I have a Gitzo G1327 camera tripod with carbon fibre (CF) legs.
The thread at the top of one of the legs where it screws into the platform(?) head of the tripod has partially stripped and cannot be tightened. The effect of this is that loosening the twist clamps for the lower sections of the leg in question turns the leg at the head end.
Wasting time with Google I have found that most people seem to use variants of epoxy resin to glue CF to all manner of other stuff including metal. Is this the case or should I search out some frightfully expensive specialist adhesive?
The leg can be fully removed from the socket which would allow for roughening of the mating surfaces of leg and socket.
I do have some JB Weld if that would do a better job that Araldite.
Any tips or solutions would be gratefully received.
Epoxy is fine. It's worth seeking out better grades than Araldite though. West System etc. (try Axminster) sell a thin epoxy that you thicken as needed with powder or fibre fillers. Mixing before filling also gives a more reliable mixture. Even model shop epoxies are better than Araldite, although you pay a hefty premium for small packages.
Once the glue has set, investigate the possibility of fitting a pin across the diameter of the tube to add more strength. A pin such as a section of a nail shank or a broken drill with the end filed/ground flush would be ideal.
that tends to stick better than epoxy. With epoxy you need to load it a bit with a filler, clean degrease and scuff the ally, and use moderated heat to get the epoxy well mixed and runny enough to get into the aluminium scratches.
A pin would be good. Unfortunately the lower sections (2) of the leg go right to the top of the outer leg when they are collapsed - if that poor description makes any sense!
) but couldn't find it anywhere across two towns and two cities. Ended
Excellent! However, I've always believed - and tried to ensure it is so - that the role of an uncle is to enable the nephew/niece to experience all those things that their parents believe inappropriate or unsuitable. ;-) Consequently, I'm in fairly high demand with the small people who all seem undamaged by things such as gruesomely realistic dinosaur books or stomach-churning fun fairs!
If the correct release agents have been used then bonding shouldn't ever be a problem if the joint is correctly cleaned.
Silicones in liquid, wax or spray form, simply aren't used by those who lay up composites professionally. Semi rigid silicones can very occasionally be used, these are similar to baking trays / cake / jelly moulds used in the kitchen.
This is for the simple reason that uncured silicones are really bad news as their presence can seriously compromise the integrity of the entire manufacturing process not only in composite sub-assembly but also when applying paint finishes.
What remains adhered to the composite needs examining. Ideally it needs removing back to the original finished surface but no further. flap wheels work quite well for this task. Then a simple degrease is sufficient.
Aluminium when exposed to the atmosphere almost instantly forms an oxide surface that reduces the effectiveness of the bonding.
Abrading should therefore be done in an inert atmosphere, for all practical purposes when working on a repair, a fine scotchbrite pad should be used for surface preparation. Initially in the air, then again when below the surface of a suitable solvent degreaser, then quickly remove the component from the degreaser and wipe with a clean lint free cloth, then immediately place in a container of catalysed epoxy and wipe again with a piece of clean scotchbrite pad keeping the newly abraded surface below the epoxy at all times. Remove and bring the two parts to be bonded together, maintaining an epoxy covering all over the bond surface, wiping any excess that exudes from the joint. Then maintain the parts in alignment, keeping a precise gap between the parts until the epoxy fully cures.
Of course you could just bang the bits together and forget the preparation, some 'experts' do just that, and members of the public, particularly those with more money than sense, experience the failings of just such an approach every day.
Ditto - and it does explain why I've had Al joints fail despite cleaning, abrading, etc. Interestingly I have not had a failure with PU glue on Al joints, admittedly in low stress situations.
What does a 'precise gap' mean; do it take it that firm clamping is also not recommended ? Are you suggesting that the bond layer should have minimum thickness and not a minimal thickness ?
Clamping is good but you need to maintain a certain thickness in the glue line whilst keeping the parts concentric or spaced by a certain distance depending on the adhesive used. This ought to be engineered into the design of the joint but often isn't.
A typical epoxy, and indeed some polyurethanes ideally require a joint gap of around 0.05 - 0.2 mm or about 2 - 8 thousandths of an inch. With some consumer products, and with repairs you'll often have much bigger gaps than that and hence more reliance on the gap filling properties and thus a greater tendency for joint failure.
When joining two flat surfaces thin shims would be fixed in a grid pattern to the surface with appropriately distributed clamping in order that a consistent glue line is maintained.
On circular parts you would ideally have a recess in one or both of the parts such that there was almost full annular contact between the two parts you were joining (and thus almost no glue) whilst in the recess would be the glue that joined the two parts together. Vent paths for air and glue are then needed when assembling these tightly fitting joints.
Fitting pins across the joint to lock the two parts together is a bodge that really isn't needed unless required for fail safe purposes.
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