Yeah I know, but the parts on the floor I would be sandblasting are rewelded sometime in the past and don't have original undercoat on.Ride_on wrote:Sandblasting ain't much good for undeseal anyway, maybe just the very thin stuff above the tank in a 360. Underseal needs to be mostly peeled + scraped with a heat gun at near burning point. The thick bits will come away very nicely in one piece but the thinner stuff has to be scraped with a thinish wood chisel. Wire brush I find is the best overall, and wire brush on angle grinder very good (but removes skin very quickly and the finger guard don't work), but only works on easy access areas.Fuse wrote:Very good results for mechanical cleaning! May I ask what did you use? Wire brush disc on an angle grinder or what? I'll have some similiar stuff to do on some sections on the floor and the compressor isn't large enough for sandblasting so I'll have to do with mechanical cleaning for now.
Anyway about sandblasting, its more about storage, no mains compressor will ever supply real time air at 10cfm @ 100psi, but if you use a really small compressor it will die quickly. I used a 3.4cfm compressor to sandblast with, it worked fine until it died, even though it was rated for continuous operation (not oil free bollocks), it was about 20 years old! Now I have a 10cfm (consumption)/150psi compressor with about 100l storage. Air flow restriction is also important, and most small regulators will give you 70psi after setting them to 100psi, when you put 10cfm/100psi through them, you also goto watch union+quick fit restrictions. The standard PCL connectors will drop about 5-10psi at 10cfm, euro ones are much better.
It's not all about the supply but most compressors which have somewhat sensible supply to even try to sandblast large areas of a car body usually have enough storage also. Most people I know who have sandblasted their cars have told me it's pain in the ass to even try to do the job with a compressor with less than 600l/min (~20cfm) of supply because you'll have to pause too often when you run out of air.
Some people have built their own sandblasting equipment by using old train engine blocks and couple 5.5kW electrical motors. Cheap way if you have time to rig up things.
Supply with those have been around 1500l/min (~50cfm) so not running out of air too quickly. 
High pressure steam wash is also nice for undercoat removing as it doesn't warp the metal but removes pretty much everything else. These industrial companies don't charge too much money for it either. Or dry ice blasting but that's quite expensive usually..
(Love those 2 shots under the car, before and after)
