Thread: Which air compressor? I need some advice please

FWIW I was recently looking for a compressor to replace my current small one which had given up the ghost. I have a friend who ran a tool shop for some 40 years, so I went to him for advice. His main point was that I should look for a machine with a cast iron pump, rather than one of alloy. He maintained that the cast iron pumps will "go on forever", while the others are less reliable. Capacity should be at least 50 litres. He further said that I should test any machine that caught my eye by emptying the tank completely, and then timing how long it took to pump up to 120 psi. A good machine will do this in two minutes or better. (As it turned out, I found a second hand Warrior brand, fitted with a new motor and an alloy pump {horror!!!!}. It was priced at $140, and pumped up to 120psi in 1 minute 25 seconds. I thought it too cheap to pass up at the price, and it is now performing beautifully for me).

Originally Posted by Nick009

I've been looking at the Scorpion XRV-14, I've only seen it in catalogues, I can't find any specs online. According to the catalogues it does Free air delivery 225 LPM and 150 PSI.

Any thoughts or advice is most welcome.

Thats a minimum spec I would go for for something like an impact wrench.

A cast iron pump alone does not mean much as even some cheap compressors use cast iron pumps.

The main difference between low capacity cheaper compressors and higher compressors pumps is that most low capacity compressors are direct drive. This simplifies the construction which means that they are cheap to make but single phase max 3HP direct drive can usually only drive one small cylinder (usually at high revs which then won't last as long) to a moderate pressure. To get more free air deliver (FAD) more and/or bigger cylinders are needed. This is possible only if indirect drive (ie belts and pulleys) are used. This type of construction makes them more expensive but with larger cylinders and pumps reving slower they will last a lot longer. Just bear in mind that a single phase (3HP, 15A) compressor cannot generate any more than about 300 L/min irrespective of the design - to get more than this 3 phase or internal combustion powered compressors are needed.

thank guys

Originally Posted by BobL

Thats a minimum spec I would go for for something like an impact wrench.

Thanks Bob, they also have a XRV-17 which claims
3HP
50ltr tank
3 yr warranty
FAD 251LPM
150 PSI

perhaps that would be slightly above the minimum spec? I won't be using it all day long, the most use it will get is when I'm changing wheels around on my 6 wheeler truck (actually 10 individual wheels).

any thoughts