Gorilla Glue failure

[pinnerite]

Let's be fair, it may not be the glue. It could be the user - me.

he items glued together are the ends of the arm of a cast alluminium patio chair. One of six. The arm is bolted at the bottom to the seat and at the top to the chairback.

The break came at the point where a bolt is screwed through the arm and into the chairback. It simply snapped.

This first happend in the summer. When I first tried to locate the sections, I realised that the joint had been under stress. So after gluing wit superglue, I filed the hole to allow the bolt free movemnt.

I thought that would be the end of it but a couple of days ago, the first when we coud sit with up to six people, it snapped again at the same point. I forgot that I had used SuperglueIt and because it looked clean glued it agin wuth two-part gorilla glue (a bit like Araldite). It was no good and came apatrt again as I bolted it in.

On inspection it hada sticky feel and instead of glinting, the brocken areas are a dull grey. I tried cleaning them with petrol. I am not sure if I was successful. So before another attempt, I thought I had better garner the benefit of experience.

TIA, Alan

[T i m]

<snip>

I think it might have been suggested the first time that the chances are, something like that would need something in the way or reinforcing, given that it broke before being further weakened (by breaking)?

So, is there any way you could brace the joint, even if only on one side with something suitable (steel strip / sheet / rod etc)?

Cheers, T i m

[pinnerite]

Sadly the shape and size prohibit this. I am going to try some alterative solvents to remove the remaining glue before trying Araldite. I will try to use a clamp.

Thanks, Alan

[T i m]

<snip>

What about drilling and pegging each end of the joint? It wouldn't have to be *that* accurate if you have enough 'meat' to drill into and use a suitable epoxy.

As (chemically) clean as possible is a good start, as might be a

*little* warmth.

Whilst Araldite used to be the go-to adhesive for many things (esp the

24 hr stuff if it really needs to be strong), personally I would first try something like JB Weld two part epoxy on the grounds that if that won't hold it, not much else will.

Std 24 hour Araldite is just a good two part resin, the JB Weld is reinforced, providing a stronger bond as it's less likely to compress on the side with compression loads and so tear away the rest of the bond.

Anything that will stop it moving whilst it cures is essential.

Once cured, some of these adhesives also enjoy further curing with some external heat (but don't go mad). ;-)

Cheers, T i m

[Martin Brown]

Unreasonable expectations of what a glue can actually do.

I doubt if there is any glue that could make a joint that will survive the load that this will be exposed to short slab casting epoxy onto it. Reinforced carbon fibre composite might just be able to hack it.

Steel and aluminium do not make good friends leading to corrosion. The repair is best done in aluminium but will cost more than it is worth.

[T i m]

+1

If it could be wrapped with some woven carbon fibre and resin, that would probably do it?

True, but 1) if embedded in epoxy they probably wouldn't be in direct contact and 2) unlikely to react unless they got wet (that they shouldn't if the brace is encapsulated)?

Not if they used ally sheet / strip / rod but that would likely be more expensive and weaker than steel.

A 6" nail cut to length and drilled and epoxied into each side of the joint as a dowel might be worth a go, given the CSA of the bench section and diameter of the nail. ;-)

Cheers, T i m

[Brian Gaff (Sofa]

Its the oxide. If it was not for that coating the metal would simply go up in a flash and a bang, trouble is its horrendously hard to make stuff stick as the oxide simply comes away. I seem to recall some kind of etching adhesive could glue it, but the best fix though it will look bad is mechanically bolting plates onto the joint I think. Brian

[pinnerite]

Thank you for your advice. Believe it or not there is oly ond syockist of JBWeld in the Greater London area. I am going to try the two-part Gorilla again, having checked all the comparative reviews.

I di think of drilling and pinning but holding a small piece of solid Alli and drilling through 3mm or so would require the kind of gear that I don't have. My Dad could have done it. He was fine engineer but I no longer have access to all his tools.

Despite my initial cleaning attempts, first with petrol and next with hand gel, I am still not confident that the edges are clean. I need another solvent to get rid of what I suspect was poorly cured adhesive.

[T i m]

<snip>

Plenty on eBay?

Erm, but you know it will fail and you will just contaminate the joint again / further?

Glues are one of those things you get to 'know' and in all my experience of gluing things, there isn't much to beat JB Weld (and there are different varieties)

A heavy weight or helper to hold each piece still on something and a an electric drill?

The key is taking your time and setup prep. Given you aren't in a position to apply a genuine engineering solution the next best thing is to do your best.

eg, If you drill as square as you can into each section (ideally more than one point, equally spread apart) using a smaller bit (say 1mm), then see how close you are using a panel pin with the head cut off and then re drilling slightly larger, making any angle adjustments as you go, you should be good to go. Remember you want a bit of slack around the final dowel(s) to proved a decent layer of epoxy.

Notch the dowels up with some pincers or a hacksaw, chemically clean everything, warm, mix adhesive, apply to holes and dowels, join parts, wipe off excess and clamp / weight / tension (Spanish windless / elastic bands / ratchet straps) the best you can, leave for a day.

Ideally you really want a clean metal to metal joint. Any impurities, especially at the edges will introduce a weakness, limiting the strength of the final solution.

Acetone / a hot air gun and wire brush?

The point is and given the csa of the joint and the potential load on it, even someone who knows what they are doing (like your Dad) may have believed to be onto a hiding to nothing and so any attempt at that sort of repair would have needed to be done to the best / most likely standard / solution.

Eg, not using the most likely to succeed glue , not cleaning fully, not keeping dead still whilst curing or then exposing to excessive forces during reassembly ... were all likely to guarantee it failing quickly.

You can often get away with less when the odds are better (it only being aesthetic or the break in a non load-bearing area or a long split etc) but this doesn't sound like one of those. ;-(

Cheers, T i m

[The Natural Philosopher]

JBweld = car body filler for most practical purposes

[Vir Campestris]

Petrol: A mix of chemicals of various volatility. Some evaporate at once, others take longer. It may even have traces of oils.

Hand gel: A mixture of water, various alcohols, and a gelling agent.

Both of those _will_ leave contamination on the surface. I suspect you'd do better with meths. Or vodka.

Andy