How does your team crimp terminals? [Archive]

BitTwiddler

21-09-2013, 22:45

I'm the electronics mentor for our team and I'm getting ready to hold a class in electrical fundamentals in the coming weeks.
I've been reflecting upon a chronic problem that seems to rear its ugly head every build/competition season - failed crimp-on terminals.
I try to watch carefully when a student completes a crimp and I make sure to do a tug test afterward. Yet later during testing, practice or worse during competition, a crimped terminal will fail. Especially at the motor controller. Its frustrating to say the least.
I'd like to hear what your team does to ensure that crimp-on terminals don't fail. I'm sure many of you have experienced similar problems. While I have experience in crimping terminals I'm no expert. I'd prefer to solder all my electrical connections but that's not always practical.

Thanks,
Dave Tanguay
Electronic & Programming Mentor
1726 N.E.R.D.S.

Whippet

21-09-2013, 22:55

We always solder our crimps to reinforce them. We've still had some come out, but not nearly as much as if we didn't solder.

BBray_T1296

21-09-2013, 23:17

Most of our smaller crimps we squeeze tightly and pull test. For our larger and most likely to be destroyed ones (Cim motors, high vibration zones, potential to get snagged on the co-opertition bridge) we soldier them. We also do regular (maybe bihourly) inspections on everything. We give all our wires a gentle tug and repair any loose connections

Ed Law

21-09-2013, 23:25

androb4

21-09-2013, 23:27

We use a 10-ton press.

Jk, a regular crimp would suffice. Perhaps soldering the connector in addition would be a great practice.

Mr V

22-09-2013, 00:45

#1 thing to do to avoid failed crimps is to not use insulated terminals.

#2 is to use a ratcheting crimper, with a die intended for the wire gauge and uninsulated terminals, they give extra leverage and don't release until the crimp has been completed.

#3 is a little dab of solder on those crimped un-insulated terminals before you cover them with heat shrink.

Nirvash

22-09-2013, 02:16

We/I use a good quality crimper, it isn't ratcheting but as long as you make sure to crimp all the way it shouldn't be an issue.
Make sure to match your connector to your wire size, too large wire in a crimp or too small will cause a bad connection.
I've never had an issue with insulated terminals, in FRC or at work with equipment that runs for thousands of hours with heavy vibration.
And of course, make sure to pull test your crimps.

DonRotolo

22-09-2013, 10:25

We do not solder wires to terminals and we never have problems with them. One thing I do is choose the right size terminal for the wire and invest in the proper crimping tool. Another thing I found out is if I twist the wires first before crimping, it is much more secure because it is much harder for the wire to "slide" out.

#1 thing to do to avoid failed crimps is to not use insulated terminals.

#2 is to use a ratcheting crimper, with a die intended for the wire gauge and uninsulated terminals, they give extra leverage and don't release until the crimp has been completed.

#3 is a little dab of solder on those crimped un-insulated terminals before you cover them with heat shrink.
We do not solder our connections, use insulated terminals, and don't have a problem with failed crimps.

#2 above is definitely the one biggest thing we have done to ensure crimp quality. We spent under $40 for a high-quality, name brand crimper with the proper die.
We also made sure it was adjusted for the right crimping pressure. The 'right' pressure is when the wire strands actually deform and form a solid mass, with (virtually) no air between strands. We have sectioned our crimps, polished the surface, and examined them under a microscope. Probably overkill, but it was a learning experience for the kids.

And as Ed mentioned, twist the wire strands together - not just so they enter the terminal neatly, but also so you don't get stray strands that can short to other wires.

When stripping, be sure you don't nick any of the strands.

When pull-testing, pull as hard as you can. Pull to destructon during training, so students get a feel for the upper limit...then pull near that for 'production' crimps.

And, of course, use high-quality connectors (name brand, like 3M) of the correct size for the wire, and check them regularly during competition.

Mr. Mike

22-09-2013, 11:04

To get good crimps it takes good quality tools. Harbor Freight Tools has a ratchet and hydraulic crimping tools that seem to be of a good quality and price.
The best crimp will still fail if the wire is not supported.

evanperryg

22-09-2013, 12:59

We just don't use crimps. The only time we use them is on the terminals for motor controllers, and each of those is made on-the-spot (no premade cables) and examined for quality before putting it on the robot. Crimp terminals are, as you said, very unreliable. It takes the right tools and considerable experience to get consistently good crimps. But, they also introduce a lot of resistance into the circuit, which can result in reduced efficiency and reduced robot performance. I would highly suggest planning out your electrical system in such a way as to completely remove crimp terminals from your design.

Ether

22-09-2013, 13:24

they [crimps] also introduce a lot of resistance into the circuit

Do you mean compared to soldering? Are you claiming this is true even for a crimp properly made with an appropriate tool and crimp size?

joeweber

22-09-2013, 18:48

Watch the direction you are crimping the terminal, there is a seam where the wire goes in. If you use the crimpers that has two half circles (which we will not use) you will just crush the connector when the seam is in the wrong place. We use the sta-kon tool that has a half circle on one side and a divot on the other side and make sure that the divot is opposite of the seam. You must crimp hard or it will not take, most students do not have the strength needed for proper squeeze pressure so make sure the person doing it has strong hands.
You can view this on one of our tips page
http://www.team1322.org/electrical.htm

theawesome1730

22-09-2013, 19:06

We use ratcheting crimpers to ensure a good crimp and then solder too just to be safe. Be sure to use the right terminals for the right gauge of wire. I prefer non-insulated and then put heatshrink on after the soldering is complete

DonRotolo

22-09-2013, 20:38

But, they also introduce a lot of resistance into the circuitLike Ether, I also question this statement. I think you are wrong.

Ed Law

22-09-2013, 21:00

Do you mean compared to soldering? Are you claiming this is true even for a crimp properly made with an appropriate tool and crimp size?

I have actually heard the opposite. A good mechanical crimp is better than soldering in terms of less resistance. But I don't know if it is true.

Al Skierkiewicz

23-09-2013, 07:55

There is no substitute for a ratcheting crimper. MCM sells a nice one that is color coded to the terminal. Terminals are colored for the wire size range they are meant for. The intent with crimping is to form a "cold weld" as Don hinted above, a proper crimp forms a solid mass of metal with no air gaps between strands. However, we still don't trust that and use uninsulated terminals and solder every one after a solid crimp and tug test. We reserve insulated crimps for the practice robot and prototypes simple to save time in assembly. When the wire size is too small for the terminal you have (fan wires for instance) simply strip long and fold the wire once or twice to fill the terminal before crimping. If you use the Thomas and Betts style crimper (http://www.specialized.net/Specialized//Assets/ProductImages/272X190_PLI.jpg), the tool has an opening with a "tooth" on one side. The terminal should positioned so that the tooth is opposite the side with the seam on the terminal. When crimped the seam should not open. If it does, remake the connection.

JamesCH95

23-09-2013, 09:17

A proper crimp connection cold-welds the wire to the connector. There will be an excellent mechanical and electrical connection.

Whippet, if your team is soldering wires to connectors and still having them come out, it is time to seriously evaluate your soldering procedures and training. Though soldering is completely unnecessary if a crimp is performed properly.

Here is an article that goes into great depth on the finer points of crimping, crimping tools, pull tests, etc. It is definitely worth a quick read through. Note that the article is 4 pages long!

http://www.pbase.com/mainecruising/wire_termination&page=1

Some of the article is specific to boats, but much of it translates directly to robot applications. Like others have said, a ratcheting crimping tool is absolutely key to reliable crimp connections.

Edit: in some of the forum discussions linked in the above article 'pull testing' is discussed. Most notably that pulling a wire by hand results in a tug test of around 20lbs of pull force, a fraction of the force required by actual pull-test specs.

iyermihir

23-09-2013, 10:05

Many people seem to use uninsulated crimps. Where do you get these? We get insulated crimps, remove the insulation, crimp, solder, and heatshrink. They hold quite well.

-Mihir Iyer

hobbes20xxx

23-09-2013, 10:48

I am always seriously surprised to hear people recommend ratcheting crimpers. In my experience, ratcheting crimpers that are under $200 seem to not work properly. Two of our mentors are master electricians with 50+ years experience combined in the field, both prefer manual crimpers (found in the electrical section of home depot, etc.) These work much better and allow the kids to crimp the heck out of any connector. Its virtually impossible to over-crimp an insulated connector with a hand tool...

Soldering has the tendency to increase more than crimps do (done properly, it will be minimal however) ever notice we don't solder battery lugs on?

JamesCH95

23-09-2013, 11:06

Many people seem to use uninsulated crimps. Where do you get these? We get insulated crimps, remove the insulation, crimp, solder, and heatshrink. They hold quite well.

-Mihir Iyer

McMaster has them. Although I have used this method in the past, with great success, it is a lot of work for little or no benefit over a good crimp connection.

I am always seriously surprised to hear people recommend ratcheting crimpers. In my experience, ratcheting crimpers that are under $200 seem to not work properly. Two of our mentors are master electricians with 50+ years experience combined in the field, both prefer manual crimpers (found in the electrical section of home depot, etc.) These work much better and allow the kids to crimp the p!$$ out of any connector. Its virtually impossible to over-crimp an insulated connector with a hand tool...

Soldering has the tendency to increase more than crimps do (done properly, it will be minimal however) ever notice we don't solder battery lugs on?

Can you cite a specific example or experience where a ratcheting crimping tool that was properly adjusted failed to work when used properly?

It's nice that two people prefer manual crimping tools, but that is a far cry from any substantiated evidence. Manual crimping tools DO NOT provide ANY consistency across multiple users. Some students can squeeze hard enough for manual crimping tools to work, but ratcheting crimping tools ensure consistent crimps and alert weaker students (no, not everyone is created equal) that they need to find someone to finish the crimp for them.

They do have to be adjusted properly to work properly. Though getting upset that they don't work when they haven't been adjusted is like getting angry when parts come out wrong on a mill that hasn't been indicated. I have a $12 ratcheting crimping tool that I bought at Harbor Freight that have served me well.

Al Skierkiewicz

23-09-2013, 11:47

It should be stated here that ratcheting crimpers are designed for the terminals to be inserted in one direction only. Generally for right handed operators. The dual crimp shown above, is intended to crimp the terminal in the two places of different diameter on the insulated terminals. Those of us that are left-handed must cope with the crimper. Since they are ratcheting, all operators will crimp exactly the same way. With manual crimpers that is simply not possible. Experienced electricians using the tool everyday know the difference. Students who only use the tool for a few weeks in the spring won't remember the "feel" from year to year.

roystur44

23-09-2013, 13:38

A good connection starts with the right tools for the job, some samples lugs connected for the kids to compare( lug fixture), and a testing procedure for the kids to follow.

Wire strippers sized accordingly
Wire cutters
The correct crimper for the lug
The right gauge wire selected for the job (Zip wire) ( standard servo wire with the right pins and hoods)
Heat gun
heat shrink tube
holding vise
Magnifier lens
conductivity testing tools( multi tester or cable tester)
The right solider gun for the wire being used
flux

Try to standardize your lugs and cables. Try to use the same lugs for motor controllers. Motors that you may use over and over or need to replace quickly it would be good to use a XT-60 or Dean's type connectors which allows you to unplug the motor quickly.

Use good pliable wire for the motors at the correct gauge for the draw.

Lastly the idea of cable strain relief is important. Making a solid connection is wasted if the cable doesn't have the proper strain relief.

MrForbes

23-09-2013, 17:34

I'm the mechanical mentor on the team that the original poster is the electrical mentor on....

I think we mostly have problems, because we have several different students working on the wiring, and some of them know about how to strip the wire to the proper length, how to find the correct terminal for the application (wire size, ring size, etc), and how to properly crimp. But not all of the students know this stuff, and we mentors don't always catch it when mistakes are made.

All this talk of adjusting ratcheting crimp tools properly makes me think this discussion has gone way over our heads here in southeast Arizona :rolleyes:

btw I have a good crimp tool, and I don't have any trouble with using it to crimp insulated terminals on wires on cars and stuff at home...but building robots with students is a whole different challenge!

JamesCH95

23-09-2013, 19:02

Richard Wallace

23-09-2013, 19:52

We do it like this (http://www.chiefdelphi.com/media/photos/38234).

As others have pointed out, a good crimp leaves no air around the strands. And it must be extremely difficult to pull out. Crimping pre-insulated terminals correctly is not an easily repeatable process -- that is why my employer does not permit that practice in our factories. Non-insulated terminals, like the ones pictured in my link above, work much better and give good results with the right tool. The one I pictured can be made to work well with practice, and is relatively inexpensive; however, if your budget allows then I highly recommend a ratcheting type crimper like the ones that previous posters have mentioned.

MrForbes

23-09-2013, 20:09

Getting students to match yellow crimp fittings with the yellow dot on the crimping tool is a whole different ball of wax though :D

The problem we have, is getting students to let someone know that we ran out of blue or red terminals with the specific ring size that they need for what they're working on at the time. They will use yellow terminals on #18 wire, etc. It's fun.

magnets

23-09-2013, 20:23

When crimping, you want to end up with a connection that won't come apart, and a big mass of metal that has no air in it. Whether this is done with a really good crimper, or by soldering, it will be OK. A good crimp can't be pulled apart by hand.

The idea behind the no air spaces is the same reason why a cold solder joint isn't good. You want the solder to melt and to go into all the little cracks and form the mass of metal that will conduct electricity just like you want all the strands to be pushed together really well.

DonRotolo

23-09-2013, 20:35

...but building robots with students is a whole different challenge!Re-quoted for truth.

But, the OP was asking about doing some training for the electrical team, and this is the direction to go...especially in light of your comments about differring levels of expertise.

A pliers-like crimper (like what Richard Wallace linked to) can delver excellent crimps in experienced hands, which I think is what hobbes20xxxx is alluding to. But as James CH95 notes, our students are often not "experienced". Or as strong as a guy who twists 400 wire nuts a day. So, ratcheting crimpers offer greate consistency and repeatability.

Soldering is extra insurance, but if you allow solder to wick into the strands (under the insulation), you have what is essentially a solid wire...and we all know how those hate stress and straing, tending to break. So, unless it's soldered properly (neither too much nor too little) it is less reliable to also solder. Sometimes even I will over-solder a connection, but I can catch my error.

So, what are the other points improtant to cover with your students? (One related pair of points is "Bad crimps lose matches" and "only people who are trained are allowed to crimp".)

MichaelBick

23-09-2013, 20:37

I know I'm repeating things, but there is no excuse for a bad crimper. Wiring problems can cost matches(not cheap at all). In previous years our wiring was atrocious and we got a LOT better this year. I believe we got this crimper (http://www.amazon.com/Paladin-Tools-8024-Ergonomic-Non-Insulated/dp/B001NDCA7O/ref=sr_1_23?s=hi&ie=UTF8&qid=1379981517&sr=1-23&keywords=paladin+crimper) but a cheaper one should be fine.

One thing that I didn't see other people mention is wire strippers. I'm not sure which one of these we got, but either should be good depending on what features you want and how much you want to pay:

www.mcmaster.com/7221K61
www.mcmaster.com/7221K24

It really helps speed up electrical and helps get more consistency. Honestly for the price of electrical failures(assuming 16 matches if you make it to finals, that $300 a match) I'm not willing to skimp on electrical equipment.

We also have our crimps in an organized box and wire on labeled rolls. I make sure students know what size wire they are using for what(drive is usually a bit bigger than everything else, we use larger wire if we have extra weight that year). Our crimper has the size of wire/crimp slots labeled and the crimps fit snugly into their slots. This has prevented most of the issues we have had in previous years.

BitTwiddler

23-09-2013, 22:38

Wow,
I see my request got a nice diversity of excellent responses.

Like I said, I've done crimping before, mostly with push-in connector pins and coaxial connectors where using a ratcheting crimper tool ($200 and up) is mandatory. I didn't realize how inexpensive good ratcheting crimpers for insulated/non-insulated terminal are. For now I think we can make do with the heavy duty manual crimpers we have. I'll put a ratcheting tool on the future wish list however.
I was unaware that I've been putting my terminals in the tool upside-down as some of you have pointed out. I always thought that having that "valley" at the seam was a good thing. Never to old to learn huh?
I now realize that I'm going to need to spend some time sharing what I've learned here and have a "learn to crimp correctly" session as part of the training for the students.
I have mixed feeling about the need to solder the newly crimped terminals. While I enjoy soldering things together I'm not convinced soldering is required in this application. If I worked for NASA I'd probably feel differently.

Thanks to everybody who contributed to my request for information.
Dave

Tristan Lall

24-09-2013, 00:23

From James' link, this (http://www.pbase.com/mainecruising/image/132575328) sums up my reticence to use solder with crimped terminals.

Also from that site, here (http://www.pbase.com/mainecruising/image/93423142)'s an internal comparison of crimps using a dimpling crimper (similar to the one Richard uses), versus a ratcheting crimper. (Like Don, he cut the crimps open to show the degree to which the strands are pressed together.)

My typical practice is like Don's, except without the microscope. It's served me well so far.

Al Skierkiewicz

24-09-2013, 07:39

Tristan's first link is something everyone who chooses to solder should know.
We teach our students to add solder from the terminal end of the connector and then to know when too much solder is causing the wicking action mentioned in the article. Please be advised that the Amp discussion in most cases refers to the practice of using a pneumatic, bench mounted crimper. The concept is the same but that tool is much more precise and repeatable than most teams can afford. The recommendations are also for long term (years) stability and function. The wicking action as discussed causes the solder to effectively produce a solid wire connection under the wire insulation for some length away from the terminal. In some case, this could be an inch or more. This effectively takes away from the benefit of stranded wire on moving objects and transmits vibration into the component (speed controller). Please note in the dicussion that under no circumstances should you dip (tin) the wire prior to termination. This will prevent any tool from properly forming a cold weld between wire and terminal. This is the same reason wires should not be tinned prior to insertion in the PD. The terminals used there are meant for stranded wire. The wire will conform to the terminal when inserted. There are ferrules specifically designed for use in the WAGO terminal that are crimp style. These are used primarily in manufacturing to speed assembly. You may use WAGO ferrules only with the PD as other types are not designed for the current specification of the terminal.

FrankJ

24-09-2013, 11:14

So I was crimping a insulated fork connector to a 18 gauge wire using a good set of ratcheting crimpers. I just could not get a good crimp even though the fork terminals were listed for 18 gauge wire. Maybe the wire was on the low end of the spec & the terminals were on the big end. The moral of the story is always look at the finish crimp. If you can pull the wire out or see it moving in the crimp something is wrong.

ToddF

24-09-2013, 15:47

sanddrag

24-09-2013, 19:14

We tackled this problem last summer. Our solution was to purchase one of these:
http://www.harborfreight.com/hydraulic-wire-crimping-tool-66150.html

We also only use uninsulated terminals, as the hydraulic crimper destroys the plastic insulation. We then use either heat shrink or liquid tape to insulate and strain relieve the wire to terminal connection.

The first terminal I crimped with this thing blew my mind. The terminal and wire are so tightly fused, they are indistinguishable. Even the seam where the terminal overlaps is just gone. Connections made with this tool now have the pull strength of the wire itself.We use that for our SB50 terminals and 6 gauge ring terminals. It works well and produces a very strong crimp, but the dies are strangely shaped, and cause the terminals to form these "wings" out the sides. I find it too bulky, awkward, and slow for smaller terminals.

We do have a problem with inadequate grip strength in our students. I have some spring clamps students must be able to squeeze and hold all the way before being assigned to any crimping duty. If they can't do it, I offer to let the students take the clamps home to do hand grip exercises to improve their strength. :D

JamesCH95

25-09-2013, 08:35

Just to demonstrate how easy it is to adjust ratcheting crimping tools, and that you don't have to spend a fortune on the tool or terminals to get good results, I conducted a simple experiment last night in my garage.

I took my $10 Harbor Freight crimping tool (http://www.harborfreight.com/ratcheting-crimping-tool-97420.html) (that I think I paid $8 for), adjusted if for the horribly inexpensive wire terminal kit (http://www.harborfreight.com/520-piece-terminal-set-67686.html) I also got a HF.

http://i.imgur.com/Eo1pG59.jpg

It took a few practice crimps and pulls to get it dialed in well, but it only took 15-30 minutes. According to this website (http://www.terminaltown.com/Pages/Page7.html), the mil-spec requirements for 10awg crimped wire connections is a 150lbf pull test. So, I figured out a way to do a reasonably accurate pull-test. I wrapped the wire tail through a link in my chain fall, grabbed the connector with a pair of vise-grips, stepped onto a bathroom scale (the same one we've used to weight robots several times!) and pulled until the connector failed. I just watched to see how low the scale read at the time of failure and subtracted that from my weight to arrive at the pull-strength of the crimp connection. I repeated it three times to ensure the results weren't a total fluke.

[note the appropriate attire]

http://i.imgur.com/4tjPCSX.jpg

Very near failure at 33.2lbs, I weighed in at 159.0lbs, so the crimp connector is sustaining about 126lbf pull right now.

http://i.imgur.com/69jhEcF.jpg

All three pull tests results in failure at around 130lbf, with a spread of around 5lbf. Very consistent, and very close to the mil-spec strength of 150lbf. Not too bad for less than $20 for the tool and terminals.

For those worried about ensuring that terminals were sized and crimped properly: the ratcheting crimping tool imprints a number (or symbol) into the connectors insulation jacket. Mine imprints a dash or a dot, another pair my friend uses imprints a number. This makes is very easy to determine that the right crimping die was used in the proper orientation with a simple visual inspection. One just needs to see the number or symbol on the terminal end of the connector appropriate for the color (size) of the connector.

http://i.imgur.com/ci2ilRv.jpg

Sold yet? :D

Chadfrom308

25-09-2013, 09:07

hobbes20xxx

25-09-2013, 10:28

My main problem with ratcheting crimpers is that at robotics we tend to have 5 different brands of crimps, all different O.D.. In this case, adjusting your ratcheting crimper to properly crimps will not work on the other brand.

Basically - do a tug test, if it pops off, redo it.

JamesCH95

25-09-2013, 10:58

We used to have ratcheting crimpers but somehow we lost them. Which is sad because they were always my favorite and worked like 100% of the time. :mad:

Anyways, when we crimp terminals, this is the method we use

1. Normally strip the insulators
2. Get heat shrink
3. Strip wire, put it in the terminal
4. Crimp it as much as you can
5. Put as much solder as you can possibly fit, you can never have too much
6. Heat shrink it (makes it look nice and insulates)
7. Pull-test it

That works for us, and we notice when we don't solder, even with a pull test, they just randomly fall out for no reason.

Hope that helps::safety::

You can definitely have too much solder. It will wick into the wire and cause stress problems in the wire.

If you're wires are falling out using just crimp connections, it is not "for no reason," it is most likely because the crimp was not done properly.

My main problem with ratcheting crimpers is that at robotics we tend to have 5 different brands of crimps, all different O.D.. In this case, adjusting your ratcheting crimper to properly crimps will not work on the other brand.

Basically - do a tug test, if it pops off, redo it.

Why do you not standardize the brand/style of crimp connector? Having five different brands kicking around is just asking for problems.

A by-hand tug test (what I assume you're talking about as I assume you don't have a real tug-test machine) does not generally result in any meaningful amount of force, as mentioned earlier. I tried a number of 'by hand' pull tests last night (putting the fitting in a vise and pulling on the wire). Results were bad, either I couldn't get a lot of force on the wire for various mechanical advantage reasons, or the wire cut into my hand quite painfully. The only meaningful test I devised with basic shop tools is described above.

Edit: that's a round-about way of saying that if a hand tug-test is causing the crimp to fail there is something very wrong in the crimping procedure that you're using. The only crimps that failed a hand tug test during my experimenting last night were ones that I accidentally made with the crimping tool facing backwards, a very serious procedure issue indeed!

Isaac501

25-09-2013, 13:07

We use a ratcheting crimper as well.

One of our sponsors, Burndy, provides us terminals and crimp tools (since this is their business). I'm told (yet to test it) that the wire will fail before a proper crimp does. We've never had a problem with any crimped terminals, including the crimped lugs for the batteries.

hobbes20xxx

25-09-2013, 13:43

Why do you not standardize the brand/style of crimp connector? Having five different brands kicking around is just asking for problems.

1. Because crimps are expensive, and people hesitate to throw out perfectly good material for the sake of uniformity.
2. I try to do as much purchasing as i can myself, but occasionally another person buys crimps and someone neglects to remember that brand makes a difference (e.g. Ideal crimps vs HF ones).

JamesCH95

25-09-2013, 15:55

1. Because crimps are expensive, and people hesitate to throw out perfectly good material for the sake of uniformity.
2. I try to do as much purchasing as i can myself, but occasionally another person buys crimps and someone neglects to remember that brand makes a difference (e.g. Ideal crimps vs HF ones).

I fail to see how wire terminals are expensive... Insulated terminals from McMaster are $8.34 (50 pack, 22-18awg), $7.84 (50 pack, 16-14awg), and $9.56 (50 pack, 12-10awg). For the $75ish it costs to get a single motor controller you could have 150 of each size. I always try to order a plethora at the beginning of the season so that no reordering is ever needed.

Now, I'm not suggesting you toss the 'off brand' connectors in the trash, just put them away during the build season and only use them for off-season projects.

I'm not trying to be a pest here :) my team was having similar issues as yours, and the solution (order lots of the same brand connector and a ratcheting crimper) has worked very well thus far. The way I look at it: ruining one match's results due to a wire failure costs something like 1 Match / 10 Seeding Matches * $5,000 Registration fee = $500, which puts the price of nicer 'consumable' materials into perspective.

BitTwiddler

29-09-2013, 00:41

From James' link,

Also from that site, here (http://www.pbase.com/mainecruising/image/93423142)'s an internal comparison of crimps using a dimpling crimper (similar to the one Richard uses), versus a ratcheting crimper. (Like Don, he cut the crimps open to show the degree to which the strands are pressed together.)

Tristan,
Thanks for the link. It made a believer out of me. My new ratcheting crimper is on its way.

evanperryg

29-09-2013, 11:54

Do you mean compared to soldering? Are you claiming this is true even for a crimp properly made with an appropriate tool and crimp size?

If you have the right tool, then sure, you can get a decent crimp. However, even a good crimp will introduce an amount of resistance into a wire. Soldering helps, but it can get time consuming and overdoing it is easy, especially for less experienced members. We use a ratcheting crimper for PWM cables, and a crimper sort of like what joeweber described earlier.

jwallace15

29-09-2013, 12:00

As Al said at the top of the last page, there is nothing better than a ratcheting crimper. We use one of those on all of our connections to motor controllers and motors. We do not solder those crimps to reinforce them, and we test them by having our electrical mentor tug on them.

As for the crimps going places such as the battery to the PD board or to the main breaker, our ratcheting crimper isn't big enough. We have a pair of very large crimpers (they resemble bolt cutters) that we use for battery crimps. We reinforce those with solder (which is then covered with shrink wrap).

I'll go a little off topic to talk abour PWM crimps. We've had a problem with our PWM crimps (inside the connectors) ripping out in the past. One of our newer electrical mentors showed our electrical team how to disassemble the existing PWM connectors, pull the crimps out, and how to solder them to reinforce them. After talking it over with the head electrical mentor, we decided to do something other than using the store-bought PWM cables. He bought 1000 feet of Red-Yellow-Black stranded 24 gauge (don't quote me on that; I'm pretty sure it's 24 though) wire. We cut multiple 2 foot and 3 foot lengths, and soldered the white Sidecar connectors onto one end in preparation for wiring. Then when we started wiring our electrical board, we cut the 2 and 3 foot pieces to custom lengths and added the black ends for Spikes, Talons, etc. (we used some of the 3 foot ones for things far away from the sidecar; most of the 2 foot ones were used on the electrical board). We hot glued the black ends into the motor controllers to ensure they didn't come out.

Here is a picture: http://www.chiefdelphi.com/media/photos/38635

Ether

29-09-2013, 14:23

even a good crimp will introduce an amount of resistance into a wire

May I ask, what's your source for this info?

It seems to me that the contact surface area of a good clean crimp is so much greater than the cross-sectional area of the wire that it would actually have less resistance.

Al Skierkiewicz

30-09-2013, 07:52

One of my references has been AMP connector site...http://www.te.com/catalog/menu/en/19231
You can search around on the site and find a lot of catalog pages that contain significant info including the correct method to use, the correct tooling for their products and the contact resistance for their connectors. Warning, the site contains a lot of info so you may get caught there for a long while. In one of the catalog pages I found a contact resistance rating for 1/4" blade contacts speced at <2mohms.

FrankJ

30-09-2013, 16:24

MichaelBick

30-09-2013, 20:27

For me the issue isn't how much resistance there is in a good crimp rather than each crimp you are adding one more place to make a mistake. Or more if you consider the crimp generally involves another element like a spade or screw connection.

I find that good crimps are easy to make with a good equipment. All the connections our crimps secure to are also very reliable. We use flanged fork connectors so that there is little chance of wires coming out. This makes for very reliable connections all over. I find that usually students have a lot harder time making reliable solder connections than crimps. Crimps are also faster and can be done without waiting for a iron to heat up. This makes crimps our favorite way of making connections.

rfolea

01-10-2013, 07:00

*** Sponsor Plug ***

Automation Direct - a FIRST Sponsor - usually has a coupon in the KOP so you can get free stuff from their catalog.

They have professional crimpers for $69 here (http://www.automationdirect.com/adc/Shopping/Catalog/Wiring_Solutions/Wire_End_Connectors/Wire_Stripping_-a-_Crimping_Tools/BM-534)

and terminals here (http://www.automationdirect.com/adc/Shopping/Catalog/Wiring_Solutions/Wire_End_Connectors).

And their normal prices are way below anything you'll find at McMaster.

They ship same day so even west coast teams get their stuff within a day or two (and shipping is FREE if you spend more than $49 over the coupon).

Look for the Coupon when you get the KOP this year.

JDL

11-10-2013, 00:25

I use my trusty Klein 1005 crimp pliers. The team uses the Channellock version. You can get both at the big orange box.

I'd like to get the team a few DN-CT ratchet crimpers from Automation Direct, that's what we use in my panel shop doing industrial control panels. Does end sleeves too which are great for wagos.

Quality terminals go a long way though. T&B sta-kons, Molex/ETC, AMP, Panduit, 3M. Stay away from auto store terminals. The stuff automation direct sells is ok but its not great.

Make sure the kids are orienting the crimps right. I see a lot crimp them sideways and they blow the seam out. Bigger problem with the pliers type crimpers. If you use the uninsulated type with unisulated dies the nub should crimp oposite the seam.

If it does this you did it wrong. ::ouch:: Customer wanted to know why one of their outlets was on fire.

http://i893.photobucket.com/albums/ac136/JDlarson_photos/2012-12-20_16-34-01_266_zps892aaf77.jpg