Globe motor backdrive!!

Our team is using a globe motor to use the mast system on our robot to pull the robot off the ground after attaching to the bar. It has enough torque to pull up but it back drives awfully! Has anyone come up with a way to stop the globe motors from back driving? Thanx!

~Steve
Team 1124

Have you tried simply putting that globe motor on a speed controler in brake mode? If that doesn’t work, you’ll have to design some form of locking mechanism. You could use a servo to insert a locking pin, or you could design a ratchet similar to this one.

Good advice. It is pretty easy to make a catch that only locks in when your robot is fully lifted. One down side is that once you are up, you are up. This is probably not a huge issue but your drivers will have to make sure they are not going to have to get down again.

Joe J.

Take a look at the gate latches at any hardware store, one of those was the cause of us nearly winning the vcu regional and getting into the finals at nationals our rookie year. Sometimes the simpleest solution is one of the best.

We’re using another motor to lift but have a brake that is applied to our tower at any elevation with a small pneumatic cylinder so we hang steady after the power is cut.

You can use a standard ratchet (like what you tighten bolts with) driven by your motor.

Another way I think you could do it would be to put a latching relay between the two leads on the motor, and have it off until you want the motor to lock then switch it to the on position. That will at least slow it down.

true but you have to beable to stop back drive after the power is shut off…i really think some of the mechanical soultions mentioned in this thread will help you out. i also was thinking of a wrap spring ( like inside your tape measure) around the shaft of your motor…since you know the total distance you will traven you can have it set to put pressure on in the forward direction of motor travel that way when if starts to backdrive the spring would be working in your favor…

also if you use another mechanciacl method why don;t you activate it by a limit switch on your grabber that way when you are at the height you want it will automaticly trigger eliminating the back drive which would take place untill the trigger is activated

While the relay thing might work for a hobbie robot their are a few issuses with using that system in FIRST.
The speed controllers can already be set to do this automatically see the section about the coast/brake jumper on IFI’s site
Only speed controllers my be attached to the globe motor
and the relay wouldent stay latched after power was removed, all of our compeition legal relays arnt latching and cant legely be made so.
this isnt ment to down the idea, like I said its a good idea, and has uses however its illegeal for us.

we have a simple sensor on our lift that once the “on bar” switch is fliped, if the button is not moved and the sensor sais that the lift is moving, to aply current in the opisot direction. this works at least till the bot is disabled. it is just a quick programing fix, but it works… im sure its tearable for the motors tho

Yea we have problems with Globe motor backdrive … Setting the speed controller to break mode doesn’t help.

What we did was use a pneumatic cylinder to engage a “lock” mechanism.

Hi, we’re a rookie team and we’re also experiencing backdrive on our Globes, since the robot has already been submitted we need to find a solution for this and fix it at the competition. Can anyone please provide me with a picture of this solution. Any help would be greatly appreciated because the Globes play a vital role in our bot because they operate the drum that raises and lowers the arms of our bot. Thanks in advance.

Is this arm used to hang the bot?

Or is this just an arm used for manipulation during the match itself?

The arm is used to hang the bot and to pick up the 2X ball.

EDIT: Hanging isn’t the problem because we set stops at that point when the arms are pointing all the way up. It’s picking up the 2X ball that we’re having trouble with.

I think that setting our Globe motor Victors to brake did help keep our arm’s wrist from “drooping” back down when the control was at neutral. There might not be enough “brake” for a robot-lifting application though…

We are using a bolt attached thru the winch drum.
This bolt is stopped by a metal bar which is actuated by a servo and tensioned by a spring.

Here we go.
Before applying power (speed) to our winch motor, programmatically we move a servo which moves the steel bar out of the way of the bolt. The steel bar is tensioned with a spring. When the speed is set to neutral the servo returns to it’s start position and the bar blocks the bolt in the winch drum.

If we are still winching when the game is done, the spring tension pulls the bar back against the winch drum effectively doing the same thing.

Now for getting down.
We send the command (toggle switch) to the robot to winch down.
Motor actually winches up for 5 loops or about a 10th of a second rotating the winch drum bolt away from the bar ( .1 seconds is the time required by the servo to rotate from one extreme to the other). Servo pulls the bar out of the way and then we set the winch speed to unwind. It works extremely well.

Phil

Yep ! Sailboats use “stop blocks” or cleats which allow line to pass through one way, but not the other unless unlocked. Very simple. :smiley:

Cleats. What a great idea!

<<Cleats. What a great idea!>>

We used one for our F-P powered lift. Th ecleat only failed when the rope was shreaded to the inner nylon by a faulty eyehook.

Very light weight too!

We had the same problem with the Van Door motor. I knew it would be a problem. We used gas springs. (those things that keep the hatch up in a SUV or station wagon)
Point the arm at its max angle (in our case its straight up) and use that as the slack point (no pressure on the gas spring) attach one point on the arm itself and the other end on the arm support. As the arm lowers it compresses the gas spring (i.e. spring puts a force upward) if you balance it out correctly the arm should sit where ever its positioned and only move because the motor puts power on it.

Hope taht helps