shop vac suction...

I recently bought my first big shop vac. For years I've had a little 12-gallon vac with the small diameter hose. It's been a workhorse, but it's always been annoying in the shop. Every dust port is rigged for big hoses, chips and shavings clog it very easily, etc.
So this year I got one of those $99 18-gallon "6.5 peak HP" combination blower/vac jobs from Lowe's. The blower on this thing is indeed mighty powerful. It took the town forever to get around to cleaning up the gravel left on the road from winter, so when we got out the bikes I went up the street around my house and blew as much of the gravel into the ditch as I could. (As luck would have it, the damn sweeper truck came by the very next day. I'll bet they were watching me out there the day before, and laughing their asses off.)
So anyway, the motor spins, and it moves a lot of air, but the thing doesn't seem to have much suction as a vac. I've never used a vac that had big pipe before, so I have no idea if this is normal or expected. It seems it could be that the size of the bore means effectively high volume, low suction. It does seem capable of sucking up sawdust, chips, and filings, but the thing won't pick up small finishing nails or tiny sheet metal screws. It so reliably refuses to pick up anything the slightest bit heavy, that I can suck dust out of my bins full of small nuts and bolts without any fear that I'll loose things down the pipe (which is sort of a feature, I guess, though I'm actually too paranoid to feel quite comfortable doing that.)
There's a conical accessory that stops the bore down to about 1". If I fit that, it will suck up nails, and then it becomes a cyclone. At the end of the session, I can dump the nails out the business end of the hose. They never go up the pipe at all.
I'm learning how to use this thing to do what it can do, but it seems I won't be getting rid of my trusty old small bore shop vac at this rate. I'd just like to know if this behavior is typical of the breed, or perhaps the side effect of some compromise from making the blower detachable. I debated on that point, figuring it was a stupid gimmick, but this one was the second or third beefiest vac they had, and the next one up had a blower thingie too.
Did I get hosed, or do big vacs suck at sucking? :)
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Michael McIntyre ---- Silvan < snipped-for-privacy@users.sourceforge.net>
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I tried several makes until I settled on one. I would take a clear hose and seal it into the vac hose of the vac and drop the end of the clear hose into a bucket of water to see how high it would pull it straight up above the surface of the water. I found that the lift varied from 18 inches to over 70 inches depending on different makes and models. Most of the manufactures have the info on their machines if you dig deep enough. The CFM (cubic feet per minute) is what the try and sell the machine on. The lift will be in sealed hose. I don't know the exact wording. HP doesn't always mean high lift. It is more related to CFM.

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spearfox wrote:

Did all that, and it seems fine. I took the filter out and brushed it clean, but it didn't make the slightest difference. (Nor did leaving it off.)
I guess it just doesn't suck.
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Michael McIntyre ---- Silvan < snipped-for-privacy@users.sourceforge.net>
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Silvan wrote:

I have the same one from Lowes and mine works great. Hell, I could suck the kids off the sidewalk with it<G>. It sounds like a serious restriction to me. Theres a drain at the bottom of the tank for getting all the crud out, maybe its not closed all the way, or maybe you don't have it fully connected where the hose fits to the tank causing a 'vacuum' leak on the inlet. I think theres a ball inside the area where the filter goes too, maybe its not seated correctly. If those don't help, take that puppy back and ask them or exchange it for another. The unit itself is an awesome.
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John DeBoo wrote:

I've had it for a few months now, I'm afraid, so I can't take it back. I should have thought to ask about it sooner, but I hadn't actually done much with it until I did the huge shop cleanup. I expected it to suck bowling balls, and it won't even pick up a 7/16" nut.
Sounds like I got a lemon indeed. I guess I'll have to go through channels and see what I can do about it.
Or sell it on Ebay for twice the retail price and go buy another one... :)
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John DeBoo wrote:

Good idea.
Of course, when I went to show SWMBO how it doesn't suck (so she'd let me buy the diesel-powered model with the intercooled, dual turbo V16 and 18-speed tranmission) it sucked up a number of rocks, screws, and whatnot using just the straight hose.
Threw some finishing nails on the floor, and fitted one of the... Um...
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thingies, and it wouldn't pick them up.
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Figure 743 watts = 1 horse power. A 6.5 peak horse power will take 4829.5 watts usually ehr turned onat the max. This means it would need 43.9 amps to operate when turned on. Of course that would requre at least a 220 volt line or a huge breaker and you and I know that this isn't needed. So ehat do you have. A shop vac which is not rated like DC motors so at you buy the bigger unit, maybe a 1/2 horse unit.
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