ibexman Posted December 18, 2005 Share Posted December 18, 2005 Im after an air compressor for the garage to run rattle gun air tyres spray ect how many litre tank ? 2HP 3HP? direct drive ? belt drive? which ones are quieter dont want to upset the neighbours cheers guys Quote Link to comment Share on other sites More sharing options...
BogMonster Posted December 18, 2005 Share Posted December 18, 2005 From personal experience, if you want to run air tools take whatever you think will be enough from the published manufacturers figures and double it.... The specs are all lies (a bit like electric winch ratings). I got one of these on the basis it was supposed to be 5.7cfm FAD and the rattle gun I wanted to use was supposed to use 4cfm. Forget it. Either the compressor only produces about 2.5cfm, or the rattle gun consumes more than 8 - less than 50% duty cycle and no oomph at all. To get alloy wheel nuts off (130nm? mine are probably tighter than that, torque setting is "1 grunt on a 3 foot bar" ) I have to crack them off with a bar first, or it takes about 30 sec to shift each nut (and waiting for ages for the compressor to catch up). It is still useful - and I still use it for wheel changes as it speeds things up no end, but it doesn't do what I wanted. However if your main use for compressed air is mostly cleaning things, pumping up tyres and stuff like that, then a little one like this is fine. It is quite noisy though! If I bought another one I would look for 3 things 1) 150psi minimum - the 100-110psi ones don't have the same amount of oomph for running air tools and while most of the air tools say they only want 90psi, that's a lie as well! Most of the smaller ones only do the lower pressure. 2) A bigger tank probably 100L minimum 3) 3KW motor The trouble is that the prices go up exponentially - there's a nice sized 150L 3HP one on that same website ... over £1000 though! When I asked much the same question on compressors a while back somebody suggested going for a bigger one second hand. I didn't because it isn't very practical to get a used one shipped down here, but if you have that option, it would be worth doing I think. I don't know much about spraying - never tried it personally - but I know the guy who does our painting at work uses a Draper one similar size to the bigger one mentioned above and reckons it can only just keep up with the air demand when he is painting a big panel like the side of a 110 or a bonnet. Running out of air half way through a panel would be kind of a PITA Quote Link to comment Share on other sites More sharing options...
rtbarton Posted December 18, 2005 Share Posted December 18, 2005 I agree with BogBuster. I think the FAD is simpler the product of the piston displacement x speed, whereas the consumption of tools is at the working pressure. For a given mass off air the FAD figure will be larger than the other. I have a 14cfm Clarke compressor with a 3HP motor, it just keeps up with my gritblaster. 3HP is the most you would expect to run off a single phase supply, and even then I installed a dedicated supply back to the consumer unit. Quote Link to comment Share on other sites More sharing options...
ibexman Posted December 18, 2005 Author Share Posted December 18, 2005 I agree with BogBuster.I think the FAD is simpler the product of the piston displacement x speed, whereas the consumption of tools is at the working pressure. For a given mass off air the FAD figure will be larger than the other. I have a 14cfm Clarke compressor with a 3HP motor, it just keeps up with my gritblaster. 3HP is the most you would expect to run off a single phase supply, and even then I installed a dedicated supply back to the consumer unit. Thanks guys machine mart have a good deal at the moment clarke 14cfm 3hp 150psi £352 sounds good going to take a closer look in the week Quote Link to comment Share on other sites More sharing options...
BogMonster Posted December 18, 2005 Share Posted December 18, 2005 That does sound like a good deal Quote Link to comment Share on other sites More sharing options...
rtbarton Posted December 18, 2005 Share Posted December 18, 2005 Thanks guys machine mart have a good deal at the moment clarke 14cfm 3hp 150psi £352 sounds good going to take a closer look in the week That's the one I've got - make sure it's the model with cast-iron cylinders. I had to mend mine - 1) the drain valve core was loctited into the housing whereas the housing should have been loctited into the receiver! 2) there was some gunge in the thin pipe that connects the non-return valve to the pressure switch which stopped the thick pipe de-pressurising when the unit switched off. This meant that next time it starts the motor is under load and it won't start. Also there is a little valve on the outlet of the pump which closes once the pressure reaches 20psi, upto that it just blows air out. I guess this is to get the motor upto speed before loading it. I mistook this for a faulty safety valve! Quote Link to comment Share on other sites More sharing options...
Troddenmasses Posted December 18, 2005 Share Posted December 18, 2005 Have to agree with most of what has been written above, however there are a few other things to think about. I would definately go for a belt driven unit for a couple of reasons. Should the motor or compressor part decide to break in a few years time, you could purchase just the broken part and replace it - they are completely separate. The main reason though is the sound. A direct drive unit has a much more 'raspy' type sound, which definately carries further and is much more annoying. I can quite happily work alongside my belt driven compressor whilst it is working. Don't take too much notice of the manufacturers cfm ratings - they are all lies anyway. The main thing to look at is the power consumption - 3hp is what you want. When it comes to tank size - go for the largest that you can afford. Remember that you can run any type of air device from any size of compressor, but if you are taking air from the tank quicker than you are putting it in, it will only last for a short time. The time is totally dependant on the size of the tank. I have a 3hp version with a 100 litre tank, and if I am using the air grinder or air sander (which both use MASSIVE amounts of air), I can use them for about 2 minutes before I have to stop for about a minute for the tank to build back up to pressure. I found that the best deals were from: www.worldofpower.co.uk (I have nothing to do with these people, apart from being a happy customer) I'm sure that you will be able to find cheaper units, and much much more expensive ones, but I think that for diy/garage use. you can't beat this type of unit. Be very careful going to ebay, all the compressors on there seem to either be 'in need of attention' ie. not even fit for the scrap man, or seriously cheap chinese imports that wouldn't blow the skin off a rice pudding. Good luck. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted December 18, 2005 Share Posted December 18, 2005 Another point I should have added, I found the Clarke unit labours a bit at 150 psi and their electric motors aren't the best in the world so I've set my cut out to switch off at 100 psi. This is quite adequate for my needs. Quote Link to comment Share on other sites More sharing options...
simonr Posted December 18, 2005 Share Posted December 18, 2005 I only have a cheap (Clark I think) one with a 25l tank. It was about £120 and it gets used for spraying & ait tools most of the time. The only thing it struggles to keep up with is the plasma cutter. It is an oil-less design - and the air does indeed come out oil-free (better for spraying without a separate filter, though you do need to oil the tools more often) Buy as big as you can - but there is nothing wrong with the cheap ones! Si Quote Link to comment Share on other sites More sharing options...
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