A Quiet Air Compressor?

There has been debate on these pages regarding air compressors/air receivers in general and one notable fact stood out - that the cheapo usually oil free compressors are extremely noisy, you can't hear yourself think when they are running and frighten the life out of you when they burst into life unexpectedly.

I have one of these, well two actually, and they are exactly that. So I came to thinking that perhaps one could build a quiet running compressor, perhaps slower running, that would perhaps solve the problem.

Now, has anyone built such a compressor and, perhaps more importantly, knows where plans for such a machine might be found?

Chris

A little off topic but I well remember riding Brisbane's trams in the 60's and noticing the operation of the air compressor for the braking system. You would be sitting there at a tram stop in complete silence and suddenly the compressor would start up. It was not loud, just a rhythmic soft thumping accompanied by an equally soft whirring of the drive motor.

Perhaps there are some design features from this type of compressor that could be copied? Similar ones have also existed in buses I have ridden over the years. Probably not oil-free though?

Chris there is a long thread from a month or so ago about quieter compressors, the ones being sold in the 60-70dB range while still being oil less are a lot better than many.

If you want a really quite one then people have used fridge compressors but the volume is low, depends on your needs.

The last OP on this subject found a ready made solution a few weeks ago.

Failing that you need a pump, a motor and a belt grafted to your existing pump air and electrical layout.

Machine mart sell pumps and their specs tell you what cfm needs what power motor.

I was told that running a lorry air brake compressor at around 700-800 rpm with a decent size inlet air filter is reasonably quiet.

Seems logical as much of the noise from the modern, cheap, oil free breed is fin ring and induction air hiss. The lorry air brake compressors I've seen are cast iron with minimal finning and I know that putting a big air filter on an Atlas Copco KE2 Vee twin compressor, instead of the standard silly 2" (ish) diameter wire mesh plates in a short drum fitted to each cylinder, seriously reduced the perceived noise levels. Maybe halved.

If you are close to my corner of Sussex I have a lorry compressor sitting on the floor that you are welcome to for experiments. Too good to throw away but where and when it appeared from somewhere in the last 30 years I know not.

Clive

Edited By Clive Foster on 05/02/2021 12:37:35

Have s look at Hydrovane compressors.

David

Thanks for the replies but I didn't want to actually buy a compressor as make one. In the absence of plans I might think about designing a little one and make it water cooled with a decent air filter - picking up on comments made.

Clive - thanks for your offer, I have sent you a PM.

Dave - have you a link to the other OP and possible solution?

Chris

this thread

Direct drive compresors tend to the noisiest. Belt driven compressors are quieter because they run more slowly, and may well be be made from cast iron, rather than the alloy of the single cylinder direct drive types

Lubrication is usually just by splash.

.Clayton Dewandre, twin cylinder compressors, with separate liners came in two versions, one with a finned head for cooling, or a watercooled head (Not unknown to have a flash wall across the coolant passage! )

They usually ran at half engine speed, circa 1,000 - 1300 rpm The single cylinder version was usually air cooled with a finned head, and would run at engine speed.

Both types were lubricated from the engine main pressure lubrication system

An effective means of silencing intake noise is to have a large volume between the intake filter and the compressor.. In vehicle installations, the length of intake pipe probably served this function.

Low frequencies, such as induction noise have to be tuned out. Having the intake filter with a long pipe between it and the compressor will tend to reduce induction noise.

High frequency noise, such as hisses, can be absorbed by a "straight through" silencer. This only need a canister packed with glass fibre around the central perforated air feed pipe.

Diaphragm compressors tend be the quietest., since they have fewer moving mechanical parts, lack cooling fins which will radiate noise..

Howard

That might have been me.

I did buy the KIEI compressor and it arrived in good order before Xmas.

It is quiet. I mean I can talk to the wife whilst it's on. I've had very little use of it so far, a) because I need to get it plumbed in and b) it's been too damned cold to go in the shed.

I've mainly used it for an air gun for cleaning swarf off lathe and mill and it works very nicely for that.

It seems well build, but there are no assembly instructions (just bolting wheels on) and the manual is very close to incomprehensible.

I don't know how it will last, but so far I'm happy.

Iain

I’ve just bought a brand new Hyundai 50 litre silent running compressor advertised as making no more than 50 decibels. I was a bit dubious about the noise but I thought being a good known brand it might be ok and worth a punt at £250 delivered. I have to say once running this thing is super silent , I think my microwave makes more noise .

The compressor is a diaphragm type which is designed for low noise and I reckon for blowing car tyres up and general workshop light use it will be ok , time will tell.

Hi All,

Just bought this last week

Swan DRS-215-50 Oil Free Low Noise Compressor

from Axminster, amazed at how quiet it is after my old one. Not cheap at over £500 but a really nice unit.

It is important to me as I do not wsh to upset my lovely neighbours and the old one was very intrusive when running.

Usual great service fro Axy, just a satisfied customer!

Cheers, Martin

Never seen a water cooled one.

Dental air compressors are generally very quiet, but not cheap. The noisy bit in all compressors is the air intake, if you can get an oil bath air filter of a tractor or old car, you will be amazed at how much quieter it makes them.

Dental air compressors are generally very quiet

The compressor where I go would not seem out of place in a garage

Edited By modeng2000 on 05/02/2021 20:42:37

I'm looking for a new compressor after scrapping mine and checked the KIEI offering on *Amazon*. The reviews were rather discouraging. Would you recommend yours?

None of those reviews surprise me, the 8cfm is calculated from the theroretical displacement of the pump, the actual CFM is around 5cfm delivered.

The kit will mostly work apart from the spray gun, there's a reason why good spray guns cost over £70. Cheap ones use more air. You need to buy a gun that needs 5cfm air.

Three reviews and one was supposedly a 5 star rating, but was actually only 1 star. A 25 litre receiver at only 6bar is way too low for any serious large scale spraying. He’s even painting below the regulated pressure (if he actually has a regulator).

As Dave, much lower output than the hype suggests. Most punters don’t know the difference when buying, I reckon.

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i have a Bambi, its quiet but a bit small maybe