# The One Motor That Could (Hang)

Anyone think a single motor geared for torque could pull off a high hang all by itself, if the robot were to be made from aluminum? My calculations seem to support such a design.

I am sure you can. But you will need to really pump up the gear ratio and the lifting will not be fast.

For sure, get the perfect gear ratio with a bit of trial and error, and you’ll be set, assuming that (like @meng said) you don’t care about speed.

Well you can do anything with a motor and a ton of gears, it would just be very slow. Or fast, depends.

I know people who lifted 20 pounds with two motors running 1:3 in torque for NBN. So maybe one motor with 1:9 might work. As said before, it will be slow however.

One motor can do anything as long as you gear it for enough torque and your materials do not fail. Teams have hung in toss up with one motor. However, teams I’ve seen prefer two for an acceptable speed

We were working on something for last year (NBN) that could theoretically have done it with only one motor. It was a pulley system with minimal friction but high MA. Still, I wouldn’t recommend it because speed while hanging will be essential IMO.

We’re going 4 motor drive, 6 motor catapult, and 6 motor lift

There are a number of ways you can use the same motors for multiple purposes, even while staying in the 10/12 motor limit

An elastic lift with a one motor release mechanism could be a good way to hang with one motor.
We saw a lot of that method during NBN, so maybe we’ll see it again.
It could be used as for a hang in autonomous, but it would take forever to get down.

I think you could get down in about 0.24 seconds…but you might not get up again, unless your robot can absorb 27.3 joules of impact energy (assuming a 9 kg robot).

To get down and get back up again, you would need a very high torque mechanism that can overpower the elastics that pulled the robot up, I think that that would take longer than 0.24 seconds.

Has anyone considered the idea of having the lifter/hanger be moving up during the entire match, and maybe actuating it at the end with a slip gear? This was one of the ideas my team had, and is very plausible!

As some posters suggested above, you could store some energy in the elastics before the match and then just release it with a trigger motor when you are ready to hang (which might be an easier solution).

However, lets try to calculate what it would take to arm elastics necessary for lift during the game.

Let say you have a 10 lbs robot that you will try to lift using linear slide with the assistance of the elastics.

Also, let say, you configured elastics such that at the bottom of the slide it generates 4 lbs force and at the top of the slide (when extended all the way up) it provides 6 lbs of force. To extend your elastics you will need a motor that could pull it with max 6 lbs of force.

After elastics are extended, the motor will reverse to start the lift and there will be 6 lbs + 6 lbs = 12 lbs of force at the beginning of the lift and 6 lbs + 4 lbs = 10 lbs at the end. This should be enough to give the robot initial acceleration and pull it all the way up until the lift is locked.

393 motor in force configuration provides about 15 in-lbs of stall torque (see specifications tab) and you could, probably, get about 6 in-lbs out of it for the lift without overheating PTC.

6 in-lbs of torque translates to 6 lbs of linear force at the end of 1 inch lever off the drive shaft. Assuming that your build quality is good and friction losses are under 25%, you should be able to drive your slide with 36t gear that has ~0.75" radius.

Now if you are getting 6 in-lbs out of force motor it will rotate at about 60 rpm and you get the climb rate of 36t per second. Rack gear is 19t per 2.5" so you will need to turn the gear 2.53 times to climb 12". This means that you should be able to hang in under 3 seconds!

Of course, it would be very hard to have everything aligned and balanced to keep the friction losses under 25%. However, even if have 50% losses you still should be able to lift the robot in 7-9 seconds if motor is geared down accordingly.

I would say that the total time to arm elastics and lift 10 lbs robot with a single motor should be easily under 15 sec or even under 10 sec with a good build quality.

Edit: Last season for Nothing But Net we had two motor lift (in speed configuration geared down 3:1) that could lift 25 lbs partners in about 12 sec and lighter robots even faster.

I know a team that can do a normal torque motor lift that is just a pinion to a rack… It works the same way as ours if you have seen it… there robot is not full size though… good luck

Why not just add a flip out hook to the top of your arm?

Yes, one of our normal motors accidentally got unplugged during a high hang. It took the hang a couple seconds extra but it still worked. If it is constantly doing the hang I’m afraid the motor will burn out. But it’s worth a shot.

Riley,
Volt Robotics 98898

1 motor hang could be risky as it might not be able to pull the robot up

rubberband/tubbing lift requires 0 motor and could lift quite some weight

It depends, because the time you’re lifting is time wasted of you not being able to shoot/dump the stars back.

I think a rubber band release mechanism released by 1 motor, or 1 pneumatic component would lift you in a second