pic: Inverted CIM 2-Speed Gearbox

[JesseK]

Originally Posted by MichaelBick

In our experimentation with a "school A" drivetrain, we've actually found that we like to t-bone and play the "pillar defense" both in high gear. We found that teams can create separation from the t-bone when we are t-boning in low gear. When we are playing "pillar defense", high gear allows us to keep up with opposing robots to effectively block the field. We now teach drivers to only use low gear in head to head pushing matches.

Mind giving traction details? I would expect that sufficiently high traction & gearing, in combination, would lead to popped breakers. I have no experience here myself, but I've read plenty of it on CD from 2014.

[MichaelBick]

Originally Posted by JesseK

Mind giving traction details? I would expect that sufficiently high traction & gearing, in combination, would lead to popped breakers. I have no experience here myself, but I've read plenty of it on CD from 2014.

The robot was geared for 20FPS @ 100% efficiency, had 4 CIMs and 2 550s, and had 2" wide roughtop traction wheels. The robot never stalled while t-boning, which probably helped in preventing blown breakers.

[KrazyCarl92]

Originally Posted by MichaelBick

The robot was geared for 20FPS @ 100% efficiency, had 4 CIMs and 2 550s, and had 2" wide roughtop traction wheels. The robot never stalled while t-boning, which probably helped in preventing blown breakers.

To give an example where breakers DID pop...

Team 20's 2014 drive train had 3 CIM WCP dual speed shifters, with 4" colson wheels, and was geared for about 5.5 fps and 16 fps free speed (theoretical).

Here is video of our second match of the season: http://www.thebluealliance.com/match/2014nytr_qm13

In our pre-match strategy, we adopted the role of post-auto hounding of any opponents that missed their auto shots while our partners cleared missed auto shots of our own alliance. At the very start of teleop we go to play defense on 116 and set an open field T-bone pin on them which they fail to break free from for 26 seconds. The pin ends because we popped our main breaker.

Post-match after discussion with our drive team and some napkin math in the pits, we decided the following events likely led to the issue:
-The driver switched to low gear after the pin was initially set
-The shifting cylinder did not have sufficient force to shift the dog from high gear to low gear under the traction limit condition, so the dog remained engaged in high gear throughout the pin
-Our driver did not let up full throttle on the pin (we wanted to pin at full throttle without worrying about popping breakers as a design objective)
-We would have been pulling around 400 A or something crazy through the main breaker in this condition, which should only last a max of about 8 seconds according to the breaker spec sheet, so I am surprised we lasted this long before popping the breakers.

To mitigate the issue, we had the drivers always let up at the best opportunity early in the pin so the dog could shift. The very next match we popped the main breaker again, and after replacing it never saw a tripped main breaker the rest of the season (they tend to become easier to trip after tripping the first time).

When hounding teams on defense we could almost always maintain a pin once we set it, regardless of the fact that we were in low gear. The only exception that comes to mind is the Killer Bees being able to slip away well due to their drive train and driver skill.

Side note: I am unsure of whether we had changed this yet or not in the above scenario, but at one point early in the season we switched from 6 CIMs in the drive train to 4 CIMs and 2 MiniCIMs to up the torque in our catapult gearbox due to an increase in the pre-load of the torsion springs.