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.

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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.

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

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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.

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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.

Re: SLU-70 Lugs
 

There is good reason to be iffy on this connector, but it is required by the rules this year. If you do not solder the wire in after you have tightened the screw, it can pull loose as you have experienced. If you solder, you need to use a larger iron and clean the copper well before you assemble the connector. Tin plating helps soldering a great deal if you have means to do this.

Re: SLU-70 Lugs
 

I've tried every iron and soldering gun I have to solder Anderson Contacts onto 6 ga wire and I just cannot get it anywhere near hot enough. The best thing that I've found is a small butane pencil torch, but mine broke so now I use the big propane torch. It gets hot enough but it is a real pain because the flame is so large.

Re: SLU-70 Lugs
 

Yeat I remember when we had the monster cable 4 Guage cable at 115 it was impossible to solder with a iron. The crimp was'nt good enough. We figured a butane torch would be the best and it wourked out. Hahah i can just image use a propane torch that would just burn the cable ends. Try a small torch you can get at home depot or online.

Re: SLU-70 Lugs
 

We use a soldering iron that runs a bit hotter than most, and has a large tip, for soldering lugs. Ours is a Hakko unit that is no longer sold, but the Hakko 456-16 iron, 60watts, 1110F, is equivalent. It is important that you do not clamp the lug in a vice, it will draw away needed heat.

If you need to solder lugs in the pits,
please remember that open flames are forbidden there.

Re: SLU-70 Lugs
 

While working with Team 1495, we soldered these with the only soldering iron available, a 25-watt Radio Shack iron. It took about a half an hour per connector. These stupid things make an excellent heatsinks.

Re: SLU-70 Lugs
 

I'm worried that in this case all you have done is created a "blob" (for lack of a better term) of solder. A good solder joint is a hot one, and hot solder joints happen quickly. You may have just filled in the gaps without providing any increase in mechanical or electrical integrity.

I have a question, assuming you only screw down the lug, do you get a better connection on more finely stranded wire? Like good welding cable as opposed to the junk battery cable they give us?

Re: SLU-70 Lugs
 

You will get better conection with the thin stranded copper cable. It is more expensive but it is easier to solder and crimps better then those wires that have barely any flexibility.

Re: SLU-70 Lugs
 

If the solder flows through the wire and joint you have a good solder connection. Someone practiced at soldering will know what good solder flow looks like. I would not try to solder the SLU-70 lugs with a 25 watt iron, however.

We use #6 welding cable for our power wiring for its flexibility and high quality rubber insulation. The problem with this cable on the SLU-70 lugs is that the wire is fine enough to work its way through gaps in the clamping mechanism. You can end up with a connection that loosens. Solder the connector after clamping the wire it in order to remove this possibility. I would never use the SLU-70 lugs without soldering them.

Re: SLU-70 Lugs
 

That is a valid concern especially when working with a 25-watt iron. I can confirm it is a good hot solder joint. I had a student hold the iron on the bottom of the lug and I applied the solder directly to the top of the wire. As soon as the whole system heats up, the solder flows through the wire and down to the bottom of the lug. The result is a thoroughly tinned wired and bottom of the lug. We even avoided soldering the screw and clamp so we can still screw that down. It was also a good lesson on what it takes to make a good hot solder joint, and that student's small wire soldering skills improved.

Team 1495 works in a school metal shop and has few electrical tools. Soldering with a 25 watt iron is fairly dangerous, since you have a very hot wire and lug near your hands for about half an hour. However it is possible, so you could do it in a pinch. A micro torch is a better idea and that is what Team 365 is going to use on all the new SLU-70 lugs we had to use after we found out that rule at Pitt.

Re: SLU-70 Lugs
 

We over looked that rule as well and this year we thought we're on top of it by soldering all our 6 gauge crimp connections - oh well - we replaced them with the SLU-70 lugs and all was well they held up through 15+ matches. I did notice a couple of rookie teams that had their lug screw pressing onto their wire instead of the screw pressing onto the V shaped clamp and then agaist the wire. Perhaps this might be why some teams had them coming loose.

Re: SLU-70 Lugs
 

Rick,
The electrical rules have changed each year for several years now. You will need to check next year's rules in order to be in compliance for your 2006 robot.

Re: SLU-70 Lugs
 

An important point that you missed is "Strain Relief". That is, tie wrap your wires to a piece of the frame near the SLU70 so that part of the #6 wire will not move. This is the biggest problem with any mechanical connect, and it can be solved so easily. I'm trying to find a lug with strain relief to solve all of out problems.

Re: SLU-70 Lugs
 

I thought it important to resurrect this thread and remind everyone that although the rules were relaxed for this last weekend (difficulty in obtaining the parts) SLU 70 connectors will be required at nationals. Home Depot, Menards, Lowes, Ace Hardware and of course Terminal Supply are all sources of this connector. Please watch for changes from FIRST, until then, Be Prepared!

Re: SLU-70 Lugs
 

Our team came in last evening and changed out the connectors on all 9 batteries. Our electrician had done a good job crimping and taping (lots of it) so it took us a lot of time to get the battery plugs off of the battery. Whew!

We also connected those Anderson plugs on all four of our battery chargers to make charging easier, safer and less likely to reverse charge the batteries.

Remember...only 9 more days to get this done!!

Regards,
ChuckB

Re: SLU-70 Lugs
 

OMG - Outside the window! Get ready to do-it-again, 21-April?

PS: Does FIRST honor the FIFTH Amendment?

Re: SLU-70 Lugs
 

Jack,
This isn't a robot part and it is not subject to the construction rules. Batteries can be kept by teams and brought with them to the competition.

Re: SLU-70 Lugs
 

Other people have mentioned that parts you get from Homedepot have a different part number and different manufacterer, but nobody has said what it is.

At my Home Depot it was a Thomas&Betts BTC0208-B2 and cost $1.71 for a pack of 2.

Re: SLU-70 Lugs
 

OIC - My bad!

Re: SLU-70 Lugs
 

I am the electrical mentor for team #571 and spotted that rule right away. We used the SLU-70's on all #6awg connections as shown by the figure specified by the rule book. To properly terminate wires with these puppies you need to use a soldering iron and a heatgun! :yikes: The heatgun made soldering a rather quick operation, although we needed to let them cool a while :eek: before adding heatshrink tubing. I also agree that strain relief is a very important factor for success with these connections. Our batteries' and bots' connections have stood up to the pounding of two regionals so far and have no evidence of loosening. :cool: Good luck to everyone going to Atlanta!

Dana Susca
Electrical Mentor Guru
#571 Team Paragon

Re: SLU-70 Lugs: Post a pic ? What about soldered lugs ?
 

Could someone post a picture of one of these against a ruler. Our Canadian Home Depot does not have anything remotely near that part number but they do have lugs that might well be them.

(Just in case anyone's interested) In my experience, copper screw lugs used with large soft twisted copper wiring are very susceptible to loosening over time and or wire strands breaking, especially in high vibration & constant flexing due to repeated install/remove cycles our robots operate in. Consequently the team has to REGULARLY inspect/re-tighten them (in turn requiring the repeated removal / replacement of the insulation). Safety, reliability and simplicity is everything for “average” teams, and in my experience, a properly sized round crimp lug SOLDERED to the wire then heat shrinked requires no maintenance, has the highest strain strength, has the lowest electrical resistance (and hence lowest heating, highest peak load), has a virtually infinite life, is easier to completely insulate or better still heat shrink (including the battery post) and is materially cheaper. The soldering knowledge is easily transferred from a mentor to the student with one demonstration or a few web pictures. Personally I think these should be allowed in future competitions.

DE

Re: SLU-70 Lugs: Post a pic ? What about soldered lugs ?
 

It appears that different parts suppliers are used from time to time. A close inspection of the lug will show at least "SL" and "70" on the face of the mounting tab (adjacent to the bend) when you inspect the connector through the bag. They will be labeled for use with #2 through #8 wire. The collar is at least 3/4 of an inch in diameter. It was my experience when inspecting, that teams regularly left too much insulation on the wire and the connectors failed due to one of two reasons. 1. The connector was gripping some or all insulation and when the PVC was compressed enough, it allowed the wire to loosen in the connector. 2. There was not enough wire exposed. The connectors have a dimple that must depress the wire bundle to hold it in place. Without enough wire in the connector, the compression will actually force the wire out, like the cartoon banana squeezing out of the peel.

Re: SLU-70 Lugs
 

We used the lugs with #6 welding cable and had no problems at all. So, I guess they are not really that bad afterall. Certainly a lot easier than to solder on terminals. Getting heat to stay in something that large is not easy.

Re: SLU-70 Lugs
 

We had no problems at all with our SLU-70 lugs, here is how we handled them.

* We dissasembled them and carefully cleaned them to prepare for plating.
* We soaked all of the parts for a half hour in a tin plating bath.
* We carefully stripped 6 gauge rubber insulated welding cable to a length that supported full engagement in the lug.
* We tightened the lug on the wire until it could not be made tighter.
* We then lightly clamped the wire, not the lug, in a vice in order to not bleed too much heat away from the lug when soldering.
* We soldered the wire to the lug where it was clamped, and the screw where it went into the threads.
* After cooling, we cut/ground any excess screw away to make it easier to insulate with heat shrink, removing any hazard associated with the stickout of the screw.
* We applied 7/8 inch heat shrink in the proper color.
* The lugs have a 1/4 hole, and the hole in the batteries is for a #10 screw. We backed up a aviation quality (AN) #10 bolt and nut with hardened washers, to avoid any tendency for this connection on the batteries to loosen.
* We insultated battery connections, and the bolt on the fuse box, with electrical tape.

Nope, we had no problems with the SLU-70 lugs at all!
Lots of build hours went into making them trouble free.

We would much rather have picked up a solid copper lug with the proper hole diameter for the fuse box (1/4"), or the battery (#10), crimped it on with the hex crimping tool designed for the lug, and them slid on a piece of heat shrink just a little bigger than the wire. This would have taken only a few seconds...

Hopefully, that is what we will be doing next year!

Re: SLU-70 Lugs: Post a pic ? What about soldered lugs ?
 

I completely agree with everything that you have written. In the prevous 4 years of competition, we have crimped and/or soldered properly sized lugs and have had no problems. This is the only year that we have had wires pull out of a lug connected to our battery (SLU-70 lug that was only screwed down). If these lugs are required next year we will definately look into soldering them on. I still have not seen a satisfactory explaination as to why they were required this year.

Re: SLU-70 Lugs: Post a pic ? What about soldered lugs ?
 

The word from FIRST (unofficially) is that lacking a donor who would supply 1000+ crimpers for #6 wire and the associated terminals to be included in kits, it is and was necessary to find a cheap alternative. Given that rookies and veterans alike have a hard time with the #6 termination, this connector was chosen for it's ease of use, price and availability. What was most surprising is the sheer number of teams who did not read the rules and were required to change the connectors at competition. At the Championship alone, Spare Parts ran out of all their inventory by 1 or 2 o'clock on practice/inspection day. This after weeks of regionals and repeated reminders here and from FIRST that the SLU was required. If you know of a supplier/manufacturer would be willing to step forward with a crimper and terminals for next year's KOP please put them in touch with FIRST.

BTW, I have our students insert a star washer between the wire terminal and the battery terminal. This simple addition will bite through any surface corrosion to give a low resistance connection and it prevents the terminals from sliding past each other and loosening. Add the appropriate locking hardware and the connections will never come apart.

Re: SLU-70 Lugs: Post a pic ? What about soldered lugs ?
 

Al, do you think that many teams would have crimpers for the #6 crimps available to them from their sponsor? I would imagine many teams would and thus there wouldn't be quite as many that first would have to get sent out. Also as an alternative to crimping soldering would work and only requires solder and a soldering iron, not an expensive crimper. I have occasionally used the crimper at electrical supply houses, if teams asked the supplier around them they may be able to "lease" the crimper, I had to do this when making some splices with my 2500 watt inverter which I used 8 2/0 crimps and if we would have been allowed to use crimps I would have used it this year also.

-Mike

Re: SLU-70 Lugs: Post a pic ? What about soldered lugs ?
 

[quote=Al Skierkiewicz]The word from FIRST (unofficially) is that lacking a donor who would supply 1000+ crimpers for #6 wire and the associated terminals to be included in kits, it is and was necessary to find a cheap alternative. Given that rookies and veterans alike have a hard time with the #6 termination, this connector was chosen for it's ease of use, price and availability. What was most surprising is the sheer number of teams who did not read the rules and were required to change the connectors at competition. At the Championship alone, Spare Parts ran out of all their inventory by 1 or 2 o'clock on practice/inspection day. This after weeks of regionals and repeated reminders here and from FIRST that the SLU was required. If you know of a supplier/manufacturer would be willing to step forward with a crimper and terminals for next year's KOP please put them in touch with FIRST.
QUOTE]


This explains why they were supplied in the KOP. But it does not explain why they were required. We only used the lugs supplied in the KOP the first year we competed (2001) and have purchased better hardware every year since. Having to go backwards and use inferior hardware just does not make sense to me.

Re: SLU-70 Lugs: Post a pic ? What about soldered lugs ?
 

Mike,
I can't give you all the data that FIRST used to make this decision. Being sensitive to rookies and wanting to keep a level playing field for primary electrical must have certainly been part of the discussion. Whatever the reasons, it was in the rulebook and needed to be followed as closely as only using the supplied motors. I can tell you that in the years that I have inspected (and before that assisting teams with electrical problems), I have seen some of the scariest electrical wiring on robots that potentially would have caused fires. As a matter of fact, two robots that I know of in Atlanta had small fires due to wiring errors. It is imperative that teams know that the battery we use is capable of producing extreme heat under the conditions that some teams use them. A simple loose connection on a battery where the drive train is pulling more than 200 amps is capable of several thousand watts in a 1/4 sq. in. area. (I^2*R=200^2*1ohm=4000watts)
I would prefer to be able to use a connector of my own choosing but we need to keep rookies (like yourself) in play. If I can take a less than desirable part and make it work so can rookies and teams without an electrical mentor. I hope that if we must continue to use this type of connector, the SUA-70 is a more suitable part for #6 wire and certainly either type would be OK. Soldering makes this a reliable connector and heat shrink insulation makes it look nice.

G,
You make the same argument that hundreds of teams made either over the connectors, the use of adhesive tape, the drill motors last year, pneumatic rules or a variety of other systems you are more familiar with. FIRST sets the rules that we all must follow. I would consider it a real world constraint (like gravity) until we can come up with a solution that FIRST will adopt. Andy Baker found a nice little crimper for various size wires and the crimp connectors used by electricians and manufacturing everyday. The tool is about $400 though and asking a team who is already shelling $6K for competition to come up with another $400 doesn't seem to make a lot of sense. Many connectors can be crimped effectively with a small vise and finished up with solder but we still have the inexperienced teams to deal with. I received several requests for help from teams who lost there electrical mentors this season and were lost as to what to do. If anyone has a good suggestion you can send them to me and I will pass them on to FIRST.

Re: SLU-70 Lugs: Post a pic ? What about soldered lugs ?
 

Wrangler Power Products, www.wranglernw.com,
has high quality solid copper lugs and crimpers.
http://www.wranglernw.com/commerce/I...temNo=38%2D101
is an inexpensive hammer style crimper (part number 38-101) for #6 and larger wire for, $45.95.
Part number 38-101J, for $203.50
http://www.wranglernw.com/commerce/I...emNo=38%2D101J
is a high quality hex crimper.
I own both of these, as well as their larger hex crimper, and
all these tools work well.

Any team that can afford a set of wrenches
can afford a $46 dollar crimper.

Gravity is not just a good idea, it is the law!
FIRST's mandate of an inferior screw attached lug is just a bad idea...

Re: SLU-70 Lugs: Post a pic ? What about soldered lugs ?
 

Which is kinda odd, they want us to make good connections but they say use #6 on a 120 amp breaker, #6 will really only properly sustain ~60 amp. But THAT, is another story


-Mike
-Electrician

Re: SLU-70 Lugs: Post a pic ? What about soldered lugs ?
 

The rating of 6 gauge wire varies, depending upon the application.
For open chassis wiring 6 gauge wire is listed at 101 amps
http://www.powerstream.com/Wire_Size.htm
and this rating is referred to as conservative.
The robot construction guidelines document, Guidelines_c.pdf, listed
6 feet of 6 gauge wire as carrying 125 amps, based on a 2.5 % voltage
drop for 12 volts. The power dissapated in by the wire in this instance
is 37.5 watts, about a half watt per inch. It is going to get warm, and
you don't want to be giving away .3 volts like that, but it is safe for short
durations in the open air.

One of the things that was refreshing in the 2005 electrical rules
was the reasonable limits for allowed current in the wiring, making
for a lighter robot.

Re: SLU-70 Lugs: Post a pic ? What about soldered lugs ?
 

I agree with Gene on the wire rating. In many cases the wire gauge tables are set for max voltage drops in normal runs (volts/ft at some current) and allowing a safe temperature rise in the wire based on insulation. (ratings differ between open air and in conduit and there is a derating factor as you add more conductors in the same conduit.) Add to that the tables for the 120 amp breaker and over current of as much as 600% for a few seconds and the wire is safe for our use when currents go above 120 amps in a two minute match.

I do not agree on the wire rules allowing #12 and #14 as I think it allows teams to shoot themselves in the foot. In thinking the lighter wire is good for weight when all it does is limit the current supplied to critical motors. I still recommend #10 be used on most motors, not a rule, just a suggestion.