Back to Testing On to Getting Ready for '02
From The St John's Newsletter following Maximus' appearance on the school Open Evening:
This article served to heighten the interest in Maximus, and Robot Wars in general.
Shortly afterwards, a photograph of the team appeared in the School Prospectus.
(It's on
the right-hand page, centre left)
Several things became apparent during the open evening, during which Max was driven round
the Design Tech Department floor at intervals between 4pm and 7:30 pm.
Firstly, he got VERY HOT! The motors became too hot to touch, and both motors feed
wires actually began to smoulder! The speed controller fared better, getting hot,
but not greatly.
Secondly, we had a failure in the solenoid which sends power to
the flywheel weapon. Subsequent replacement of the solenoid got it all working
again, but after several operations of the weapon, the second solenoid burned out too.
When it was working, the flywheel weapon moved at a rate which could safely be
described as "Frightening". Several members of staff who witnessed the
rotating disc were seen to pale visibly and edge slowly out of the room. We have yet
to measure the speed of the disc, but we are confident that it is a good match for
Hypno-discs spinner.
Andrew Newby was the driver on the evening, and showed a good degree of control (apart from one instance which we won't mention - ahem!). Karl Warren, our weapons operator was left with little to do on the evening due to the solenoid problem, and our lack of a reliable pnuematic system. However, he did get to drive for a brief period when Andrew relinquished the controls.
So, we are now working on several fronts; Sourcing motors with more torque and durability, discussing the building of a custom speed controller with the help of 3M engineer Derek Williams and curing the solenoid problem with the help of Paul Rodway, an RAF Sergeant instructor.
Mr Adair has been busy strengthening the axle mountings, and
securing the flywheel driving motor.
Andrew was able to obtain a replacement (new!) solenoid from Wards of Bishop Auckland -
many thanks!
Karl has been tasked with improving the chances of an opponent being dragged up Max's
front and into the flywheel weapon - in case we don't have the opportunity to hit them
with sufficient speed.
As a way of saying thanks, we produced a booklet covering the story of Maximus to date, and presented it to each of our sponsors, along with a framed, colour copy of the Northern Echos' photograph of the team.
Following trials of the spinning weapon, we decided to use a stroboscope to
measure its' rotational speed. However, after applying power for
over 30 seconds, and finding that the disk was still accelerating seemingly beyond
the range of the strobe, we made the decision to change the gearing of the pulley
system. This should have two effects - it will slow the disk down to below light
speed, and it will give the flywheel more Torque (turning force). This way, when it
hits something, it will tend more towards keeping going, rather than slowing down.
The gear change required us to make some changes to the
motor/pulley assembly, so it was a few days before we could test it again.
Karls dad, Mike, did the conversion. Many thanks!
The gearing changes meant that we could run the flywheel at much
lower speeds.
When fitted to the smallest pulley on the drive motor, and the largest pulley on the
flywheel, we found that the wheel turned at 35 revolutions per second. That's 2100
rpm!
As a 'slowest speed' that was quite impressive;
Hypnodiscs' weapon only rotates at 750rpm and if you are a Robot Wars fan you will already
know how much damage that can do!
Some basic calculations based on the rpm, and the distance of the
teeth from the centre of the disc resulted in the following conclusion; The
cutting teeth on the disc are moving at approximately 91mph!!! (Hypnodiscs
teeth travel at approximately 85mph)
With the belt in the position shown, the starter motor rotates three times for every
rotation of the flywheel (3:1). If the belt is then moved to the opposite end of the
pulley arrangement, the starter rotates once for every three rotations of the flywheel .
Heres the 'mathsy' bit.....as it is shown, the motor turns 3 times to get 1 flywheel turn,
(3:1) but in the other position, if the motor turns 3 times, the flywheel will turn 9
times (1:3)!
Theoretically, if we had a powerful enough battery, and plenty of time, the
flywheel would then rotate at 2100rpm x 9 or 91mph x 9! Is that
scary or what?
During the testing, we burned out the new solenoid, so a
Bishop Auckland company called Mechetronics was contacted to try to give us some clues as
to 'why'. We did some experiments with the replacement solenoid, and found that
after switching it on with 12volts, it stayed on even when we dropped down to 4volts.
This should put a lot less strain on the solenoid coil, and reduce any heating
caused by the current passing through it.
As we wind up for the 2001Christmas holidays, we are aware that we have only until early August before we have to be ready for qualifying at theNewcastle Telewest arena. Robot Wars Extreme and the World Championships are being broadcast on BBC Choice and BBC2, and we are still looking to incorporate new ideas into Maximus to ensure that we are fully prepared for Battle. I will be going to visit the Gemini team over the New Year, and I am sure that they would wish us well. (Hello Brian and Shane!)
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