01-27-2015, 08:12 PM
I have a loud direct drive compressor -- looking forward to the time when it dies and I can buy a quieter one.
An interesting point about the oiless direct drive ones, mechanically, and maybe besides the 3450 RPM, a contributor to more noise: they use a wobble piston. There is no separate conrod and wrist pin. The piston is one piece with the rod. The piston metal is thin in the bore direction, and uses a teflon seal, and the cylinders are also plastic coated to allow the piston to wobble and still seal. The speed is high and stroke small, necessarily to get the same air, and not wobble too much. So they are grossly over-square -- big bore, tiny stroke, high speed......and lots of noise.
An interesting point about the oiless direct drive ones, mechanically, and maybe besides the 3450 RPM, a contributor to more noise: they use a wobble piston. There is no separate conrod and wrist pin. The piston is one piece with the rod. The piston metal is thin in the bore direction, and uses a teflon seal, and the cylinders are also plastic coated to allow the piston to wobble and still seal. The speed is high and stroke small, necessarily to get the same air, and not wobble too much. So they are grossly over-square -- big bore, tiny stroke, high speed......and lots of noise.