion.
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Storm II allowed the whole arm mechanism to sit 'inside' the arm itself
which was the only space spare in Storm II - and the whole mechanism,
gearbox, motor and arm only weighs 12Kg.
HPC Gears provided us with the machining
to carry out the work which includes some intricately machined gears and
half shafts.... On the right you can see the gearbox unit which sits
under the arm. On the back you can just see the S28-150 Magmotor
that runs it. It drives through a reduction ratio a worm, which in
turn turns the worm wheel, into the third stage of the reduction onto the
geared quadrant gear which is affixed to the two half shafts on either
side of the arm.... At the front you can see a pot which is driven
by a pair of crossed helical gears - the pot provides feedback to the
speed controllers for positioning and end stops. The arm can be run
in two modes, the pot can either give end stops and the stick on the
controller simply controls the speed of up and down motion, or we can
switch to 'servo' mode when we can absolutely position the arm just like a
server. Anyway....after much testing and fiddling we got something
which seems to work ! |
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The arm itself is a totally interchangable
module of the robot - we can literally swap it in and out as a whole
unit.....Here are a few nuggets of information about the design.
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- Full travel from down to up : 0.3
seconds
- Maximum lifting weight (at 200amp
current limit) 200Kg
- The arm itself was machined out of a
solid billet of 7075 aluminium. You simply can't get U channel in
anything stronger than 6082, which simply wouldn't have been strong
enough
- The gearbox itself was machined from a
solid billet of 7075 aluminium. It took 2 days to program up the
CNC machine with the model, and days to machine up.
- The levers on the sides of the arm are
the most likley parts to break - that's why we have 4 sets of levers....
should one set fail, we can just swap them out.
On the right you can see a cut through
model of the gearbox showing all the gears, bearings, drive and pot
feedback system.
Getting the arm system just right has
taken a long time, and a lot of work between John Reid (Thz) and Team
Storm - however without John's help and input we wouldn't have learned
how to use CAD systems which we now consider invaluable to the
development of our machines.... and we wouldn't have this rather funky
lifter weapon. |
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As you can see from the illustration on the
right, when the arm is fully retracted the arm channel sits down over
the mechanism. In designing the solution this way we were able to
produce a very compact lightweight system which was the only way we were
going to get a weapon into Storm II without having to make changes to
the chassis To this day (May 2008
at time of writing) the chassis for Storm II is the very same chassis
that was first built for it back in 2001. One of the rear bars has
been replaced, and some changes have been made where we've added parts
to the robot - but 7 years on, Storm II is still the same machine it was
when it was first concieved to go to the US and take part in Battlebots.
To see the arm working in CAD,
click here to view a Quicktime file. |
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