claw design

what has been the most effective claw design that can effectively grab cubes without trouble?

Hybrid Claw with fork bottom. But your robot would benefit from a 2 motor 5:1 ratio that are geared together. I would try a 30long c channel then a 45 degree gusset that connects to a 10 long channel. As long as your robot is the same main idea as it was in January.

is anyone willing to post a picture of there gearbox.

I don’t have a picture but a 14 hole c-channel (this is the minimum holes needed) will work with the following setup:
60:12:36:36:12:60

The motors would turn the 12 tooth gears and the two 36 tooth gears would allow them to run together. The 60 tooth gears on the ends would have the c-channels for the claws attached.

If you aren’t wanting to run a 5:1 ratio, you can change out the 60 tooth gears for 84 tooth but you would have to make the channel 16 holes long. This will give you a 7:1.

@3921 our team has an effective hugger that uses 2 motors with these ratios. +1 from me!

You don’t need to gear the two sides together. Software can take care of that, and often times it may be better to have individual control over the two claw arms. But a 1:5 seems to be the go to gear ratio for now.

Our team uses sprocket lol, it seems to be working well (6:30). Keeping the claw in sync is a bit of a problem.

So our team in match has never dropped a cube. We use a split claw design where a claw is on either side of a six bar system. We then have 2 angled pieces of d channel per side. We then use standoffs at different sides creating a curve effect and attach a rubber band stretched between the standoffs. The only reason it would drop out and the only reason we’ve seen it drop out is because one of our team members hit it with their hand. This isn’t a problem in match, that’s why we’ve never had a cube drop out.

It seems like people are talking about claw design here. So. Has anyone had issues with their claw stalling when they are connected on a gear train? Our claw is good for a couple of open and closes, but then stalls. Is there an easy way to fix this? (Ratio is 1:5)

I am not sure why multiple posters (in multiple threads) ask for pictures of the claw design and nobody have posted hi-res pictures yet.

A “classic” 60:12:36:36:12:60 isn’t such a big secret this time of the season and we have seen it in multiple competitions before building our own. It could be driven by two speed geared motors and has some elastics for extra closing force:

VEX-20170209-clawTopFront.jpg

It is a bit on a heavy side, but seems to work well for holding both stars and cubes. 60:12:36:36:12:60 is not the only effective design. I’ve seen a claw with 84:36:36:84 gears driven by two torque motors working just as well.

I think the secret to the motorized claws is the distance between arms that is wide enough to hug the cube and narrow enough not to drop a single star. Also rubber bands and/or anti-slip padding help to hold onto the cubes as well.

In this particular design the bearing blocks are sanded on one side to go into the corner of the c-channel. This allows to mount central blocks with just one screw and without the risk of them twisting out of alignment. The c-channels should, probably, be 4 holes wider to allow easier access to motor screws without a need to remove the arms:
VEX-20170209-clawFront.jpg
VEX-20170209-clawTopSide.jpg
VEX-20170209-clawBottom.jpg

I would say from experience that the best claw design that can effectively pick up cubes is a long c-channel with another short piece attached by a 45 degree gusset on a 5:1 gear ratio.

I am a big supporter of L-channel for claw as I think it cradles the stars better. I also differ in that I like my 7:1 claw for picking up 6-7 star loads without prongs. I think the little details of claws are more personal preference and what works for you.

Yeah same. Our team found that the L-channels are much better for picking up stars and cubes. Our team also runs a 7:1 claw with a ton of rubber bands so that we can pick up to ten stars, not that we would ever have to in a match. We also prefer running prong-less as we find you can pick up stars and cubes much easier.

I’ve seen many ways to attach claws to the lift itself. What ways do you think are the most effective?

We only use 2 screws and 2 zip ties and we have had zero problems with it.

We don’t run prongs either and we can get 6-7 stars in match conditions

One word: pneumatics.

Well, most of the competitive Texas teams and teams with high skills scores use motors for the claw.