Sandblasting engines

This is something I often do to enhance the appearance of engines that I am restoring.

Machines aluminium is easy to polish and remove marks but cast aluminium can be difficult. On PAW engines, the castings are a softer grade aluminium and marks, scratches, gouges ...... are difficult to remove.

The rounded and smooth nature of the casting makes it difficult to smooth out the rough bits with files, emery cloth...... as there is a tendency to leave flat spots that show in the light.

So I resort to blasting - it is a finish used on many engines anyway. If you already have a compressor suitable for airbrushes then the "airbrush" for use with grit is not too expensive an addition and 1kg of Aluminium Oxide lasts ages (as long as it is kept dry)

The stuff I use is



and the tool



The blasting gives the crankcase a more uniform look and "disguises" blemishes.

Here is the before



The during



and the after



The surface after this is prone to accepting fingerprints and so I "oil" it to seal it and it puts a nice and permanent sheen on the aluminium. It also repels dirt and and exhaust residue is easily cleaned off.

Dinsdale recommends ArmourAll protectant, as used on motorbikes - one of my fellow restorers uses a teflon spray that he uses for the tables on his woodworking machines. It does need sealing though and the blasted aluminium absorbs the oil.

I use



I leave it overnight before wiping off any excess.

Here is a crankcase being oiled - the first picture highlights the difference.



A few words of warning. The aluminium oxide is extremely abrasive and I only do this outside. Although I seal the crankcase - some always gets in and I blow it out with a much larger air compressor before oiling. The crankcase must be dry before starting the blasting - any moisture or oil will accept the dust and make a very efficient grinding paste. The powder is very fine and blowing it out is the best option or it will end up in any crevices.

It is very hard to "wash" it out.

There is also an alternative and that is to let the blasted crankcase age naturally. It will darken and eventually and porousness will disappear as it oxidises. It must be stored dry for that and it takes months.

The sand blasting also works well on small steel parts and removes rust.





Nearly all the engines I get to restore have missing propeller washers and retaining nuts or they are rusted, butchered or deformed. It is very time consuming cleaning these up and so I just make new ones.

Buying replacements can be expensive - postage cost alone! - and these PAW 09s use a 1 BA thread. 1 BA nuts (any odd size as well) are not easy to find. 0 and 2 BA are easy to get hold of.

That is one of the reasons I restore groups of engines and then produce "extras". Once my lathe is set up - a washer rolls off every two minutes and nuts every three minutes. So 5 minutes for a new nut and washer!

Here is an old one (not in too bad a condition) with one of my spares.



Now - the trio of 09s (149s) ready to run



This process won't appeal to everybody and is involved. It changes the appearance of the engines and they are no longer original but for me they look better than the gummed up, scratched, neglected and battered things I started out with.