Thread: I scored a Hafco DC-3 dust collector - should I do a cyclone conversion?

Yes.

Why?

It's not about the bags filling up it's about the filters clogging up and prematurely reducing the air flow, ie. long before the bags get even 25% full. Nobody can tell you what will work best for you though, do some more reading and chart your own course.

Hehe. I was being a bit facetious.

I think dust collection is one of the most pressing emergencies in all workshops. Dust, floaties and crap going in your lungs strikes me as a very bad thing.

With a cyclone, it may be initially about collection - and I'd admit being in the wide country area and no neighbours it would seem rather unnecessary - but the quality of your air needs to be considered. A big DC moves an absolutely enormous amount of air... every hour, all day. All of that super fine dust is going to end up in the air outside floating around... and it doesn't take much imagination to see that vast invisible cloud of fug filling up the workshop as it descends on you like a Beijing Fog Of Death.

Also, the designs of cyclones makes for a much easier cleanup. The bin/baggie comes right off and doesn't need strong clamps or tape to stop leaks. The bucket literally sucks itself onto the bottom. Cleanup is the worst on any DC. The little cyclone I have is trivial to clean, but the DC is a nightmare.

The biggest drawbacks to a BP cyclone for us city slickers is 3-phase availability, noise, height and outside-ness. None of these apply to you, so with the restrictions lifted the choice is easier.

How rural are you? I have a DC7 type unit which I use in the suburbs in an enclosure next to my garage. I've often thought that if I were deep in the country I would try to find some way of ditching the bags and just blowing into a large vented box which gets emptied occasionally. No cyclone or bags, just try to direct the air out in a way that doesn't make too much mess.

No way you'd get away with this in the burbs. But out in the country, and possibly with a very coarse filter you might make it work. You could possibly structure things so that the amount of dust released into the air is no worse than what you'd get from say using a chainsaw or a mulcher.

Originally Posted by woodPixel

The biggest drawbacks to a BP cyclone for us city slickers is 3-phase availability, ...

My DC-7 is single phase, 3hp.

Originally Posted by WoodyNZ

How rural are you?

Rural residential. I'm on 1 & 3/4 acres. Neighbors house is about 30 meters away from the back wall of my shed.

And I don't like them...

I'm considering buying a DC 7 this week. I would like to buy a cyclone to go with it connected via a 150mm hose.
However:
A. Is the air flow sufficient?
B. Space is limited so I'm wondering if this is practical in my case.
I have 1m between the shed and the boundary on 2 sides. An ugly lean to on the free side where the lawn is wouldn't be ideal.

I have a mini cyclone on the shop vac. Absolute magic!
In fact, vital because otherwise the filter would not be filtering fine dust and I'd just be blowing fine dust back into the shed.

Although the dusty would be outside, I can see the same principle applies because in my case I can't get it very far from a window so some fine dust may waft back inside.

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A 3hp DC does not have the flow rate to support a Clearview cyclone, let alone a poorer design with even more pressure drop. You need a 15" or 16" impeller and a minimum of 4hp to overcome the loss of the cyclone, and that gets you back to around the flow rate of a 3hp DC running at 60hz with a 14" impeller and new bags. You loose between 2.5" and 4.5" of vacuum depending on the cyclone.

I agree with M&J.

Folks should realise that 4.5" of WC can represent as much as half the vacuum loss on even a 3HP DC. It's no good using your hands to measure flow rates as they are just not sensitive enough. Removal of visible dust is not much use either.

Lots of folks that make cyclones or chip catcher with smaller DC marvel how little dust come out of the end and how infrequently they have to clean filters. From this they believe their cyclones are really efficient but often all that has happened is their DC failed to catch a high proportion of the fine dust at source.

Thanks for the comments but I have no idea what 2.5" or 4" is. Even if you explained what that is it would still be nonsensical to me. It may as well be written in Greek.

All I understand is that I'd loose some pressure. However since I started with 2.2kw and opened it up to 150mm ducts in my little single garage shop then I guess it would all be sweet. Correct?

Given that others are starting with 1.5kw machines like a DC 3, that have half the flow of the DC 7, wouldn't I end up with close to what others are doing with their 1.5kw dusties?

Am I missing something?


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Originally Posted by DaveVman

Thanks for the comments but I have no idea what 2.5" or 4" is. Even if you explained what that is it would still be nonsensical to me. It may as well be written in Greek.

The degree of "suck" or vacuum generated by a DC is often measured in "inches of water column" (" of WC). Think about putting a straw vertically just into some water and sucking it up. Most 1HP small DCs have about 6" of WC, mid size DC's have about 8-9" of WC and it takes a big impeller and big motor to generate >12" of WC.
[Its not much is it, but the difference between you sucking on a straw and DC suck, is the bigger DCs can generate that suck in a much larger pipe than a straw.]

If you subtract 4.5" from those values above you can see that you aren't left with much suck.

The BP DC design uses a 15" impeller and 4HP DC only loses 2.25" of WC leaving nearly 10" of WC.

[QUOTE]However since I started with 2.2kw and opened it up to 150mm ducts in my little single garage shop then I guess it would all be sweet. Correct?[QUOTE]
Yep- fine for a single car garage.

Given that others are starting with 1.5kw machines like a DC 3, that have half the flow of the DC 7, wouldn't I end up with close to what others are doing with their 1.5kw dusties?
Am I missing something?

"what others are doing with their 1.5kw dusties" is nothing to get excited about and still not really enough, so I would avoid the cyclone and just clean the bags more often.

My intention isn't to add a cyclone to the DC7. I want to just use the motor and blower from the DC7 and throw the rest away.

My workshop is just a double garage and I'll only be hooked up to one machine at a time.

My fixed equipment will consist of a radial arm saw, thicknesser, small table saw, bandsaw, router table and pedestal drill.

Surely a 3hp motor driving the DC7 blower with a cyclone and 6" ducting would be better than the 1hp, 4" jJet DC I've got now?