Many years ago I started using paint remover t chemically strip the Alfatross. It may have been due to a defect in the way it was repainted in 1965 or 1966, but something was causing the paint to separate from the metal in big flakes. It was hard work and I didn't like breathing the solvents that are in paint removers. After doing most of the exterior I could see that cleaning the bottom, interior, and engine room would be just about impossible. So I put it aside until a better option presented itself. The advent of soda blasting was the answer to my prayers--and Dave bought one for his shop!
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A section of peeling paint on the Alfatross's hood. There is a clean separation
between the aluminum body and primer--repainting was mandatory! |
Turn Up the Volume!
We got the Alfatross up on the rotisserie last Monday evening. On Tuesday I was still examining my options for procuring a compressor that could provide the necessary volume and pressure. Soda blasting is not a job for your average shop compressor--and mine is pretty wimpy anyway. According to the soda blaster manual you could need as much as 50 CFM at 90 PSI depending on what size orifice and restrictor combination you use. You would spend $8,000 or more to buy a compressor with those specifications. It's more than I want to spend for something I use only occasionally.
The solution was to rent a trailer-mounted, diesel-driven compressor like the kind used to power jackhammers. The local United Rentals let me have one for $200/day or $600/week. All I had to do was cobble together the proper connections. Piece of cake.
Blasting with sodium bicarbonate (NaHCO
3) is like blasting with any other type of media, but it has special properties that make it desirable. It won't scratch hard metals like chrome and it usually won't damage rubber or glass. But compared to sand and other more common types of media it is somewhat pricey. A 50 lb bag of the formula I like costs $80 by the time you factor in shipping--and you can go through a couple of pounds per minute! Dave's soda blaster can be used with water jets if desired, but I am electing to go with just soda for the time being.
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The Alfatross mounted on the rotisserie BEFORE soda blasting. Note the patches
of paint and primer still left on the surface after chemical stripping. |
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At the risk of spoiling the suspense, here's the Alfatross after just 3.1hrs of
actual compressor time (spread out over 8 hrs of fiddling around and setting up). |
I was doing a lot of new things at the same time, experimenting to find out which soda formula worked the best, which pressure I should use, whether I should use a restrictor to reduce the amount of media being used, how to turn the Alfatross on the rotisserie safely, etc., so I didn't spend that much time actually blasting. Still, I used the 150 lbs of media I had on hand in only 3.1 hours of actually compressor time.
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The rented diesel-powered 160+ CFM compressor. The perfect solution to high-volume,
low pressure requirements. It delivers air at 140 PSI but the regulator on the
soda blaster reduced the pressure to 87 PSI. |
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The soda blaster and some of the paraphernalia needed. Clean up was much
easier than I expected. |
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Rotating the Alfatross on its rotisserie enables me to get to all the difficult
places. Note the difference between the places that have been blasted and
those on the roof that have not. |
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The bottom of the chassis is going to take a lot of time and perhaps a different
blast media. I'll experiment with the three types offered by Eastwood Automotive
to see which ones work the best.
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| Yes, it is a dusty job best done on a day with a gentle breeze! |
Thanks!
I want to compliment the Car Museum guys, particularly Rich Heinrich and Jean-Marc Freslon for coming up with the unique solution to how to mount an Alfa 1900 Zagato on a rotisserie. They saved Dave and I an enormous amount of time and effort. If you guys are reading this, how about commenting on how you came up with the idea?
From the time spent so far soda blasting the Alfatross, I can tell that I am going to need a lot more soda, so I've ordered another 7 bags (350 lbs). In order to maximize efficiency I'm going to wait until that order arrives before renting the compressor again. In the meantime I'll get back to the numerous other sub-assemblies needing attention.
