DIY AN665-20 threaded clevis's?

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skeeter_ca

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Has anyone or would anyone build your own clevis's? On my build I am looking at buying 32 AN665-20L/R clevis's for the drag/anti-drag wires in the wing. Just the fittings alone will set me back $406! Would, could or has someone cut their own out of 4130 solid rod, slot, drill and thread it to the same size? Could you expect the same strength as store bought ones even if you had to oversized it? Is this a reasonable idea?

skeeter
 

Matt G.

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Could you? Sure. Will they meet all of the requirements that the commercially-available item does? Who knows. You'd have to test them. And then make more after destructively testing your first batch. What is your time worth? $400 for 32 fittings is not a great deal of money in the grand scheme of things...
 

Dana

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The AN parts are almost certainly forged to the basic shape before final machining, which gives much better grain structure than a part machined from bar stock.. As such, any homemade substitute would probably not be as strong unless made larger (and heavier).

Dana
 

BJC

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Has anyone or would anyone build your own clevis's? On my build I am looking at buying 32 AN665-20L/R clevis's for the drag/anti-drag wires in the wing. Just the fittings alone will set me back $406! Would, could or has someone cut their own out of 4130 solid rod, slot, drill and thread it to the same size? Could you expect the same strength as store bought ones even if you had to oversized it? Is this a reasonable idea?

skeeter
Could the Pitts approach be adapted to your wing? BTW, what are you building?

The Pitts uses wires that go through the spars and are tensioned with nuts on each end. Light, simple, low parts count, strong.


BJC
 

lr27

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I'm pretty sure you can find all the required specs. If they look doable, and you're a good machinist, I'd say go for it.
AN665 can be found here, though I don't see a -20:
http://www.abbottaerospace.com/wpdm-package/an665-terminal-threaded-clevis-type-tie-rod
Judging by a quick look at the drawing, it looks pretty simple, and overbuilt. The part looks like it uses unnecessary material. I doubt if the thread spec is anything special, but I guess it might be worth looking up.
material and plating spec:
http://miscellaneoushardware.emilspec.com/MIL-DTL-5683/index.html
Note that you have a choice of number of alloys, and that it's supposed to be hardened. If I was making one of these, I'd consider leaving a smooth, gradual bump on the outside around the area where the threads end to reduce stress concentration at the sharp inside corner. Just a little one. Sharp inside corners are generally a bad idea, as the stress gets much higher there. I don't know if it's going to be worth your time, unless you have some kind of automation.

On the other hand, you might be able to get something a bit less expensive that will safely do the job. I'd check the plans of other reputable airplanes. Does anyone know if the Baby Ace kept this size of tie rod end:
baby ace tie rod end detail.jpg
This doesn't look like a great design to me, but the Baby Ace has a good reputation, doesn't it? I don't really like the inside corners bent into that strap.
 

lr27

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The AN parts are almost certainly forged to the basic shape before final machining, which gives much better grain structure than a part machined from bar stock.. As such, any homemade substitute would probably not be as strong unless made larger (and heavier).

Dana
Wouldn't they say that it had to be forged in the specs? I don't see it. The spec does say it has to hold at least 2,760 lbs. So just hang your car from it. If it holds, it's good. ;-) It only has to be stronger than the tie rod itself. The minor diameter of a male 10/32 thread is around .150". So at the nominal 2400 lbs, that would be about 136,000 psi, neglecting the stress concentration. The clevis will need to have significantly more than 75,000 psi strength, though one could beef up certain areas without making it much heavier. Say, a bit thicker right around the hole for the pin, and a bit thicker over the threaded section. I'll admit I haven't looked into the properties of the various alloys allowed.
 

Pops

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I'm pretty sure you can find all the required specs. If they look doable, and you're a good machinist, I'd say go for it.
AN665 can be found here, though I don't see a -20:
http://www.abbottaerospace.com/wpdm-package/an665-terminal-threaded-clevis-type-tie-rod
Judging by a quick look at the drawing, it looks pretty simple, and overbuilt. The part looks like it uses unnecessary material. I doubt if the thread spec is anything special, but I guess it might be worth looking up.
material and plating spec:
http://miscellaneoushardware.emilspec.com/MIL-DTL-5683/index.html
Note that you have a choice of number of alloys, and that it's supposed to be hardened. If I was making one of these, I'd consider leaving a smooth, gradual bump on the outside around the area where the threads end to reduce stress concentration at the sharp inside corner. Just a little one. Sharp inside corners are generally a bad idea, as the stress gets much higher there. I don't know if it's going to be worth your time, unless you have some kind of automation.

On the other hand, you might be able to get something a bit less expensive that will safely do the job. I'd check the plans of other reputable airplanes. Does anyone know if the Baby Ace kept this size of tie rod end:
View attachment 58648
This doesn't look like a great design to me, but the Baby Ace has a good reputation, doesn't it? I don't really like the inside corners bent into that strap.
I made the tail wires on the JMR just like the Baby Ace wire ends. Even made the nipples on the lathe. Its called homebuilding and I do as much as I can. No, I buy my props, some things are beyond my job title.
 

skeeter_ca

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Yucaipa, Ca
Could the Pitts approach be adapted to your wing? BTW, what are you building?

The Pitts uses wires that go through the spars and are tensioned with nuts on each end. Light, simple, low parts count, strong.


BJC
I had considered that but for some reason I dismissed it. I'll have to recheck that option.

I am building a Volmer VJ-22.

skeeter
 
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lr27

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I made the tail wires on the JMR just like the Baby Ace wire ends. Even made the nipples on the lathe. Its called homebuilding and I do as much as I can. No, I buy my props, some things are beyond my job title.
Why are props beyond your job title? Seems like, in the past, people often used to make their own. Might be handy if you need to change pitch or something. Of course you'd have to be careful about the grade of wood you used.
 
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