Broken PD board terminal?

[Toa Circuit]

We broke/sheared the bolt off the main screw terminal (negative side) when trying to screw on the terminal. There was enough bolt left over that we coupled a nut and bolt and nut on top of that, and it works. Would this be okay for inspection, should we repair the board (Is this even possible?), or should we replace it?

[Teamcodeorange]

I doubt it would get through if the inspector notices. If you repair it yourself you would not be able to use it in competition, however if you wish to repair it you can. Look on the bottom of the product page here.

I would recommend that you repair the old one to use for practice or something and replace the one on your competition robot.

[EricVanWyk]

As an inspector and the PD designer, I would be extremely hesitant to pass a PD with a repaired shank, for two reasons:

1) Safety. There is too much current in that connection for me to be comfortable with a rework. The shanks are force fit with enough pressure to cold-weld the square pins to the too-small round holes to better connect it to the >8 oz copper layers.

2) As a favor to the field crew, the CSA(s), and the team. It is extremely likely that a faulty repair here will randomly and briefly re-break and then re-attach, causing the robot to reboot and/or fail on the field. It simply isn't worth the risk.

That isn't to say that it is impossible to do correctly - I am just saying that it is a difficult high risk low reward rework.

[Toa Circuit]

Alright, I somewhat figuired that. We do have a spare, its just I/we were a bit lazy to undo all our wires from the bot, at least at the time. It shall be fixed!

[Mk.32]

Originally Posted by EricVanWyk

As an inspector and the PD designer, I would be extremely hesitant to pass a PD with a repaired shank, for two reasons:

1) Safety. There is too much current in that connection for me to be comfortable with a rework. The shanks are force fit with enough pressure to cold-weld the square pins to the too-small round holes to better connect it to the >8 oz copper layers.

2) As a favor to the field crew, the CSA(s), and the team. It is extremely likely that a faulty repair here will randomly and briefly re-break and then re-attach, causing the robot to reboot and/or fail on the field. It simply isn't worth the risk.

That isn't to say that it is impossible to do correctly - I am just saying that it is a difficult high risk low reward rework.

Just wondering, why the 6mm threads and not just a 1/4-20?

I have seen a few teams break them because they try to use a 1/4-20 Nut on the shank. I am wondering if this is how this team broke it as well....

[EricVanWyk]

Originally Posted by Mk.32

Just wondering, why the 6mm threads and not just a 1/4-20?

I have seen a few teams break them because they try to use a 1/4-20 Nut on the shank. I am wondering if this is how this team broke it as well....

That part family only comes in metric.

[JDL]

We broke one one year, new one went on the bot. No easy way to repair it to same as factory new condition.

Not being one to waste a otherwise perfectly good power component I cut the stud flush and drilled and tapped for a 1/4"-20 button head for test purposes.

[FrankJ]

We broke the negative side a few years ago. We ran the negative into one of the negative Wago terminals. You could do the same for the plus side, but you would be limited by the size of the breaker. Obviously this fix is not close to legal for competition. We are using the board on a test bed with low power demands.

[slijin]

Originally Posted by EricVanWyk

That part family only comes in metric.

Would something like this work?

[EricVanWyk]

Originally Posted by FrankJ

We broke the negative side a few years ago. We ran the negative into one of the negative Wago terminals. You could do the same for the plus side, but you would be limited by the size of the breaker. Obviously this fix is not close to legal for competition. We are using the board on a test bed with low power demands.

I've done this as well, and it is completely fine as long as you can deal with the 40A breaker "in the way".

Originally Posted by slijin

Would something like this work?

All of the revisions of the PD and PI that we had to solder by hand used normal bolts and washers from the local hardware store, which is functionally equivalent to what you linked. The extra plastic would have made them look a good bit less janky :-)

That method works well enough as long as everything is tight and you use the right types of washers. Almost all of the conduction path is through the washers - you have very little contact area with the bolt itself. It is really easy to get it to look perfectly good and then fail under vibration. You need literally cut in to the board and then provide compression in to it.

The real advantage of the Wurth shanks is that they make a remarkably solid connection to the board. When they are placed, they slice through the vias and cold weld themselves in place. (Awesome).