ideas for a strong hook

[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.

[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.

[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)

[Trish Fisher]

Originally Posted by Greg McKaskle

Repurposing some C-clamps might be a reasonable approach. Particularly ones similar to this http://www.sweetwater.com/store/detail/CClamp

Or use them as inspiration for building your own.

Greg McKaskle

Everyone, thank you for your hook suggestions! We used the one posted by Greg. The sweetwater clamp works perfectly! We used two of them on top of our ascent mechanism.

Thanks again to everyone!

Trish

[G Fawkes]

Originally Posted by Trish Fisher

Everyone, thank you for your hook suggestions! We used the one posted by Greg. The sweetwater clamp works perfectly! We used two of them on top of our ascent mechanism.

What is the thread diameter and pitch on the lower threaded hole? Would be sweet if it threaded straight onto a Bimba.