Troubleshooting my Grizzly conversion ... pics

[pdxer]

I'm finishing up a baffle install on my 2 HP Grizzly DC based on TIMMYG's recent post: http://www.jpthien.com/smf/index.php?topic=227

I fitted the DC barrel with a hardboard baffle using the specs found on this forum, mated the barrel to a standard metal trashcan with an MDF ring, and moved the impeller downstream from the separator. I am also experimenting with venting the exhaust outside, and I'm currently set up with a run of 4" PVC (which I had on hand) going out my shop window. If I can get things working well I will replace the exhaust run with a shorter run of 5" or 6" pipe mounted permanently to a hole in the wall. I'll attach some kind of hood or diffuser outside.

The problem I'm seeing is that I'm getting much more debris in the exhaust than I was expecting. If I drop a small handful of dust/chips into the intake, I see a big puff of dust out of the exhaust. With a more steady feed rate it's less obvious, but after short time I do find a clear scatter pattern at the end of the hose outside (see photo). My eyeball estimate is that 1/3 to 1/2 of the dust is exiting the system. I can't really tell if it's a poor separation problem (debris failing to fall into the can), or if it's scrubbing (debris getting pulled out of the can). Here are a few pics of my setup --- please let me know if you see any problems or have suggestions.

Barrel upside down before attaching baffle
The baffle sits about 1" below the inlet
The metal pipe extends about 2" into the barrel

Discharge scatter from pipe outside
Inside the can -- does the clean spot suggest cyclonic scrubbing?

Thanks for your thoughts, and thanks to Phil for your work on the baffle design!

Nate

[phil (admin)]

How far beneath the lid is that outlet tube (the one leading to the blower) extending?

[pdxer]

The metal outlet tube between the 5" flex and the barrel extends about 2" below the MDF. That puts the end of it close to flush with the lower end of the funnel part of the barrel. I can post a pic if needed.

[phil (admin)]

Okay.  The next thing to check would be for leaks.  I'd get some masking tape and wrap the seam between the DC ring and the MDF donut you made, and then the MDF donut and the can.  Finally, I'd also wrap some around the ring and the MDF top you've added to the ring, and any seams on the can itself.

Then give it another go and let me know.

[pdxer]

I sealed everything up with duct tape today. I only had time to do a brief test, but I do think the tape helped quite a bit. I'll do more testing this week and let you know.

I noticed that the more sealed things are, the quieter it gets, especially with the exhaust going outside. I never realized just how much of the DC noise is from air hissing through the bags and any other little leaks. It's not exactly quiet now, but it's noticeably quieter. It makes me want to spend some time carefully sealing up all the duct work in the shop.

I'm not so sure that you can expect zero dust to escape out the exhaust.

I'm definitely expecting that there will always be some fine dust in the exhaust. I'd be very pleased to get it clean enough to vent outside without sending big plumes toward my neighbor's house or seeing debris accumulating on the ground over time. I will say that the dust I have been seeing in the exhaust so far appears to be of the very fine variety -- no chips of any size.

Could part of the issue be the lack of filter on the output, and so less back pressure at the separator? What differences would you expect when I change out the current 4-inch x 15 foot exhaust pipe to a 5 or 6-inch x 4 foot long run?

[phil (admin)]

There are other guys that are exhausting outside (no filter).  They don't get accumulation.  Most of them keep the outlet up a little higher (typically towards the top of the structure).  One other fellow at sawmillcreek put the outlet at the bottom of his structure w/ an elbow, so the exhaust is blowing directly at the ground.  That seems to work w/o accumulation, too.

Most of the problems w/ excess material making it out the exhaust come from leaks.  The problem is plugging those leaks w/o making it a pain to empty the bin.

[pdxer]

I have a basement shop with poured concrete walls, so I'm somewhat limited on how I can route the exhaust. I plan to run the venting duct through the rim joist, which is about 3 feet above ground level outside. From there I could go up, down or sideways. I'll definitely take a look at what others have done, and I might try it a couple different ways before I make it permanent. One option I have is to bring the vent out underneath the front porch, which would hide it and might help cut down on the noise.

What size hose are you useing that goes from the separator to the blower, 5" ? If so, theres a better way to connect it to the separator.

CharlieL: Yeah, I'm using the 5" hose that came with the original DC. Can you describe your method of attaching it?