Grizzly provides a complete fan curve for the 1 1/2 HP G0443 cyclone which clearly shows 1025 CFM at 2" SP. Testing this in my shop has shown that the numbers are correct.Originally Posted by Larry Frank
Contributor
Grizzly provides a complete fan curve for the 1 1/2 HP G0443 cyclone which clearly shows 1025 CFM at 2" SP. Testing this in my shop has shown that the numbers are correct.
Contributor
Wood Magazine tested quite a few 1.5 hp Dust collectors and NONE of them reached 1000 cfm.
I see what Grizzly provides for a performance curve but still have my doubts based on what similar DC can do.
Please show us what you used to test the flow.
Contributor
They tested 11 dust collectors, all of which appear to be single stage dust collectors, judging from the pictures. They did not test the Grizzly G0443, which is a two stage cyclone. So apples to oranges. Further this was in 2008, nearly 11 years ago, about the time the first iPhone came out.
Further the G0443 is listed at 1 1/2 HP, but it's closed to 2 HP, with it's 19A draw at 110V.
I used this anemometer, at the outlet of my various ports. It's guaranteed by the manufacturer to be accurate to +/- 40 FPM. I know your next complaint will be that it's not a hot wire Anemometer, but those devices have issues with high velocity air flows, where high velocity is measured as being over 2000 FPM, which is about half the 4000 FPM necessary to get the 1000 CFM air flow. A vane based anemometer can be better in situations like this.
I'm not sure who the manufacturer was for the pitot tube I used to measure the static pressure.
Contributor
If you are happy with a fan type anemometer, then good for you. Measuring with such a device is just not accurate especially at the end of a pipe or hose.
If you are interested enough try the Australian woodworking forum and read BobL's on measuring flow. He is a true expert and does not believe that type of instrument and measuring location are accurate at all.
Contributor
I'm happy enough with it. The truth is that I am able to borrow that tool for free, which is about as much as I'm willing to pay for such a device.
Now that my ducting is setup, and I've tested it, I'm unlikely to do any additional fiddling with it for a long time. What testing I have done has shown me that there are no issues with any of my runs. This includes the longest run at ~40' to the miter saw, which also hits 1025 CFM. At which point the dust shrouds are the primary area of performance loss.
If somebody is curious enough to send me a hit wire anemometer in the mail I'd be willing to do the same tests, and mail back the tool.
If it's not accurate at the end of a pipe, then how does the manufacture intend for it to be used? Why do they show the tool being used at the end of a pipe? Also, if you look at the spec sheet for their hot wire anemometer you'll see that it lists +-60 fpm from 400 fpm to 2953 fpm of air flow, +-20 fpm MORE than the vane based instrument. I can only assume that it's even worse at the ~4000 fpm of air flow necessary to hit Bill Pentz's magic 1000 CFM.
Contributor
The problem at the end of a pipe is unstable air flow and creates unreliable measurements. This would be true no matter what instrument is used at the end of a duct. I have tested a fan anemometer at the end of a duct and got numbers all over the place from 1000 fpm to 5000 fpm.
Accurate measurements are made in the middle of a long straight pipe. The hot wire anemometer is small and is less disruptive to the air stream compared to a fan anemometer.
Why does a mfg show using it? That is easy because he wants to sell it.
Contributor
Turbulence would have the effect of creating a slower reading, rather than a faster one. This why you don't want to use flex pipe if possible.
Member
This report from the US Department of the Interior Bureau of Mines can help you better understand your anemometer readings.
Beranek's Law:
It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.
Contributor
Thanks, a couple of things I get out of this report.
First that they're showing the anemometer going over the end of the pipe. They do indicate that putting it into the pipe is better, but with diminishing returns as the pipe size gets larger.
Second, the inaccuracy is attributed to the area of the pipe blocked by large surface the anemometer they're using. It varies by as much as 10% depending on whether or not they're using a 4 or 8 vane anemometer, and decreases to about 15% difference in larger tubes, with the effect dropping off entirely in 12" or larger pipes. Since these instruments were made in the 80s (which is when the report dates from, they could be even earlier), it's not clear if the problems that plagued them are the same as those for more modern instruments. It's certainly possible to make adjustments in software now that were not possible in the time frame. Further the anemometers used in this report are about 2-3x the size of the Testo model I used. They are described as being "4 in vane anemometers", while the testo is about 1" vane, albeit with a slightly larger body. As such the Testo should be much more accurate on smaller pipes, because it blocks less air flow.
[OP]
Member
I hereby transfer ownership of this thread to Andrew More because he is killing it through dry and understated repartee. Go Andrew. And, I am going to up my stake in the dust collection subject by buying a Testo 410 anemometer.
Member
You might want to look at the Testo 405i. With it you can make measurements in accordance with established standards. Of course these measurements are more difficult than waving a fan in front of an intake (see this for example) but you will have more reliable data.
Where the vane type really falls short though is measuring flow with an actual tool connected. Take a planer for example. It's very difficult to actually access the air entrance, and even if you do, what area do you use for calculation? How do you average the readings? How about a jointer or a table saw with blade shroud and top side collection?
With a hot wire anemometer or pitot tube there's one section of duct that's traversed for all measurements. It doesn't matter what the entrance looks like, you use the same method in the same place for everything.
Both Larry and I have experience with both methods, it's your choice.
Beranek's Law:
It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.
Contributor
I've made this offer to loan test equipment before and I'll repeat it now, see the attached thread... https://sawmillcreek.org/showthread....ffer&highlight=
E.T.A., It all fits in a medium flat rate box, so figure on $40 round trip for insured shipping.
Last edited by John Lanciani; 07-08-2019 at 7:34 AM.
[OP]
Member
I was just looking at both! At $92.65 for the 410i and $106.25 for the 405i, why not buy both?! This dust collection is turning into some math and science fun. In answer to your question about the planer measurement, I would make a test section of duct with ports for either or both probes that I could interpose into the planer branch (or any other branch). A probe on a wand would be better than the 410i for inside the duct. I am getting excited!
On experience, I have that too. I was a research scientist for 40 years in heat transfer and fluid flow. Just to admit to my high level of geekiness, I was up this morning at 5am programming the intersection of the fan and system loss curves in Mathematica for my planned dust collection system. This is the fun part for me.
Thanks very much for your help. It is great to find someone interested in the same esoteric technical things.
Contributor
Cool, it would be interesting to do some more testing. PM sent.
Contributor
I borrowed John Lanciani's instruments and made measurements of my system allowing of course with static pressure and amps. It was quite a big job to set up a test pipe and jigs to do repeatable traverse across the pipe. I spent a week on and off getting it set up and a couple of weeks making measurements. My performance curve was similar to the one provides by Oneida but about 10% lower. Now, I have a good curve and can just take static pressure readings and use those to estimate flow.
I have a technical engineering background in thermodynamics and this was an interesting exercise for me.
Posting Permissions
Reply With Quote