These compressors sufficient for blasting?

[Tehrawk]

This site seems to be the most knowledgeable on the subject. I'm sorry that its yet again a question on a subject that has been asked a million times all ready. But I really need advice before I throw down all this money.

I am restoring a Beetle chassis for a buggy build, and will be chopping the body for a separate Volksrod build sometime down the line. I have been trying to research compressors suitable for soda blasting, and possibly walnut blasting. It depends on what, not too abrasive, medium I can readily find. The compressor will also be used with various air tools, and for HVLP spraying.

The two compressors I have found that are just about in my price range are
http://www.donedeal.ie/for-sale/tools/2360606
and
http://www.jebbtools.ie/.270-Ltr-Compressor-SIP-Airmate-B2800-270_05247.htm

The blasting pot I was looking at is this one. With the soda blasting adapter kit.
http://www.donedeal.ie/for-sale/tools/1506041

Which of these compressors would be the best option. SIP obviously has the brand recognition, and possibly reliability and build quality as a result. The Rand one I'm not sure about. As its obviously not Ingersoll Rand, and probably just using the name to sucker in some sales.

Would that blasting pot be up to the job? Would it be a good fit with either of those compressors, or is there a better option out there.

 

[Shox Dr]

The first compressor is better than the 2nd. However it is really at the low end for blasting, it will work, but it will be working all the time you are blasting

The pot looks like a Machinemart/Northern Tools etc etc, variant. So will be good to go.

 

[stormin]

As shox I would go with the first compressor purely on air volume than qulaity. Vast amounts of air volume are what you need for blasting.

If you are thinking about blasting the full car with Soda and the small pot, be prepared to spend a very, very long part of your life on the job. Think trying to colour all panels with a felt tip pen, that's about as quick as you'll go.

Using Soda will make it even slower, I would suggest a reasonably abrasive media such a Jblast supafine. Jblast will at least get you to bare metal a lot quicker than soda.

 

[tigler]

Out of the 2 go for the first one but as per the comments already it will be marginal at best.
Some years ago a guy in business I knew wanted to set up a blasting rig and asked me to find a suitable compressor as cheap as possible. Now I know that 100 CFM is the minimum capacity required for even a medium sized commercial blast cab that needs to run all day without stopping to wait for a compressor to keep up, but that was out of his budget. I managed to find a nice Atlas Copco, V twin, 15 HP, which I think was a 25 or 30 CFM unit, on a 400 LTR receiver for only slightly more than his budget that needed some TLC. He just would not stretch to a screw unit.
Stripped it all down, cleaned it up, remounted on the receiver, found and installed a contactor, changed the oil and filter, wired and plumbed it in, job done !
That was until he called me, whining about the operator needing to stop every 10 mins for pressure to build up ! I had warned him but he chose to ignore me
Then a bit later, another call, he'd had his electricity bill and almost fainted when he saw how much the compressor had increased it by ! What a jerk !! I had mentioned the motor was rated at 12KW, what did he expect !!
Blasting is an expensive game, basically it's just a big air leak !

 

[Dave H2]

Why Soda and Walnut, as neither will have much effect on rust and that chassis will be more rust than paint.

BTW you will not damage the chassis with grit - if you get holes then you had rust through anyway.

 

[Tehrawk]

@ Shox Dr: Sounds good to me. It is not a huge job ahead of me, I don't mind stopping and starting. As long as the stopping doesn't exceed the starting.

@ stormin: OK, definitely reconsidering my decision. I had a general idea of what effects the different mediums had, but I didn't fully consider the effects a smaller pot would have on them. That Supafine stuff definitely looks ideal.

@ tigler: The electricity bill will be the scary part all right. I haven't done the maths yet, but I know it wont be pleasant. Perhaps now is a good time to get started on those wind generators I've been meaning to build.

@ Dave H2: True enough, perhaps I will hit the chassis with abrasive medium. And see where I should go from there with regards the body work.

Thank you all for your advice. There are so many factors with regards to compressors and blasting pots, that it is hard to get your head around how they all interact. I definitely feel more confident in what I need now though.

 

[tigler]

There is another issue using an undersize compressor that is running continuously, duty cycle. Basically, non industrial compressors are not continuously rated so their life will be reduced if used as such. You would need to rest the compressor at least every 30 mins for 10 mins or more so it can cool down.

 

[Tehrawk]

There is another issue using an undersize compressor that is running continuously, duty cycle. Basically, non industrial compressors are not continuously rated so their life will be reduced if used as such. You would need to rest the compressor at least every 30 mins for 10 mins or more so it can cool down.

Ah yes, something that I am used to with my portable airbrush compressor. Just another layer of irritating.

It is proving quite difficult finding a supplier of medium in Ireland. So far the best place I have found is Campbell Machinery in Bray.
http://www.campbellmachinery.ie/pages/blast_medias_abrasives.htm
They seem to have a good selection. From what I can tell, their product Saftimetal would be a good choice for my chassis. Should be somewhat re usable.
http://www.guysonlib.co.uk/lib/consumables/guyson_saftimetal_datasheet.pdf

 

[eddie49]

Since it sounds possible that you may have a few Beetle engines lying around: you can use 2 of the 4 cylinders as a handy 60 CFM compressor, powered by the remaining 2 cylinders. Then instead of electricity, you just have to worry about the price of petrol...! Try searching the Web for "Volks-air" and "Dunn-Right".

 

[FranV8]

That is very cool! I don't have that much need for air, but for some reason I now really want one!

Anyone not wanting to bother Googl-izing this - http://www.dunnrightinc.com/

 

[Tehrawk]

Since it sounds possible that you may have a few Beetle engines lying around: you can use 2 of the 4 cylinders as a handy 60 CFM compressor, powered by the remaining 2 cylinders. Then instead of electricity, you just have to worry about the price of petrol...! Try searching the Web for "Volks-air" and "Dunn-Right".

Wow that is impressive. Reminds me of the compressors build from two engines on a few episodes of Scrapheap Challenge. I only have the one car for now, and it doesn't have a dual port engine. But that is a seriously elegant piece of engineering.

 

[tigler]

There's a youtube vid of one of those. It's been done for years in the USA. Even better would be to use a Porsche flat 6, or even a V8 something or other !!

 

[stormin]

I believe the old grey fergie's used to come with a tyre inlfator that relied on removing one of the spark plugs in the engine and using the air output.

 

[Engineer]

Unless you are going into the restoration business, then wouldnt it be a lot less costly and much less hassle to simply pay someone to do the blasting work required professionally?

 

[FranV8]

This demands the use of the Corvair engine! Didn't Tartra do a flat eight air cooled?

 

[tigler]

I thought it was an aircooled V8 ? It would be epic with a Porsche 917/30 flat 12 !

 

[Tehrawk]

Unless you are going into the restoration business, then wouldnt it be a lot less costly and much less hassle to simply pay someone to do the blasting work required professionally?

I wouldn't be too sure of that. When you factor in the cost of blasting two chassis, and one body. Then having to bring them to some other place to have them painted. Then the cost of having someone transport everything back and forth, because I really don't have the means to do that myself. Plus the second build wont be for a long while, so we are talking about separate trips per build.

Even if it does cost me a bit more to do it myself. The fact that all the equipment is there, logistically makes it a lot simpler. It will be there for any future jobs that crop up and I will have learned a new skill... Granted its one that an untrained chimp could do, but still.

 

[FranV8]

I thought it was an aircooled V8 ? It would be epic with a Porsche 917/30 flat 12 !

I thought it was - but then had an inkling that it wasn't. Wikipedia was my friend on this one!

I'd love to know what's special about the camshaft to make it work as a comp. Even the big ones we have at work (660 cfm each) just use a sprung loaded diaghragm valve on inlet/exhaust - but admittedly that wouldn't be an easy conversion to do for the outlet valve - or thinking about it, perhaps it would? (one way valve after the exhaust port) - as I was thinking compression volume. (Change the inlet valve spring to a weaker one so that vacuum alone opens it)

Of course that opens up the possibility of using any old 4 cylinder engine? (maybe add some flywheel weight)

Apologies for the OP about flying off on a tangent on this!

Back to the original idea, would it be worth looking for a trailer diesel compressor on the 'bay or otherwise, may be a cost effective way to buy lots of capacity cheap and without the infrastructure limitations of how much electrical power you have available (or are you three phase?)

 

[stormin]

I'd love to know what's special about the camshaft to make it work as a comp. Even the big ones we have at work (660 cfm each) just use a sprung loaded diaghragm valve on inlet/exhaust - but admittedly that wouldn't be an easy conversion to do for the outlet valve - or thinking about it, perhaps it would? (one way valve after the exhaust port) - as I was thinking compression volume. (Change the inlet valve spring to a weaker one so that vacuum alone opens it)

I would guess that the cam is changed to have double lobes on the compressor cylinders so these effectively act as two stroke cylinders. No point compressing thin air on one revolution and waiting for the fuel and spark less power stroke to end until you can get your air out of the cylinder. Double lobes would effectively double the air output of the compressor side.

Agreed though if you want to do serious blasting you need a diesel road compressor, they can be cheap off Ebay but can also be a major liability if they've not been looked after. It's good to have all the kit to blast yourself so you can do what you want when it suits you. Big downsides are the noise in residential areas and the mess from all the grit. Plus chances are you haven't got a space to do it inside so you are at the mercy of the good old british weather.

 

[Tehrawk]

Apologies for the OP about flying off on a tangent on this!

Haha no worries, its interesting stuff.

Back to the original idea, would it be worth looking for a trailer diesel compressor on the 'bay or otherwise, may be a cost effective way to buy lots of capacity cheap and without the infrastructure limitations of how much electrical power you have available (or are you three phase?)

It will have to be single phase, the cost of going three phase would be too much right now. €800 is really pushing my limit, I haven't seen a half decent trailer compressor go for less than a grand and a half over here. I have a number for a guy who reconditions compressors. Ill give him a shout, if he has nothing better to offer than that "Rand", then I will just go with that. Should be OK for my needs.

@ stormin: I'm lucky enough as I live in the country. Plenty of farms nearby, so noise pollution wont be an issue I have a big enough shed also, which used to be a barn. I haven't measured it but I should be able to just about fit the body through the double doors. Everything else on a Beetle breaks down so much you could fit it through a single door.