Thread: The Generic 2HP DC

Originally Posted by bill pentz

What is far more telling though, is the impact on the working areas of the fan curves. The larger the diameter the higher the pressure and more air we actually move when dealing with higher working resistance levels, so chip collection becomes far better with these larger diameter impellers as the resistance increases.

Amen!

Originally Posted by John Samuel

Amen!

????

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.

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.

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

Originally Posted by Lappa

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.

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.

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

Drum connected

IMG_0879.jpgIMG_0878.jpg

Finished the Thien extractor today.

IMG_0880.jpgIMG_0881.jpg

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.

IMG_0882.jpgIMG_0883.jpg

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.

IMG_0884.jpg

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.

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.

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.

Originally Posted by bryn23

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.

Have a read of this
Air flow calibration measurements

And this
DRAFT: FAQ - Dust Extraction (Practical Aspects)

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

Thanks BobL and Lappa,

Its something I'm curious about, but just didn't know the science of air flow or measuring tools.