25-03-2011 13:50

Racer26

Re: pic: Twisted Hex Shaft

Impressive. A harsh reminder of the kind of force that FRC bots exert.

25-03-2011 13:54

Jared Russell

Re: pic: Twisted Hex Shaft

3/8" diameter, 2024 aluminum?

I'm curious to know just how much torque that took...

In 2008, our arm was able to rotate the keyway of a piece of hardened 1/2" steel keyshaft almost 90 degrees. It's impressive how an FRC robot can destroy itself!

25-03-2011 14:14

Andrew Y.

Re: pic: Twisted Hex Shaft

waht kind of aluminum is the turnbuckle?

25-03-2011 16:25

rahilm

Re: pic: Twisted Hex Shaft

1/2" 7075, which is why we were pretty surprised.

Not sure the alloy, but it was some small diameter (bad idea in hindsight)

25-03-2011 16:31

Andrew Y.

Re: pic: Twisted Hex Shaft

gotcha 7075 was the number iw as looking for. Just to be nosey it wasnt 7075 -0 right?

25-03-2011 16:48

Cory

Re: pic: Twisted Hex Shaft

I've never seen Al hex in anything other than T6

25-03-2011 16:56

Brandon Holley

Re: pic: Twisted Hex Shaft

Wow, that is quite a failure for a 1/2" 7075 shaft. Can you explain in a bit more detail the application this was in under failure?

-Brando

25-03-2011 16:58

Andrew Y.

Re: pic: Twisted Hex Shaft

never seen dosent mean never exists.

most common types of 7075 is 0, T6, and T631. Although there are MANY different types such as T7362 is also a common one.

25-03-2011 17:07

rahilm

Re: pic: Twisted Hex Shaft

T7351 Actually.

It was on our arm. Basically we have 2 Banebot's gearboxes with chain running up to the arm. We have approx. 50 lb-ft of torque (don't worry, 1:4 chain reduction, only 6.25 lb-ft on each gearbox). We have chain on either side of the arm, and we decided to change the tensioning method to turnbuckles. Almost immediately as we raised the arm, the turnbuckle one side (the twisted side failed) while the other one held. The torque of the arm in addition to tension being held by the chain all released in one instant twisting the shaft, as the tension still held on the other side (on which the gearbox's rollpins sheared)

25-03-2011 17:24

Andrew Y.

Re: pic: Twisted Hex Shaft

thanks for the assist...my brains all scrambled this morning

27-03-2011 17:10

sometimestommy

Re: pic: Twisted Hex Shaft

Whew! thought that was a lead screw

28-03-2011 04:57

ligiahag7902

Re: pic: Twisted Hex Shaft

I also think so.