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bolts with low profile heads?

J

jwilbur

Well Known Member
Where my mixture cable attaches to the control arm I've got some interference with the bolt head hitting the FAB. My solution was to simply sand down the head of an AN3 bolt by about half and that did the trick.

Now I'd like to find a "real" one (i.e., one manufactured this way) but can't seem to find anything like it on-line. Does anybody know if they make a low profile head AN3-10A and where I can buy them?
 
Bicyclops said:
You want AN23 clevis bolts. You can get them at Aircraft Spruce and elsewhere. Ed Holyoke
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Maybe. I'll have to check if there's enough clearance at some point in the control arm travel to get a screw driver on the head. I'd rather a bolt for this reason, however.
 
I wonder if a Hilock would work? There's nothing on the head to grip; the threaded end has a hex (Allen) recess so you'd use a hex bit/key and a wrench to tighten.
 
snopercod said:
What about NAS6203 SHEAR BOLTS (.189" dia)? Head height is between 0.110 inches and 0.125 inches. The NAS6204 are .249 dia.
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Not really,

NAS6203 head height is 0.110 to 0.125 inches

AN3 head height is 0.109 to 0.141 inches

With it being that close you might be better off just getting a bunch of AN3 bolts and measuring the heights to get one at the low end of the tolerance.

But, do you really want any control system to have moving parts with a clearance measured in 10s of thousands?
 
Joe,
If you didn't install the optional VA-131Q Recess on your FAB, would doing so eliminate the interference issue?
 
Auburntsts said:
Joe,
If you didn't install the optional VA-131Q Recess on your FAB, would doing so eliminate the interference issue?
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The recess is installed. It's the recess it's scraping. ... All I can say is that it used to fit before I put the rivets in. Very annoying, but that's another story.
 
Spit-balling here -- is there any way to move the mixture outboard on its shaft a little to create some clearance?
 
Last edited:
Auburntsts said:
Spit-balling here -- is there anyway to move the mixture outboard on it's shaft a little to create some clearance?
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This would be a perfect solution and I thought about it last night. The clock-able control arm tightens against the mixture mechanism with teeth, like a gear. In other words, I can back off the nut holding the arm enough to clear the teeth, rotate the arm and then tighten the nut to lock it in a new clocked position. A theoretical spacer would look like a jagged washer which could receive the teeth on one side and engage on the other. I don't have the first clue how to even search for something like this. What would it even be called?

Does anybody know if such a thing exists?
 
Well my only other idea is to modify the recess to increase the clearance, which is kind of the option of last resort, but might be the best permanent solution.
 
Auburntsts said:
Well my only other idea is to modify the recess to increase the clearance. which is kind of the option of last resort, but might the best permanent solution.
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I don't think there's any clean way to mod the recess. Drilling it out is going to make meatloaf of the FAB which would require enough repair that I'd just as well start over. But I'm not so sure sanding the bolt head is such a bad idea. The stress on the bolt is in shear and it's tiny at that. Would a bolt head shaved down from ~1/8 to ~1/16 be a safety issue in this case?
 
Don at Airflow Performance has a variety of different arms for throttle and mixture controls available, I had to swap a couple of mine around to fit.
 
Follow-up

This is a follow-up. I always run pretty much everything by Ralph Hoover, friendly neighborhood EAA Tech. counselor. He's helped me with numerous issues over the years. He said my solution with the shaved bolt head was safe, ... but, "it's just not done." He followed up with, "what are you going to do if you have to replace it? Shave another one?"

He asked me if I had a Ball-Peen hammer. I didn't but had a couple of boxes of tools from my Father-in-law in the corner and I thought there might be one there. There wasn't. Ralph saw something in the pile of tools and asked if I had an angle grinder. I did. He then made a ball-peen hammer from an old hammer in the pile. Then with the hammer he had just created, he took my FAB and worked the recess so that the original hardware would clear. I had thought this to be impossible to do without destroying the FAB.

I can't say how impressed I am with Ralph and his generosity with his time and talent. He (and so many like him) make this hobby very rewarding (and educational).

Thank you, Ralph ... yet again.

This is the hammer:
IMG_20170325_125433_929-768x432.jpg


This is Ralph.
IMG_20170325_120547_476-768x432.jpg
 
jwilbur said:
This is a follow-up. I always run pretty much everything by Ralph Hoover, friendly neighborhood EAA Tech. counselor. He's helped me with numerous issues over the years. He said my solution with the shaved bolt head was safe, ... but, "it's just not done." He followed up with, "what are you going to do if you have to replace it? Shave another one?"

He asked me if I had a Ball-Peen hammer. I didn't but had a couple of boxes of tools from my Father-in-law in the corner and I thought there might be one there. There wasn't. Ralph saw something in the pile of tools and asked if I had an angle grinder. I did. He then made a ball-peen hammer from an old hammer in the pile. Then with the hammer he had just created, he took my FAB and worked the recess so that the original hardware would clear. I had thought this to be impossible to do without destroying the FAB.

I can't say how impressed I am with Ralph and his generosity with his time and talent. He (and so many like him) make this hobby very rewarding (and educational).

Thank you, Ralph ... yet again.

This is the hammer:
IMG_20170325_125433_929-768x432.jpg


This is Ralph.
IMG_20170325_120547_476-768x432.jpg
Click to expand...
We have so many limitations, not having the right tool shouldn't be one of them. Good for Ralph, if you don't have the right tool, make one!!

Great to hear you got past the issue Joe.
 
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