We finished assembly in-between photo shoots and interviews and prepared for the filming and fighting to begin
The first fight went very well, and we were selected and able to move over to the nice tables in the space studio.
We were in full control for the majority of the fight. The weapon worked flawlessly and we managed to lift the opponent.
The robot was really we balanced and very nice to drive. It was fast, and we were able to out push everyone.
However, in the last 15 seconds or so all 4 of the short drive motors burned out!
After the first fight I replaced the 4 burned out drive motors. I did not have any vee belts attached in the first fight, so I fit 2 on each side to mechanically join the two wheels and drive motors.
I also set the current limiting on the VEX BB to 65Amps.
Between the vee belts and the current limiting, I thought I would be able to nurse the drive motors though a full 3 minutes. We were running up to about 2minutes 40seconds, and we did a lot of pushing, so I wasn’t asking for too much more from them.
We changed weapon configuration to the scoop, and the plan for the second fight was to keep the jaw open to protect from overhead blows from hammers.
If anything, the belts and/or current limiting made the problem worse, and the motors die earlier under very little load.
We took a hammer hit in the first few seconds, which landed on the self-right linkage. The arms did their job and the blow caused no damage, but the shock popped the cap off the hydraulic reservoir.
This isn’t a big deal for us, as the hydraulic unit can still function and move the actuator while pulling in air, but we got oil all over the arena and other robots.
Again we left the arena with no real damage, other than smoked drive motors!
The small Ampflow was a little underpowered for the hydraulic unit, maxing out at about 160-180bar, depending on how much smoke I made come from the motor. On my 40bore actuator, this gave me between 2075- 2335kgf at the actuator, and 691-778kgf at the crushing tip.
The competition limit is set at 600bar. The hydraulic power system and all hydraulic components are proof tested to at least 250bar, however I don’t think it would be a good investment to put more weight into getting more force from the hydraulics.
As the purpose was more of a grabbing, controlling weapon, the opponent couldn't escape the jaw, so the weapon served its purpose.
I was very happy with the speed that the jaw moved.
Working with the off the shelf hydraulic power pack system, it was the bulkiest component so the robot really had to be designed around it, and smaller things, like the batteries just had to fit where they could.
I would have liked to have come up with a better solution for where the batteries and speed controllers were situated.
I simply was not able to figure it out in CAD in the time available, so left various options open and figured it out in the workshop.
I would also do some testing on the self-righting, as I’m sure there are probably scenarios and angles where it would sit and the arms wouldn’t work that can be fixed through trial and error of bolting things on the end of the arms.
I might also consider bolting on more sacrificial pieces of thinner UHMW in future.
Although the damage wasn’t threatening, I can imagine after a few fights of taking hits and shaving away in the same places, the plastic would begin to wear through, and being plastic, it cannot be repaired!
Finally, the drive
I can smell this photo every time I see it.
Unfortunately, the 150series Ampflows were not up to the job of driving a heavyweight robot.
We burned out 8 of them in 2 fights, and ultimately this killed the Griffins chances of getting further.
I did leave scope in the design to replace the 4 short Ampflows with 2 of the long series on the front wheels, and we would have done this if we were to have continued in the competition.