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Thread: The Generic 2HP DC
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9th September 2017, 06:54 PM #241Woodworking mechanic
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One more modification
I thought I was finished with all the modifications after altering the whole system to 150mm but have come to a realisation that the system is struggling to breathe with the filter too small for the increased air flow. I can't go for a higher filter due to shed height limitations or more filters inside because the shed is small so I've decided on an external Thein filter utilising the now closed off 125mm port on the separator. If it doesn't work I'll just seal it up again.
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I picked up two "used only once" drums with sealed lids. One will be the filter and the other will replace the collection bag.
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More work for tomorrow
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9th September 2017 06:54 PM # ADSGoogle Adsense Advertisement
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9th September 2017, 08:24 PM #242... and this too shall pass away ...
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9th September 2017, 08:29 PM #243Woodworking mechanic
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9th September 2017, 09:50 PM #244... and this too shall pass away ...
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We measure lots of things like amps and static pressure when discussing air flow for our dust collection systems. However, the fan curve is mission critical. A good, modern fan and cyclone might only look OK when we look at static pressure. Even the cheapies look like they have good air flow with a naked intake and no duct work or machines connected. However, a correctly sized fan with a superior fan curve will perform better than gear with similar static pressure but an inferior fan curve. The good fans are better at overcoming the resistance caused by hoods, machines, duct work and fittings, and will move more air resulting in better dust collection, especially the fine dust.
So, discussion about HP, Amps, static pressure or air flow with a naked intake are all relevant, but what really matters is the amount of air we can pull through machines, hoods, pipe and fittings. To understand this we also need to have a feel for the fan curve.
One of the forum members here (Ronboult) was kind enough to come to my shop and measure the actual air flow through my system for each machine in the shop. (The data are here Making 150mm DC ports for workshop machines) The static pressure of my system was OK, but not overly impressive. However, the airflow when connected to duct work and machines is quite good, because of the effective fan curve and cyclone design.
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9th September 2017, 09:58 PM #245Woodworking mechanic
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I have also measured the flow in my system, with and without with machines connected. This has allowed me to tailor inlets to machines to ensure flow is not restricted. I don't intend to replace my DC in the near future (unless I can pick up a 3hp cheap) so I have to live with what I have and modify it to get the best out of it.
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9th September 2017, 10:31 PM #246
Lappa, thanks for the wok readings.
My new DC, which is strong, completely lacks the internal donut - so one will be added, plus a wok.
Thanks for the photos too
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10th September 2017, 08:25 AM #247... and this too shall pass away ...
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That's what I like about BobL's work on the 2 HP dusty and this thread. It allows woodies to optimise a 2 HP dusty and get reasonable dust collection inexpensively. Many of us owe BobL a vote of thanks. He has helped a lot of woodies improve their dust collection, including me. My shop was a dust disaster before I became a member of this forum.
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11th September 2017, 08:06 AM #248Woodworking mechanic
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Connected the new outlet to the separator 125mm outlet and side of shed, still haven't gone into the Thien separator but the figures and visuals look good.
Bag on only - back pressure 58 mm H2O. Now 38 mm
- Flow 549.4 CFM. Now 612.47 CFM
Bag and Filter - back pressure 93 mm H2O. Now 65 mm
- Flow 467 CFM. Now 564.00 CFM
Sucked up a bucket of sawdust and chips - now sure it's only a visual thing but only minor amount out new outlet, most into the bag. Will measure how much when I build the separator but happy so far
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11th September 2017, 08:07 AM #249Woodworking mechanic
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Drum connected
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15th September 2017, 01:44 PM #250Woodworking mechanic
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Thien extractor
Finished the Thien extractor today.
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Fitted it to the drum and did a test run with the same bucket of sawdust and chips and strands (from planing) as last time.
This time I had a downward facing elbow into a large garden vase to see what heavier particles and chips came out.
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Clean as a whistle, not even any signs of dust
Checked the drum - plenty in there, so both the normal bag on the standard separator and the extended drum and Thien extractor off the 5" outlet are working with an increase in system flow. I'd call that a good result.
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Temptied to build a 6" Thein separator and see if I can do away with the standard separator and pleated filter but that's for another day.
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15th September 2017, 02:07 PM #251
I've had a similar idea in mind for a while, especially with a split output on my 3HP unit. I'm about to try a cyclone on one side (outlet), the idea being that I'm not trying to flow the full air volume of a 150 mm duct, but in reality around half the volume, therefore loss should be less with a smaller cyclone, if the loss is less than my partly dirty filter bags then I'll try a second on the other exit port.
Thanks for posting.
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15th September 2017, 06:00 PM #252Senior Member
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What are you guys using to measure the Suction on your dusty's
Would like to see what this Felder AF16 does in real life compared to the paperwork.
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15th September 2017, 06:09 PM #253.
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Have a read of this
Air flow calibration measurements
And this
DRAFT: FAQ - Dust Extraction (Practical Aspects)
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15th September 2017, 06:16 PM #254Woodworking mechanic
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Bryn23,
i use a hand held Testo HotWire Anemometer which I "poke" into a hole in the ducting - on a long run. It measures temp, and air speed. The program runs on a computer or a phone or iPad. You enter the pipe diameter and the atmospheric pressure and it calcs. CFM
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16th September 2017, 09:40 AM #255Senior Member
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Thanks BobL and Lappa,
Its something I'm curious about, but just didn't know the science of air flow or measuring tools.
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