Does anyone know if pultruded carbon tubing has ever been used in push-pull tubes?
If so, does anyone know what method was used to attach the carbon tube to the rod ends?

Thanks.

Hi, Dave,

I've bought a Dominator tandem kit from Taiwan last year, it has carbon
push-pull tubes 26mm dia. on it. The inserts are glued into it (no idea what
is this glue) and secured with one 5 mm bolt at each end of tube. Since the
inserts are glued I couldn't see what is the real wall thickness but the
outer ends seem to be somelike 1.0 to 1.2 mm thick. The tubes are apparently
professionally manufactured in standard fishing-rod manner.
First time I and collegues were curious about using carbon tube in this
application but some of local guys who is skilled in carbon fibre told me
that it's OK for it. The inserts are long enough - at least they 55 mm of
thread in them.
I've sold this gyro to another party and they had a crash on it one month
ago - after approx. 40 hours of flying (trying to take-off from rough
terrain with very heavy TO weight, no injury to both aboard). Rotor and
rotorhead were destroyed, lower and upper control forks had broken, but both
tubes were OK with no signs of wear or damage. I've test flown this gyro
after repairing right yesterday.
Since this Taiwan company cheated Ernie Boyette (I knew about this after I
bought the kit), I had no contacts with them after Ernie announced they are
cheaters so I hadn't a chance to ask if they had any calculations to these
tubes or to get any technical info on these particular tubes. I've asked
Ernie about these tubes but he didn't comment this particular question -
don't no why.

Just my 2cs.

Cheers,

Alex

Sure has. I have just returned from doing an EC-665 (Tiger) course at the
Eurocopter Academy in France and many of the primary push-pull tubes are
carbon fibre with bonded end fittings. No knowledge of the adhesive used -
EC won't reveal everything!

Glenn

Bonding metal fittings to composites is done on a regular basis in aerospace
composites fabrication. However, a word of caution - the bonding procedures are
an exacting science and require verification testing. In some cases, the use of
mechanical fastners in conjunction with the bonded fitting becomes a source of
failure. So you can't simply add a bolt as a safety factor. A bonded
composite/metal fitting on a critical control rod needs profesional design,
tested materials, and preformance verification.

Bob

Sure, it has been used. It is important to choose well the diameter and the wall thickness related to his length.
Usually, at the ends, some machined metal ends are glued to the OUTSIDE of the tube, so to avoid local delamination at the edges.

Roberto Bracchi