Wood Mag. Tests DC incl. HF DC

[LCHIEN]

Wood magazine, March 2008 issue just came with Niki's pic as most prolific tipster on page 14. They also have a comprehensive test review of DCs from 1.5 to 2 HP and it includes the HF.

Here's a link to their accompanying video (the link in the magazine doesn't work).
http://link.brightcove.com/services/...ctid1358275259

One thing, I always knew the HF's claim of 1600 CFM was way high, but the HF tested at the bottom of all the 1.5 to 2 HP DCs, making only 536 CFM at 4.25 inches of water. It did, however, blow away the 1 HP machine they included for reference.

Now thay also had some comments on bags and filters, noting that the coars filter bags liek 30 micron passed all kinds of stuff. but the 1 and 2 micron bags and the 1 and 2 micron pleated filter canisters worked much better. They also noted that the restriction loss of the coarser filters was much worse, the canister being the best. In fact a canister over a 30 micron bag was noted to allow as much as 80 CFM more.

They only tested bag variations on one un-named machine but apparently it extrapolates to the other machines. Which means maybe the HF is not quite as bad as it seems (since it is handicaped by its bags) if you upgrade to decent bags or a canister.

The cream of the crop was the Delta 50-760 which had the most CFM under certain conditions... it has different construction with the motor/impellor housing built into the center ring with no hose as all the others, this apparently raises the CFMs by lower restriction but it does not have the power to pull great pressures, thus it would be good for single machien hookups, not long piping runs.

I think this mirrors another review in another magazine last year, showing similar results.

You who read my posts know I'm into measuring things, it seems like they did a pretty good job in this test and I can't find much to fault.

[ironhat]

Gee, you inspired me to upgrade to a cartridge, Loring. I had been of the opinion that because my DC isn't in my workspace I wasn't too worried about the 'fines' getting loose in the garage. Now there's a performance upgrade for me to consider - well, I knew this before but put it off and forgot about the benefit. Thanks for cutting to the chase of the test!

[final_t]

Is there any way to reasonably measure the CFM and/or static pressure in our typical shops without restoring to some obviously specialized expensive equipment? I would be interested to see what the results would be on my heavily modified HF system.

[leehljp]

Would it be economically viable to have two smaller (small-mid size) DCs - one on a permanent tool and one mobile for different units versus going to a larger unit and lots of duct work?

I am not ready for a DC system yet but I will be in 3 years. I am sure there will be different DC systems available. I also know that I will not be able to install a 220V. But I would like to have everything ready in my mind.

I will have a 12 by 18 shop with a 6 X 18 attached side room. The 6 X 18 will be lathe room and I hope to put a small to mid DC to for two lathes.

[burrellski]

You who read my posts know I'm into measuring things, it seems like they did a pretty good job in this test and I can't find much to fault.

I studied under Dr. Maxwell at Iowa State and can say without a doubt that these results are as accurate as it gets. He's thorough, and I've still got boxes of lab reports to prove it.

[affyx]

Thanks for the post - I just set up my first DC (and uploaded a video of the set-up on my blog if anyone's interested).

The coolest thing about your link to the video is the dueling dovetails video on the same page - that was really neat!

[cgallery]

Is there any way to reasonably measure the CFM and/or static pressure in our typical shops without restoring to some obviously specialized expensive equipment? I would be interested to see what the results would be on my heavily modified HF system.

You can get somewhat decent measurements using a Kestrel weather-vane type anemometer. You wouldn't want to publish the results in a peer-reviewed journal. But if you want to get relative #'s (for example, at the DC and then at the end of your piping run), you can hardly beat them.

I have access to a Dwyer hot-wire anemometer but rarely ever ask to borrow it any longer because I've become quite confident in the #'s I get from the Kestrel.

The Kestrel is perhaps the cream of the small wind meter crop. They claim that their calibration can be traced back to NIST. In the three that I've tried (two of one model, one of a second) they were all within .1-MPH of each other.

It is interesting to note that Kestrel makes a high-end model targeted at HVAC contractors. I think it is the model 4200 and I've seen Johnson Controls employees using them at a large research hospital that I do consulting work for. I just got the Kestrel 1000 which doesn't compute the CFM for me, but I can do that w/ a spreadsheet using the MPH data.

http://www.nkhome.com/ww/wwindex.html

[final_t]

[...]
I just got the Kestrel 1000 which doesn't compute the CFM for me, but I can do that w/ a spreadsheet using the MPH data.

http://www.nkhome.com/ww/wwindex.html

$90 ain't terrible for something like this, but I dunno if I would use it more than once or twice. Can't think of other uses for it right off the bat.

[Knottscott]

You'll definitely get improved filtration by upgrading the bags on the HF DC, but the impeller is small enough that you might not get much in the way of improved air flow.

Bob Dodge, who hangs on out various forums, is very knowledgeable on DC systems. Here's his quote:

"The HF's problem, is not one of excess back-pressure at the filter; the problem is the small impeller. Increasing the filter surface area, will help with filtration efficiency (for a while), but will not provide a significant boost in suction-pressure or CFM."

[cgallery]

$90 ain't terrible for something like this, but I dunno if I would use it more than once or twice. Can't think of other uses for it right off the bat.

You can get less expensive ones on eBay. Just make sure it can handle the higher wind speeds on the ducts. I think the Kestrels go to 84-MPH and 100-MPH won't damage them. If you're patient you can find units on eBay for $40.

[milanuk]

Phil,

Very interesting! I happen to already have a Kestrel 4000 that I use pretty frequently for long range ballistics at the range; I presume you would just hold it in front of the inlet of a length of ducting (length shouldn't matter too much if one is just looking for a relative measurment, right?) to test 'before' and 'after' a change?

Loring,

I've been tryiing to get to that woodmagazine.com page since I got the issue in the mail with no luck. Unfortunately I can't get to the one you linked to either (work nanny filter) for the moment. Would you care to explain to a DC-dummy the importance of the relatively flat curve of the 50-760 as shown in that test vs. the others which seemed to to be more sloped/curved?

TIA,

Monte

[LCHIEN]

Phil,

...
Loring,

I've been tryiing to get to that woodmagazine.com page since I got the issue in the mail with no luck. Unfortunately I can't get to the one you linked to either (work nanny filter) for the moment. Would you care to explain to a DC-dummy the importance of the relatively flat curve of the 50-760 as shown in that test vs. the others which seemed to to be more sloped/curved?

TIA,

Monte

I think that curve is due to the different construction of the Delta unit, it has an integral impellor/DC Ring connection which is achieved by placing the motor higher and eliminating the hose that is used in all the other designs to connect the impellor housing to the DC ring where the filters are mounted. That involves tradeoffs,

one they have a smaller motor (not so heavy, easier to mount mid-level)
two, they have a lower loss due to the lack of that connecting hose and tight turn,
three the combo of lower loss and smaller motor give better CFMs at lower pressure loss.
Seems like a win-win but there are tradeoffs.

This is going to require some graphics aids I'll add later today.

[milanuk]

Thanks Loring. I kind of grasped the sense of the lower losses due to not having a connecting hose between the blower and the collector itself... I guess what I don't get is why it would then not be able to match/exceed performance with any of the other units (which the graph seems to show as being able to pull a higher SP, i.e. support more ducting) of comparable size. I'm sure its something simple that I'm overlooking.

Monte

[maxparot]

Having a test like this in hand I'd like to see what could be done to hotrod the HF DC. Since it is probably the cheapest unit in the test it is worthwhile to invest some time and a few dollar to improve it's performance. If we were to have all the possible gains documented well enough to minimize the investment of materials for others, it would make the unit of more value.
I know that many of us have added pleated cartridge filters and nuetral vanes. I remember reading of modifications to the impeller. Are there any other mods worthwhile? Having a baseline it would be great to see that against each mod separately and then in combination showing the percent of increase in performance for flow and suction.

[LarryG]

I replaced my HF DC's impeller-to-bag-ring hose with 5" stove pipe, making the curve as long and as gentle as I could. The mod required a single two-foot length of pipe, two adjustable ells, and about half a roll of electrical tape to seal the joints. Total cost: under ten dollars. Total time: under an hour.

The WOOD test touched on the importance of maintaining smooth airflow through this connection. I'm persuaded that the mod gave a significant improvement, although I don't have any hard data to support my observations.