# Another Dumb DC Question



## DustyM (May 16, 2016)

I know everyone is sick of these, but what the heck, I've got a question:

I've been using my HF DC in combination with a cheap trash can lid separator and venting outside. Predictably, air flow isn't great, but it's mainly used as a chip collector for my jointer and planer (Note: I am not looking for a perfect DC solution out of this setup). Unfortunately, that separator is pretty lousy, and I have to empty the can before it hits 2/3 full, otherwise I just blow everything outside (on the plus side, it exhausts directly over a flower bed). Also, there's still a fair amount of chips left around my planer and jointer.

My question is this: would I gain anymore suction swapping out the trash can separator for a super dust deputy? I read that cyclones tyipcally produce about 2.5" of static pressure, but those cheap lids are closer to 4.5". I would think that reducing the pressure by ~2" would significantly aid my CFM and do a better job tidying up, but didn't want to drop the money on a SDD for very little payout. A new DC isn't in my future for quite sometime (and the 8ft ceilings in the current shop seem problematic to boot), so I was curious if I'd feel like I truly got my money's worth from switching separators, or if I'd just be putting lipstick on a pig.


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## AZWoody (Jan 18, 2015)

I did a test side by side running a molded trash can separator and an SDD and I had minimal difference between the 2.
I'm sure the separation might be better on the SDD but in terms of cfm, they were pretty much identical. 
The problem is the HF blower. It's just really not that good of a unit in terms of static pressure loss. The impeller is just too small to handle static pressure efficiently.


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## DustyM (May 16, 2016)

> I did a test side by side running a molded trash can separator and an SDD and I had minimal difference between the 2.
> I m sure the separation might be better on the SDD but in terms of cfm, they were pretty much identical.
> The problem is the HF blower. It s just really not that good of a unit in terms of static pressure loss. The impeller is just too small to handle static pressure efficiently.
> 
> - AZWoody


Much obliged, Woody, you saved me some money!

Even though it takes up more floor space and offers no protection for the impeller, I'm considering reassembling the unit as designed and wheeling it close to tools to connect with a short hose. I've heard the back pressure generated by the filter bag has substantially less impact on CFM than a separator.


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## AZWoody (Jan 18, 2015)

> I did a test side by side running a molded trash can separator and an SDD and I had minimal difference between the 2.
> I m sure the separation might be better on the SDD but in terms of cfm, they were pretty much identical.
> The problem is the HF blower. It s just really not that good of a unit in terms of static pressure loss. The impeller is just too small to handle static pressure efficiently.
> 
> ...


Well, it still may be worth it for the separation though. If you're going to put it on a cart, you won't be able to pump it straight outside so you would need a filter and the SDD would keep it from clogging very fast from the finer dust.

If it's just about cost, then the trash can separator is by far the better choice or many people build their own Thien style baffle which I believe will separate better than the trash can separator.


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## CharlesA (Jun 24, 2013)

I'm pretty happy with my Thien baffle.


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## brtech (May 26, 2010)

Theins and DDs have been tested to be about the same in insertion loss and separation efficiency. I would have thought an SDD would be considerably better than a simple trash can separator, but this thread suggests not.


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## DustyM (May 16, 2016)

Well, shucks, now I'm back to considering the SDD. Found this video:






While it may not be the most accurate CFM measurement available, it does show an apples-to-apples testing comparison between a Thien and an SDD, with the Thien causing far more CFM loss than the SDD (and presumable my trash can lid is even worse). Hmm…


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## crank49 (Apr 7, 2010)

Ok, you asked so here it is.
You state that you just vent outside, so I assume you are not using the filter bag at all.
You did not state what size ductwork you are using so I will conclude it is 4" since that is the most common.
If you were running 6" duct for this unit it would probably overload the motor from excess airflow without the filter bag in place. In theory you could run 5" duct for optimum performance. Or, a 4" and a 3" and combine them right at the cyclone/baffle inlet.
Cyclone and Thien baffles both create static loss on a dust collector. The more static pressure loss they create the better the efficiency of separating dust from air. The fan on the HF collector is rather small and does not have much capacity to waste, but without the filter bag there might be enough capacity to do what you are doing.
If you don't have enough air flow with the trashcan lid you are going to have even less with a true cyclone. The more chips and dust you separate the less airflow you will have. That's the. nature of the beast.


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## pintodeluxe (Sep 12, 2010)

Fan diameter and design must have a lot to do with a dust collectors performance. I was trying to test the CFM and air velocity on my Tempest 2hp cyclone with an anemometer. It has a 14" or 15" impeller, and I darn near lost the anemometer up a vertical run of 6" ductwork. It was all I could do to hang on to the tool.

Suffice it to say it maxed out the air velocity on my testing tool, so I concluded it was "A Lot."

My vote is for a complete cyclone package if you can swing it. Preferably a wall mounted unit with hard piping. I messed around with a small portable Jet DC for years, and the difference between that and a full sized unit is astonishing.


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## CharlesA (Jun 24, 2013)

I've never used a robust dust collector, but in my shop I'm pretty happy with the performance of the HF DC ported outside with a thien baffle. Probably better that I don't know what the difference would be.


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## fivecodys (Dec 2, 2013)

> Probably better that I don t know what the difference would be.
> 
> - CharlesA


Yep. Same here!


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## Lazyman (Aug 8, 2014)

To ask the obvious question…did you check to make sure that the lid on the trash can is air tight? If you are losing suction without a filter, make sure you just don't have air leaks. Also, if you are using one of those lids that has the right angle nozzles to create the cyclone effect in the can, those right angles add even more resistance. I think you would get better separation with a nozzle that injects the airstream from the side instead for straight down from the top with a right angle. Finally, a Thein baffle might help reduce how much dust gets swept past the separator by keeping the turbulent air away from the collected dust. Easy to make and might improve how much dust actually ends up in the can versus blown outside.


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## DustyM (May 16, 2016)

> To ask the obvious question…did you check to make sure that the lid on the trash can is air tight? If you are losing suction without a filter, make sure you just don t have air leaks. Also, if you are using one of those lids that has the right angle nozzles to create the cyclone effect in the can, those right angles add even more resistance. I think you would get better separation with a nozzle that injects the airstream from the side instead for straight down from the top with a right angle. Finally, a Thein baffle might help reduce how much dust gets swept past the separator by keeping the turbulent air away from the collected dust. Easy to make and might improve how much dust actually ends up in the can versus blown outside.
> 
> - Lazyman


Well, the lid is as air-tight as I can reasonably get it. I'm aware of the flaws inherant to the cheap design, and that's what really drove my main question regarding whether a dust deputy would not just seperate better, but whether it would add less static pressure to the system than the current lid and thus allow for a little improved airflow.

On that note, did anyone check out the video link I posted? It does seem pretty indicative that performance from an SDD is substantially better than that with a Thien.

Also, again, I'm not trying to turn this thing into something that functions like a true cyclone system that costs 10x the price: I'm just wandering if putting a little more money in it would scale the performance according to my investment.


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## CharlesA (Jun 24, 2013)

Dustin, I'm around the next 3.5 weeks before I start moving to Atlanta. If you want to see how mine works with the Thien, feel free to come by. Mine has 4" pvc ducting to every machine and vents outside. You may be able to compare to your current system, but I don't measure my performance.


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## DustyM (May 16, 2016)

> Dustin, I m around the next 3.5 weeks before I start moving to Atlanta. If you want to see how mine works with the Thien, feel free to come by. Mine has 4" pvc ducting to every machine and vents outside. You may be able to compare to your current system, but I don t measure my performance.
> 
> - CharlesA


Charles, I'll have to take you up on that. I was hoping to get a chance to see your shop before you relocated. And congratulations on the new position!


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## CharlesA (Jun 24, 2013)

Give me a yell.


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## coxhaus (Dec 14, 2015)

Some people with HF DCs are upgrading the impeller they buy from Rikon. It increases your air flow. Google it.

You might try the smoke test to see if you have leaks.


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## CharlesA (Jun 24, 2013)

I have a replacement impeller I was going to install, but I never did.


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