Nicopress and Swaging

[robcaldwell]

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.

[way_up_north]

Very well made video....its hard to know what makes a viral video...there are intangibles ....but this video has the makings of the shot heard around the world...

Thank you for making videos about the good and the bad....we need to hear it.

[whee]

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.

[robcaldwell]

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.

[whee]

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.

[BTAZ]

For those that haven't seen it, formal manufacturer instructions attached.

Nicopress instruction32.pdf

[schu]

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:

sleeve.jpg

schu

[robcaldwell]

I completely agree.

[svyolo]

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.

[way_up_north]

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

[zkelley2]

A machine swaged terminal is probably best, but not something a home-builder is going to own. Something like a MS20667/8 If you have really exact lengths that you need for each cable, spruce has a custom cable thing you can use to order any length and any fitting. https://www.aircraftspruce.com/catal...?clickkey=4047 The machines used to put those on usually cost about 5k.

[svyolo]

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.

[Archer39J]

Rob, have you had a technical counselor visit your build yet?

[robcaldwell]

Yes. Twice. Do you see something I should be concerned about?

[Archer39J]

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.

[robcaldwell]

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.

[gregc]

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.

[robcaldwell]

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.

[Mark Goldberg]

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

[Nev]

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.
image_8611.jpg

[Battson]

I also used that tool and found it did a great job, needs a little fiddling but gives good results.

[Ray Strickland]

Ditto here

[davzLSA]

thats the same swage tool I'm using, seems to wprk well

[alaskabearhawk]

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

[schu]

My flying wires are swaged, I had them done at wolf lake by a guy that has a tool like that.

[jim.mclaughlin924]

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.

[whee]

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/displa...g=257722&row=3

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.

[svyolo]

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.