Sticking brass to mild steel

Can you braze what ever it is? might be better than glue. otherwise without knowing the application or any more details I will hazard a guess that an expoy will do.

Dave

What about old fashioned soft solder? Alan

If it has to be glue rather than solder then use epoxy but make sure the surfaces are completely clean and don't touch them between cleaning and applying the adhesive. If you can heat the parts to about 100C for an hour or so once the epoxy has initially hardened, then the joint wil be even stronger. Adhesive jointing is even more sensitive than soldering to surface cleanliness.

About 60% of the skin of a Boeing 747 is held together by adhesive bonding - mostly epoxy.

I confess I'd overlooked the possibility of soldering (though I'm not very good at it). I might go that route, else it'll be an epoxy.

Thanks.

Brendan

Normally I'd solder it in place ( silver solder for strength, soft for a quick job ) - but if access is limited or the application of heat might damage something you might try JB Weld ( a sort of tough epoxy resin ).

I used this stuff to stick a brass tube filled with wadding onto the cover of my Land Rover's Fairey overdrive - the vent hole would spray out a fine mist of gear oil which eventually ended up all over the rear of the vehicle. It stayed put for years and eventually had to be knocked off with a hammer when the overdrive was removed.

Regards,

If you gave us some idea of the application/dimensions we might collectively be able to come up with some additional pointers.

Regards,

If that is really the case, then they've over-engineered them & they will probably be looking into reducing the weight.

Regards, Tony

....except that, if it's 'new technology', they'll perhaps be anxious to keep it a bit on the over-engineered side until it's been proved in service. They wouldn't want a Comet-style series of failures. I thought I had read somewhere, a few months ago, that the project was a bit behind schedule because they were having to sort out issues with the attachment of wings to fuselage.

Tim

Hi Brendan If you are not confident to solder, have you consideed solder paint. This is a very useful mix of powered solder and flux, you just brush on the prepared surfaces and heat till the solder melts. It is not too good at gap filling but at least it will tin the surfaces ready for stick solder. Cup alloys (NCEASC) sell it in little pots quite cheaply., other suppliers you will have to check that they are not selling you "soldering paste" which is often just a flux. T.W.

Further to my last;

T.W.

Cheaper here...

John

Thanks for all the info, chaps. I went with Araldite, when it's set I'll give it a whirl and see how things hold up. I'll look into the solder stuff and maybe have a practise on some scrap.

The "thing" was just a clamping plate, steel to steel and I wanted a bit of brass inbetween to avoid too much marking of surfaces. Will there be more friction between brass and steel than there would be between steel and steel? Unlike surface materials do something friction-wise, but I can't remember what!

Brendan

There will be less - see:

Steel to Steel coeff 0.8, steel to brass 0.35 for dry surfaces. However, much less and almost the same if grease/oil is present.

I would suspect the coeff. will be less for "engraving brass"/steel. (i.e., leaded brass, as used in clockmaking).

Regards, Tony

Unalike materials are generally used in sliding things to ensure that the easier one to replace wears faster than the harder one to replace (assuming the designer was awake at the time of design)

Dave

It's a little more complicated than that.

Both the Boeing and the Airbus wings have been tested far beyond the maximum stress expected on the wings, more or less the point where either the wing, the fuselage or the passengers would have failed.

If I remember correctly the safety factor is Maximum *1.5. The Airbus designs failed at around the critical point (actually slightly below it but within 3%) The Airbus wing flexed 7.4 metres before rupturing.

I remember reading somewhere (High Performance Composites?) that a Boeing design had had a similar failure.

The design problem is enormous, whereas one can look as a piece of aluminium as a single piece, the equivalent composite part may be mutiple layer of a material in a matrix . Each layer may be laid at a different angle and where the material is woven, there is a stress point whereever one thread crosses another.

So instead of the fairly precise data that is available to the metal engineer, one has to work with approximations of behaviour.

Another problem is that effectively you 'create' the material every time you make a component part. Imagine if you had to mix, melt, roll and treat and test every piece of aluminium instead of relying on the manufacturer to do so. Indeed the Americans have the AGATE database which defines how to put the various materials and resins together to make a standard material and the various figures that one can use for that material to avoid some of the problems.

So 'overengineered' is a relative term, given the large variables possible and the many modes of failure that have been identified.

I've seen video of composite wings being laid up. They use a big CNC device which applies the fabric in strips in a certain pattern. The machine lays down the fabric remarkably fast. The angle of the fabric changes depending on which layer it is and where on the wing it is. So the effector at the end of the arm applying the fabric is constantly turning. 5 degrees of freedom, or maybe 6. There are the X,Y,&Z axes along with roll and yaw. Maybe tilt too. And different weaves are used also. Must be hard to get all the bugs out the first time. ERS