Six-bar Clawbot

So, thanks to some helpful tips, we got our six bar working pretty well. Unfortunately, the pitchfork-ish scoop we were working on didn’t go very well. We could go back to it, but would much rather do a claw. Here’s a picture of what we have so far. The bad thing is that this design reaches just over 18 inches in length, at 18.25 due to the motors being on top. We’re switching them to the bottom, but I’m wondering what others have done for claws, or even the scoops. I prefer a claw due to it being less weight and strain on the six bar, but I’m open to tips on getting this to work once we code it.
moar vex.jpg

Can you provide more photos. I’m sure you would get some good feedback but it’s hard with the photo provided. Perhaps a profile photo of your six bar extended and of your lift motor/gear assembly.

1:7 or 1:5 works wells for the claw or lift so I would start woth going for a bit of a higher gear ratio on your claw (allows you to grab more) also rubber bands on your claw on standoffs also improve grabbing of stars.
And then for your lift it would be helpful tosee more pictures. Hope this helps!

Not to be critical but i would love to se a 1-7 on a bar lift. I think you are trying to say 7-1

Sorry guys. Here’s some more photos. ANY tips are appreciated, even if we need to scrap the claw and rebuild. This is our first robot.

EDIT: We just coded and tested the claw, and it seems to be jerky and not running smooth. One arm won’t run at all. In addition, the six-bar can’t lift the added weight.

Instead of using the claw ends for the end of your claw. (Thats an odd sentence) I would suggest attaching standoffs pointing inwards, this will make it a lot easier to grab stars. You can also use those standoffs to attach elastics which run on the inside of the claw for its entire length, which improves grip.
You also might as well add some elastics to that lift to cut down on motor strain.

As my team learned in Skyrise, the arm needs to be built out of aluminum. The steel 6 bar is too heavy for 1:5 strength gear ratio. My Skyrise robot uses a 1:5 strength gear ratio with an aluminum arm and is still able to pick up 4 pounds of objects without strain. However, if you do not have aluminum available, I suggest using elastics to connect the joints that move towards eachother. The elastics will take a large amount of load off the motors.

Looking at this picture, which numbers would the elastics go on? I’ve tried up to 12 elastics going from 1 to 5 with no effect.

Make sure that you use bearings at the joints in your 6-bar. You should have two bearings, a spacer, and (typically) a long screw with a nylock nut at each point. Tighten the screws and then back them off 1/4 turn so the arm moves easily.

Test each motor individually so that you are sure they are turning in the right direction.

Finally, to increase the reach on your lift you should move the vertical rails up so your top bar is higher. This is where the 6-bar gets its advantage.

For the elastics you want them to be something like this:

Just keep adding more until the lift starts floating up by itself.