Hey folks,
Having watched air compressors on ebay for quite some time now, it does appear that unless you get super lucky it's a bit of a waste of time trying to find something second hand and in decent condition with suitable specifications..
- The primary objective of this exercise:
- - Being able paint things - Panels etc
- - Being able to use a air compressor to do other stuff.. no idea what you can use them for..
- Secondary objective:
- - Being able to do a car in one go..
I get the SGS newsletter and was wondering if this would be a suitable candidate:
https://www.sgs-engineering.com/sc50v-50l-compressor?utm_source=SGS+Engineering&utm_campaign=c197b773c2-EMAIL_CAMPAIGN_2020_06_22_Compressors&utm_medium=email&utm_term=0_cc26f39420-c197b773c2-109743789&mc_cid=c197b773c2&mc_eid=772187e056
I've asked so many times now.
Basically I keep getting conflicting answers.
Someone actually said 20L is fine, as long as you do panel by panel and the bonnet is a push, but definitely doable.
50L comfortably allows for panel by panel with headroom.
100L is full car territory.
This is why I still don't have one :)
Can't get a damn straight answer!
Cheers man- so I guess you have to do the maths on cfm to work out how long you have to wait for the compressor tank to recharge... bah..
You basically want to see how long you get holding down the trigger vs how long it takes to refill.. you can roughly work out panel by panel how many passes you'd do and then total that for the car... and that way see how long you'd have to wait in-between passes/ panels in order to make steady progress.
It's all in here https://www.sgs-engineering.com/help-advice/what-cfm-air-compressor-is-needed-to-run-air-tools/#3
It all depends on the tools you intend to use. If you have survived without one, then you obviously don't need one!
Patrick,I just found this link that seeks to explain the guide line criteria for a compressor for painting. The last sentence seems to be the killer, "50 Gallon tank", that's around 250L in new money!
https://craftsmanprotools.com/air-compressor-for-spray-painting/
Quote from: Joesson on June 26, 2020, 09:35Patrick,I just found this link that seeks to explain the guide line criteria for a compressor for painting. The last sentence seems to be the killer, "50 Gallon tank", that's around 250L in new money!
https://craftsmanprotools.com/air-compressor-for-spray-painting/
Agreed.
Have to watch out for the liter vs gallon thing.
The rule of thumb seems to be 25+ GALLONs is the minimum for a full car
Right, I've read through the articles.
SGS is saying you multiply the min cfm of the gun by 1.5 to understand what the min cfm is that you have to deliver. Most guns on their website seem to state between 6 and 12 cfm. So you'd need between 9 and 18 output.
Then in terms of capacity they're saying you multiply the cfm requirement by 6. Which means you're looking at a range of 54 - 108L.... so getting the one I linked to whilst providing sufficient flow, it seems that it is lacking in the duration dept.
For air tools, or paint spraying you do need a big receiver. That also means a big compressor, if you want reasonable recovery.
Did more reading and found the below equation:
V = volume of tank in cubic feet
U = SCFM (verify that the compressor output is Std Cu Ft / Min) CFM is another animal.
W = Final tank pressure in psig (gauge pressure)
1. Assume the compressor manufacture put a label on a compressor that indicated it would deliver 4 SCFM @ 100 PSIG [W].
2. Determine the volume of the tank V in Cu Ft.
3. Then V x ((W + 14.7) / 14.7) / U = T (time in minute)
Just for fun say the tank in 2.5 Cu. Ft Then 2.5 x (114.7/14.7) / 4 = 4.877 min.
Because I'm not correcting for scfm to cfm I'm (probably wrong here) assuming that there is up to 10% error in the final value.
BUT given the values that sgs supply and my probably bad maths it's about 1 min to refill the 50l tank ~10% error...
That's not that bad is it??
Quote from: jvanzyl on June 26, 2020, 16:40Did more reading and found the below equation:
V = volume of tank in cubic feet
U = SCFM (verify that the compressor output is Std Cu Ft / Min) CFM is another animal.
W = Final tank pressure in psig (gauge pressure)
1. Assume the compressor manufacture put a label on a compressor that indicated it would deliver 4 SCFM @ 100 PSIG [W].
2. Determine the volume of the tank V in Cu Ft.
3. Then V x ((W + 14.7) / 14.7) / U = T (time in minute)
Just for fun say the tank in 2.5 Cu. Ft Then 2.5 x (114.7/14.7) / 4 = 4.877 min.
Because I'm not correcting for scfm to cfm I'm (probably wrong here) assuming that there is up to 10% error in the final value.
BUT given the values that sgs supply and my probably bad maths it's about 1 min to refill the 50l tank ~10% error...
That's not that bad is it??
Never seen a compressor that could recover that quick!!
Something like this is what you need:
https://www.ebay.co.uk/itm/SIP-Workshop-420-200-Air-Compressor-Single-phase-240v/124234632592?hash=item1cecf60d90%3Ag%3AzPYAAOSwiE9e85YF&LH_Auction=1
I have a 14.6cfm 50 litre and it works well for the impact gun, air ratchet and other small air tools but not yet tried it for anything for any sustained period. I quite fancy a DA but not sure it would cope with it - maybe a 150+ litre tank would suit you better. I move mine round so it's easier being a bit smaller.
Other thing I have thought of is buying a spare tank as compressors with knackered motors come up fairly regularly for peanuts. Not really looked at the logistics of piping it up yet but I guess it would be piped inline and the outlets used would be from the extra tank!
Quote from: Carolyn on June 26, 2020, 17:00Something like this is what you need:
https://www.ebay.co.uk/itm/SIP-Workshop-420-200-Air-Compressor-Single-phase-240v/124234632592?hash=item1cecf60d90%3Ag%3AzPYAAOSwiE9e85YF&LH_Auction=1
Fair enough! Now where was Shropshire again...?
Think I'll be sticking with aerosol cans for the foreseeable future I guess!
Quote from: tets on June 26, 2020, 17:22I have a 14.6cfm 50 litre and it works well for the impact gun, air ratchet and other small air tools but not yet tried it for anything for any sustained period. I quite fancy a DA but not sure it would cope with it - maybe a 150+ litre tank would suit you better. I move mine round so it's easier being a bit smaller.
Other thing I have thought of is buying a spare tank as compressors with knackered motors come up fairly regularly for peanuts. Not really looked at the logistics of piping it up yet but I guess it would be piped inline and the outlets used would be from the extra tank!
Now that's an interesting thought!... I could shove a few cylinders up in the roof of the garage (drain plugs on the underside!)...
I have a 50L 14.5 CFM compressor, it is good enough to run air tools including an air DA, I use it to spray with using a HVLP set up, for your basic DIY you dont need any bigger capacity, if you are going to use one for spraying ensure you have a separate air outlet, the vast majority are Chinese made with a double assembly outlet and are shite
Rob
Quote from: Zxrob on June 28, 2020, 23:52I have a 50L 14.5 CFM compressor, it is good enough to run air tools including an air DA, I use it to spray with using a HVLP set up, for your basic DIY you dont need any bigger capacity, if you are going to use one for spraying ensure you have a separate air outlet, the vast majority are Chinese made with a double assembly outlet and are shite
Rob
Interesting! I'll need to read up in the separate air outlet vs the double assembly outlet that you speak of.. thank you!
I assume the one that I linked to in the first post falls under the "poo" category?
Quote from: jvanzyl on June 28, 2020, 23:56Quote from: Zxrob on June 28, 2020, 23:52I have a 50L 14.5 CFM compressor, it is good enough to run air tools including an air DA, I use it to spray with using a HVLP set up, for your basic DIY you dont need any bigger capacity, if you are going to use one for spraying ensure you have a separate air outlet, the vast majority are Chinese made with a double assembly outlet and are shite
Rob
Interesting! I'll need to read up in the separate air outlet vs the double assembly outlet that you speak of.. thank you!
I assume the one that I linked to in the first post falls under the "poo" category?
Ok, let me re-phrase that
They are not very accurate for monitoring pressure, you are always best having (or installing) a separate outlet in the end of the tank, especially for spraying, I will take a pic of mine tomorrow to show you my set up
Rob