Well, I'm sitting in my living room looking out the window at my partly flooded garden - boy did it rain last night - and feeling a bit fed up because I've now been thwarted yet again in my attempts to get on with renewing Becky's rear wheel cylinders (probably metal pipes too). Put the TV on and it's wall to wall Boris and Brexit. So, in an attempt to cheer myself and avoid committing suicide, I decided to have a wander into parts of our forum I don't usually visit.
However, as I opened the door to the forum I did my usual check to see if anyone had liked/thanked/replied to any of my recent posts and found myself rereading my "Compressors, Rattle guns, plumbing and "real" air pressure" when I suddenly remembered a recent interesting incident.
It was when I was visiting a local tool supplier looking for a "chuck type" retainer for my air chisel - didn't find one but was seduced into buying something else I thought I needed (oh dear). I was doing my usual browse round the store and looking at some of the "juicy" equipment near the check out when a chap came striding up to the desk with a small direct drive compressor. (I would guess maybe 1.5hp on a 25 litre, or thereabouts, air reciever) It was dribbling a small but steady drip of oil from under the pump cowling. I heard him say to the sales staff "This one's broken too" (or words to that effect). I didn't want to be a "gooseberry" so moved away a bit so they could talk without me being intrusive and I got distracted with what I was looking at but as I re-approached the counter with my proposed purchase he passed me, carrying a replacement, as he headed for the door.
There was a big puddle of oil on the counter, which the sales chap was trying to mop up with a rag, which I commented on. Yes, said he, that's the second one he's had. We got talking about it and the sales chap's opinion was that whatever he was doing with it was causing it to run almost continuously and overheat. He had apparently given advice to the effect that a much larger, belt driven unit was probably what the chap needed but this had been rejected on the grounds of portability. He, the salesman, was confidently expecting the customer back again in the near future. He didn't say whether any warranty was being honoured and I felt it better not to ask.
So, now reflecting on this, I'm thinking back to when I had to decide on the replacement for my very old compressor (about 4/5 years ago now). I had two main parameters to fulfill - and lots of lesser ones - which were Cash constraint (it had to be justifiable to Mrs Jock) and Performance - it had to drive my air tools, The "Hooligan" needs around 9cfu free air. If you don't know about free air and pump displacement, very briefly, free air is what the pump can actually usefully output. Displacement is the theoretical amount of air displaced by the pump and takes no losses into account so is not very helpful (my new compressor is rated at 14cfu in it's advertising but actually has a free air delivery of around 9cfu, which was not stated anywhere in the advertising) Had I bought one advertised at 9cfu displacement it would really not have driven the gun for very long before I would have had to wait for the compressor to refill the tank, so be careful with this one!
Then you are faced with the other major decision - Do I go direct drive or belt driven? I was very fortunate in that I've worked with both types from very large belt driven types in the workshops I've worked in during my career as a mechanic to a small direct driven one, very similar to that mentioned above which failed on that chap in the shop, which was bought for blowing out lawn mowers covered in mowings and blowing up tyres on cultivators and ride-ons when I worked with the grounds maintenance squad in semi retirement. With this experience I was probably better placed to make a sensible choice that the average DIY chap so I thought I'd share this with you all.
I'd really no experience of small direct drive units. We didn't need a big one for the machine maintenance tasks and the boss asked me to keep the cost down which was why I went for it. I was astonished at how noisy and high revving it was. The compressor pump also got very hot, much hotter than any of the direct drive ones I'd worked with but mostly the noise was horrendous, particularly the pitch of that noise. I worked with it for the last four, or was it five, years before I retired and it worked well (oil changed yearly) but oh dear the noise - good job we were in commercial premises! Although direct drive is not "quiet" it's the quality of the noise which is so much more acceptable. So when I chose my own one I went for a 14cfu (so around 9cfu free air) 3hp direct drive on a 90 litre tank and it drives all my air tools with comparative ease. At 3hp it just manages to run on a 13 amp plug but trips an rcd on startup so I run it on a fused only spur so this doesn't happen. I'm going to have a 16amp socket installed in the garage when my pal's son (electrician) can find the time - but, as he's on contract somewhere in the middle east just now, I'm not holding my breath (he's been promising for two years now). It is located at the back of my garage and I've asked neighbours if it annoys them. They are all very happy with one chap's wife saying she didn't know what I was asking about!
Here's a couple of highly relevant videos you might find interesting if you're thinking of acquiring a compressor in the near future:
On reflection I wonder if it was the heat aspect which had caused the one I saw in the store to fail? I could imagine that if it was running almost constantly for long periods the oil would get far too hot (there isn't much of it in the sump) and eventually break down causing the compressor pump to fail?
Hope some of these "ramblings" are helpful. Even knowing what I know about these tools I found it a difficult decision to make - and an expensive one to get wrong.
Regards to all
Jock
PS Sorry folks. CFU? don't know where that came from? Of course I actually meant CFM (cubic feet per minute)!
However, as I opened the door to the forum I did my usual check to see if anyone had liked/thanked/replied to any of my recent posts and found myself rereading my "Compressors, Rattle guns, plumbing and "real" air pressure" when I suddenly remembered a recent interesting incident.
It was when I was visiting a local tool supplier looking for a "chuck type" retainer for my air chisel - didn't find one but was seduced into buying something else I thought I needed (oh dear). I was doing my usual browse round the store and looking at some of the "juicy" equipment near the check out when a chap came striding up to the desk with a small direct drive compressor. (I would guess maybe 1.5hp on a 25 litre, or thereabouts, air reciever) It was dribbling a small but steady drip of oil from under the pump cowling. I heard him say to the sales staff "This one's broken too" (or words to that effect). I didn't want to be a "gooseberry" so moved away a bit so they could talk without me being intrusive and I got distracted with what I was looking at but as I re-approached the counter with my proposed purchase he passed me, carrying a replacement, as he headed for the door.
There was a big puddle of oil on the counter, which the sales chap was trying to mop up with a rag, which I commented on. Yes, said he, that's the second one he's had. We got talking about it and the sales chap's opinion was that whatever he was doing with it was causing it to run almost continuously and overheat. He had apparently given advice to the effect that a much larger, belt driven unit was probably what the chap needed but this had been rejected on the grounds of portability. He, the salesman, was confidently expecting the customer back again in the near future. He didn't say whether any warranty was being honoured and I felt it better not to ask.
So, now reflecting on this, I'm thinking back to when I had to decide on the replacement for my very old compressor (about 4/5 years ago now). I had two main parameters to fulfill - and lots of lesser ones - which were Cash constraint (it had to be justifiable to Mrs Jock) and Performance - it had to drive my air tools, The "Hooligan" needs around 9cfu free air. If you don't know about free air and pump displacement, very briefly, free air is what the pump can actually usefully output. Displacement is the theoretical amount of air displaced by the pump and takes no losses into account so is not very helpful (my new compressor is rated at 14cfu in it's advertising but actually has a free air delivery of around 9cfu, which was not stated anywhere in the advertising) Had I bought one advertised at 9cfu displacement it would really not have driven the gun for very long before I would have had to wait for the compressor to refill the tank, so be careful with this one!
Then you are faced with the other major decision - Do I go direct drive or belt driven? I was very fortunate in that I've worked with both types from very large belt driven types in the workshops I've worked in during my career as a mechanic to a small direct driven one, very similar to that mentioned above which failed on that chap in the shop, which was bought for blowing out lawn mowers covered in mowings and blowing up tyres on cultivators and ride-ons when I worked with the grounds maintenance squad in semi retirement. With this experience I was probably better placed to make a sensible choice that the average DIY chap so I thought I'd share this with you all.
I'd really no experience of small direct drive units. We didn't need a big one for the machine maintenance tasks and the boss asked me to keep the cost down which was why I went for it. I was astonished at how noisy and high revving it was. The compressor pump also got very hot, much hotter than any of the direct drive ones I'd worked with but mostly the noise was horrendous, particularly the pitch of that noise. I worked with it for the last four, or was it five, years before I retired and it worked well (oil changed yearly) but oh dear the noise - good job we were in commercial premises! Although direct drive is not "quiet" it's the quality of the noise which is so much more acceptable. So when I chose my own one I went for a 14cfu (so around 9cfu free air) 3hp direct drive on a 90 litre tank and it drives all my air tools with comparative ease. At 3hp it just manages to run on a 13 amp plug but trips an rcd on startup so I run it on a fused only spur so this doesn't happen. I'm going to have a 16amp socket installed in the garage when my pal's son (electrician) can find the time - but, as he's on contract somewhere in the middle east just now, I'm not holding my breath (he's been promising for two years now). It is located at the back of my garage and I've asked neighbours if it annoys them. They are all very happy with one chap's wife saying she didn't know what I was asking about!
Here's a couple of highly relevant videos you might find interesting if you're thinking of acquiring a compressor in the near future:
On reflection I wonder if it was the heat aspect which had caused the one I saw in the store to fail? I could imagine that if it was running almost constantly for long periods the oil would get far too hot (there isn't much of it in the sump) and eventually break down causing the compressor pump to fail?
Hope some of these "ramblings" are helpful. Even knowing what I know about these tools I found it a difficult decision to make - and an expensive one to get wrong.
Regards to all
Jock
PS Sorry folks. CFU? don't know where that came from? Of course I actually meant CFM (cubic feet per minute)!
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