Standard Bambi duty cycle has always been specified as 50% maximum with run time under 10 minutes. My experience is that they last a very long time at 30% or less duty cycle with run times of 5 minutes or less in normal ambient conditions. Run longer, harder and in hotter environments life rapidly falls off. One reason a Bambi is so quiet is that there is effectively no cooling. Just conduction onto the case. No ring-ding-dingy fins to add noise but they can get way too hot inside if not given a decent cooldown period between runs.
If you want serious air, to run air tools or a blaster, a hydrovane is about the only realistic option. Not as quiet as legend says but certainly not noisy. Cooling fan mostly. My 502 will run the gun in a small Guyson blast cabinet using the smallest nozzle pretty much continously and keep ahead of ordinary air tools. Uses 10 cfm nominal at 100 psiI think. Have a504 in stock that was supposed to replace it but motor is 440 volt delta and I've not figured a sensible way to run that without full fat three phase.
Unfortunately the import silent compressors are anything but. Just as noisy as local brands with the same configuration. Unsurprising as the engineering differences are basically badge and colour.
Cylinder spacing on my old Atlas Vee twin was just right to take a Saab 9000 air filter. A long cylindrical thing. Mad a big difference to the noise. Sold it to a mate who prompty ripped the filter off, refitted the standard wee cans with a bit of mesh inside to each head. Then complained about the noise.
Bottom line is that with small "consumer affordable" piston compressors you are getting around 3 cfm at 100 psi per hp. Which isn't going to come quietly without careful engineering. Quiet usually means low pressure or low delivery. But 30-40 psi is more than enough for most home shop things so daiphragm units can be avery good match in practice.
Ex lorry air brake compressors driven by a standard induction motor can work well if you must have higher pressures. The ones I've seen are fairly hefty iron castings which don't ring like the lightweight alloy heads. But sorting out what you actually have can be a nightmare.
Clive
Edited By Clive Foster on 15/09/2020 23:11:22