How to prevent elevator from crashing down

Hi All,

We have a front linear elevator to raise and lower our cube intake mechanism. The intake mechanism turns out to be quite heavy. Best guess 5+ lbs.

My concern is that we raise it in the air 6+ feet to reach the scale. When the robot is deactivated it all comes crashing down. Unfortunately these incidents have damaged parts on our robot so as a programming mentor we have had very little elevator testing time before bag day.

Will the transition from autonomous to teleop during competition briefly deactivate the robot as well. We have some autonomous modes where I could see the transition happening while the elevator is fully extended.

Right now we are just using a SPARK motor controller. We created an algorithm which controls it pretty nicely when the robot is activated.

Please share some ideas for helping with this design.


Do you have the Spark set for Brake mode?
That helps slow down moving parts when the robot is Disabled.

Devise a mechanical counter balance of the elevator, such as surgical tubing or constant force springs, to offset some of the intake or elevator weight on the way down.

We use a pawl that engages a gear on the elevator motor that the software disengages whenever the elevator is commanded to move.

For mechanical solutions, I would recommend adding either a one-way friction brake or surgical tubing/constant force springs to your mechanism. The friction brake will help hold the elevator in place, and the surgical tubing/constant force springs can help with that and help lift it as well.

Constant force springs are preferable, but surgical tubing is more readily available. Surgical tubing will also be lighter, so that would be a quick solution if you’re concerned about your weight.

In your kick off package you should have received black stick rubber bump stops. They work awesome on our elevator when it comes crashing down. completely stop the metal to metal contact.

The spark defaults to not brake on disable. As far as I know you cannot change that. Weighted mechanisms are going to free fall. The other motor controllers (I am not sure about the new victor) can be set for dynamic braking on disable which will slow but not stop the descent.

Thanks all.

We originally used the SPARK limit switches and the braking was not strong enough. So I moved the limit switches over to the RoboRio so we can better control when on the limit switches. We do have other motor controllers if need be.

The other difficulty is we are right at the weight limit.