Threaded Inserts for Ally tube

[4CA]

Hi guys,

I'm looking at using aluminium instead of chromoly for the Push Pull control tubes on a new build. Thought I would ask about the threaded inserts guys have used for aluminium previously. I was looking at turning up 7075 inserts and threading them to take the heim joints (rod ends), bolting the inserts into the ally tube etc.

However have heard of guys using 6061 for this purpose as well. Do people usually stick with a steel inserts otherwise?

Any feedback appreciated,

Cheers

Paul

[aussie_paul]

RAF 2000. my Firebird, and several single seaters we built used alloy inserts into alloy tubes, all 6061 T6.

Aussie Paul.

[tonydenton]

I bought a system years ago and it has ally in ally tube , but im going to change it to stainless steel inserts. with out checking the tensile strength of a female ally nut [ the insert ] I would prefer stainless steel ]

[Waddles]

G'day 4CA,

ASRA has no records of push rod failures using AL threaded inserts going back 20 years.

Incident Registrar
aka Waddles

[tonydenton]

thanks allan, it was a reputable buy so I will probably leave it now.

[4CA]

Thanks very much for the replies guys, I will go ahead with the Al inserts.

Tony, as much as I like using SS as well, I have had previous issues with dissimilar metal corrosion between the 6061 and SS so will steer away from that combination these days.

Anyway, thanks again,

Paul

[tonydenton]

wow, that would be unusual I would of thought. depending on the grade of stainless steel material thou. best part of gyro's is each to his own.

[4CA]

[Tim]

To test the integrity of the control system Ross and I strain tested a short section of 6061 T6 push rod fitted with a 2" long ally slug (secured by an AN3 bolt 1 1/2" down) and a swivel rod end screwed 2/3 the way in, using a press 'calibrated' to read lbs. pull. Total failure occurred at just over 1.5 tons, but not before the AN3 bolt had 'torn' a slot approx 3/8" along the pushrod. The total failure was the swivel rod end breaking open at the top where the small nylon injection hole is. The thread in the ally slug did not appear to be at all damaged and the broken rod end unscrewed normally.

[4CA]

Thanks Tim,

Thats great info and helps make the decision an easy one.

Assume your tube was 1/8th wall?

cheers

Paul

[Tim]

No Paul, it was a few years since I have been involved in manufacture but I'm pretty sure our pushrods were either 1/16" or 2mm wall.

[tonydenton]

that's a good test tim with great results. I never thought of testing like that .
in saying that I had tested my swagging several years back almost the same way. I swagged the 3mm marine cable [ double swag ] and looped it around a 1" shaft and had the thimbles at both ends hooked onto digital scales [ pulling] under the press. I have a video of it too.
pulled to 1000kg. and I thought that was good enough but may as well go further. I got to 1250 kg and thought i'll go all the way to destruction the wire cable broke where it was wrapped around the 1" shaft . because it is pulling flat as it wasn't supported by a thimble . so it broke the cable @ 1350kg. swages still in tact. I cant push that hard with me feet so good enough for me. .

[chook]

4CA I believe there was an AD stipulating a minimum of 75% of the threaded must be within the plug after all adjustments have been made.

Regards.............Chook.

[4CA]

Hi Chook,

Thanks for that, I'll make sure I have that covered. Appreciate the feedback,

Cheers

4CA