Ghostbusters

Ghostbusters. I am there !
You could probably pay for it with graffiti removal services, and do your aeroplane parts after hours.
If it would remove wrinkles and fat, it could be paid off in two weeks.

CD, it is Dagger, chunky style for 5000 RPM, big crank journals, pee wee piston. It was a ballsy design for the 30’s. It would have sounded quite different.

Yes the driving point of all explorations and enquiries is how to make 80 year old, rusty bits airworthy. If something is pitted, then this is unlikely, but I would still like to learn and explore. In fact the most simple and probably stupid thought has occured, stimulated by Farlams comment about using sacrificial iron anodes to restore corroded, iron based components.

Now if you took a 5% nickel-steel alloy conrod with pitting, and cleaned it up with, say, vapour blasting (mild, no peening), followed by dilute sulphuric acid pickling, followed by freshwater cleaning and you ended up with a conrod, that under the microscope, looked like the surface of the moon could you :

Use another, broken, 5% nickel steel conrod as a sacrificial anode, and via patient electro-deposition, fill the craters, sufficient to mitigate the propensity of stress corrosion cracking to develop from filled pits ?

Now this is an idea which is utterly sub economic from the perspective of a 1930’s parts manufacturer or operator with access to new spares. There would be no existing procedure that contemplates such a repair. But what if you dug up a Dagger from the ground today and over weeks and months restored otherwise unavailable conrods to service ? I have this gut feeling that electons are shed from pores in preference to uniform, bound surfaces.

DH82, Farlam and Alex, thanks for your comments. I try not to be too serious. Serious is for when you get pulled over by a four foot police woman with a truncheon.

Some years ago I tried to get to the bottom of molasses and as Alex indicates, any rust dissolving action is due to the mild sulphuric acid action, as well as a few organic ‘pot luck’ acids, acetic, butyric. In a commercial setting, such as ‘pickling’ before metal treatments like galvanising, dilute sulphuric acid is used to same affect, albeit quicker. So the same action results from mild sulphuric acid in water. If you have time, molasses is a lot safer, smells better and will probably biodegrade if tipped out into the back paddock. The requirement to wash down parts introduces ‘dirty water’ by a magnitude of ten into the whole equation, but this is a non issue where you accept 27 litre V12s burning holes into the space-time equation, making alien eyes water, as they should, for being so big, spooky and black. In fact everybody should keep some sulphated molasses around, to spray on and dissolve aliens, if they ever come. I hope some of these observations are useful. [ I did travel to Roswell, New Mexico, once, at night, alone, and it happened to be a lightning storm. So I pulled the car over, got out, looked at the sky and said “C’mon on.” No one came, except for a few deer. I guess the aliens were looking for intelligent life, and found nothing…]

Trumper, thank you for your thank you, may you stub your toe on protruding metal in the grass and discover it to be a buried Spitfire, overloaded with gold bars…

Maxim, thank you for your insight – I do like plastic but the greenies are now going to chase you down for releasing ‘microbeads’ into the environment! I guess the whole advantage of dry ice is no blast media working its way into nooks and crannies, adding another ‘job to do’, to get it out.

Any subtle coriolis affects are dampened out by beer, down here, though you have to hold the glass to the left hand side of your face.

ZRX61, thank you for your insights on different media, and laser – most interesting.

I would be interested on any ideas on treating the conrods in the pictures below – both over 80 years old, one looks like it was chromium plated ( Napier Dagger) and one ‘furry’ with surface rust. I assume, back then, that a polishing wheel was used on a machined part for the smoothest possible surface on a highly stressed part subject to cyclical fatigue cracking. What magical steps could remove the least material but still develop the smoothest possible finish today ?

Paint removal -supercharger

A complex object to treat, because of the many different faces, small features, mixed metals (brass dataplates, piping and unions)and heavily adherent, thick enamel paint was a supercharger. The original brass dataplate had been exposed, I assume, with paint stripper and wire brush. In this case the brass dataplate had scratches from wire brushing.

80% of the paint came off quickly and easily, in the same way it would with grit blasting, but with no marking of the aluminium or brass surfaces.
The balance of 20% was thick material pooled into hundreds of nooks and crannies, which started to become annoying.

The whole point of paint removal by blasting is to generate the same sense of result that firing 4 x 20mm cannon, 4 x MG and 8 x underwing rockets from an FB Mosquito does, that is complete and utter destruction of the thing in front, in this case paint. The fact that some of the paint refused to surrender and kept on fighting made my mind drift back to the Katyusha Rocket salvo of grit blasting, which brooks no nonsense from paint, dammit.

Was dry ice defeated ? I think I was asking too much. Any student of military science understands that the synergy of ground and air forces is the foundation to a tactical success. Maybe I should use some solvent to soften the paint ?

In thinking about the options, a lot of traditional caustic based paint strippers are no good for the lungs of penguins, because the stuff ultimately ends up there. I thought I would give limonene a go, the ‘orange oil’ extracted from peel and often used in grafitti removal concoctions. I created a past from cornflour and tried to mix it with limonene but the twain would not mix. In the end the goop was spread over what remained of the case and left overnight. As a solvent, rather than caustic or acid, I was looking for something that would not chemically interact with the aluminium or brass, that would also allow me clean it off without spreading toxic chemicals around.

When I returned the next day the aluminium and brass was unmarked, but the limonene had evaporated. It did not appear that the paint had softened appreciably. The next time I might wrap the whole in plastic film. I would be interested to find a non toxic, biodegradable thickening agent for limonene ‘oil’ that stops the limonene running down surfaces. I think limonene is a slow acting solvent for old enamel paints, renewable, biodegradable and it smells zesty and good. It is no more expensive than off the shelf paint stripping preparations, which act faster, but are no good for penguins.

To finish the job the nozzle was held against every last pocket of resistance, unflinchingly, like the 14th Army’s campaign in Burma, until all traces of paint were gone. Again, no blast media was forced into the delicate innards of the supercharger, as glass, soda, walnut shell or plastic beads would. I was able to direct the flow into the casing to get the supercharger to spin, to give it a bit of a dusting and encourage the redback spiders out. Again, dry ice is a fantastic process for preserving the original surface finish and fine, light inspection stamps, preserving important information such as material, heat treatment, identification and inspection stamps. What becomes apparent was that this casting was exhaustively fettled in the factory, the light chisel marks around every feature becoming clear and taking you back to a dusty, busy workshop filled with hundreds of ghosts fussing over well made castings. I say well made in the context of the day, because dry ice also exposes small gas holes in the casing, the bane of the foundry striving to make sound castings. When you go back to the literature you can see photos where twice as much metal is cast into great risers above the piece, in the battle to clear entraped vapours. They did a bloody good job, but they were not perfect.

Exhaust manifold

A heavily heat affected and oxidized stainless steel exhaust manifold was tested with aggressive treatment. Loose oxide was removed but dry ice can’t turn water into wine.

QldSpitty, I would say that Ultra Sonics would be cheaper, but ‘horses for courses’. Dry Ice blasting is ridiculously expensive to set up, but can be affordable if you have many and varied objects to treat.