I have a MaxAir 5hp 60gal compressor about 7 years old. I've been reading on how to quiet it down but when I stand near it a lot of the noise always seemed to come from the fan guard/shroud vibrating. If I grabbed it and really leaned into it it would quiet it down a bit but nothing substantial. Still, just listening to it, it always sounded like a rattle rather than the intake was making a lot of the noise.
I looked into it and found the shroud was a 2 piece box about 26" x 13" x3". More importantly it was only mounted to the main mount plate along the bottom of the inner shroud by 5 bolts. The outer shroud attaches to that with just 3 small bolts.
The 3" thickness is made up of the tin being bent on all four sides but for corner joints there is just one small tack weld in the middle of the flap. Just holding it and tapping it lightly you could feel and hear the resonance as if it were a tin speaker.
I had some rubberized webbing so cut a strip 26" long to run between the inner shroud and the main mount plate and cut some small pieces to put inside so the shroud was sandwiched between the main mount plate and the bolt heads. There was only about 5/16" clearance between the inner shroud and the flywheel/fan so the thin webbing was about the maximum thickness of isolating material I could use.
I used fender washers inside to cover the large rubber washers there.
The 3" thick section is where the 2 pieces join. The inner shroud has a 1" lip bent into the metal where the 3" lip of the outer shroud is screwed to it with the 3 bolts (1 on each side and 1 on the top). I put a strip of silicone along the 1" lip of the inner shroud and laid 1/2" wide strips of very large rubber bands all the way around this lip and held it in place with a strip of cloth tape. This added about 3/16" to the dimension of the inner shroud so I had to bend the flaps of the outer shroud slightly outward so it would fit over the inner shroud lips.
I felt the shroud needed better mounting other than just along the bottom so I drilled 2 holes in the top of the inner shroud and added 2 angle iron struts which bolted to the main compressor mount plate and really made the shroud a solid component.
I couldn't wait for the silicone to set before testing it so I just ran it for about 10 seconds and am happy to report it sounds a whopping 50% quieter than before. I wished I'd taken some decibel readings.
I looked into it and found the shroud was a 2 piece box about 26" x 13" x3". More importantly it was only mounted to the main mount plate along the bottom of the inner shroud by 5 bolts. The outer shroud attaches to that with just 3 small bolts.
The 3" thickness is made up of the tin being bent on all four sides but for corner joints there is just one small tack weld in the middle of the flap. Just holding it and tapping it lightly you could feel and hear the resonance as if it were a tin speaker.
I had some rubberized webbing so cut a strip 26" long to run between the inner shroud and the main mount plate and cut some small pieces to put inside so the shroud was sandwiched between the main mount plate and the bolt heads. There was only about 5/16" clearance between the inner shroud and the flywheel/fan so the thin webbing was about the maximum thickness of isolating material I could use.
I used fender washers inside to cover the large rubber washers there.
The 3" thick section is where the 2 pieces join. The inner shroud has a 1" lip bent into the metal where the 3" lip of the outer shroud is screwed to it with the 3 bolts (1 on each side and 1 on the top). I put a strip of silicone along the 1" lip of the inner shroud and laid 1/2" wide strips of very large rubber bands all the way around this lip and held it in place with a strip of cloth tape. This added about 3/16" to the dimension of the inner shroud so I had to bend the flaps of the outer shroud slightly outward so it would fit over the inner shroud lips.
I felt the shroud needed better mounting other than just along the bottom so I drilled 2 holes in the top of the inner shroud and added 2 angle iron struts which bolted to the main compressor mount plate and really made the shroud a solid component.
I couldn't wait for the silicone to set before testing it so I just ran it for about 10 seconds and am happy to report it sounds a whopping 50% quieter than before. I wished I'd taken some decibel readings.