Compressor droop

[Chris GillParticipant @chrisgill22114]

Hi

I have a cheap and noisy (not sure about cheerful) compressor that I bought from Aldi a couple of years ago. I had to swap the couplings to UK standard before I could do much with it and set the relief pressure to more than the low pressure switch. It now runs up to 8 bar (as intended) and seems to work OK even if it frightens the life out of the grandchildren.

The problem comes when I try to run models at low pressure. If I set the regulator to, say, 1 bar it will drift down until the model stops even though there's still plenty of pressure in the reservoir. I then have to keep adjusting the regulator up a little every time it droops. I would really like to run at a consistent 0.5 bar on one model and 1 bar on others.

Is this about par for a cheap compressor and is there anything I can make or buy that will achieve good control at the low end while still being able to do things like pump up the van tires?

[Chris GillParticipant @chrisgill22114]

Why does regulated output from a compressor drop

[Pete.Participant @pete-2]

How we always did it with spray guns was set it a little above what's needed at the compressor, then with a mini regulator at the spray gun make the fine adjustment with air flowing, this will give you the actual pressure at the work end while it's flowing.

[EmgeeParticipant @emgee]

Hi Chris

You need further pressure control devices to obtain the 2 different pressures from the tank pressure, when I last bought a reducer they were pretty expensive but like a lot of items should be quite cheap these days.

Emgee

Search Amazon, £10 each

1/4" BSP Air Filter Regulator Compressor Moisture Trap Oil Water Lubricator

 

Edited By Emgee on 05/06/2021 21:50:49

[old martParticipant @oldmart]

You will probably need to buy a quality regulator like a Norgren and connect it downstream of the one on the compressor. The compressor regulator could then be turned up to a pressure range it can cope with. 1 bar is so low that the spring in your regulator is close to being unloaded.

https://www.solenoid-valve.world/category/48?gclid=EAIaIQobChMIgqSrsq-B8QIVBsPVCh0VlwyqEAMYASAAEgLhxPD_BwE

Edited By old mart on 05/06/2021 21:52:08

[Chris GillParticipant @chrisgill22114]

Thanks guys

I had seen some precision regulators at around £400 each but if I can simply add a second one rather than replacing the one on the tank, that makes it easier. I rather like the ones suggested by Old Mart so I'll double check things and get one ordered.

thanks again

[Clive FosterParticipant @clivefoster55965]

Chris

Adding an air bleed in parallel with the model is a quick and dirty method of pushing air consumption up to alevel that the regulator can handle. Probably noisy tho'.

Could also try restricting the supply to the model. I've used a screw down device clamping a flexi hose with a loose ball bearing in the past. But that was to get a stupidly tiny airflow.

Another trick is to put a slug with a small drilled through hole in the line. Think carburettor jet.

Low pressure and low volume air is aright pain to do on the cheap.

Clive

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Chris Gill on 05/06/2021 22:06:47:

.

I had seen some precision regulators at around £400 each …

.

Is there any reason why this would not work on Air ?

**LINK**

https://bullfinch-gas.co.uk/regulators/bullfinch-regulators/variable-tinyreg-for-propane-0-1-bar-detail

MichaelG.

[JasonBModerator @jasonb]

I don't have any problems with my Machine mart one, I set it to about 5psi as my models don't need more than that and it stays constant and just kicks in when the tank pressure drops. Same when I'm running the CNC at about 1 bar it stays constant can be "on" for an hour or more.

I do set the regulator with air flowing and on the models have a Flow not pressure valve to set the speed, infact I have a manifold with several of these valves so more than one engine can be run at it's desired speed.

[John ReeseParticipant @johnreese12848]

Precision regulators are available on the bay for reasonable prices.

[Stuart Smith 5Participant @stuartsmith5]

Jason

What type of pipe and fittings do you use? Is the manifold a commercial one or did you make it?

Thanks

Stuart

[JasonBModerator @jasonb]

Just push fit PVC pipe and fittings off the likes of MSC or Bearing boys. I made the manifold, it's just a bit of flat ali bar drilled along most of its length and threaded for a Q/R at teh end then tapped along one side for 4, 6 & 8mm flow valves.

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