21-03-2010 15:59

Squeakypig

Re: pic: How to lift your robot safely

i can never understand how you guys hang, everytime i see it happen it happens in 2 seconds and i dont understand what just happened. Do you have a detailed explanation or perhaps, even better, a video?

21-03-2010 16:15

Alex Dinsmoor

Re: pic: How to lift your robot safely

I just posted a video of us hanging on youtube for your enjoyment

To hang we release our arm, and using break cable we release our hook. The hook is positioned against the horizontal bar, and when we start our winch, the hook falls off the arm and arm falls down. Then we winch ourselves up for 2 points

21-03-2010 16:42

Jonathan Norris

Re: pic: How to lift your robot safely

great motion on your arm, I can see you put a lot of effort into making the deployment of your arm attach to the bar quickly. It certainly must make it easier on your drivers.

21-03-2010 16:47

Alex Dinsmoor

Re: pic: How to lift your robot safely

It was definitely a long design process for the arm to get it right, but it payed off. Our base driver only has to line up in the general area of the tower, and with the pressing of 2 buttons we are in the air.

We were having problems with the arm at Kettering, but after switching our steel cable out for sailboat rope (I'm not sure the technical name), we can hang in 1/3 of the time, and it won't get tangled on the arm!

21-03-2010 17:20

raffi383

Re: pic: How to lift your robot safely

Here's a detailed explanation of how the arm works.

There is a gas strut that is attached to the lower portion of the arm. When a latch at the back end of the lower arm is released, the strut raises the lower portion of the arm.

When the lower arm is near its fully upright position, a cable attached to the robot and to the bottom end of the upper arm begins to tighten.

Once the lower arm is at its upright position, the cable attached to the upper arm is holding the upper arm in its fully extended position.

As the upper arm gets near its fully upright position, a second cable (bike brake cable) that is attached to the lower arm and a release hook that retains the hanging hook holder in its folded position is pulled and the hanging hook holder swings into position.

With the hanging hook over the tower bar, the winch is turned on. The kevlar line that we use to lift (instead of the original steel cable that looked like a screwed up pretzel after Kettering) is routed through another retention hook that holds the bottom of the gas strut in place. Since we didn't want to have the arm in the deployed position when lifting to avoid bending it and didn't want to have to compress the gas cylinder to bring the arm down, we just release the bottom end of the gas strut and it slides rearward which lets the arms drop.

The hanging hook is held to its holder by magnets. Once the gas strut retention hook is released and the arm begins to drop, the magnets disengage from the arm and the hook remains on the tower.

For resetting after the match, we have a clutch on the winch that we can pull out by hand so we can unwind the line from the pulley without power. There is also a ratchet on the winch to keep it from backdriving after we turn the power off. The gas strut is automatically reset when the arm is manually lifted to the extended position.

There is a lot of "magic" in our arm. It took a while to get it to work.

Hopefully we will be in Ypsi hanging around at the end of the Finals.

Stop by the pits for a demonstration.

Raffi

21-03-2010 22:58

ExTexan

Re: pic: How to lift your robot safely

Tell Louis that is a great video, a very quick hook, hard to measure. See you at States!

THE HOOK!