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-   -   Blower impeller design & comparisons (

vishnu Wed 01 October 2008 11:47

Moved from another thread:

Hi Irfu,

Thats really nice. Working on the Impeller and want to see them in One piece before i start them. Nowadays i think you working a lot buddy. . . . . .


Gerald D Wed 01 October 2008 12:09

Curious about your impeller design . . . . .

Only yesterday we compared two impellers that were giving very similar performance curves, but one needed double the Amps of the other!

Gerald D Wed 01 October 2008 12:46

3 Attachment(s)
Here are the results:

Attachment 2238
305mm impeller . . . . . . . . . .. . 300mm impeller

Change attachment's .txt to .dxf to open with CAD:

javeria Thu 02 October 2008 00:07

Folk's thanks for the thumbs up, what me and Vishnu thought was to copy the impeller on the Bill Pentz site. Its the red one with dimensions marked on them. As a first try we will have a straight blades instead of curved ones, I dont think I have a photo here with me.

its on this link though

G' the forward curved ( If I am right) are more efficient than the straight blades,

The cyclone I am building is a 18 inch dia one.

Today we are celebrating Eid, so work will start next on Monday and meanwhile I am finalizing BOM for my Mechmate and me and Vishnu have finished finalizing the electrical BOM.


javeria Thu 02 October 2008 00:10

G' did you use a anemometer to measure the CFM? I dont see the CFM figures / velocity figures

Gerald D Thu 02 October 2008 00:23

No, only used the pressure change across a known hole as a comparison. The actual CFM are of no interest to me.

javeria Thu 02 October 2008 00:33

ok, true as the CFM will depend on the ducting too.

Greg J Thu 02 October 2008 06:14


I know your test setup is very straight forward, but you lost me on the chart where you have "water sucked up hole". There is a 0 mm hole (:confused:) and so forth with associated numbers (water column height ??).

In the past, I've taken a clear plastic tube and made a U-tube manometer. Water column height was the only variable.

Would you explain your test setup?


Edited: After rereading your reply to Irfan - Are you measuring pressure differential across an orifice plate (hole) ?

Gerald D Thu 02 October 2008 07:02

Setup exactly as you have done it yourself (mechanical engineers are trained alike :)). My wording was "water sucked up pipe" with the pipe being clear plastic dangling in a tub of water.

Actually, a cheap plastic funnel was held over the inlet of the fan, and the pipe/tube tight over the sharp end of the funnel. holes were then made in the conical part of the funnel to leak air into the fan.

Gerald D Fri 03 October 2008 11:46

Here are 2 different dust collectors, both 2 HP, both with 1 micron bags. From their pictures and specs, they could be the equivalents of our Martlet and Huester:
Here they are stocked by two different suppliers and they are claimed to be identical of each other's 2HP units. "They are all from China". The Jet brand could be one, or both, of those.

vishnu Fri 03 October 2008 12:48

Dust collector Comparisions
Yes the the two units looks more or less identical, but i really doubt the suction capacity quoted at 1600 CFM, because of the size of the impeller and the motor capacity. I think 900 - 1000 CFM may be the actual results that can be obtained. I think for a one machine shop these units may be a good alternative to a cyclone. I have my own doubts whether it will achive the desired results obtained as equivalent to the cyclone dust evacuator. The DIY build of a cyclone will be in the range quoted in the retail price. i think its worth a try :)


DMS Tue 15 September 2009 10:01

Dust Shoe
Following comment made in this post - moved to this thread

I am in process of building 2 HP cyclone.

DMS Tue 15 September 2009 18:01

Your lasercut supplier could also do Martlet (curved fins) type Impeller? becoz these are better one.

javeria Wed 16 September 2009 04:30

Oh the impeller was just a copy from the Bill's website. if you want I can pass on the DXF.

btw do you have the dimensions of the martlet type fan?


javeria Wed 16 September 2009 06:01

Got it - I think the one I have made is performing superb - so no complaints and would certainly make one for others too. Getting a curved profile might be easy with the right tools but straight one is just much more easier!


DMS Wed 16 September 2009 06:07

Thanks Gerald for dxf's
I copied dxf from this link,

I calculated 12" dia Impeller for my design from Bill's excel sheet, I prefer Martlet after seeing Gerald's comparision. But problem is where to get fins bent evenly ? I wonder if your laser cut parts suppliers could do it ?

Another option for impeller is I can finish it in wood, which can be supplied to foundry for Mold making where Aluminum alloy or Iron impeller could be molded.
Someone may suggest which is better Sheet metal Impeller of molded one ?

javeria Wed 16 September 2009 06:22

casting is a good way- but when at high speeds there is possibility of it disintegrating if there are some anomalies in the cast. better to go for sheet.

G' told me once that since in US motors are faster due to the higher frequency (60Hz) here its 50Hz - so I went in for a inch more on the dia.

If the backward curved fan works for me - then it should work for you too.

I got tired of trying to get to the best and went for one shown on the Bill's website!


Gerald D Wed 16 September 2009 06:39

Just to be clear; "Martlet" is a local/UK trading house that buys goods in Asia and then put on their own label. Tomorrow Martlet can decide to put their name on the other fan, so the actual name means nothing about fan design.

DMS Wed 16 September 2009 06:40

Wow that was quick ;)

OK I go for 90 degree fins. Are you satisfied with performance and energy consumption ?
Where did you got laser cut impellers ? You remember mine charged higher, so no dealing with him.

javeria Wed 16 September 2009 06:57

Sharmaji - go for the backward curved fan - I will send you the drawings -

I put it on only when the cut is complete ( I am chicken to keep it on contineously with the GI case :D). you can get them cut manually on oxy torch also - no need for laser cutting

just be sure to get it dynamically balanced.

I already sent it out! chk ur email

DMS Wed 16 September 2009 07:16


What the calculation basis of using 14 " I mean +10 Hz for + 2" ?
Mine motor is 50 Hz is 12 " ok for 2HP as per excel sheet?

What's the thickness of GI sheet you used?

javeria Wed 16 September 2009 07:54

oh 2 hp - I used a 3 hp one - cost difference only Rs 500 so.

i think i used the least thk GI sheet - used for manufacturing the AC ducts.

at 60Hz the fan spins faster than at 50Hz. so to compensate the loss in speed we increased the dia - again bhai I dont have anything to prove except the fact that its sucking thru 6mtrs of flex duct and 2mtrs of PVC pipe. and I have no complaints.

Just be sure to mount the motor properlly

DMS Wed 16 September 2009 08:44

Thanks Irfan,

2 HP saves power also.
Awaiting till tomorrow for pic of hose.

javeria Wed 16 September 2009 08:51

no yaar 2 hp will pull more current if it gets loaded, once a motor is running the current consumption drops.

so a 3 hp will consume the same power as a 2 hp will once its started rotating, but a 3 hp will take it smoothly(does not heat up) due to the additional power capacity.

Read points 5 and 6 here


DMS Wed 16 September 2009 09:22

You are right !!!
Only if it gets loaded.
So I must balance HP, Hose dia, Inlet dia, outlet dia clearance and impeller size so that motor does not get loaded.

I have seen huge dia furnace blowers with lesser HP motor, smaller fins covered with plate to make pocket, having tremendous air pressure with smaller outlets.

javeria Wed 16 September 2009 09:37

ok - take your call dear :)

Gerald D Wed 16 September 2009 10:09

The reason for the heavy starting load is the energy needed to get that heavy "flywheel" spinning up to speed. The thicker the material used in the impeller, the heavier the initial current draw. A bigger motor gives spare torque to reduce the time of the high current.

DMS Thu 17 September 2009 17:48


plz post photo.

javeria Thu 17 September 2009 23:37

sent -

Marinus Sun 08 November 2009 08:59

Is a cyclone better that a conventional dust extractor?

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