Never Do This, and Other Good Ideas Gone Bad

[EricH]

I accidentally tip your robot over with your gravity-down lift up. Oops, your lift doesn't go down anymore.

330 always adds a "gravity" cable to lifts for the case where you're tipped over and you need to unblock the field. It also helps to retract the lift for other cases like hanging on a bar. It's not that hard to add to the drum, either, if the winch is sized right.

Scissors lifts can be really nasty to get right. If you do get them right, they work OK... but they do have their weaknesses. I've seen a single-joint arm clean game pieces off the top of a scissor lift with one sweep, back in 2005. Hit a scissors lift so that it sways and... well... not pretty.

330 does have one team rule: All deployables shall be retractable (exception--we decide it's not necessary to pull them back in). Reason: We don't want to have to be dragging something around all match because it deployed too early by accident--and it's really surprising when we pull up ramps and go defend a spoiler (2007) or do other similar things.

[Madison]

Originally Posted by EricH

I accidentally tip your robot over with your gravity-down lift up. Oops, your lift doesn't go down anymore.

What difference does it make that a gravity-lowered lift no longer works when the robot's been tipped over? Talk about not seeing the forest for the trees.

It's usually not difficult to power lifts in both directions and it's sage advice to do that whenever possible, but not doing so is not necessarily a catastrophic decision. There are all sorts of things that can be done to mitigate any problems that might arise from relying solely on gravity.

[EricH]

Originally Posted by Madison

What difference does it make that a gravity-lowered lift no longer works when the robot's been tipped over? Talk about not seeing the forest for the trees.

If a gravity-lowered lift is up, and the robot is tipped over, that lift is now blocking the field. Because it's gravity-powered, it can't go down (robot-relative) any farther. This can lead to penalties (the 84" cylinder, for example--a gravity-lowered lift that falls over while trying the top peg could easily be over 84" from the floor, causing a cylinder violation) or difficulty in getting the robot upright (longer moment arm, so more motion needed to go the same rotation).

If it could be pulled down relative to the robot (not the floor), then there is less chance for penalties, it's easier for a partner to get the robot upright, and depending on design, the robot itself may be able to assist the righting process.

There have also been some comments--some time back--that dirt could jam the guides, or some other such things, that would interfere with gravity.

Can you mitigate it? Sure. But Murphy says that the problem will happen when the mitigation isn't happening right.

[GaryVoshol]

Originally Posted by EricH

This can lead to penalties (the 84" cylinder, for example--a gravity-lowered lift that falls over while trying the top peg could easily be over 84" from the floor, causing a cylinder violation)

Nope - the cylinder falls over with your robot.

Originally Posted by <R07>

(note: these limits are defined in reference to the ROBOT, not the FIELD).

[thefro526]

Originally Posted by GaryVoshol

Nope - the cylinder falls over with your robot.

In previous years, this wasn't always the case.

[IKE]

As many have noted "Never" is a really strong word. Most posters got the intentions of this thread which were to talk about some ideas that should ahve worked, but had major issues in implementation.

[Al Skierkiewicz]

Although the games lately haven't brought out shopping cart wheels on the front of a robot, don't use them. They are especially bad when the game has an uneven playing surface. The robot goes where the wheels tell it to go so you can't climb a ramp with shopping cart wheels.
Don't ever believe someone who says "of course that's legal, we have been using them for years." That is why at least one team will be down hearted when I have them remove their Globe motors this year.