Thread: New DC advice sought

What you are paying for there is the cyclone and the pleated cartridge. If you look at the single bag version, it has the same specs without the pleated cartridge and it's only $280.

I have the twin bag version, which is 3HP and 2300 CFM. More than enough for my needs. It does not require 15 amps. The two biggest issues with it are that there are two bags to empty (but you only have to do it half as often - although one always seems to fill up faster) and it is a big ungainly thing to lug around and takes up a lot of space. If I ducted it in and put it in a shed outside it would be significantly better.

So I guess you have to weigh up whether you really want the cyclone. The advantage is that it is supposed to be more consistent performance-wise with less things to clog up as the bags fill. Having said that I have yet to have an issue with performance with mine - although that could change if I ever plumb it in. It has been 10 years now so don't hold your breath.

I'm sure the cyclone is better, but is it $700 better? That is the question I would ask myself.

Also the one you are looking at claims to need 15 amps so you need to consider that in conjunction with any machine that will be running at the same time. It will probably come with a 15 amp plug.

The 1200 cfm figure will be based on a naked impeller single point measurement in the middle of the air stream but in practice will be much less.
In addition the cyclone is an old design meaning it will further reduce airflow.
If 4" ducting is used no more than about 400 cfm will flow, if 6" is used I doubt whether it will get 800 cfm.
The collection bin is woefully small and you will need to empty it way too often.

SilentC's 3HP claiming 2300 CFM will also be based on a single point measurement.
With clean bags and if 6" ducting is used all the way and machines are opened up to take advantage of the ducting the most that will flow will be about 1250 cfm. That's all the 6" ducting will allow. If 4" ducting is use only ~420 cfm will flow no matter what else is done.

2HP is in most cases still too small for most applications
The only 2HP that comes even close top the (1000 actual CFM) is the generic 2HP DC that has been modified according to this thread https://www.woodworkforums.com/showth...ht=generic+2HP.
Note it still does not meet the 1000 cfm specification but it is the closest you will get with a 2HP.
If it is not modified it will be too far from the 1000 CFM spec.

For the price of that 2HP cyclone you will be far better off buying a large 3HP unit.

Bear in mind that the DC is only one clown in the circus of dust collection.
The DC should be vented or located outside the shed
To achieve 1000 CFM a minimum of 6" ducting much be used all the way
and machines air outlets must be modified to be able to use the 6" ducting.

Thanks heaps guys,

so the conclusion I draw is:

That cyclone - largely waste of time and will reduce airflow too much & a lack of "horses" anyway.

In terms of bang for the buck, better to go for: http://www.machineryhouse.com.au/W329

Place outside if possible (which is somewhat easier said than done ... and I don't want to p!ss off the neighbors too much).

Augment with "current" cyclone later (Pentz) ...

Is that a fair synopsis ?

That's the one I have.

The reason I bought it was that I intended to make a cyclone one day and the motor would be sufficient for that. I have every reason to make one because my brother in law is a sheetmetal worker and I have access to all the equipment and materials to make one easily. The reason I haven't is that I am still dragging it around from machine to machine (not as bad as it sounds, I actually only usually have to move the connecting hose) and it sucks up all the dust I need it to. One of those if it ain't broken don't fix it scenarios. Or just lazy, depending how you look at it...

Originally Posted by Glenn.Visca

Thanks heaps guys, so the conclusion I draw is:
That cyclone - largely waste of time and will reduce airflow too much & a lack of "horses" anyway.
In terms of bang for the buck, better to go for: http://www.machineryhouse.com.au/W329
Place outside if possible (which is somewhat easier said than done ... and I don't want to p!ss off the neighbors too much).
Augment with "current" cyclone later (Pentz) ...
Is that a fair synopsis ?

Yep.

Thanks again guys ...

I have something of a blank canvass to work with because we only moved into a new house last November and I have the luxury of a two car colorbond garage at the rear of the blocky as a dedicated workshop.

The garage attached to the house (larger again) is for the caravan and non workshop stuff.

The only machine I have with a dust port is my new Jet 16" thicknesser ... All other machines pre-date dust collection.

Hey bob ... Here's a question for you ... With a story first. I once owned acreage property, and was going to irrigate with 1" agg pressure pipe. When I spoke to an irrigation mob, they said it would not work due to hydro friction ... Regardless of how much pressure one can generate. So, despite the property being fed by a 1" main, we ran a 2" ring main around the property which significantly reduces the hydro friction. They even said the 1" output from my tank pump would be better opened up as quickly as possible to the 2" ring main.

So similarly, does the cfm reduction by say a 4" duct get worse with distance?

Such that a 4" port that quickly opens to 6" main ( say within the first foot) is more effective than a 4" port that might open to 6" after say 10 feet ? The total length of duct in the above is constant, and the main input to DC is also constant.

The difference is just the duct composition.

I hope the question makes sense.

If I can but in here, I don't think Bob will mind, if we look at one particular set of terms in the Darcy-Weisbach equation for flow loss in pipes due to friction we have (L/D), L=length and D=diameter, so if we have a long pipe and small diameter, say 10/.1=100, if we double the size of the pipe 10/.2=50 or shorten the length of pipe 1/.2=5 the smaller this number is the smaller the total flow loss will be, (from friction) so big diameter and short pipe length are good.

Hope this helps,
Pete.

Originally Posted by Glenn.Visca

Hey bob ... Here's a question for you ... With a story first. I once owned acreage property, and was going to irrigate with 1" agg pressure pipe. When I spoke to an irrigation mob, they said it would not work due to hydro friction ... Regardless of how much pressure one can generate. So, despite the property being fed by a 1" main, we ran a 2" ring main around the property which significantly reduces the hydro friction. They even said the 1" output from my tank pump would be better opened up as quickly as possible to the 2" ring main.
So similarly, does the cfm reduction by say a 4" duct get worse with distance?

Yes you will lose pressure and that translates to less flow.
Of course opening something up a s quickly as possible to the a bigger pipe will produce a better flow than, not but using a constriction in the pipe in the first place is what really kills the flow.
A 4" orifice in a 6" line acts like a gateway or limiting step in a sequence. It's like squeezing 4 lanes of traffic into one and then back to 4 lanes again, you will never recover the traffic density flow because of this choke point
At normal DC pressures them most you can get through a 4" orifice irrespective of length. is about 400 CFM.
Then if it is attached to a 4" pipe the longer the pipe the even slower the flow


The difference between water flow and sawdust is that it doesn't matter if the water flow gets really slow in huge pipes, but for saws dust it does matter because if the flow is too slow the sawdust will fall out of suspension and will only be picked up if the flow in the big pipe is increased - this is a problem for 4" pipes feeding into a 6" pipe

400 cfm in a 4" pipe translates to a linear air speed in the pipe of about 4600 ft per minute (fpm). This is above the 4000 fpm limit needed to keep sawdust in suspension so all is OK.
Now if that is connected to a 6" pipe the 400 cfm translates to only 2000 fpm so the sawdust will fall out of suspension.
To prevent this happening you will need a DC that can generate at least 800 cfm and to open up at least one other unrestricted 4" opening into the 6" line.

Loverly !! And many thanks for such speedy and informative responses !!

Hi again ...

Still trying to get my head around a little of the sciences here.

So ... What are the implications of say breaking a 6" out to 3 x 4" near the machine ? Say a table saw ? 1 overhead, 1 underneath and 1 ... Ummm ... Underneath somewhere elae ( best I can think of)

Equally (and by comparison), would 3 x 6" be more effective ? Or less ?

Apologies if I haven't expressed the question well.

Originally Posted by Glenn.Visca

Hi again ...

Still trying to get my head around a little of the sciences here.

So ... What are the implications of say breaking a 6" out to 3 x 4" near the machine ? Say a table saw ? 1 overhead, 1 underneath and 1 ... Ummm ... Underneath somewhere elae ( best I can think of)

Equally (and by comparison), would 3 x 6" be more effective ? Or less ?

Apologies if I haven't expressed the question well.

There's two KPI's needed
1) Max flow (Cubic Ft per Min [CFM]) removes fine dust and is best achieved using the duct with the greatest diameter or more ducts.
and
2) Max air speed (Ft Per Min [FPM]) holds sawdust in suspension and it means not using ducting of too large a diameter. It turns out that there is minimum air speed of 4000 FPM needed to keep saw dust suspended so this is the figure that systems are usually built around.

If you use 3 x 6" pipes on a generic DC the flow is split across the three which drops the air speed which means the sawdust will not stay suspended.
If you use 6 x 2" pipes you will have great air speed but the flow will be low so it won't collect enough fine dust.

On a table saw the usual split is 4" at the guard and 6" at the cabinet.
3 x 4" is sometimes used on a bandsaw

To use 3 x 6" ducts and maintain 4000 fpm through all 3 requires a DC that could pull a real 2400 cfm - that's about a 5HP motor and 16" impeller.

Thanks again Bob.

Not long ago, I remember seeing some pictures / diagrams etc. of suggestions for housing a dust collector in an indoor cabinet, but vented to outside - but be buggered if I can find them.

Could I be so bold as to ask you to either re-post them here / or re-post the link ? Sorry to do that ... but I have searched and searched with no luck.

Originally Posted by Glenn.Visca

Thanks again Bob.

Not long ago, I remember seeing some pictures / diagrams etc. of suggestions for housing a dust collector in an indoor cabinet, but vented to outside - but be buggered if I can find them.

Could I be so bold as to ask you to either re-post them here / or re-post the link ? Sorry to do that ... but I have searched and searched with no luck.

Zelk's setup is one of the neatest on the forum.
It starts at post 45 in this thread https://www.woodworkforums.com/showth...t=46103&page=3

Wow ... you are right - that is very neat. I can see how I might be able to alter it and have the grilled vent lead outside rather than back into the shed.

I would also expect one needs a vent to allow cool air to the motor or it could run the risk of cooking ... would it not ? Or does the general air volume through the whole cabinet allow for cooling of the motor ?