DIY Shotblasting

[merckx]

My brother has a shotblasting cabinet like the one in the picture below, I had a go cleaning up a brake caliper from my van but it's nowhere near as effective as I was expecting.

 

The compresser I'm using is 50 litres, 3hp . I know it's not adequate as the pressure drops very quickly and the pump can't keep up. But even when it's running at 100 psi for a few seconds with a small 4mm nozzle on the gun it's still poor at removing paint and corrosion.

 

I've been using 60/80 grit aluminium oxide which is quite fine but it's working better than a coarse aqua grit or supa grit which both require a larger nozzle which obviously slows down the speed of the grit leaving the gun.

 

 

http://www.ccw-tools.com/uploads/images_products/2754.jpg

 

Has anyone had any experience using a shotblasting pot that you put the grit into and pressurise with the compressor keeping it topped up, like the one in the picture below?

 

http://img.tradeindia.com/tradeleads/2/org_1894795.jpg

[Tricky-Ricky]

First off your average piston/tank type compressor is nowhere near powerful enough for sensible sand/shot blasting, unless its a big bugger, with a big tank IE 3-500lts.

I used to run a 5hp hydrovane in my workshop and that was only just enough.

 

With the setup you are using, its only ever going to be slow and not particularly efficient, you could try a lighter blasting material which may help.

 

The secret is providing enough CFM, the pot is pretty much immaterial, a 3-5mm nozzle will require at least 300CFM to work well, and ideal pressures from 60-120psi.

 

When doing outside work i used a large road drill compressor, so you get the idea of just how much air you need to shift.

[Chris Wilson]

I am well into this, been blasting stuff for years. My current machine is a suction cabinet big enough to take truck wheels or engine blocks, fed off a 32 CFM petrol engined compressor. It's slow and patience is needed. You REALLY need a pressure type cabinet with the pressure pot built in below it. I have bid on one on Ebay but am not hopeful of getting it as they fetch very good money. If you don't have 3 phase and a BIG 3 phase compressor to run one you need, as Tricky says, a diesel rod drill type compressor. I am fortunate in having a full size blast room 1/2 mile up the road big enough for an artic trailer to go in, at pretty much my disposal, as the gent we bought the house off uses it for prepping the agricultural machinery he makes. Now that does have a SERIOUSLY big three phase compressor bank Unless you are doing it commercially or need on site instant access to blasting it's going to be a lot cheaper to farm stuff out. It took me 15 minutes to properly blast a Mazda MX-5 cam cover today, by way of example. A pressure pot type cabiet would take maybe 5 minutes.

[merckx]

Thanks for the replies, some good points made.

 

You're both right in saying that the compressor I've got isn't much good.

 

I'll look for a bigger compressor and a pressure pot as they do require less air.

 

I've been looking at the hydrovane compressors on ebay but they aren't cheap, I'll keep looking to see if I can find a bargain.

[colsoop]

Have you thought about vibratory polishing / cleaning as an option ?

[merckx]

Have you thought about vibratory polishing / cleaning as an option ?

I've never heard of it before but I can visualise what it might be.

 

Ill have a look on Google.

[cheekymonkey]

Want to borrow mine?

[merckx]

Want to borrow mine?

Impressive, must've cost a bit.

[Chris Wilson]

Want to borrow mine?

 

Is that a pressure pot fed cabinet, or suction? It looks a nice custom build, of some quality

[Tricky-Ricky]

Here is an example of the results when using a proper compressor;) brings back memories, not all good.

 

[Youtube][/Youtube]

[Chris Wilson]

This is the modern way, I have seen some stunning results from manky old shells prepped by these people. The videos are fascinating, the place is like something from a horror film.

 

http://www.surfaceprocessing.co.uk/for-cars.html

[Tricky-Ricky]

Looks impressive, however presumably they cater for shells that are in need of more extensive work IE corroded panels cut out and welded, so i wonder if either stopping the process after stripping would have any detrimental effects?

 

Or is it worth doing the whole process to primmer and then cut out the corroded parts and weld, and finish using your own primmer without the zinc process.

 

IMO there is something to be said for the old methods as it will reveal where there is thin metal that needs replacing as well as the really bad bits, rather than cover it up with the coating and primer.

[Chris Wilson]

They dip it in a microns thick primer that can be welded through. If you took it away bare it would be red rusty as soon as it saw ANY damp or rain. They used to send them out bare but the deficiencies soon became apparent, so they started the etch primer option. Cost is about £1700 for an escort sized car, to strip, process and prime. It de rusts and cleans INSIDE box sections and seams, which is the real bonus.

[Tricky-Ricky]

I have done numerous shells and parts both inside and outside, and if treated sensibly, there have never been any problems, in fact i often see a restoration that i blasted 13 years ago, and it has no sign of any corrosion.

In fact i think the older metals had far better corrosion resistance,

For instance i once blasted an Hispano-Suiza chassis, and due to unforeseen circumstances it was untreated for two weeks and was only just starting to show the very first sign of corrosion.

 

I also have a spark plug from a 1919 Harley Davidson and it has no treatment and it simply refuses to rust.

[Guest SM SXOC]

They dip it in a microns thick primer that can be welded through. If you took it away bare it would be red rusty as soon as it saw ANY damp or rain. They used to send them out bare but the deficiencies soon became apparent, so they started the etch primer option. Cost is about £1700 for an escort sized car, to strip, process and prime. It de rusts and cleans INSIDE box sections and seams, which is the real bonus.

 

Hi Chris Hope you are well.

 

Sandblasting my shell (the vid posted above) was £150 and didnt have to transport the shell more than 15 feet

 

Although there is sand everywhere now, still trying to get a 30M radius clear of sand outside, and the shell clean enough to paint... the sand gets everywhere! Is a cheap and easy way to get to bare metal. Although there is a danger to panels if the operator isnt careful. I kept away from the roof as that is the only visible panel - rear 1/4ers having fibreglass arches.

 

 

... sorry to butt in here, just vid was linked to from here and was noisy

 

Kev

 

 

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