What's inside a cylcone muffler?

[Perry Holbrook]

I'm in the middle of a redesign of my cyclone system. The cyclone is outside and currently venting to the outside. So currently I've got no dust or sound returning to the shop. I will be returning the air inside into a large filter covered plentium, so I've got the dust taken care of. I would like to reduce the sound from the cyclone, which sounds like a small jet outside.

Grizzly, has a cyclone muffler on their site that looks to be a small cylinder filled with some type of foam material. Has anyone bought one these mufflers and if so, are they effective and what is that foam material?

BTW, I've read a lot of comments about venting outside doesn't really make that much difference in heating cost. To those people, I would like to invite them to my shop in the dead of winter and watch the 11 kw electric unit heater try to keep up with a 5 HP cyclone running for hours non-stop exhausting heated air to the great outdoors.

Perry

[Dave MacArthur]

The muffler is just a 18" tube of chicken-wire material surrounded by some foam. The inside is empty. Here's a pic of my Oneida muffler from the end.

[Paul Wunder]

http://billpentz.com/woodworking/cyclone/Muffler.cfm

You may also find the above link to Bill Pentz's website useful for specific instructions on building a cyclone muffler. There are specifics re length and diameter that should be considered.

Paul

[ian maybury]

You can build one, but circular section fan exhaust mufflers are pretty much a standard HVAC accessory that can be bought in various lengths and internal diameters from fan and ductwork supply houses - over here anyway. Here's some typical examples: http://www.troxuk.co.uk/uk/products/silencer/cylindrical_attenuators/

An 8in bore sheet metal model of about 1m length with a perforated inner tube wrapped in some sort of mineral wool for the Pentz system i'm mid install of cost me about €50 from a local ductwork outfit - it's probably cheaper in the US. I can't say how well it works yet, but they must do OK given that they are pretty standard usage.

You could make your own. Some talk of using insulated flexible ducting for the same purpose...

[Jim O'Dell]

I've often wondered if one built on the principal that a car muffler is built on would work. Still has the perforated tubing with some sort of absorbing material around it (think of glass packs). But inside a regular muffler, the direction is changed twice. This may cause the sound waves to change direction hitting other sound waves, thus canceling them out to some degree. (Think again of the glass pack...it's straight and therefore louder.) If you've read Jim Becker's folded air return, it works on this principal to help reduce noise. Of course, tight turns even on the exhaust will cut air flow, so if you try this, expand to 12 or 14" piping. Just some random thoughts! Jim.

[Bruce Wrenn]

Mine is just a section of 8" pipe in line with the 6" stuff between cyclone blower and bag plentium. I was going to line it with 1" acustical foam, but my blower makes less noise than any machine in my shop.

[Perry Holbrook]

Thanks for the info, I can take it from here. Sounds like my unit may be much louder than most, but I'll fix that.

Perry