Nicopress and Swaging

robcaldwell

robcaldwell

Model B Quick Build Kit
Over the weekend I put out a video where I discussed my confusion with the Nicopress tool and swaging. I was a little hesitant to do this concerned over the reaction to my "rookie move". Confirming that I made the right decision, I have been overwhelmed with responses in the comments section on YouTube, email and text messages from others who shared the same thought process as me... That "Nicopress" was a method that could be performed with any tool designed for crimping and swaging copper sleeves. Even in conversations, I would hear "I nicopressed my control cables the other day", for example. I have since learned the distinction between the method of swaging and using an actual Nicopress tool, AND, the enormity of difference between using the proper tool and copy cat tools that provide similar yet inferior (potentially catastrophic) results.

 
Great video! It’s awesome that you shared your experience how you corrected things.

I read that same article back when I was making my cables. I had a different takeaway that I’d like to share but I’m in no way saying either of us is right or wrong.

Forever ago I bought one of those “copy cat” tools from Home Depot when I needed to make cables for a non-aviation project. When I came time to make cables for my airplane I recalled I had that swaging tool so I dug it out while I read though AC43.13. I knew I needed a go-no go gauge so I thought rather than buy one and wait for it to be shipped I’ll just lookup the spec and measure the crimps with my calipers. While looking for the specs I found “The Big Squeeze” article. My takeaway was that extra caution needed to be used if someone wanted to use a “copy cat” tool; adjustment of the tool prior to use is required and repeatability of the swaging could be an issue. I thought about buying a Nicopress crimper but decided I ought to at least see how my tool preformed once I had specs.

I found the crimp specs in one of the code books reference in “The Big Squeeze” article. I used my calipers and adjusted my Home Depot swaging tool so that every swage was within spec. The swaged sleeves looked just like they are supposed to and every crimp was within spec. There is a tolerance, you can over crimp the sleeves.

The only issue I had what if you got sloppy while crimping then a curve could be formed into the sleeves. This same thing is possible with any of the other swaging tools but since the Home Depot tool takes some muscle to use more likely to happen.

So, I made my cables with a “copy cat” tool but I adjusted it before hand, gauged each swage, and I have 100% confidence in the cables. They aren’t even something I think about other than during an inspection.

Maybe something to consider, putting shrink tube over the sleeve isn’t recommended. It makes visual inspection impossible and can hold moisture in the swaged sleeve. The article shows how some people recommend using shrink tube, it only covers the pigtail of the cable to not the sleeve. There a forum post somewhere about rather than using shrink tube just align the tail end of the cable so once the swage is complete than tail is close to flush with the sleeve. That’s how I did some of my cables.
 
Good points, Whee. I'm sure you can make non-Nicopress tools work as long as the resulting diameter meets spec and the copper is not over squeezed. On some of the swages I did with the copy cat tool, some were squeezed too much and pushed some of the copper out of the dies. Looked like little ears on the sleeve.
 
The most important thing is NOT the tool you bought, it's understanding how it works and checking to make sure it worked with a go-no-go gauge.

You don't want an over squeezed sleeve any more than an under squeezed sleeve. If you are very closely looking for a uniform 3-section crimp with the right dimensions then it should be safe, regardless of how you got there.

If you want the easiest path to good crimps then the $300 tool is the best way to get there. If you are handy and know what to look for, this can be done repeatably with the $43 bar tool:

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schu
 
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Nico press are not the best cable terminals, but they are more than adequate for what we are doing. But like everyone said, if they are not done right, they can slip, with catastrophic results.
In general, crimping anything, don't be in a hurry. With nico press that is especially important to get the sequence correct, and the spacing as good as you can. But when you crimp, hold it. At least 5, 10 seconds is better. Crimping causes stress and heat. Waiting that time lets the heat and stress equalize a bit. It happens pretty quick with copper sleeves.

Pinch the narrow end of the thimble with plyers so that the corners fit into the copper sleeve. Crimp 3,1,2, in that order. Keep the pressure on at least 5 seconds, 10 is better. Check with a go/no go every time. If in doubt, make a new cable.

Practice making perfect swages on the bench. Cut foot long pieces and practice. The sleeves are cheap, as is the cable when you do this. Cheaper than throwing away 15 foot pieces of cable.

Nico press are adaquate, but they need to be near perfect to be adequate. If in doubt, take Robs advice. A go/no go gauge or checking with a micrometer is essential for every terminal.
 
For those of us new to the Nico press scene ... if they are not the best and just adequate .. what kind of cable terminal is the best ?

Thanks
 
What I should have mentioned in the video... Many of the crimps on the copy cat tool reached the correct diameter to pass the go/no-go gauge. However, there was no consistency or uniformity in the crimps. Many times the copper would squeeze or push out of the dies. This suggested to me that less of the copper was actually contributing to the grip of the crimp. Again, maybe this would have sufficed but the ounce of doubt created was enough for me. I'm sure others may have proceeded differently. I would have always been haunted if I had done nothing. And I just couldn't have that especially if my family will someday be strapped in the bird.

I have since re-rigged all of the control surfaces. I am pleased with the consistency of my new rigging. If I were to do it all over again, I would run strings through all of the cable routing areas and would fish all of the cables and make the swages and connections at the same time. I am pleased with the outcome of this challenging situation.
 
First, thanks to Rob for the video. Also, I applaud his decision to do the re-work since he was not comfortable with his cables. And yes, it is import to follow the appropriate procedures.

But.. I think it is important to note that nicopress cable failure is not a common problem and that a safe cable is not beyond the skill of the average builder. A query of the NTSB accident database filtering on amateur built aircraft with a search string of "nicopress*" or "cable failure*" or "eye end*" or "cable end*" returns 14 out of >7000 records with the most recent in 2007. Reading the summary reports shows that only 5 of these appear to be nicopress related failures. This is a pretty rare event. So yes, due to the critical nature of a failure we should pay very careful attention to our control systems but it's probably not at the top of the list of safety concerns.
 
Bob Barrows has served as a tech counselor in his local EAA chapter. He told me once that the most common error he finds when doing visits to members is bad nico press work. So apparently there are few builders who will benefit from the video. At least it will make builders aware of the problem.

When I finished my first homebuilt, a FlyBaby, I took a bunch of 1/8" 1 x 19 cable (non stretchable) pieces made up to an engineering firm to pull them to failure. I took them USA McWhyte cable and also imported cable. Some with one nicopress sleeve and some with two. They all failed at between 1900 - 2100 lbs of force. The USA cable did about 5% - 7% better than the imported cable. The double nico press sleeve made no difference as I recall.

These wires on the FlyBaby are the wing struts. They go from the top of the wing to the fuselage and the bottom of the wing to steel fittings bolted inside the heavy axle. Slippage or failure would be bad. I wonder how much load is placed on the control cables in our Bearhawk planes? That question is beyond my knowledge to even guess. But I somehow doubt the load approaching anywhere near the failure point of 2,000 lbs I saw when doing the testing.

Just thought my testing of the nico pressed cables would be of interest while discussing this subject. Mark
 
I love statistics and frequently state (in my business life) "the numbers don't lie". And yes, comfort was a real issue for me. I've learned that control surface cable rigging has many interpretations and meanings to different people. Some desire absolute harmonic balance and buttery smooth hands off flying in stable conditions. Others say that as long as the connections are solid and the outcome is accomplished from the intended input, then good enough. I get it. For me, I have this stupid perfectionist affliction that I have to live with. It literally pisses some people off and I have been told as much. As I rigged the airplane, I could sense how real my work was creating an extension of what my body will be telling the airplane to do. Corny? Probably. But the sense of feel applies to everything we do, not just flying. For it to be right, it has to feel right. And so maybe statistics may have suggested otherwise, I just did not feel right about it.
 
It's disappointing/concerning they didn't catch this then. Mine was very interested in the quality of my crimps and from what can be seen yours do stand out, or did anyway. Good you caught this. Thanks for sharing.
 
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I don’t feel that I had to “make it work.” Once properly adjusted it just worked unless the operator did something incorrectly. Operator error may be more likely with the Home Depot tool since the handles are short and the sleeve have to be properly placed in the jaws.

I think I understand what you mean by “ears.” A ridge that forms where the jaws come together. My tool only makes those ears when I put the sleeve in the jaws crooked. After swaging my sleeves looks just like the one in schu’s pic.

Regardless, I’m glad you got things fixed up and are moving forward.
 
I bought and used an “economy swaging tool”. After making all my cables I took them to a local LAME and he tested them in a hydraulic device. Not sure what tension they were tested to, but there was a small deforming of the thimbles as a result. All passed and as a result I’m confident to use them. Getting them tested was inexpensive, and I think probably a very good way to establish actual integrity (rather than probable) with a variety of tools in use, and my own inexperience.
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I used this very tool and was please with the outcome. It comes with a GO-NO GO gauge and I checked every crimp per advise from my A&P friend/inspector. I will however remove all shrink tube on final assembly after reading this thread and related articles. It makes sense to me to leave the sleeves visible for inspection.
Good thread, thanks Rob!
 
I used that one too. I keep the bolts well lubed up, and use a cordless impact driver, alternately on the bolts, and tighten them down by hand with a ratchet. I used to have a real nico press tool but I think I sold it years ago.
 
There are a few places on the BH where the cable changes angle as it pulls. The Nico press plus a shackle make a really nice U-joint. The shackles are actually pretty pricey. ACS only charges something like 6 bucks to put a machine swaged terminal. I have a threaded stud on one end of every cable for either a turnbuckle, or fork.
BH cables are only under 30 lbs of constant tension, and cyclical loading of maybe hundreds of pounds. Cables used for structural applications are under constant heavy load, plus cyclical increased load. Either a swaged terminal (steel), or compression style terminals of which there are many types is better for this type of load. At least in the marine world.
 
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I'm fortunate in that I was able to get a Kearney roll swager for nothing by buying and selling government auction tools. There are maybe some FBOs in your area that may have a roll swager that can do your ends for a fee. The terminal hardware isn't cheap, but there are advantages to having low-profile hardware on certain cable ends such as flap lever connections where clearance is a concern.

http://www.mykitlog.com/users/display_log.php?user=yeeeha&project=527&category=6618&log=257722&row=3
 
alaskabearhawk said:
I'm fortunate in that I was able to get a Kearney roll swager for nothing by buying and selling government auction tools. There are maybe some FBOs in your area that may have a roll swager that can do your ends for a fee. The terminal hardware isn't cheap, but there are advantages to having low-profile hardware on certain cable ends such as flap lever connections where clearance is a concern.

http://www.mykitlog.com/users/display_log.php?user=yeeeha&project=527&category=6618&log=257722&row=3
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Rotary swages are awesome. A local shop here has one and let us use it when we needed to make cables for the Luscombe we restored. I wanted to do the same on the BH but there is some areas where the longer ends wouldn’t work and didn’t know about the ball end version. If I could do it again I’d use the rotary swage for sure.
 
I have a kearney swager and prefer swaged fittings. A lot of sailboat riggers use these and might be a place to check. You can use a micrometer if you do not have go nogo gauges.
 
If you live on one of the coasts there is a good chance a local sailboat rigger has the tool. ACS doesn't charge much for the service and their turn around time is good. It is best to use actual cable to measure how long they need to be. If you search on "custom cable assemblies" they have a page on how to measure the cables with the various fittings.

If you start with the longest cables first, if you screw one up you can cut it shorter and use it for a shorter run.
 
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gregc said:
A query of the NTSB accident database filtering on amateur built aircraft with a search string of "nicopress*" or "cable failure*" or "eye end*" or "cable end*" returns 14 out of >7000 records with the most recent in 2007. Reading the summary reports shows that only 5 of these appear to be nicopress related failures. This is a pretty rare event.
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Mark Goldberg said:
Bob Barrows has served as a tech counselor in his local EAA chapter. He told me once that the most common error he finds when doing visits to members is bad nico press work.
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So, the actual NTSB data indicates that bad cables experience exceedingly few failures. On the other hand, we have the other anecdotal evidence, where Bob Barrows had, during his time as a tech counsellor at one EAA chapter, witnessed quite often poor Nicopress work. From this statement, we should be able to infer that poor Nicopress work isn't all that rare; if Bob witnessed it at that one location, it seems logical that among builders around the country (and the globe), the incidence of sub-optimal cabling is a fairly common occurrence. And yet, we still have an extremely low failure rate.

If these conclusions are valid, this tells me that the forces on these cables experienced in flight are significantly lower than the maximum forces at which the connections would fail, when done correctly. And this significant difference between the regular use and failure point allows enough room for inadequate work (or cheap tools).

I haven't built an aircraft yet, but when I do start working on it, I'm sure I'll look for the best tool (or possibly for a professional shop to cut and finish the cabling for me), but it is good to know that there is plenty of tolerance for sub-optimal workmanship.
 
It could be that the tech councillors like Bob are catching the poor work and filtering it out before it becomes an issue. But it could also be that in the case of a swaged cable there may be a significant difference between “looks bad” and actually being a weak joint or failing.

I say this because a number of mine didn’t look textbook, yet when tested they proved to be very strong. (I also through a couple in the bin before getting to this point !)

My own perspective is that by testing the end result you remove the “should be fine” from the equation and replace it with “is fine”. This takes the expensive vs cheap tool, and builder experience out of the equation. Just my thoughts.
 
I can't imagine that all the builders are having the benefit of tech counsellors such as Bob. I'm sure most are quite careful and meticulous, but if what Bob says is true (that he has witnessed a lot of inadequate work), then I'm guessing that those without the benefit of an overseer may well have gone on to eventually fly.
 
Nev, has a pretty good point about testing. Just curious but does anyone know where to get cables tested? It's not something that any shops local to me do.
 
Hi Greg. I went to an engineering testing firm who had equipment to just this type of testing. I think it is not really needed if the swage is done properly and passes the go.no test. Mark
 
I'm curious if anyone knows the typical failure mode for nicopress ends. Do they let go suddenly, or is it a gradual migration through the fitting until eventual failure?
 
whee said:
There is a tolerance, you can over crimp the sleeves.
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I think my Nicopress 64-CGMP tool is over crimping out of the box but I'm having troubles finding enough information to adjust it with confidence. The instructions that came with the tool (same as the pdf BTAS posted above) says "Sleeves should enter slot freely. Adjust tool if sleeve does not enter gauge.", but I can't really find anything specific to over crimping. An M crimp with this tool is 0.0315" less than the slot in the gage the tool came with.

I'm guessing there is a max/min or target with +/- for each cable size that I haven't found yet. Could anyone point me in the right direction?
 
Hey Colby, before I acquired the same Nicopress 64-CGMP as you have, the cheap copy-cat tool I was using over squeezed to the point that the cooper deformed the sleeve. The copper literally pushed out and away from the swag no longer belonging to the crimp itself. I knew that wasn't right. You may want to contact the manufacturer for guidance. https://www.nicopress.com/contact.
 
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Thanks, Rob. The crimp with my tool looks ok to me, but it's the first one I've ever done so hard for me to say. It's difficult to show in a photo, but this is what it looks like.

IMG_4917.JPEG

I'll give Nicopress a call on Monday and ask them how to specifically identify an over crimped sleeve.
 
I am curious to hear what they say. A small suggestion based on the picture - slightly grind down the very sharp tips on the thimble (I just touch them to a scotch-brite wheel). That way they don't get pinched in the sleeve and cause the end to twist/bind.
 
I believe the tips are supposed to inside of the copper sleeve. I didn't try grinding them - I squeezed them slightly together at tips with plyers. Not my idea, I don't remember where I got that from. But it makes it easier to get the tips in the sleeve,

In the picture you can see the tip of the thimble on the right side is impinging on the copper sleeve and forcing the whole loop to the opposite side. I don't know if that is bad or not. I also don't know if "overcrimping" is bad. The go-no go gauge in the pic definitely shows overcrimped.
 
Appreciate the tips. I spoke with Mike Parker at Nicopress this morning and he said you can't really over crimp the sleeves. He told me as long as you can easily slide the go-no-go gauge over the crimp, it was fine. But it doesn't really matter if it's "by a millimeter or by a mile." He said one thing you don't want to do is re-crimp an existing crimp, as it could cause fatigue. Someone recommended to me to rotate the sleeve 90 degrees and re-crimp, so I asked if that classified as re-crimping and if it was bad. He didn't specifically say it was bad, but he said they don't recommend that practice.

I think I'll back my tool off so the crimp comes closer to filling the appropriate slot in the gauge, just to make myself feel better.
 
My 2cents on the subject. Look for a shop that builds custom rigging for cranes. A shop that is qualified to build wire rope lifting slings & lifting chains slings will have certified test equipment to test everything. As well as proper crimping tools.
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Sorry for the long delay. I was out of pocket, then attempted to stay off the internet, then tried to find the info source I used. Unfortunately I can’t find the source, I saved it to an old phone back when I was building. It was a national code book and it provided a chart with max and min dimensions for a swaged sleeve.
 
I do not mind spending the money for Nicopress Tool, but I rigged my cables with the "bar" many moons ago. I used the No Go gauge, and they all passed. However, out of an abundance of caution, I am leaning towards redoing them with the proper OEM Nicopress tool after reading and viewing way too much info on YouTube. I think Rob's video scared me a bit or was a wake-up call. I am a sharkfisherman and and have some 1000 lb test line. I wonder it incorporating it with the cable would serve as a safety back up.
 
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