Chief Delphi - torque spec?

Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Robot Showcase (http://www.chiefdelphi.com/forums/forumdisplay.php?f=58)

- - torque spec? (http://www.chiefdelphi.com/forums/showthread.php?t=70705)

Re: torque spec?

...yah i think i will be getting a new nickname this year...

the damage was done with a common 1/4" drive ratchet with about 6" or 8" arm, a seemingly harmless tool for the job. ...and yes, we were using the M6 nut that came with the board, and it's the same one that's on there now. I've used PEM studs before on a number of projects and I've never seen them torque out or snap like this one did. I'll definitely be contacting AndyMark and see what we can work out on this. We'll probably front the money for a new one and see if we can wait until after the competition to return the broken one and see if it was a metallurgical flaw (I hope that's what it was). The broken portion has an odd texture to it that I'm unfamiliar with, although I must admit my training is EE and CS, not so much mechanical.

Re: torque spec?

Attaching the nut by only 1-2 threads has probably increased any effective 'resistance' the terminal has as well. If you overloaded the terminal with 120A, you would probably severely damage something, or really burn someone's hand if they touched it at the wrong moment. The point is -- it can't stay like that.

I'm also surprised the bolt snapped before the PCB cracked. I wonder if there are stress fractures where the stud connects to the PCB...which would again significantly increase the resistance of this terminal.

Sure, you can 'patch' it with a standoff as mentioned above, but for safety and reliability reasons, I would get a new one.

Re: torque spec?

Wow...a $200 mistake! Time for all teams to have a "be extra careful with the electronics" discussion.

http://andymark.biz/am-0265.html

I wonder if it would be possible to get repair parts for the power distribution board? The red/black plug in wire connectors are probably all soldered on...and there are some surface mount parts on the circuit board too....this might get interesting. If you can get the housing apart, the studs might be bolted on?

Re: torque spec?

Quote:

Originally Posted by cdennisxlx2 (Post 785234)

AndyB is correct, you wont get a second one in your KOP [until 2010, lol]. The good thing is you can buy a new one Here

Don't count on getting a new one next year. http://frcdirector.blogspot.com/2008...ol-system.html

Quote:

Originally Posted by squirrel (Post 785542)

If you can get the housing apart, the studs might be bolted on?

Eric and Russ already described how they were attached. Unfortunately, it's not that easy.

Re: torque spec?

I just talked with Ben at Diversified Systems. He was initially thinking that this can be repaired, but recently he concluded that it cannot. So... the only thing to do is to replace this unit.

Thank you for posting this issue so that teams know that this is something to watch for.

Eric, Al, Mark, Russ, and all have given great advice in this thread, and the only extra suggestion I can give is to go out and get a 10mm nut driver to tighten this nut.

Sincerely,
Andy Baker

Re: torque spec?

Quote:

Originally Posted by Engineer (Post 785248)

I have not seen the part either but here is a "handyman/shadetree/garage mechanic" fix for broken studs like this. Use a long nut to hold both pieces together. Drill down the center with an #30 or #29 drill in a drill press. It is important to go straight down. Drill through both pieces. You can remove the nut after you've drilled the hole. Now get a 1/8" brass rod and cut it the length of both pieces. File a flat on one side of the brass rod the entire length. File or cut a slot at one end about .030" wide and .0625" deep. Use a good flux and cover the surface of the brass rod and the hole you just drilled in both pieces. A Q-tip works well for getting the flux in the hole. Now you are going to solder the brass rod in the hole to join both pieces. The flat you filed in the rod will give the solder a path to flow down and the slot will allow you to use a small screwdriver to turn the brass rod to help all surfaces get covered with solder for good joint while it's hot and the solder is molten. Use a high wattage solder iron/gun or a torch works well also to produce enough heat over the large area.

Watch the heat carefully so you don't melt something you down want to melt.

Be very careful tightening the nut as it will only handle less than half the torque it did before you broke it. Good luck.

This may work as a stop gap fix to make the thing work, but everyone should be aware that based on the rules from pretty much every year this would be highly illegal on an actual competition robot.

Re: torque spec?

Wow!! I can see this being a serious problem if caution is not taken. I had a team member tighten it without really considering the "Break Point". I was real close and was sure they didn't use excessive force. But WOW!

BTW...Awesome pics!!