Winch Issues

Hey, all, My team is using the am-2774 (It’s a winch) http://www.andymark.com/product-p/am-2774.htm And today we tried it out for the first time lifting the robot. It starts off working well but then once it gets the robot off in the air it stalls out but luckily holds the robot up. But it can’t lift anymore. We are using a 2.5 Cim how do you guys think we can get the power to lift the bot. In the photo https://slack-files.com/T0AA4H2J1-F40C3A9QS-5d05cb9fb8 , it got to that height because we assisted the bot up

The image isnt working but you get the point

The picture is broken. But if I had to take a guess, I’d say that as the rope winds around your spool, the effective diameter of your spool increases to the point that the motor doesn’t have enough torque to continue lifting. Get the picture fixed, and we may be able to confirm this. But when the robot stops climbing and stalls out, how big is the spool WITH the rope wrapped around it? If it’s ~2x as large a diameter as the spool by itself, I’d say that’s your culprit.

Not with my bot now but I can get a pic soon http://imgur.com/a/FdjNv
http://imgur.com/a/FdjNv

From that imgur picture, looks like your spool is getting significantly larger as the rope wraps around it.

Yep

You’ll need to either gear lower or add another motor. I would look into gearing lower first, but a MiniCIM added on would probably do the trick. The problem with adding on is that it requires having a place to mount the second motor–doesn’t look like you’ve got that right now, unless you were to mount a second gearbox on the other end of the shaft.

It would be very helpful if you can tell us what gear ratio you have the gearbox set up at.

For a single cim, assuming your output shaft gets up to a diameter of 3" as the rope winds around it, you’d probably want a gear ratio of 35 or 40 to 1. This would create a stall load of 460 pounds, and raise you in around 1.75 seconds.

I’m guessing your gear ratio is less than 15:1. At that point, you’re right near stall torque with gearbox inefficiencies.

Looking at the web page the stock ratio is something like 8:1.

Tomorrow this will all be delivered

our team has done some calculations into the subject regarding spool length and the ever increasing rope diameter. Our current setup is a cim to a 100:1 that baby can lift a 300 pound weight 10-15 feet by our calculations. If I am remembering correctly.

Giving a motor and gearing specification is useless without also providing the spool diameter.

Woops! forgot the spool is about an inch or so in diameter, come to think of it I believe we used the wrong diameter in our calculations.

You also have the option of choosing a rope that has a smaller diameter - the rope that you have looks somewhere on the order of 1/2"-1/4", whereas a web strap or similar will have a pretty negligible diameter.

That being said, if you’re having issues, it may be good to consider changing up your gearbox or motor setup as well, so as to give yourself more margin.

Forgot I big thing and I slept on it to remember we never cut our rope yesterday to the desired length because its a 20Foot rope so it had a lot of extra so we will test it today with the rope cut hopefully that helps

Unless you’re winching more than ~8’ of it, rope length shouldn’t make a difference. You’re basically going to have to add more torque to the system.

We are winching 20FT of rope XD

20 feet? Why?

…might want to review I04 again, particularly B and C.

Emphasis mine.

Unless most of it was on the floor, you should have some belay points, as required in 2013 (R10).:eek: ::safety::