Nicopress and Swaging

[auburntsts]

For the visual learners out there, like me, here’s a few EAA how to videos on cables.

https://www.eaa.org/Videos/Hints-for.../2293635648001

https://www.eaa.org/Videos/Hints-for.../4291215048001

https://www.eaa.org/Videos/Hints-for.../4315630248001


For those that aren’t aware of these EAA videos, they have hundreds of them on just about every subject related to home building.

[davzLSA]

lots of good info on those videos

[predragvasic]

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.

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, 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.

[Nev]

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.

[predragvasic]

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.

[gregc]

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.

[Mark Goldberg]

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

[btdobie]

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?

[Battson]

Both are possible, sudden total failure is much more likely in my opinion as a Mechanical Engineer.

[coosbo]

There is a tolerance, you can over crimp the sleeves.

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?

[robcaldwell]

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.

[coosbo]

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.

[whee]

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.

[gregc]

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.

[svyolo]

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.

[coosbo]

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.

[robcaldwell]

That is good to know. Thanks for sharing your discussion with Nicopress.

[Sir Newton]

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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[David Weber]

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.

[Utah-Jay]

I get to venture into this next week.