Big crimper question

I borrowed a big electrical terminal crimper from a friend for my battery, starter, and ground cables. It works great, but I'm not sure if I should be crimping from the front or the back of the terminal. There's a seam on the front of the terminal, otherwise I wouldn't think it would matter. Anybody know for sure?

Different crimper but

In the case of split terminals you always want to drive the open ends into to crimp interface not out of it. I bought the AMP crimper from Aircraft Spruce ($348 as I recall back when I was doing that work) which produces a diamond shaped crimp for more uniform compression on the wire. One thing I learned as a radio mechanic in the USAF, in the aerospace biz, in building electronic equipment and in building my RV-6A - never skimp on crimpers. Good ones are very expensive but you don't want the kind of problems bad crimps can give you.

Bob Axsom

Thanks Bob. That's what I figured too. I don't see a large terminal crimper on Spruce other than the economy one from EPM.AV. The crimper I borrowed was $200 from a discount marine store. It's hard to tell from the pictures, but it does have a pyramid shape to the plunger. The wire is held very firmly, and the strands spread out nicely through the terminal.

Should be Fine

Should be fine, your description reveals that you are sensitive to the right things. I just rechecked the Aircraft Spruce catalog and the big yellow crimper I bought for the heavy gauge power wires is still in there. It is on page 520 of the 2005 catalog (the red one). It is called Bantam Rota-Crimp Tool by AMP P/N 601075 - now $329. Your $200 crimper looks like a good buy. I looked reasonably hard before I broke down and bought mine. The one I had to buy for the Apollo connector crimp pins really made me squirm - crimp a few pins and set it on the shelf. As it turned out I did have an application for it later for some maintenance.

Bob Axsom

Why not solder the terminal ends instead of crimping them? Isnt a soldered joint stronger and less prone to future corrosion?

cobra said:

Why not solder the terminal ends instead of crimping them? Isnt a soldered joint stronger and less prone to future corrosion?

Click to expand...

Good question. On smaller wires, I've read (thought it was Aerolectric) that a solder joint can concentrate the fatigue at one point on the wire and is thus more likely for the wire to break. On larger wires, Bob seems to advocate using copper wedges and solder as a low-cost alternative. Seems to me that the big wires should be well-supported and thus won't be as big of a breakage risk either way.

Personally, my friend bought the crimper for re-wiring his old boat. Crimping is much easier than soldering, so I borrowed it.

Solder Should be avoided

Solder is not a good alternative to to crimping in a vibration environment. As you heat the joint area heat travels up the wire and the solder follows it. That turns the stranded wire intended to provide flexibility into a solid conductor that is exceptionally ridged and it is prone to crack propagation across the entire cross section and it breaks. Solder quality is also very subject to the technique used on every joint. Cold solder joints and disturbed joints used to be a major source of reliability problems in the aircraft industry until the solder pot pin connectors were replaced with crimp pins in the '60s.
Solder does work however. If you go that way be sure to use SN63 solder to eliminate the plastic state and improve your chances of consistently good solder joints.

Bob Axsom

Dave,
Really nice crimping tool. I purchased some of those brazed/split ring terminals (Amp brand) from ACS. With a rear mounted battery in an 8A, soldering would make a real mess. I wanted to crimp, but don't trust split terminals. I mentioned this to another member of my local EAA chapter. He's a networking geek and avionics tech. He turned me onto the nicest big wire terminals I've ever seen. They are made by an electrical company called Burndy. These terminals have no split and are twice the thickness of the Amp terminals. They have a variety of types. I chose the ones with extra long barrels. I found that by using the terminals for 1AWG wire, I could actually insert the Tefzel insulation of a 2AWG wire into the terminals. These extra long barrels allowed me to "triple crimp" the terminals. I put 2 crimps on the bare wire, and one crimp on the insulation that I managed to shove in. These things are **** for stout.
Several listers on the Matronics RV list have reported failures of the Amp style terminals out at the starter. (lots a vibration there) After crimping the wires, I install 3M's triple thickness heat shrink tubing. It really supports the big wires nicely. Cosmetically, it makes the termination look very professional.
For some reason, I can not upload photos onto this site. I've tried numerous times, with no success. I can email photos if you are interested.
I get these terminals at my local Graybar industrial electrical supply house.

Charlie Kuss

You can get a good crimper from NAPA for about $230. I agree with other comments that 1) don't try to save money on crimpers, and 2) barrel crimpers will provide you a better crimp than the split/pin crimpers.

Also, it would be very difficult to do a good job of soldering these big wires. To get it hot enough to get the solder to flow will require a torch. The solder wicks up the cable and makes it stiff, which might create a problem with vibration on such a heavy cable. I've tried to do this in the past, but eventually gave up and put out the bucks for a good crimper.

I soldered and am happy with it

f1rocket said:

...it would be very difficult to do a good job of soldering these big wires...

Click to expand...

FWIW, I soldered my 2AWG welding wire following the neat suggestion in the Aeroelectric Connection to use bits of 12AWG solid copper to expand the wire to very tightly fit the uncrimped connector. I used a small torch to heat the joint, and as the 'Connection and Bob both recommend, 63-37 solder. My soldered connections are very tight and shiny (good joints), and do have a solder-added stiffness that tapers off to zeroish by about three inches from the back of the connector. I provided support (clamps, padded passthroughs, etc.) for all cables near the ends, so I don't expect an undissipatable amount of vibration-induced energy at the joints. I agree with many that an excellent crimp is better than an excellent solder job, but I don't feel that I've compromised safety by soldering in this case - my decision was based on the fact that I can do an excellent solder job, but am unsure of the quality of crimp I could achieve with hand-operated crimping tools.