|Forum topic by JeffP||posted 09-17-2015 09:42 PM||982 views||0 times favorited||15 replies|
09-17-2015 09:42 PM
Let me start by apologizing for what is likely to be an over-long and somewhat disorganized posting. You see, as the title says…I’m confused.
Here’s the setup. I’ve been using a small “filter bag and plastic bag” style portable dust collector for awhile now, just hooked straight up to my saw with a 4” flexible hose.
With that setup, the suction and dust collection have seemed “adequate” or “expected”.
Now that I finally have my planer set up and in use, my shop is simply covered in chips…time to actually execute some of the plans I’ve had for dust collection for a long time.
Main plan is to put this unit outside the shop wall under a lean-to addition I just built, along with a trash-can style “cyclone” and remove the filter and the collection bag. That’s where this story actually begins…last couple days I’ve been throwing together a super-cheap and not very inventive trash-can separator. Confusion came from my testing of same.
I finished putting it together (just a Lowes $24 metal trash can – two 4” holes in the lid with one straight and one elbow – blow the dust around the perimeter and suck the air out the middle at the top). It works remarkably well…just sucked up enough stuff off the shop floor for about 3 inches of dust/chips in the bottom of the can…nary a dust mote in the plastic bag.
Now for the confusion, which as the title stated, has to do with hose size. When I went to test this thing I realized I only had ONE 4 inch flexible hose…needed two. Wanted to test it anyway, so I stole the remarkably whimpy hose from my shop vac (barely an inch diameter at the business end) and made a reducer ring out of plywood to make an air-tight connection between the separator and the little hose.
Well, I was absolutely shocked at how little suction power I had at the other end of that dinky hose! I stretched it out and peered down it to verify there wasn’t a mouse or something stuck in there…nope, can see daylight out the other end. What’s the deal? This big hefty dust collector isn’t pulling even a quarter of the air through that hose that a shop vac would pull?
If I take the reducer out and feel the air at the input of the trash can separator…seems about the same as what I get right at the “nozzle” of the dust collector. Not loosing it all in the separator as I feared. Verified by hooking dinky hose right up to the input of the DC. Same result.
So I’m confused. I wasn’t expecting as much air moving with the tiny hose…but I expected to feel good suction when I put my hand on the end of the tiny hose. Nope, wimpy. Sadness and confusion ensue.
It is messing with my mental model of how suction works. Just based on what happens with a shop vac when you put your hand over the end of the hose…seems like this big sucker should be at least comparable.
My plans for the larger system originally included putting in a blast-gated connection for this kind of a hose for general clean-up around the shop. This makes me think it would have to be hooked to a shop vac instead.
Can somebody clear this up for me?
-- Last week I finally got my $*i# together. Unfortunately, it was in my shop, so I will probably never find it again.