Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by skeeter_ca, Jan 31, 2017.

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1. Jan 31, 2017

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4. Feb 1, 2017

### BBerson

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5. Feb 1, 2017

### 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

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6. Feb 1, 2017

### BJC

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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

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7. Feb 1, 2017

### 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:
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:

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.

8. Feb 1, 2017

### lr27

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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.

9. Feb 1, 2017

### cluttonfred

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PerhPs you could find a source for surplus milspec items rather than making your own?

10. Feb 1, 2017

### Pops

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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.

11. Feb 1, 2017

### skeeter_ca

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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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12. Feb 2, 2017

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