Sandblasting, and transport
Discussion
In a way I'm glad that my project was initially too far gone to think about sending off for dipping or blasting - it would have come back in some small boxes. By the time I'd got it strong enough (in my opinion) to put it on a rotisserie the majority of the work is done and I've repaired box sections and painted inside them before closing them up, so I don't want it taking off again with an acid dip.
Rotisseries are good - I wish I'd thought of using a couple of engine stands, though I thought they (stands) were quite expensive when I was looking for one. Mine was a home-made one, someone had made it for an Escort, done the job then sold it on, I think I paid around £70 for it. I had to modify the mountings to fit my car, it has no wheels (though I don't care about that) and it doesn't have any easy to lock it in anything other than two positions, but it's been well worth the money. Chap I know restoring a Firenza made one out of some strong wood.
Rotisseries are good - I wish I'd thought of using a couple of engine stands, though I thought they (stands) were quite expensive when I was looking for one. Mine was a home-made one, someone had made it for an Escort, done the job then sold it on, I think I paid around £70 for it. I had to modify the mountings to fit my car, it has no wheels (though I don't care about that) and it doesn't have any easy to lock it in anything other than two positions, but it's been well worth the money. Chap I know restoring a Firenza made one out of some strong wood.
Minor surface rust and Underseal in awkward places was one the main drivers for me to finally get it done, I'd probably have taken a finger off with the grinder eventually!.
And yes thinking about it, if I had done it before starting it wouldn't have the strength to go in the Frame either.
And yes thinking about it, if I had done it before starting it wouldn't have the strength to go in the Frame either.
DeanR32 said:
I reckon I could get a couple of welders I know to make me a rotisserie. I think they'd love to give it a go.
When making a rotisserie keep the CoG as low as possible and the rotisserie track as wide as possible. The car and rotisserie need to be very stable. A few folk have made the mistake of not understanding CoG. The car rotates to certain a point, CoG takes over and the car will force its own very quick rotation...and you don't want to be holding on when this happens.It's actually quite tricky to get the geometry right on the Rotisserie. In my case I needed to keep the rotation point low enough so the side of the car didn't hit the garage roof or floor, so I only had about 50mm to play with. Then judging the centre of Gravity is interesting too, this will vary as you take bits off or add bits on.
In the end I got it about right and on mine I can just about rotate it on my own and reach around to put a locking pin in as I hold it steady, but I can't quite let it go fully upside down as the roof will hit the floor.
All good fun!.
Putting castors on allows me to roll it around in the garage too.
In the end I got it about right and on mine I can just about rotate it on my own and reach around to put a locking pin in as I hold it steady, but I can't quite let it go fully upside down as the roof will hit the floor.
All good fun!. Putting castors on allows me to roll it around in the garage too.
500 is way too cheap for blasting a car. its a days work at least on a smaller vehicle - say a mini - if you dont want any distortion, and a competent chap will be 100 - 125 p/hr.
You could always do it yourself - a full size recon pot is around £1500, and a 250 cfm compressor will be 125-150 pr/week hired. Then you have materials on top. There is not as much mess as you would imagine. I did mine at 35psi, took me 2 days, but no distortion - which in a roof or quarter panel is a huge amount work to rectify, if not impossible when it has been hit at high pressure.
You could always do it yourself - a full size recon pot is around £1500, and a 250 cfm compressor will be 125-150 pr/week hired. Then you have materials on top. There is not as much mess as you would imagine. I did mine at 35psi, took me 2 days, but no distortion - which in a roof or quarter panel is a huge amount work to rectify, if not impossible when it has been hit at high pressure.
Thanks for that mate.
In my line of work I could borrow the father in laws two tool compressor (100 psi) and the gas board have all the blasting equipment. The problem is somewhere to do it, and having the knowledge to do it.
I'll see if I can find somewhere to do it and take it from there
In my line of work I could borrow the father in laws two tool compressor (100 psi) and the gas board have all the blasting equipment. The problem is somewhere to do it, and having the knowledge to do it.
I'll see if I can find somewhere to do it and take it from there
Every stripping system has its pros n cons.
The biggest problem with sandblasting is it destroys flat panels, I would imagine the Alfa in the pics is rippled to buggery and will need the entire car covering with filler and sanding down to make it right again. Red oxide primer doesn't adhere to panels very well either - that's what Etch primer is for.
Sand won't touch seamsealer or underseal (anti-stonechip) coatings, it just bounces off - think about it, anti-stonechip coatings are rubberised, flexible and designed to withstand exactly that kind of abuse.
It also gets into all the cavities making paint spraying a nightmare, you might think you've blown it all out, but as soon as you start painting the odd bit comes out here and there and ruins the finish.
If the surface is pitted the blast media doesn't get into the centre of the pits as they are so small, you are often left with little brown dots which is of course the rust still there.
Chemical dipping is much more effective, cleaner and gets into rusty seams where other methods can't, the following fluids flush out and neutralise it and then re-coat it with chemicals which prevent corrosion from reoccuring.
If all the horror stories were actually true about chemical strip plants they wouldn't be in business.
Soda is the best media for blasting panels with as it doesn't cause distortion and it covers the panels with a temporary coat which doesn't rust (this needs removing before painting).
I was once at a classic car show where a guy rocked up with his demonstrator for Soda blasting, it was a bare shell which he'd towed on an open trailer through the rain that morning, it had no flash rust on it whatsoever.
Sand is cheap, but the labour afterwards making it right is expensive so it eventually becomes an a par with chemical dip and Soda.
The biggest problem with sandblasting is it destroys flat panels, I would imagine the Alfa in the pics is rippled to buggery and will need the entire car covering with filler and sanding down to make it right again. Red oxide primer doesn't adhere to panels very well either - that's what Etch primer is for.
Sand won't touch seamsealer or underseal (anti-stonechip) coatings, it just bounces off - think about it, anti-stonechip coatings are rubberised, flexible and designed to withstand exactly that kind of abuse.
It also gets into all the cavities making paint spraying a nightmare, you might think you've blown it all out, but as soon as you start painting the odd bit comes out here and there and ruins the finish.
If the surface is pitted the blast media doesn't get into the centre of the pits as they are so small, you are often left with little brown dots which is of course the rust still there.
Chemical dipping is much more effective, cleaner and gets into rusty seams where other methods can't, the following fluids flush out and neutralise it and then re-coat it with chemicals which prevent corrosion from reoccuring.
If all the horror stories were actually true about chemical strip plants they wouldn't be in business.
Soda is the best media for blasting panels with as it doesn't cause distortion and it covers the panels with a temporary coat which doesn't rust (this needs removing before painting).
I was once at a classic car show where a guy rocked up with his demonstrator for Soda blasting, it was a bare shell which he'd towed on an open trailer through the rain that morning, it had no flash rust on it whatsoever.
Sand is cheap, but the labour afterwards making it right is expensive so it eventually becomes an a par with chemical dip and Soda.
Edited by 226bhp on Tuesday 20th May 07:34
Yes, the sand has rippled some panels, I'm a bit dischuffed, but there you go!, you make these decisions you have to live with them. 
The problem comes when you ask too much of sand blasting, I did want the underseal taking off in places and it's those areas which got damaged. It's going to cost me more in panels than I expected, but at least I'm not patching old ones which may have been a bit too far gone to begin with.
The problem comes when you ask too much of sand blasting, I did want the underseal taking off in places and it's those areas which got damaged. It's going to cost me more in panels than I expected, but at least I'm not patching old ones which may have been a bit too far gone to begin with.
velocemitch said:
Yes, the sand has rippled some panels, I'm a bit dischuffed, but there you go!, you make these decisions you have to live with them.
The problem comes when you ask too much of sand blasting, I did want the underseal taking off in places and it's those areas which got damaged. It's going to cost me more in panels than I expected, but at least I'm not patching old ones which may have been a bit too far gone to begin with.
Out of interest, do you know how it buckles thin panels? The problem comes when you ask too much of sand blasting, I did want the underseal taking off in places and it's those areas which got damaged. It's going to cost me more in panels than I expected, but at least I'm not patching old ones which may have been a bit too far gone to begin with.
When you've blown/vaccuumed out as much as poss from the cavities (and just before it goes for painting) blow paint into there (we used a tube with holes in it like a Dinitrol applicator) to seal any dust/sand so it couldn't get out during the painting process.
Noted about the sand, I'm vacuum it out regularly as it drops out of the box sections when the car is turned.
My understanding of the distortion is that it is due to the impact of the blast medium at high pressures deflecting the thin steel beyond its elastic limit.
I discussed this with blaster and he to be fair he did warn me that he would need to hit it hard to shift the under seal. He explained it was a risk and I suppose I accepted that risk. Tops of the front wings are where it's occurred I'm not sure I can do much with one of them, the other I might, but it's patched anyway and one area is so thin, it might be beyond hope. I'm still deciding if I'm replacing or repairing them.
Paint isn't just red oxide, it's a decent paint, colour chosen to contrast with the grey steel and the white primer I will be using.
My understanding of the distortion is that it is due to the impact of the blast medium at high pressures deflecting the thin steel beyond its elastic limit.
I discussed this with blaster and he to be fair he did warn me that he would need to hit it hard to shift the under seal. He explained it was a risk and I suppose I accepted that risk. Tops of the front wings are where it's occurred I'm not sure I can do much with one of them, the other I might, but it's patched anyway and one area is so thin, it might be beyond hope. I'm still deciding if I'm replacing or repairing them.
Paint isn't just red oxide, it's a decent paint, colour chosen to contrast with the grey steel and the white primer I will be using.
Many people think it's the high pressure, but it isn't, It's actually the heat of the sand hitting the panel. If it was pressure it would push the panel the other way, but if you use it to hit isolated spots here and there you notice it buckles up towards you.
Take a coin from your pocket and do a scratch test on your primer, it will break away from the metal.
If you do that with good quality etch you can actually split the coat, part will peel away, part will stay attached to the metal. It isn't just a coating, it's chemically bonded.
Take a coin from your pocket and do a scratch test on your primer, it will break away from the metal.
If you do that with good quality etch you can actually split the coat, part will peel away, part will stay attached to the metal. It isn't just a coating, it's chemically bonded.
Thinking about yes, you are right he mentioned it was the heat. Mind you the worse point on my wing is bent upward and I would have thought the sand would have been hitting it from underneath with more force than above. Either way it's bent!, I tried to heat it in the hope it would shrink back on cooling, but it didn't. I'm not sure if there are any shrinking techniques which can be used with any affect. So any fix will mean pushing it back into a dent rather than a bulge and filling it, not ideal.
Will have a look at the paint, I have taken some off though and it does take some shifting, so I don't think it's rubbish stuff. I don't intend it to be used under areas where the final coat has to be good quality.
Will have a look at the paint, I have taken some off though and it does take some shifting, so I don't think it's rubbish stuff. I don't intend it to be used under areas where the final coat has to be good quality.
Few things need to be cleared up here!!!!!!
Sand blasting is not legal now, so very few people do it - silica.
It is neither the pressure or heat that causes distortion, it is the planishing effect of an incorrect blast media expanding the surface area as you would to make a bowl out of a flat sheet with a ball pein hammer. A plastic media designed to clean paint from steel without marking the surface will make a bowl out of a piece of aluminium.
Soda is good for paintwork, and is cheaper than plastic media for the same job, but it doesn't dig out rust. Bengal Bay garnet is the thing for car bodywork that is corroded,but needs good equipment and an intelligent operator hence price.
Dipping has pitfalls. it leaves ALL the hidden internal surfaces and spot welded flanges absolutely naked and roar even if the neutralising solution has done its job.Blasting leaves all those areas alone. If a car is dipped you really do have to then use an immersion priming process to repaint all the internals. that generally near doubles the cost.
Glass beed is good for fine finishing.
Vapour blasting cleans castings perfectly (carbs etc)without dangerous residue.
I use five suppliers in order to cover those bases properly and get no scares!!!
Sand blasting is not legal now, so very few people do it - silica.
It is neither the pressure or heat that causes distortion, it is the planishing effect of an incorrect blast media expanding the surface area as you would to make a bowl out of a flat sheet with a ball pein hammer. A plastic media designed to clean paint from steel without marking the surface will make a bowl out of a piece of aluminium.
Soda is good for paintwork, and is cheaper than plastic media for the same job, but it doesn't dig out rust. Bengal Bay garnet is the thing for car bodywork that is corroded,but needs good equipment and an intelligent operator hence price.
Dipping has pitfalls. it leaves ALL the hidden internal surfaces and spot welded flanges absolutely naked and roar even if the neutralising solution has done its job.Blasting leaves all those areas alone. If a car is dipped you really do have to then use an immersion priming process to repaint all the internals. that generally near doubles the cost.
Glass beed is good for fine finishing.
Vapour blasting cleans castings perfectly (carbs etc)without dangerous residue.
I use five suppliers in order to cover those bases properly and get no scares!!!
Sandblasting is a very misleading name, Last thing anyone should do is use sand as it IS a cause of Silicosis(V. Bad), Crushed glass I find is grand,(It looks like beech sand, not sharp chunks of broken bottles), If there's access to a big compressor, at least a 200Litre a decent blaster isn't expensive. Then a big shed and a roll of polythene, Make an upside down tent with the car in the middle and your away! a good respirator and face mask too, Then clean and etch or epoxy prime as soon as, Then the joy of standing back and let it sink in, Can expose allsorts of horrors or not, fun if it isn't your car
I would concur with what is said above.I have my own hodge clemco pot. I blasted my mk1 golf but spent days with a heat gun scraping all the underseal off as I was not going above 35psi for risk of distortion. I think the trouble starts when an average blaster wants to get on with the job and blasts it at too high pressure. If you are prepared too pay and tell them what you want I think blasting is the way to go.
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