How Does a Winch Work?

[Mike Norton]

Originally Posted by MBF

Do you have any more pictures or diagrams? My team is trying something similar this year, and any information would be helpful. Some of the doubters are still not quite seeing how the arm would work, and any concrete evidence would be useful.

go to http://www.valleytech.k12.ma.us/robo...photos2000.htm

there more there.

[generalbrando]

Originally Posted by Raul

The van door motor can be back driven unless the bearing screw (at the end of the worm gear) is tightened quite a bit. The problems with doing this are:
1) You lose power output by tightening it
2) It wears out and you have to keep tightening it to keep it from backdriving

Plus it might still back drive if it sees excessive force.

Also, if you're worried about keeping a motor from slipping (such as when the power gets cut at the end!) you could use a little pneumatic piston to lock something in place. If you were pulling in a cable on spindle like thing (i'm bad at the right names, forgive me) then on the side of that you could have ridges (think raised spokes) and then all you have to do is fire the piston into the side of the thing to lock the spindle in place. As long as you set up the pneumatics right, it won't move when the power gets cut.

[MBF]

Originally Posted by Mike Norton

go to http://www.valleytech.k12.ma.us/robo...photos2000.htm

there more there.

Thank you.

[Jeff D.]

Back on the subject of winches:

Planetary Gears are what gear down most winches for automotive purposes. (Warn Winches, etc.)

I'm working on getting some write-ups from some fellow Jeepers.

Stay Tuned.

Jeff

[Adam Krajewski]

Originally Posted by Raul

The van door motor can be back driven unless the bearing screw (at the end of the worm gear) is tightened quite a bit. The problems with doing this are:
1) You lose power output by tightening it
2) It wears out and you have to keep tightening it to keep it from backdriving

Plus it might still back drive if it sees excessive force.

And when it wears out, no amount of tightening will do you any good.
During the summer of 2000, I did a study on the brakes. What they are exactly is a set screw (did someone inhale?) with a spring mounted 'brake pad' on the end. When you tighten it, you force the 'brake pad' onto the side of a plastic (final drive?) gear in the motor. This pad will eventually wear down and break. At that point, tightening it will do no good, as it is just a tapered end of a set screw with a hole in the middle against hard plastic. I have pictures somewhere of various van door motor brakes, but I can't seem to find them right now.

However, the bottom line is the brake should really only be used to get rid of very minor problems with backdrive. In '99, we used a van door as a winch motor to raise the lift carrying floppies over 8 feet and friction plus the brake kept the lift in the air without a hitch. In 2000 we tried to do the same thing, burning up brakes in the process on the motor that drove the shoulder of our arm. The final solution I came up with was to use a PD control system for the arm, so that 'sag' during a match didn't matter because the motor always ran to keep it in the right position, something it could do easily for 2+ minutes.

I would suggest something along the lines of what generalbrando said, and using a pin to stop the drum from rotating or perhaps some type of one-way action with a release like what rachet straps and come-alongs use.

[BillBartell]

There are many types of gears that drive different types of motors but the most popular for high torque winches is called a planetary gear. This type of gear is used on the bosch drill motor gear box. It allows for nearly a 500:1 reduction which surpaces any other type of gear box drastically. As far as Telescoping arms go...i dont want to give away of any of my teams secrets but think power car antenna.

[Max Lobovsky]

correct me if I'm wrong, but arent all these spring loaded or pre tensioned systems that are released during the match illegal because that is considered another source of energy (not compressed air tank or battery)?

[KenWittlief]

spring loading or pre-tensioned is ok this year (the rules for how much energy can be stored in your bot at the start have been backed off this year)

but if your arm is going to be used to go after the chinup bar, its tip cannot extend faster than 10 feet per second - so you cant just have some big piece of springy material that you release and it snaps out - you would have to dampen the rate at which its released somehow.

[KenWittlief]

BTW - the telescoping stuff is off topic for this thread, but I have a really cool idea, so I will try to find an appropriate thread and post my incredible idea for it there. :c)