SLU-70 Lugs
 

Rule 48, Section 5.3.5, Electrical System Rules, page 16 and Inspection Item #28

"The ES-18-12 Battery, the Main 120 Amp Circuit Breaker, and the IFI CB/Distribution panel must be connected as shown in the diagram. The ES-18-12 Battery must use the Anderson Connector and the copper SLU-70 lugs provided in the Terminal Supply Bag. The Battery terminals and the SLU-70 lugs must be insulated with shrink tubing and/or electrical tape. You may use additional lengths of #6 red and #6 black wire to reach the panel as needed to make the above connections. The circuit breaker must be readily accessible for inspection and testing at each competition event."

Teams MUST use the SLU-70 screw lugs on all batteries used in competition, on main breakers and on distribution panel. Most teams missed this rule by not carefully looking at the diagram.

At the Great Lakes Regional competition this rule was enforced. The rule was explicit in the manual with accompanying diagram making their intent even more obvious.

Words of advice: “Strain Relief”. All mechanical connectors will loosen with movement. This includes screw lugs and crimp terminals. Somehow add strain relief to each lug by tie wrapping the #6 wire to the frame or some solid object to prevent any wire movement. Your robot is a moving, vibrating machine. Wire movements and vibrations can loosen any connection.

Check the tightness of the screw on the lugs between rounds. (I was told not to use Loctite on the threads - it acts as an insulator and releases when hot.)

FIRST tried to solve a repeating problem of improper crimps loosening by switching to the SLU-70 lugs. Few teams really know how to create a proper crimp connection. And pliers just don’t work at all (and I have seen crimps made with pliers).

The SLU-70 is an improvement that requires only a screwdriver to install instead of an expensive crimping tool. But you must remember that it is a mechanical connection and is prone to loosening without strain relief.

Strip off enough wire insulation so that the copper wire extends all of the way through the compression area of the lug for the best grip. If the conductor length is too short the jaws may not seat properly.

The advantage of the SLU-70 style lug is that the screw never touches the wire. Other type of lugs where the screw touches the wire do not make as effective of a connection for stranded wire. (We allowed this alternate style of connecter at GLR because it complied with the spirit of R48 and was still available.)

Be gracious and kind when you go to a competition… Take some extra SLU-70 lugs for other teams. We cleaned out both the local Lowes and Home Depot by noon on Friday. A number of teams gave out SLU-70 until their supply ran out – cudos.

Lead inspector
Great Lakes Regional

Re: SLU-70 Lugs
 

This rule came as a surprise to us. We completely looked it over and wouldnt have passed inspection if it was not for the gracious teams at the Ypsi. regional. Thank you to the teams that borrowed us these connectors at Ypsi.

Re: SLU-70 Lugs
 

For those teams that had been using high quality solid copper lugs
with a hex crimping tool, this rule was an abomination resulting
in a much less secure and harder to insulate connection. We had
invested several hundred dollars in crimp tooling in prior years,
making this rule very unfortunate.

We noted the rule in the documentation, however, and tin plated a bag
of SLU-70 lugs so that it was easy to solder the wire in after clamping
the screw. If you need these lugs at the San Jose regional, we have a
few of our tin plated ones left and will be happy to hand them out in
hopes of a rules change next year that will allow us to return to aircraft
quality crimped lugs. Using the SLU-70 lugs are a fine example of
"building down to code," but if you are going to have such rules they
should be enforced.

Re: SLU-70 Lugs
 

We switiched all our 6AWG wires to the SLU-70 lugs this year .. we havent had any problems with them at the competition (but we did have 1 wire slip out of the lug before we shipped)

In Sac, they checked the lugs also. There were numerous annoncements over the Pit PA system for teams looking for the lugs.

A word of advice - Dont order them from some supplier off the net. Check you local hardware "superstore" like home depot. We got 2pks of the lugs for $1.79 each. The other local hardware store "Ace" wanted $2.79 for a single lug, that didnt even look like it was the right one. So shop around a little bit. I'm sure teams will be greatful to borrow some if they need to.

Re: SLU-70 Lugs
 

Can't agree with you more here. Yes they are good for teams who cannot do quality electrical work but if people have the access to higher quality tools and materials, let them use it. It is like saying everyone must build their robot our of wood because some teams don't know how to use carbon fiber.

I hate it when rules restrict us from doing our best.

Re: SLU-70 Lugs
 

Well for us, they are an impovement over what the head of our electrical team did last year. We found many lugs that were just squeezed on with pliers and taped. :ahh:

This year, the SLU-70 lugs tightened down, the screw is soldered in place, the little moving piece is soldered to the side, so it cant back down and the wire is soldered to the lug itself. I did most of these myself and I inspected all of them. I'm happy with how they turned out.

Re: SLU-70 Lugs
 

I can't deny your complaint. However, over the last three years I have seen many lose connections. This is a step in the right direction for the majority of the teams.

Re: SLU-70 Lugs
 

The SLU-70s are easy to put on a wire, but, at the same time, they come off way too easily. Our team now checks them before every match. They worked just fine for us for a while, but right before the second match of our quarter finals, we did a power check, and nothing happened. It seems our ground from the battery came out of the lug. We had to rip off all of our insulation and find a flat-head while someone bought us a few minutes. As much as I know its to help with the problem of bad crimps, I really wish FIRST goes back to the crimp-style connectors next year--we never had a problem with them.

-Tony K

Re: SLU-70 Lugs
 

This rule came as a surprise to me. Really, that just means I didn't read the manual close enough. I just didn't think that FIRST would issue a rule about the use of a specific type a lug where there has never been one before.

I've always been satisfied with my teams use of typical crimp connectors. We have 5 year old robot that still powers up today with it's original wiring. All of it's crimps are as tight today as they where 5 years ago. While the SLU-70's are easier to use, I don't feel that they add much to the security of the connection. As everyone has noticed, they tend to loosen up. This is a pain not because you have to tighten them, but you have to strip off your electrical tape to do so every match!

I realize that there is a real disparity between the level of mechanical work and electrical work for a lot of teams. I cringe sometimes when I see the electrical boards of teams that have otherwise amazing machines. But, I would rather see the inspectors trained to recognize a bad crimp rather then to have to mandate the use of a arguably inferior lug.

Besides that, they are heavy. I don't like heavy.

-Andy A.

Re: SLU-70 Lugs
 

It should have been enforced across the board at all regionals.

Re: SLU-70 Lugs
 

We are iffy on this new connector, our robot got hit causing the wire to pull out of the connector in a seeding match (our second of the day). We were very dissappointed that it came out considering we originally had a really good crimped connection.

Re: SLU-70 Lugs
 

This rule will be enforced at Boilermaker and Midwest Regionals over the next two weekends. If you are attending either or both, please plan now to have a supply on hand if you didn't check the rule.

In case this missed your attention, each team needs to name a team inspector (student) whose responsibility it is to check through the inspection list for their robot's compliance before meeting with the inspector(s). Please check the FIRST site for the latest update to the checklist.

Re: SLU-70 Lugs
 

Since im going to be doing wireing next build year, what about soldered lugs?

Re: SLU-70 Lugs
 

I soldered lugs. They were very nice connections, shrink wraped and all. We couldnt pass inspection until we got the SLU-70 lugs.

Re: SLU-70 Lugs
 

Although at first I was not a fan of these - they are a large improvement over what most teams were using in the past, particularly now that FIRST no longer includes a crimping tool truly capable of crimping 6 gauge connectors in the kit. I'm pretty picky about electrical connections, and every non-signal connection on our robot is crimped then soldered and heatshrinked, including the SLU-70's. We also put a little bit of solder into the setscrew of the lug to add something to prevent it from loosening. Solder isn't really good at doing mechanical things, but its an improvement over just leaving it. All of this, of course, requires that you have a soldering iron capable of heating up the copper connector and 6 gauge wire.