HF DC - converting to larger diameter inlet?

[Greg Peterson]

Recently purchased the HF DC, installed the Wynn Spun Bond Polyester filter and 4 mil poly bag, so I'm thinking I'm ready to go.

Well, actually, I need to get my hands on some flex hose first. I will be hooking this up to each machine as the need arises. Eventually I'll get something a little more permenent, but my main concern for now is to try to reduce as much fine dust as is possible.

So I'm looking at the impeller housing and notice that the inlet is a single sheet of sheet metal mounting onto the impeller box. This inlet could be removed and replaced with a piece of 3/4" plywood, with some sheet metal attached to the inside surface to prevent damage to the plywood, and a five or six inch diameter inlet.

Is the impeller to small to for a five or six inch inlet?

A four inch inlet has a limited amount of CFM at a given RPM of the impeller. Without changing the RPM's or impeller diameter, will increasing the inlet also increase the CFM's? I'm sure there is a very fundamental flaw here, I'm just not seeing it.

Anyway, I was just thinking.

[Jason Beam]

Stranger things have been tried. Keep an amp meter on the thing while it's running and be sure you don't cause it to overload. These devices use their most power when actually moving air so if you increase how much air it can suck, it could be too much for it's motor. That said, I know that many of these blowers are built to keep the airflow in a safe area and some overcompensate. Worst case, you see a big amperage spike, freak out and put the original sheet metal back on it :P

[Nissim Avrahami]

Any increase of the duct dia will increase the flow.
The impeller will move the max air quantity if it was just in a free air but...

You must increase both the inlet and the outlet. Lets say that the inlet is 4" dia and the outlet is 2" dia. In this case, increasing the inlet to 6" would not help you and you'll get the same airflow that is limited by the 2" outlet that is acting as an aiflow restrictor.

Another point to consider is the motor load (or Ampers).
If you'll increase the inlet and outlet ducts dia, the motor will work harder, consume more Ampers and will get hotter. Usually, the makers are protecting the motor max Amperage by limiting the inlet and/or outlet duct diameter otherwise you'll get the "6.5 peak HP" just a second before the motor starts "smoking".

I think that the best way to increase the airflow is to change the motor/impeller (and duct) to a one that is designed for the required airflow.

[Greg Peterson]

Alrighty then. No free lunch.

I'll leave it as is for now.

Thanks guys.

[M Toupin]

Greg,

BLUF- modifying the inlet will increase the flow a bit and it's a quick and easy mod.

I did just that, replaced the inlet with a 6" and added a Wynn filter. It made a noticeable improvement, though I can't say how much each effected it. It just stands to reason if you increase the inlet it'll be able to pull more air (to a point). I did not do anything with the outlet which stock is 5" which is obviously a limiting factor here. Modifying the outlet would be ideal, but it's a lot more work too. I've never put a amp meter on it, but I've run it for hours and the motor has never got excessively hot.

Now, stand by for the DC snobs who will be along shortly to provide all the dire predictions that you're going to die a slow and agonizing death for even thinking about a HF DC, much less owning one.:rolleyes:

Mike

[Bruce Benjamin]

So I'm looking at the impeller housing and notice that the inlet is a single sheet of sheet metal mounting onto the impeller box. This inlet could be removed and replaced with a piece of 3/4" plywood, with some sheet metal attached to the inside surface to prevent damage to the plywood, and a five or six inch diameter inlet.

Is the impeller to small to for a five or six inch inlet?

A four inch inlet has a limited amount of CFM at a given RPM of the impeller. Without changing the RPM's or impeller diameter, will increasing the inlet also increase the CFM's? I'm sure there is a very fundamental flaw here, I'm just not seeing it.

Anyway, I was just thinking.


I'm guessing you haven't already measured the stock inlet. The inlet on my HFDC is already 5" with a, "Y" that splits it into two 4" inlets. I bring this up because you're talking about converting it into a 5 or 6 inch inlet.

I can't give you any info on whether or not a 6" inlet will work with the stock impeller or not but I do believe I've read of someone else doing this before. If I were you I'd just leave it at the stock 5". It's not a high powered unit that moves a ton of air and I haven't read a lot of success stories of people trying to use 6" pipe with the HFDC. I'm very satisfied with mine with the Wynn cartridge filter and a 4" flex hose. I move it from machine to machine and it works well for me.

If you do decide to convert to a 6" inlet report back and let us know if you have an increase or decrease in performance. I'm curious to see how this works out.

Bruce

[M Toupin]

The inlet on my HFDC is already 5" with a, "Y" that splits it into two 4" inlets.

That's interesting, mine came with a 4" and the 4" X 4" "Y". There seems to be lot a of differences in various HF DC. Mine came with a 11 3/4" impeller, I know they also came with a 10 1/4" impeller as a friend has one. I'm not sure what's shipping now as mine is several years old. Guess it depends on who's making them for HF at the moment.

I'd agree, if the inlet is already 5" then it wouldn't make much difference if the outlet is still 5". In my case the inlet was 4" and I opened it to 6" and left the outlet stock at 5".

Mike

[Greg Peterson]

I'm just going to leave it stock for now. If in the future I to experiment I'll post my results.

Is there any benefit to running a five inch flex hose and using a reducer at the tool versus using a four inch flex hose with the reducer at the impeller box?

My intention is to provide better DC in my attached shop (garage) than I currently have, which is none. We've seen the disparity of opinions about DC and I'm in no position to endorse, confirm or deny any opinion offered.

I am merely attempting to address my concerns about DC in a manner that is effective and efficient.

I believe the Wynn filter kit is a step in the right direction. I am also purchasing a particle counter as part of a group buy. Link (http://www.sawmillcreek.org/showthread.php?t=73903)

I haven't been working in the shop for a few weeks now, so I think that I'll be able to establish a reasonable baseline with for the meter to determine how effectively the HF/Wynn unit is collecting fine dust particles. Granted the conditions will not be perfect, but I'll be able to at least get a fairly good idea of how much fine dust is in the air and how long it takes to settle.

[John Williamson]

If I read you correctly and you will be moving it from machine to machine it will work fine with 4" hose connected to the DC.

[Curt Harms]

......Is there any benefit to running a five inch flex hose and using a reducer at the tool versus using a four inch flex hose with the reducer at the impeller box?

Preface: I have no numbers to back up this line of thought. Having said that, I think there is benefit to using flex hose with a diameter larger than the inlet diameter. There has to be a "boundary layer" effect from the rough interior of the hose, so that a 6" flex hose will not move the same CFM at the same velocity as a smooth 6" pipe. Therefore having flex 6" might pass about the same CFM as the same velocity as a short 4" smooth inlet. Am I nuts?

Prolly:o

Curt

[Phil Thien]

Preface: I have no numbers to back up this line of thought. Having said that, I think there is benefit to using flex hose with a diameter larger than the inlet diameter. There has to be a "boundary layer" effect from the rough interior of the hose, so that a 6" flex hose will not move the same CFM at the same velocity as a smooth 6" pipe. Therefore having flex 6" might pass about the same CFM as the same velocity as a short 4" smooth inlet. Am I nuts?

Prolly:o

Curt

Reductions as close to the terminus as possible will maximize CFM.

[Greg Peterson]

Clarifications:

1. DC will be connected to single machine at a time.

2. Inlet and outlet are five inches in diameter. Lip on the inlet is curled inward slightly, reducing the actual ID about a quarter inch.

Phil, if I understand you correctly, reduce the diameter of the DC line as close to the tool as possible? In my case, I would run a five inch hose to the tool and then reduce to the outlet size of the tools DC connection.