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.
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.
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”.)
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 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:
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.
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
From James’ link, this sums up my reticence to use solder with crimped terminals.
Also from that site, here’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.
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.
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.
We tackled this problem last summer. Our solution was to purchase one of these:
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. 
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 (that I think I paid $8 for), adjusted if for thehorribly inexpensive wire terminal kit I also got a HF.
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, 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]
Very near failure at 33.2lbs, I weighed in at 159.0lbs, so the crimp connector is sustaining about 126lbf pull right now.
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.
Sold yet?
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
- Normally strip the insulators
- Get heat shrink
- Strip wire, put it in the terminal
- Crimp it as much as you can
- Put as much solder as you can possibly fit, you can never have too much
- Heat shrink it (makes it look nice and insulates)
- 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::
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.
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.
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!
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.
Why do you not standardize the brand/style of crimp connector? Having five different brands kicking around is just asking for problems.
- Because crimps are expensive, and people hesitate to throw out perfectly good material for the sake of uniformity.
- 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.
Tristan,
Thanks for the link. It made a believer out of me. My new ratcheting crimper is on its way.
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.
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