ideas for a strong hook

[EricH]

Modify a climbing carabiner, large size, by removing the gate or the locking mechanism of the gate (depending on whether you want to lock onto the bar or use the hook elsewhere). I've seen teams lift robots with them before. If they can hold a 200lb human, they should be able to hold a 150lb robot--just make sure you get one rated for that weight.

As an added bonus, they're not going to be terribly expensive.

[Phyrxes]

Carabiners are traditionally rated in kN (approximately 225 lbs). The ratings are specific along the different parts of the carabiner, if you are going this route talk to your local outdoor store and see what they have.

[WileyB-J]

Originally Posted by Phyrxes

Carabiners are traditionally rated in kN (approximately 225 lbs). The ratings are specific along the different parts of the carabiner, if you are going this route talk to your local outdoor store and see what they have.

Most carabiners are rated to 23kN, which is close to 5000 lbf. I warn, if you compromise the alloy structure of the 'beaner you significantly reduce its integrity, thus its holding strength. So if a team is going to use (aluminum) climbing 'beaners you need to design a coupling device that does not drill, cut or otherwise damage the unit. Steel ones are another story.

[ferret_guy]

Originally Posted by Phyrxes

Carabiners are traditionally rated in kN (approximately 225 lbs). The ratings are specific along the different parts of the carabiner, if you are going this route talk to your local outdoor store and see what they have.

I am an avid rock limber and when the gate is removed the holding force along the long axis drops considerably usually from around 25kN to around 7kN it should be stamped right on there though but 7kN is still far more than you would ever need (about 1500lbs-force)

[s1900ahon]

For Breakaway, our team fabricated a hook out of carbon fiber. It wasn't used in competition, as we followed our normal path of late mechanical construction and the winch mechanism was never integrated on the robot. It continues to be the object of strength testing to this day.

It was moderately simple to make (compared to the rest of the Breakaway robot that also used significant CF components). The mold was made by gluing+screwing a couple of 2x4 pieces together, and cutting out the hook shape on the bandsaw. After sanding and sealing with epoxy, we polished and waxed the surface, and then used PVA for a mold release. The hook layup was done with a wet process: 3 layers of 3K 2x2 twill CF, one layer of segmented 0.25" Nomex honeycomb, and 3 more layers of CF. Wrapped in a vacuum bag and left overnight. The whole thing took about 4 days in total to fabricate (3 for the mold making, and 1 for the layup).

Having described this, I believe the team will use a conventional, non-locking hook this year fabricated from aluminum. CF is a fun material to work with, but you have to be particularly careful of post-layup machining as the dust becomes hazardous.