Honda Twins banner
1 - 20 of 46 Posts

·
Registered
Joined
·
70 Posts
Discussion Starter · #1 ·
I could use some help/ suggestions.

I picked up a shop blast cabinet this weekend (harbor freight <$200 with tax on sale!), and could use some recommendations on a new compressor size.

THe cabinet is rated at 12-16 CFM.

I'm looking to get a minimum 60 gal size tank, with 10cfm @ 90 psi.

I have been reading that most people suggest adding 50% to the cabinets requirements. so I would be looking at 18-24 cfm for a compressor.

Is that total overkill?

Price is the major factor or else I would just go out and buy a $2500 compressor.

The nicer ones which would be 2-stage, 60-80 gal tanks, with around 5hp.

I'm wondering if I can get by with a compressor that puts out 10-12 cfm @ 90 psi.

I wont be doing 24/7 blasting but it would be nice not to burn out the compressor the 1st week I get it.

Any suggestions would be greatly appreciated!
 

·
Premium Member
Joined
·
1,003 Posts
r6100mph said:
I could use some help/ suggestions.

I picked up a shop blast cabinet this weekend (harbor freight <$200 with tax on sale!), and could use some recommendations on a new compressor size.

THe cabinet is rated at 12-16 CFM.

I'm looking to get a minimum 60 gal size tank, with 10cfm @ 90 psi.

I have been reading that most people suggest adding 50% to the cabinets requirements. so I would be looking at 18-24 cfm for a compressor.

Is that total overkill?

Price is the major factor or else I would just go out and buy a $2500 compressor.

The nicer ones which would be 2-stage, 60-80 gal tanks, with around 5hp.

I'm wondering if I can get by with a compressor that puts out 10-12 cfm @ 90 psi.

I wont be doing 24/7 blasting but it would be nice not to burn out the compressor the 1st week I get it.

Any suggestions would be greatly appreciated!
That's 12-16 Cubic Feet per Minute, lets make an average 14cfm :)
And the tanks is 60 US gal or 8 cf ;)
so you will use the 8 cf in just over 40 seconds, then the compressor will need to cut in and supply the volume, if the compressor is delivering only 11 cfm (average) (delivering 11 cfm - using 14 cfm =-3 cfm) then every 60 seconds the tank will lose 3 cf and as you only have 8 cf :cry:(8 cfm -3 cfm every 60 sec) then in under 3 minutes your out of air/pressure/blowy stuff/fun, did you get all that :)

So if you are doing any sort of compressor work, match the compressor with the largest user of cfm. This will only give you matching volumes so the compressor will be working constantly. So yep, max cfm plus %50 sounds about right :D

Remember that this is only my option and could be very wrong, i am falable :oops:

Rod from OZ :cool:
 

·
Registered
Joined
·
208 Posts
You should get a compressor that will flow the necessary cfm requirements for the blast cab. A smaller compressor could do it, but it will run non-stop.

i have a 2 stage 25 gallon craftsman comp. and when i use my cut off tool or grinder it just wont keep up. i even turned the psi down to around 60 so it wouldnt consume so much air at once.

If you can, get the compressor that will supply the cfm needs. otherwise just use the blast cab intermittenly.
hope this helps
 

·
Registered
Joined
·
70 Posts
Discussion Starter · #4 ·
All sounds about right, I just don't want to face the reality of buying a pricey compressor.

But on the other hand if I spend $4-$600 on a lower cfm compressor, I don't think I would be happy. So I'm probably looking at the price range of around $1000-$1200 for a 60 gal 2-stage compressor.

so here is one, I basing my comparisons on. an Ingersoll - Rand

http://www.aircompressorsdirect.com/Ing ... /p705.html

Would a larger tank like an 80 gallon be worth it? Or would a 60 gal be sufficient. Things are pretty tight in my garage, so I like the smaller dimension of the 60 gallon.

Thanks again for the input!
 

·
Registered
Joined
·
70 Posts
Discussion Starter · #5 ·
Also, I'm not going to be using the blast cabinet 8 hours a day 5 days a week, but will be using for cleaning engine cases (motorcycles obviously), smaller parts, carbs, heads, etc.

But if I'm blasting a part it would be nice to have enough air to blast the part and be done with it. Sure I could take a break when blasting, but don't want the compressor to run the entire time. I'd really hate to buy an $800 compressor and burn out the motor in a few weeks.

I guess I'll keep researching, and trying to find a second job!
 

·
Premium Member
Joined
·
1,003 Posts
r6100mph said:
All sounds about right, I just don't want to face the reality of buying a pricey compressor.

But on the other hand if I spend $4-$600 on a lower cfm compressor, I don't think I would be happy. So I'm probably looking at the price range of around $1000-$1200 for a 60 gal 2-stage compressor.

so here is one, I basing my comparisons on. an Ingersoll - Rand

http://www.aircompressorsdirect.com/Ing ... /p705.html

Would a larger tank like an 80 gallon be worth it? Or would a 60 gal be sufficient. Things are pretty tight in my garage, so I like the smaller dimension of the 60 gallon.

Thanks again for the input!
I do like that :D just remember these can be noisy blighters :( Mine lives under the house and in a timber (ventilated) Box.
Rod from OZ :cool:
 

·
Registered
Joined
·
70 Posts
Discussion Starter · #7 ·
yeah, i'll just have to crank up the stereo volume (#11!)

I really don't have any other location other than inside my detached 2 car garage. I guess if I won the lottery I could build a shed for it!
 

·
Registered
Joined
·
363 Posts
you can always search the classifieds, better to buy a used professional HEAVY DUTY unit than spend the big bucks on a crap item masquerading as one. there is a great disparity on the rating of motor hp, just because it says 5 hp does not mean squat, look for an motor that looks the part, massive size, cooling fins and ridiculous weight are all indicative of a quality product. same goes for the compressor. that and wire for 220 volts single phase. (bonus points for 3 phase, but unrealistic for most homeowners.) much more efficient and much easier on the equipment.
 

·
Registered
Joined
·
71 Posts
Hi R6100mph
Check out the electrical wiring to your garage. Also check the wiring that goes into your house. Do you have enough electrical power coming in to power the air compressor that you are looking at? It would be best if the air compressor is on it's own circuit 220 circuit with it's own breaker in the main box in the house.
TomC in Ohio
 

·
Registered
Joined
·
70 Posts
Discussion Starter · #10 ·
About a year and half ago, I upgraded my service to a 200 amp to the main house with a 60 amp sub-panel into the garage. Should be more than enough. I'm running a dedicated 30 amp circuit for a small mig welder, and another dedicated 220V 30 amp cirucuit for the shop heater.

I plan on running another dedicated 220v circuit for the comp
 

·
Premium Member
Joined
·
771 Posts
I do it all on the cheap, and I just have patience.

I don't know the gallon size of my compressor off-hand, but it's about 1.5 ~ 2' diam x 4' tall. It has a 110-volt oil-less compressor that pumps the tank up to 150psi. I think it's rated at about 9 ~ 10 scfm @ 90psi. It was not a particularly high-dollar machine. I have a $250 free-standing Harbor Freight blast cabinet. Probably the same unit you have.

My compressor will not keep up. I'll get about a minute blasting at 110psi, then I pause while the compressor takes 2 minutes to pump back up. I do the one on / two off for up to 45 minutes at a time. I've been doing this for 2+ years now with no problems. I've blasted many MANY items on 3 ~ 4 full resto/refurb projects. No problems so far. I'll get ~ 2 minutes blasting at lower psi's using a whole variety of blast media.

That said, it gets frustrating after a while, so it's really up to your budget. It CAN be done the cheap way and it's not a killer. But, like so many things, buying really good quality tools usually tells.... You really need to assess how many projects you'll be doing vs. your budget.

I'm happy enough with my set up.
 

·
Registered
Joined
·
70 Posts
Discussion Starter · #12 ·
One other major concern I have for the shop blaster (HF 40 Gal Blaster) is that if the cfm is low, with a smaller compressor, you won't get the same results as with a larger compressor. is that true or no?

I would assume with a larger cfm compressor, it will take of oxidation and other crap much quicker than a lower cfm compressor. Maybe with a smaller compressor you will eventually take off the same amount of oxidation / crap but will just take you much longer. Would that be the right idea?
 

·
Premium Member
Joined
·
607 Posts
The problem with an undersize compressor is that the pressure will drop after a few minutes of blasting, so you end up blasting for a minute, wait a minute for the pressure to come up, blast, wait, blast, etc. If you try to keep going with the pressure too low, it won't work well. I've been using a 5hp compressor with my blast cabinet for over 20 years, it WON'T keep up, so I blast, work on something else for a few minutes, blast some more, etc.
Be sure to use a good water seperator on your air line too.
Put junk bolts in the threads of aluminum parts to protect the threads, and don't blast any internal motor surfaces- the glass beads can embed in the aluminum and be released later into the motor-bad poopie.
If your blast cabinet does not have a dust collection system you will find gritty glass on EVERYTHING in your shop-more bad poopie.
 

·
Registered
Joined
·
70 Posts
Discussion Starter · #14 ·
Thanks for the recommendation!

My budget defintely won't go for a compressor above 5hp. I just don't want to spend that much on an item which is basically a hobby or an addiction. My friends and family may get an intervention lined up for me if I spend more than a couple thousand on a compressor!

That brings me to my next question; regarding the vacuum / dust collection aspect.

Right now I'm going cheapo style and just have my shop vac hooked up to it. It does a pretty good job of filtering, but there is some dust that gets spit out of the exhaust of the vacuum and all the sudden I'm sitting in a cloud of dust. I wear a respirator when using it, but need some thing more clean.

Does the water system help a lot of the bulk before it gets to the actual vacuum?

Oh and by the way, 99.9% of the time I will be using sodium bi-carbonate (blasting soda).

Is it ok with soda to blast the gasket surfaces? Like heads or cylinders, or mating surface of engine cases?
 

·
Premium Member
Joined
·
2,386 Posts
r6100mph said:
Thanks for the recommendation!

My budget defintely won't go for a compressor above 5hp. I just don't want to spend that much on an item which is basically a hobby or an addiction. My friends and family may get an intervention lined up for me if I spend more than a couple thousand on a compressor!

That brings me to my next question; regarding the vacuum / dust collection aspect.

Right now I'm going cheapo style and just have my shop vac hooked up to it. It does a pretty good job of filtering, but there is some dust that gets spit out of the exhaust of the vacuum and all the sudden I'm sitting in a cloud of dust. I wear a respirator when using it, but need some thing more clean.

Does the water system help a lot of the bulk before it gets to the actual vacuum?

Oh and by the way, 99.9% of the time I will be using sodium bi-carbonate (blasting soda).

Is it ok with soda to blast the gasket surfaces? Like heads or cylinders, or mating surface of engine cases?
Do you have the filter installed on the shop vac? When you use the shop vac for water pickup it's usually removed and sometimes they don't get put back on. With the filter in place, the shop vac should work fine as a dust collection device for the cabinet.
 

·
Registered
Joined
·
70 Posts
Discussion Starter · #16 ·
I do have the filter installed with a bag. I still get some dust coming out the exhaust port on the vacuum.

Yes the filter is pretty dirty, and probably could use a new one and new bag.

Speaking in terms of NOT using the water filter, just dry, should you use a bag, filter and a pre-filter( the sock type that goes over the actual filter?)

When using the water filter, you should remove the bad and filter.....is that correct?
 

·
Premium Member
Joined
·
771 Posts
Hmmm.... you're gonna have to start NUMBERING your questions.... :D

I use a shop vac and I point it outside the garage. No further worries. No mess in the garage. But, it mandates that the blast cabinet be close to the garage door. And it can limit work in inclement weather. Not a real concern here in central FL.

As for a lower compressor cfm affecting the work, that isn't the way it works unless you keep blasting to the point the pressure in the tank drops.

The cfm rating is the quantity of air the compressor puts into the tank. The amount you draw out of it is determined by the blast nozzle size. Certainly, the pressure setting affects the total amount of air delivered, but again, that's not the way to look at it.

Lets say you have the delivery pressure regulator set to 90 psi. And then, lets say the compressor cycles on at 100 psi and off at 125 psi. As long as you don't blast away to the point that the pressure in the tank drops BELOW the regulator setting, you'll always be seeing a constant flow rate at the blast nozzle - that is, whatever 90psi delivers. If you blast away to the point that your compressor can't keep up and the pressure in the tank drops to, say, 60 psi for example, then yes, the amount of air delivered to your blast nozzle will drop and the blasting will be less effective.

So your concern about not taking crap off, or taking longer to GET the crap off, is not correct. If you have the pressure regulator set up high, it'll take the crap off regardless of the cfm rating of the compressor. You'll just have to pause more frequently to let the compressor catch up.

As several (including me) have mentioned, you just blast until the compressor starts, then wait till it stops and start blasting again and stop again when the compressor starts. Blast, wait, blast, wait. Larger cfm = longer blast time, less wait time.


*update* - I just checked. I have a Craftsman 6HP 30gal, 150psi, upright tank, 110-volt single cylinder oil-free compressor rated at 6.4 cfm @ 90 psi. It cycles between 120 and 150 psi. I blast at 100 psi or less, depending on what I'm blasting, what media, etc. I bought the compressor 5 years ago for ~$250. Never had a single problem with compressor or blasting.

Go for it!
 

·
Registered
Joined
·
70 Posts
Discussion Starter · #18 ·
Well I just got back in from the garage, where it's 3 degrees outside and -15 with windchill. Luckily last winter I insulated the entire garage and installed a nice little Dayton elec. garage heater.

I see exactly what you are saying about the psi and cfm. Let's say my compressor puts out 5 cfm at 90 psi. As long as the psi doesn't drop below 90 psi, it will continue to put out 5 cfm. Got it!

I did a through cleaning on the shop vac, blew out the filter and changed bags, and now it's definitely much much cleaner. I was just too excited and hooked up the blasting cabinet, and vac (dirty) to try it out.

I still think I might try out the water filter in addition to shop vac.

1) From what I understand you are to take out the regular filter, and install one of those wet type filters and remove the bag. Then I guess you will get some water in the tub of the vac but shouldn't be a whole lot. Does that sound correct?

I'm still doing a bunch of research on compressors and have my eye on an Ingersoll Rand compressor- 60 gal tank 2-stage, 5 hp 1 phase. These typically go for around $1200. I like the 60 gal for lack of more space in the garage. I believe this comp puts out around 15 cfm @ 90 psi

Thank you to everyone for helping me out with this. I guess you have to start somewhere, and ask a bunch of stupid questions.
 

·
Premium Member
Joined
·
1,374 Posts
Having worked for an Ingersoll rand distributor for 32 years and without blowing my own top a few words of advice:-
1/Look into the nozzle size you want to use and the cfm it will consume at what pressure?.Bear in mind different medias that you blast can use different pressures so less cfm then add 40-50%.Piston machines don't like to be run flat out.
2/5HP 3 phase is usually the smallest machine I would recommend for a small workshop enviroment but even this will work hard if not intermittent use. These are usually piston machines and like varied load just like your bike 30mph 70mph etc If 5hp is not keeping up check nozzle not worn(Consumes more cfm) no air leaks and also check valves & that the non return valve into the air receiver is working OK.Single phase compressors not recommended for blasting unless you've plenty of time to wait .You will always be using them flat out and still not have enough air.Single phase motors don't like to be stopped and started more than 6/8 times per hour and always bear in mind the start up amps required are normally about twice the running current used.Just like your bike or car start-use more petrol.
3/Ideally look for at least a two stage machine,sec hand screw or rotary vane compressor if all you are doing is blasting.
4/Bear in mind you will only get about 3CFM per HP. A 3 HP machine would be sold as 13.5 cfm -note this is always given as a piston displacement figure you will only get about 10cfm FAD(Free air delivered -no piston machine is 100% efficient)
5/Look into running costs per HP-don't just think of initial cost of machine .I think even before I retired a 3HP motor was about £400pa on average use in electricity cost.Hope that helps.Regards Chris.
 

·
Premium Member
Joined
·
1,374 Posts
On the subject of water traps on the airline.These are usually only about 75% efficient.They will only remove water in the form of a condensate.Always mount these as near to the point of use as you can .If you put them on the outlet of a compressor that is working flat out the moisture will always be in the form of a vapour and will pass straight through cool down the line and water will be at the point of use. If you want dry blasting and have the money install a fridge dryer.
 
1 - 20 of 46 Posts
Top