Help with buying a diesel road compressor for blasting.

[conor1n]

Evening all...and happy new year!

Following on from this great compressor/blasting capacity thread, I said I would start a new thread to ask for help buying a suitable road compressor. Hopefully a new thread will be useful in search/other users down the road.

My current chinese pot + piston compressor has worked fine for a few spots on my SL, but for my upcoming business it just won't be enough.. and I am likely going to kill as I proceed to reach it's limit.. changing it from a useful workshop compressor to a piece of worthless junk!

So, with that in mind - I need to buy a "bigger boat"

I have decided a road compressor will suit me better than a stationary screw compressor - as it will open up the possibility of going out on the road and blasting large items for people on their site. e.g. masonry, plant machinery, vehicles etc, if I need to find extra work.

That said, my main objective right now is to blast chassis etc of 4x4 and cars kind of thing. I am concerned about using a compressor too big for a small nozzle.

I have found a seller relatively local to me, who has 3 for sale. He used to blast, but has a mechanics business now. Alternatively, I see there is no end to the supply of compressors for sale in the UK - where I am happy to purchase from if it makes sense.

He has 2x ~100 CFM units (€2000) and 1 x ~300 CFM unit with a 6 cylinder perkins engine (€5000)

I have the following questions right now, if anybody has any idea:

1. Where do I start, it seems to be very difficult to find information, or any kind of "buyers guide" for road compressors.. especially used ones.
2. Is there such thing as too much flow (CFM).. I mean, the 300 CFM sounds like a great idea but what if I use a smaller blast pot with smaller plumbing?
3. Are there any engine to stay away from? My understanding is that Perkins and Yanmar are most common, and should be fine.
4. What are the concerns and considerations when buying used? What parts need to be inspected?
5. At what point is a compressor a write off and passed it's useful life?
6. How many hours is considered reasonable?

Thanks a lot in advance.

 

[brightspark]

100 cfm is the bare minimum using a 6.0mm nozzle not much use than doing car wheels and probably a car chassis i have one anything more than that bigger is better along with the pot otherwise a waste of time. a good comp will be a lot of money . high hours comps may not be reliable and cost you a lot of downtime if they give bother

 

[brightspark]

most portable blasting firms buy the pot and hire the comp and charge it to the jobs accordingly its tax deductible and reliable with no maintenance costs

 

[conor1n]

100 cfm is the bare minimum using a 6.0mm nozzle not much use than doing car wheels and probably a car chassis i have one anything more than that bigger is better along with the pot otherwise a waste of time. a good comp will be a lot of money . high hours comps may not be reliable and cost you a lot of downtime if they give bother

Ok good to know.

I think 100CFM and a 6mm nozzle would probably do me OK, to get the business underway - potentially.

When I talk about cars and chassis. I just mean subframes, ladder frames and underside. Not whole vehicles, if that makes a different.

But I think as much CFM as I can get my hands on is the thing to do.... because I really do like the idea of being able to go out and do big machinery etc..

 

[conor1n]

most portable blasting firms buy the pot and hire the comp and charge it to the jobs accordingly its tax deductible and reliable with no maintenance costs

Fair enough .. but I need it mainly for blasting chassis every now and then. It would be much easier to have it there.

 

[Erie Fred]

There are charts everywhere, nozzle size air consumption, amount of abrasive used etc.

https://www.raptorblastingsolutions.com/wp-content/uploads/2016/03/metric-compressor-air-abrasive-consumption.jpg

 

[Roger440]

Following, as will probably need to buy one also. Though it will see rather less use than yours i suspect, so will go for something more budget.

 

[Erie Fred]

Local classified paper just listed a IR portable 375 cfm.....with a screaming Detroit Diesel on it.
Must be at least 35 years old with that engine.....from Amish country.
$2500 cash

 

[Turbo]

They used to be a lot cheaper but with the contractors now using them for umbilical slurry spreading the price of second hand ones has went up considerably.

I'm keeping an eye out for a cheap one with a knackered engine but no luck so far. I want to hook it up to our tractor pto to use for blasting.

 

[lincoln2013]

Don’t forget to factor in a bit of reserve air for your air fed mask and for example a 6 mm nozzle will increase in size as it wears. That said if you buy one of the 100cfm compressors and you find it isn’t big enough it will always sell again.

 

[brightspark]

Don’t forget to factor in a bit of reserve air for your air fed mask and for example a 6 mm nozzle will increase in size as it wears. That said if you buy one of the 100cfm compressors and you find it isn’t big enough it will always sell again.

a 100 will run the 6,0mm jet at 90psi all day long as well as the air fed helmet

 

[conor1n]

Afternoon all,

Thanks for the continued insight into this. I now find myself at a bit of a crossroads and need to decide on a path.

My current thoughts are:

If I am buying a road compressor I probably want it big enough to be able to competitively blast agri/plant machinery and masonry. Not as fast as the biggest guys, but I don't want to be super slow. I see that @brightspark has says 100 is fine. Which is cool.. I wonder what size nozzle? According to some research, that's approximately a #4 - 6.35mm nozzle. (93CFM @ 90PSI) which should cover the air mask too.

Is #4 enough to commercially blast at a reasonably competitive rate?

My feeling is that if I am going to blast mobile, I want the bigger ~300CFM compressor on offer which should allow for a #7 nozzle - 7/16"/11.11mm.

If I am settling for a 100CFM compressor due to budget - I might be better off buying a 3 Phase screw compressor (which would be cheaper, possibly) for the workshop and save up to buy a larger road compressor...... that makes sense right?

Now, here is the thing... which I think is important. If I do get the screw compressor and the underbody rust business is slow.... then I will be stuck. I won't be able to go out on the road and access the wider market of mobile/plant/agri/masonry blasting.. which would help things along and be a decent market.

....Perhaps I need to just get the big 300CFM and be done with it!?

Thinking out loud and answering my own question at this point... but curious what others thing. I'd be really keen to hear from people who have experience blasting masonry/plant with a 100CFM compressor.

Many thanks again.

 

[Erie Fred]

5/16" nozzle seems to be a sweet spot.
I had enough air to run a 3/8" but could not run fast enough (was blasting 18" high x 40' beams)
and so was wasting sand. To many turns & changes in direction to effectively use it.

Local sandblast shop does all manner of large stuff, inside a booth, runs a 50 hp electric screw, and a 5/16" nozzle.
They loaned me the 3/8 nozzle as they find it's too big.

If you were doing larger flat areas like a boat, you could use the larger nozzle.

Again, consult the chart, and you'll also find that your small pot is way too small for the air compressor
you looking at.

 

[conor1n]

5/16" nozzle seems to be a sweet spot.
I had enough air to run a 3/8" but could not run fast enough (was blasting 18" high x 40' beams)
and so was wasting sand. To many turns & changes in direction to effectively use it.

Local sandblast shop does all manner of large stuff, inside a booth, runs a 50 hp electric screw, and a 5/16" nozzle.
They loaned me the 3/8 nozzle as they find it's too big.

If you were doing larger flat areas like a boat, you could use the larger nozzle.

Again, consult the chart, and you'll also find that your small pot is way too small for the air compressor
you looking at.

Ok, great I hear you. So a large nozzle is really only useful for large flat surfaces..

The other thing I forgot to mention is operator ability. I'm not weak - but i'm not a big burly man.. somebody mentioned the large nozzles at 90 PSI are like dealing with a 30KG weight!? Is that true?

Regarding the blaster - you are correct. My plan is to invest in a new pot alright.. I just wanted to get going with the small cheap one I currently have. And to be honest, it has served it's purpose i.e. Gave me a feel for blasting and also let me do the rear underside of my Mercedes SL.

What happens if I have a big compressor, suitable pot - but want to run a smaller nozzle for more delicate work.. is that possible?

My SL job, for reference...

I still need to go over it a bit more and tidy up a few places, but I am very happy with it. Should I ever expect to be able to remove the seam sealer with blasting or is that a more involved job? I want to remove the areas where it has failed.

Also, would you say that this blasting is SA 2.5 - where I did blast?

 

[brightspark]

as i said a 90 cfm comp will run at 90 psi using a 6.0mm jet doing car wheels a car chassis a lathe cabinet etc its fine anything bigger doing it for profit as a business and it wont cut it .you will soon get disillusioned also you need a reasonable sized portable pot

 

[dave h 2]

Ok good to know.

When I talk about cars and chassis. I just mean subframes, ladder frames and underside. Not whole vehicles, if that makes a different.

But I think as much CFM as I can get my hands on is the thing to do.... because I really do like the idea of being able to go out and do big machinery etc..

You need to ask why the local guy selling the comps gave up. It may just be 'blasters back' or a lack of work.
Be aware that blasting the rust off the underneath of a bonnet can visibly buckle it permanently.
If you start using steel shot the speed things up you will soon find out what blasters back is + if you then do a masonry job with out cleaning the gear properly you can get steel shot imbedded in the wall and a customer ringing you weeks later complaining of rust streaks.
Get a single bag Guyson pot, there was one on here recently.
You SL might have been 2.5 except for all the black rust spots that you left. When you've done it properly put a flood light underneath and I bet you get little stars shining somewhere. Mastic with rust underneath will come off with a hand scraper. Bung the box section holes up or they get full of media and when that gets wet the rot out is spectacular.

 

[conor1n]

OK thanks a lot guys.... again.

Great feedback.

For the SL I was just wondering in general. I think rhe specs are flash rust as the photo was taken a day later.

Unfortunately I had to pause the SL work as I need to get a 2.5mm setup to spray my epoxy mastic.

I'll go back over everything again before I paint. But my u deratanding is that the odd bit of rust spec here and there is fine for the Jotamastic 90.

All good tips .. especially blasters back LMAO. I was watching a guy the other day blasting steel shot... he said there was an effective weight of 30kg at the nozzle.

 

[weldingnovice]

I know of a bloke set himself up mobile blasting business, was a plater by trade.

Iirc compo from some accident was his way in. Made the machine himself all new gubbins, and a decent job of it.

Was doing a lot of boats and some architectural work and what ever else. Recons clean up was biggest problem, think he sometimes ran with water in it?

Anyways compressor end shat itself went back into fabrication.

 

[conor1n]

I know of a bloke set himself up mobile blasting business, was a plater by trade.

Iirc compo from some accident was his way in. Made the machine himself all new gubbins, and a decent job of it.

Was doing a lot of boats and some architectural work and what ever else. Recons clean up was biggest problem, think he sometimes ran with water in it?

Anyways compressor end shat itself went back into fabrication.

Interesting.

Yea I live near a lake and large river so there would he an element of boats too.


In Ireland there seems to be a growing appetite for blasting machines, as unfortunately the price of everything has gone up with brexit (among other things).

Interesting that it was something trivial like an air end that sent him out of the business.... that shouldn't break a business.. maybe he was just looking for a reason.


My primary objective is to focus on car underbody restorations.

 

[weldingnovice]

Live on the coast, boats were commercial and pleasure. Preparation for antifoul paint, blasting off barnacles etc.

Did anything that was offered and I think he was busy.

Masonry brick/stone, timber windows, wraught iron, cars, bikes, trucks,

Thing needs a new compressor and doesn't/can't spend on it.

Won't sell it I asked.