# 127C - Constellation

What if you had your claw start at a 90 degree angle and just flip it out.

Have you done any experimenting with the angle in which your pneumatics close the claw? I noticed a star slipped out the very front of your claw at one point. Was that due to the lack of range on the claw or lack of force from the pneumatics?

My team is having similar problems with our pneumatic claw. Ideally the force vectors on the cylinders would be 90º to the load correct? Can anyone weigh in on this?

Yes, torque is the cross product of force and the radius, or the sine of the angle times force times radius. The sine of 90 degrees is 1, and everything else is less than that, so you get maximum torque at 90 degrees.

Edited to use cross product and not for product

Follow up question, with the range of the angle in the claw’s movement, where do people think the most force is required? In the beginning to pull stars toward the center? Or perhaps toward the end of the cycle to hold a large load in?

Every time we switch ours to the beginning or the end of the cycle it seems like the other half lacks torque needed. Very frustrating, but maybe I just have too high of expectations…

Not to nitpick, but I think you mean cross product and sine, not dot product and cosine.

The issue is that that it would be very hard to have anything to hold it in that position before matches.

It was, I guess to use your words, “lack of range on the claw.” I would phrase it as the claw not closing far enough, but I think we mean the same thing. We made the claw close more and it’s not an issue anymore, though sometimes they slip through the corners. I have to take a close look at a few things on the claw after our last tournament.

My team originally had a similar flipping out problem where we had to lift before we can flip it out. So I attached an extra long screw to the back of our hinge in order to hold the claw at a 90 degree angle before we flip it out… the screw essentially stopped the hinge from going past 90 degrees. This solved our problem. Of course our bots are different and this might not work for you but it’s worth a try.

The ends of the claw also have to be held in.

Once again, It was just an idea that worked for us. Since our bots are different, it probably won’t work if the idea doesn’t change. But you were smart enough to build the bot so you can probably figure out something. Good Luck!

Yes, I understand. Thanks for the suggestion
Good luck to you as well!

Here’s match video from Finals 1 at the Queen Creek High School qualifier:

(I will also post this in the OP.)

And apparently I can’t edit the OP, must be too old. So I just quoted it here, and then edited this post when I realized my error. Oops.

Hey guys,

Today we switched our motors from high speed to torque (1:5 now). The speed difference is noticeable, but not too bad (it’s just as fast on big dumps). I’m excited to get some video out tomorrow. We lifted 8 stars easily, although two fell out before scoring. We scored 7 stars successfully, and two cubes, and 4 stars and a cube. Unfortunately, my phone battery died, so I’ll get video of it tomorrow.

The benefits are that it pretty much can’t burn out no matter what I do, and it can easily lift whatever fits into the claw, which is pretty massive. Expect video tomorrow!

Why didn’t you just add more rubber bands? 20 is nowhere near enough.

Hahahaha! Yeah, at that point we’d have to power it to go down all the way, so no thanks.

Well… our version 1 robot had 80 rubber bands which were all twisted, effectively equating to 110-120 rubber bands. Constant power of 10-15 and some interesting rubber band geometry can do wonders. For example, no rubber band assist could effect the lift until it lifts an inch or two.

Yeah, I’m not looking to put that kind of strain on my parts… lol. I understand how the energy would not affect the lift until it lifts a little bit, but that strain is still pushing something, and that sounds like a pain to replace all those rubber bands.

You’re very right. It’s difficult to make a system as such which works well and doesn’t strain with lethal force. That being said, getting it right is amazing.
Also, we only had to replace about 10 rubber bands over the course of the whole build.

As promised:

Video of 4 stars and a cube dump: https://youtu.be/J1zneYak2EM

Video of 8 star dump: https://youtu.be/BYt4hKBxjzA

Objects do not need to be in the corner or against the wall. They just take a lot of space, so I don’t really have much room to place them, lol.

We may have gotten 5 stars and a cube off-camera, but I can’t remember. Doesn’t matter at that point, not very realistic.