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Bad Crimping on Main Cables

B52Brian

I'm New Here
My airplane partner and I are the 3rd owners of our RV-7A and we have had it for 5 years. For the last 3 years, the engine has been difficult to start, barely turning the prop before the engine reluctantly turns over. Obviously a battery issue. Gets about 6 months before it starts to drag again. Bad battery? Bad starter or alternator? Standard Odyssey PC680. Put it on a trickle charger which seems to sort of help for a little while. Different A&P's have looked it over and after confirming all connections are tight, they all conclude it's either the battery or the starter going out.

Earlier this year I was watching an EAA webinar from Vic Syracuse about buying a used EAB and the need for a pre-buy inspection. Vic Syracuse also happened to be the DAR who initially signed off our airplane! One of the things that he said that stuck out in the video was that when he does a pre-buy, he has the cowling off and he tugs on the different cables to check the crimping of the terminals onto the wires/cables. Could it be that easy of an answer to our problem?

First I looked on the VAN's web site under support and there is actually a Notification and Letter affecting all models of RVs, dated Oct 18, 2006. It states that "It has come to the attention of Van's Aircraft that some #2 battery cable terminals may have been improperly crimped." more info... and "If one or both ends fail, return the cable(s) to Vans and we will provide replacements."

I went to hangar, removed the cowling and started to do the procedure that Vic said he does in a pre-buy and yes, you guessed it - not one but two terminals had loose crimping and the #2 AWG cable easily pulled out of the terminal. I called and talked to Kevin Miller at Vans. They don't do the replacements, but we talked about what to do to fix the problem. Very helpful and he also provided a wiring harness diagram.

Now to the end of this overly long discussion. I bought some new terminals. I also bought a slaging tool from Home Depot for $40 and proceeded to crimp on the new terminals with some shrink wrap over the connection. I reattached the terminals to both the Master and Starter Relays/Contacters/Solenoids (whatever you want to call them). Problem solved!! Engine fired right up perfectly. Took it for a test flight and monitored the voltmeter. A very steady 14.1 to 14.2 volts instead of bouncing around from 13.8 to 14.3 volts like it also had been doing.

Moral of the story - If your engine is difficult to start, you may not have a battery problem or a starter problem. It may be as simple as bad crimping on your main power cables from the battery to the Master and Starter relay/contacter/solenoid. Hope this helps anyone with a similar issue. Thanks to Vic Syracuse, EAA webinar series, and Kevin Miller at Vans!

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Brian - RV-7A - N947CB
Retired B-52 Pilot
Retired SWA 737 Pilot
CAF PT-13D Pilot
 
Thanks to Vic Syracuse, EAA webinar series, and Kevin Miller at Vans!

Yes (Vic), Yes (EAA webinars) and Yes (Kevin M.)! When the cowling is off, I tug my cables (not euphemistically) thanks to Vic's books and webinars. He was also the DAR for my -14A, and I specifically requested him b/c of his vast knowledge of all things RV.

Thanks for the post.

_Alex
 
Found these while poking around in someone's cowl.
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Moral of the story - If your engine is difficult to start, you may not have a battery problem or a starter problem. It may be as simple as bad crimping on your main power cables from the battery to the Master and Starter relay/contacter/solenoid. Hope this helps anyone with a similar issue. Thanks to Vic Syracuse, EAA webinar series, and Kevin Miller at Vans!

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Great tip, Brian. Just curious, were the cables pre-fabricated or made by the builder? Reason for asking is that if they were made by the builder, I can see why they might have come loose. When I was making mine, it was the first time I had ever put a terminal on such a large wire, and I had no idea how to do it. There are a lot of hints on the internet and some books, and I did a lot of experimentation - thankfully I had a lot of spare welding cable and terminals. I used one of those "hammer-activated" crimpers, and it took a very forceful hit to get the crimp right so that it would not come loose. There are also some big crimpers which are (were?) expensive.
 
I'm not sure if they were fabricated by the builder or supplied by Vans. I am taking a leap and assuming that they were included by Vans as part of the FWF package, hence the verbiage from the Notifications and Letters in the Support section on the Vans web site. By the way, the pics from DanH are almost identical to what my cables were.

Brian
 
I borrowed a heavy duty crimper for the lugs on my #2 cables from a local electrical contractor. Its been a while but I remember it had big handles and still took quite a bit of muscle to set the crimp.
 
Yes (Vic), Yes (EAA webinars) and Yes (Kevin M.)! When the cowling is off, I tug my cables (not euphemistically) thanks to Vic's books and webinars. He was also the DAR for my -14A, and I specifically requested him b/c of his vast knowledge of all things RV.

Thanks for the post.

_Alex

Is there a written definition of "tug" somewhere (AC43.13?), for the purposes of determining crimp quality? Like approximately how many pounds of force should a 2AWG wire crimp withstand vs for a 10AWG wire crimp?
 
brake break

For 24 AWG, the wire should break before it pulls out. I think this is true down to 14 AWG. I dont think it applies to 2 AWG, but I think one gets the idea. It should never just pull out without damage to the wire
 
My memory is a little vague on this, but I seem to recall Nuckolls suggesting some solder on these larger electrical joints, which is different than the crimp only suggestion for the smaller wires. Will likely take a torch to generate enough heat. Anybody else recall this?
 
My memory is a little vague on this, but I seem to recall Nuckolls suggesting some solder on these larger electrical joints, which is different than the crimp only suggestion for the smaller wires. Will likely take a torch to generate enough heat. Anybody else recall this?

Yes - there used to be good instructions on his page - don't know if it is still there. It is a little more involved than simple soldering, using copper wedges to really hold the conductor in place before wicking in the solder. I have used the technique, and never had such a joint fail. I generally crimp now because I have the tools, and it is quicker (and less likely to set the workbench on fire…..).

Paul
 
This is how I did my welding cable to the starter and one of two case grounds. Purchase the terminals from welding shop or auto parts if using welding cable.

You can see the fixture I made to crimp the end to the cable. Drilled and slotted the aluminum bar to fit the part being crimped. Then cut a piece of bar stock or bolt that will just fit the slot. Clamp in vise and hit with hammer.

The hole you see was then filled with solder.... do not over fill, it's used to add seal between the wire end and the terminal, not to flow all the way through the sleeve. I used a pen torch.

The 1/16" cable that you see in the photo was crimped with a crimper used for non-insulated small wire terminals. It was tested to failure at just over 500 lb. load. The cable failed, not the crimp.
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I bought one of these hydraulic crimpers from HF. I’ve used it many times on the last two airplanes and so have several others at our airport, and it does great crimps. Just give it the Ford pull test.

https://www.harborfreight.com/hydraulic-wire-crimping-tool-66150.html

I bought the battery terminals from Stein. On my current build, I’m using 2 awg welding cable for starter, ground, and battery cable. The 2 awg terminals are very loose on the stripped cable, so I had to modify the terminals for this size. I cut a gap in the barrel of the terminal with my cut off wheel in my die grinder and then squeezed the barrel closed in the vice - quite easy since it’s tinned copper. It took three cuts with my relatively thin cut out wheel, but got it to a diameter to fit the cable snugly. The crimper applies a six sided crimp around the circumference of the terminal barrel and it is quite solid.
 
Something must be missing from your description.

I bought one of these hydraulic crimpers from HF. I’ve used it many times on the last two airplanes and so have several others at our airport, and it does great crimps. Just give it the Ford pull test.

https://www.harborfreight.com/hydraulic-wire-crimping-tool-66150.html

I bought the battery terminals from Stein. On my current build, I’m using 2 awg welding cable for starter, ground, and battery cable. The 2 awg terminals are very loose on the stripped cable, so I had to modify the terminals for this size. I cut a gap in the barrel of the terminal with my cut off wheel in my die grinder and then squeezed the barrel closed in the vice - quite easy since it’s tinned copper. It took three cuts with my relatively thin cut out wheel, but got it to a diameter to fit the cable snugly. The crimper applies a six sided crimp around the circumference of the terminal barrel and it is quite solid.

Slitting a terminal that is supposed to be compression yielded to make the connection sounds like a terrible idea. Stuff it with extra copper, crimp it 6 times with progressively smaller dies, anything but slitting it.

If you don't mind not using tefzel, this company is low cost, excellent quality and very fast. I have gone to them several times for my generator build. I got an assortment of terminals and custom cables. The terminals are much like my Stein parts.

I had to add extra material inside the sides of my eebay 10T hydraulic crimper to get a happy crimp. I could only generate 500lb of pull force to test it.
 
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Slitting a terminal that is supposed to be compression yielded to make the connection sounds like a terrible idea. Stuff it with extra copper, crimp it 6 times with progressively smaller dies, anything but slitting it.

If you don't mind not using tefzel, this company is low cost, excellent quality and very fast. I have gone to them several times for my generator build. I got an assortment of terminals and custom cables. The terminals are much like my Stein parts.

I had to add extra material inside the sides of my bay 10T hydraulic crimper to get a happy crimp. I could only generate 500lb of pull force to test it.

The ‘slit’ connector looks and performs identical to the non-slit ones because the slit is squeezed close before crimping, and stays that way after it’s crimped. In fact aside from some shiny copper showing up on the slit line from cutting it, you can’t tell. I’ll try to post a picture of a completed crimp, but the ones I’ve made are all cover in heat shrink and installed. I’ll at least take a pic of a modified connector and try to post it.
 
The ‘slit’ connector looks and performs identical to the non-slit ones because the slit is squeezed close before crimping, and stays that way after it’s crimped. In fact aside from some shiny copper showing up on the slit line from cutting it, you can’t tell. I’ll try to post a picture of a completed crimp, but the ones I’ve made are all cover in heat shrink and installed. I’ll at least take a pic of a modified connector and try to post it.

You can state that it performs identically but it simply can’t be true. Forms similarly, maybe. The crimp inside of a die strain hardens that material fairly uniformly. That simply can’t be true with the method you describe. It may perform adequately for you but I would caution others against the approach. Best of luck, Sir.
 
The ‘slit’ connector looks and performs identical to the non-slit ones because the slit is squeezed close before crimping, and stays that way after it’s crimped. In fact aside from some shiny copper showing up on the slit line from cutting it, you can’t tell. I’ll try to post a picture of a completed crimp, but the ones I’ve made are all cover in heat shrink and installed. I’ll at least take a pic of a modified connector and try to post it.

You may have success with this electric connection if you also solder it. As described above, I would expect it to fail by simply clamping the end in a vise and giving the cable a good tug. A crimp connection, besides holding the wire in place, must also be tight enough to not allow any moisture to enter the joint. It can be done with a good compression or solder.
 
I bought one of these hydraulic crimpers from HF. I’ve used it many times on the last two airplanes and so have several others at our airport, and it does great crimps. Just give it the Ford pull test.

https://www.harborfreight.com/hydraulic-wire-crimping-tool-66150.html
.

+1 for that crimper. I also solder more to seal it than anything else, making sure the solder does leach up the cable affecting its flexibility. I put just enough to seal the terminal. Might be over kill but who cares.
 
You may have success with this electric connection if you also solder it. As described above, I would expect it to fail by simply clamping the end in a vise and giving the cable a good tug. A crimp connection, besides holding the wire in place, must also be tight enough to not allow any moisture to enter the joint. It can be done with a good compression or solder.

Actually clamping the completed crimped terminal in my vice and giving it a good pul is what I refer to as the “Ford pull test” in my post #14. I always do this, even on the terminals I didn’t modify - which is most of them. The only difference between my modified terminal and the unmodified ones is that the slit line is braised on the unmodified ones. This allows you to crimp at any position around the barrel of the terminal without worrying about it coming open. On my modified terminal, I needed to crimp with the slit line on one of the flats on the crimper die.

The first pic is of two identical terminals 2 awg , with the left one being the modified one.
Second pic is those same terminals looking down the barrel. The modified one is a little larger than a 4 awg terminal, but just right to let my 2 awg wire slide in without too much slop.
Third pic - an unmodified 2 awg terminal with the 2 awg cable inserted.
Fourth pic - same cable inserted into the modified terminal.
Fifth pic - a crimped modified 2 awg terminal on braided ground cable that Stein says is 2 awg equivalent.

43B3CA29-5208-4117-88C3-582FAF38D8DE.jpg

E1C16F43-4B47-46C4-A503-0334FDD663D9.jpg

4C996471-712E-4A8A-881F-A484143BCE62.jpg

85CB12FC-199D-4686-AA52-F66B05F63E48.jpg

2DFD632E-C445-4DC5-B615-A374F30D3B61.jpg

I have a piece of tefzel 2 awg cable that I tried in my #2 terminals and the fit was the same as the welding cable - very loose. The tefzel wire had larger strands of wire than the welding cable. This helps the welding cable to be very flexible, and I believe will seal inside the terminal better after crimping. I too sweated some solder into the end of one of my connections, but not sure that’s necessary.
 
Good Photo's Scott. It looks like you started with terminals that came with a slit, so it was designed that way with thicker walls. It also looks like you were sold the wrong size terminals for the cable size you are using and caused you some extra work.....:mad: Things like this can burn up a lot of time. But the end results look good.
 
Scott, I can't imagine doing all the extra work rather than just getting the correct size terminal.
I'm also pretty sure you've jeopardized the long-term integrity of the connection by cutting the brazed terminal barrel.
Brazed seam terminals are the industry standard, you've weakened the terminal by turning it into a butted seam.
 
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Scott, I can't imagine doing all the extra work rather than just getting the correct size terminal.
I'm also pretty sure you've jeopardized the long-term integrity of the connection by cutting the brazed terminal barrel.
Brazed seam terminals are the industry standard, you've weakened the terminal by turning it into a butted seam.

“All the extra work”? It took less than 5 minutes to make this alteration. The only thing brazing that terminal does is allow the crimp to be applied in any orientation around the barrel. I compensated for that by making sure the crimp was applied with the cut seam on the flat of the crimper die, which squeezes it so tightly together that it can’t possibly come open, and the connection with the stranded wires internally is very secure without any gaps. If I were to just order the correct size terminal, what size would that be for #2 wire? I have 1/2 dozen #2 terminals purchased from Stein and Aircraft Spruce, and they are all the same. I even have a couple plain copper ones from NAPA (which I don’t use on my airplane), and they are equally loose and sloppy like in the picture. A #4 terminal is too small for the 2 awg wire to fit in. I have used the Vans FWF kit fat wires on previous kits, and found them to be loose a couple times. Bruce Brielmaier came over and borrowed my hydraulic crimper a couple days ago to re-crimp a couple of his FWF kit wires from Vans on his RV14 build because they were loose. He used the #4 crimp dies for those #2 wires/terminals, like I did when I crimped my modified terminals, and that made them secure.

Honestly, when I first posted on this thread, I was just trying to show the Harbor Freight hydraulic crimper that I and several others have used, and found it to be a good crimper for fat wires. I only mentioned my modification to show a method I used to make what is a very secure electrical connection. I didn’t mean to imply that everyone should do this. I did it, it works for me, and is no different in security, both mechanically and electrically to the many crimps I’ve made with my crimper that were not modified. If you don’t feel comfortable with a modified terminal, then don’t do it. I just found that the #2 terminal was too big for a #2 wire, and a #4 terminal was too small. It works for me. YMMV.
 
Thanks for posting your terminal photos, Scott. The pull test for a #2 is 550 lb according to the mil-spec chart posted above. If you soldered, then you are probably fine, but you have enough experience to make the call.

From what I read, and was told, the solid sleeve crimps should have the wiring inside crimped and deformed to a near solid condition. This is self protection against internal corrosion. The curious part is that without a continuous sleeve around the circumference, the hoop stress tension created by the crimp to retain the wire would seem to be compromised. The retention forces would be limited to bending of the sleeve, as the slit can not support tension.

Here is a paper of analyses of crimped sleeve.
 
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You can get any size terminal that will fit almost any wire size through Digikey or other supply house.
Hydraulic crimpers are available at low prices from many sources (Amazon, HF etc.) at $40 and up. With what we spend on these planes, there is no reason not the get the right tool for the job. I actually ended up with two as I loaned my first out and forgot who had borrowed it. By the time it was returned, I had already purchased a second one.

As an aside, I was heavily involved in crimping in the automotive industry. There are whole sections of books written on making proper crimps. A proper crimp will compress/deform the copper wires to a fully closed compact bundle (i.e. no air spaces between individual strands) without necking down the cross sectional area of the wire. It is very hard to do correctly without a proper crimping 'press' even on small wires, and especially large wires.

I can't resist telling my best 'swaging' story. I worked with a company that made swaged connectors for large electrical transmission lines. They are 4 to 6 feet long, tubes wrapped in explosive det cord. The cable is inserted in each end and the explosive set off to crimp the connection. At a product demonstration, one enterprising supervisor pulled his company truck under the connector to support the cables in question. When the smoke cleared, the cab on his truck was gone!
 
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