View Full Version : what size cyclone?
09-11-2008, 12:52 AM
I'm looking for a cyclone to add to my shop.
I have an old 2 HP dust collector (by Delta), but it is really a Cincinnati Fan model SPB-12 blower on a 55 gallon drum. It has a 12-3/8" straight blade impeller, and is rated for: 1340 CFM at 1" SP, 1060 CFM at 4", 710 CFM at 8" SP, and 400 CFM at 10" SP.
I'd like an "add on" cyclone to use with the this old motor/impeller combo that I already have. My workshop is the "2 car garage" type of hobbyist shop. One tool operation at a time. I don't have ducting designed out to the tools yet.
My question is basically which cyclone should I use, the 14" or 18" model?
Thanks for any help.
09-11-2008, 01:25 AM
When I first started looking into this, my first thought as well was to add a cyclone to my own Delta, but mine is the 1 HP version rated, I think, around 700 CFM. Also mounted on a 55 gal. drum, and best described as a two stage. And if yours is like mine, the final filter bag is at best 5 micron, and ends up spewing as much dust as it captures.
I gave up trying to make it better by adding a cyclone. In the end I was going to have a huge yet underpowered contraption, and I'd also have to figure out a better final filter arrangement. You may have a better shot at it because yours is higher power.
If you've found Pentz' site, there's an Excel spreadsheet he put together where you can play with HP rating (and maybe even CFM, but maybe not) and the routine solves for the cyclone design. From memory, which may be rusty, I think at 2 HP, Pentz' routine results in a 22" diameter cyclone. Which will also be tall as he uses a cone ratio of 1.64.
It is sort of counterintuitive. One might think lower HP would yield a smaller cyclone, but it actually takes a larger cyclone body. Setting up the swirl takes more power as the diameter shrinks.
Though Ed and / or Matt may slap me for this, I will note other manufacturers sell cyclones with smaller HP motors. It may be possible to adapt your fan and motor unit to one of their bodies, though I'm not going to make any performance predictions.
I'm also going to point out that if your dust collection needs are on the small side, and funds are tight (who's aren't these days) your needs may be met with a Mini hooked up to a good shop vac. Or the Mini adaptor for the two Ridgid models listed on CV's homepage.
09-16-2008, 12:28 AM
Thanks, dwdrury. Pentz literature and sizing spreadsheet are a bit contradictory, but somewhere in the 20" to 24" diameter seems to be recommended. The spreadsheet says 24" diameter for a 2 HP motor and "standard" impeller, but most of Bill's write-ups seem to point to 20" or 22". I'll probably go with 22" since I don't have height limitations (vaulted ceilings, 9' to 14') and I'll have a local sheet metal outfit quote me to build it. I'd love to buy a Clear Vue (they are just too cool!), but I'll probably spend 1/2 as much on a sheet metal version and based on Pentz' info, the 18" just isn't quite big enough for my smaller fan motor/impeller combo. I can't afford to invest in the larger motor/impeller system, and need to work with what I have.
09-16-2008, 02:30 AM
Good luck with it, Mountaingrover. Hope it works out for you. Seems Ed and Matt are quite open with these forums and the photo gallery. Some might be interested in the your results, what worked, what didn't, that sort of stuff. So I'm fairly sure if you wish to post here or in the gallery, that would be OK by them. Plus, if you run into other obstacles, that's what the forums are here for.
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