dyson motors

[damunk]

So to get a good flow with the Dyson motors all 4 of them would have to be turned on using 1600w x 4 = 6400 watts.

That's crazy power. Thats like 6 air conditioning units switched on together. I don't think I could this.

I'm only using the flow bench for a small 1.4 litre head so don't know if that affects how much cfm flow I require. I am guessing at max 140CFM.

[Tony]

Vacuum motors vary rather a lot in efficiency, the usual range falls between about 8 and 16 CFM per amp, with only a few extreme freaks above and below that range.
By the time you have fitted all the motors you have the available power to run, the difference in bench airflow capacity can be about double.

Its WELL WORTH taking the time to seek out the most efficient motors you can lay your hands on, you will always be glad you did.
Obviously cost comes into this, but if you are patient, a really good deal will eventually be possible.
Motor choice is probably the single most important decision you will make, so don't rush it.

[damunk]

http://www.ebay.co.uk/itm/New-Genuine-A ... 4d31e7e3b7

Can you use 110v motors in the UK? The above ametek is in 110v. Lower wattage and I pressume a better motor than the Dyson.

[Tony]

Can you use 110v motors in the UK? The above ametek is in 110v. Lower wattage and I pressume a better motor than the Dyson.

Yes you can connect two 110v motors in series, and it will work on 230v, but its not recommended.
When the motors are brand new it will work fine, because the voltage will split fairly evenly between the two motors. As the motors wear and age, one motor will begin to hog more power than the other eventually leading to excessive heating, commutator arcing and other problems that will eventually cause one motor to spit the dummy.
And it usually also kills its neighbour.
So although its o/k in theory, it can over time lead to problems of short motor life and less reliability than it should have had if each motor had been connected directly to 110 volts..

A quick Google found the data sheet for the 115923, and it says 10.5 amps for 84 CFM which is also 8.0 CFM per amp. No better than the crappy Dyson.

Its probably a pretty good motor, but its just not efficient enough running at 44 inches of back pressure where you will be running it.

That is the problem. Some motors can work pretty well, but not in a flow bench.
What we really want is highest possible motor efficiency at normal flow bench operating pressures.
And that is what makes one motor more desirable than another.
Size is not really an issue.
Lots of small ones, or fewer larger ones do not matter, its CFM per amp you are looking for.
Then just fit as many as you have the power to run, plus one or two extra.

[Brucepts]

A quick Google found the data sheet for the 115923, and it says 10.5 amps for 84 CFM which is also 8.0 CFM per amp. No better than the crappy Dyson.

Pssssst . . . . that's one of the good motors recommended for the PTS Flowbench

[Tony]

Pssssst . . . . that's one of the good motors recommended for the PTS Flowbench

OOps my mistake ! ! !

Just had a second look at the data sheet, its a 120 volt motor not a 230 volt motor.
That makes a very big difference.
That 10.5 amps represents only half as much motor power at 120 volts, so its really 16 CFM per amp if you ran two of those in series across 230 volts.

That 16 CFM per amp puts it right up near the top for efficiency.
I still have some reservations about connecting motors in series though.

[RACEPUMPER]

Researching 230/240 Volt motors has become an unwanted but necessary hobby of mine. Not sure about availability or cost in the UK, but in Australia the clear winner in my files is the Ametek 119996-00. If theres a better one I haven't found and anyone knows about it, please, please let me know and I will buy it next build. There are motors with higher flow, less amps and cheaper cost, but the 996 is the one I use, I think it has approx. price of $65 AUD and its a small single stage

Jim

[Hotz]

Vacuum cleaner engines always leave me puzzled.

I bought the engines are specified in this way.

Eletrolux_Ameteck
1600 Watts power.
220V.
53 liters of air per second.
8 Amperes.

Conversions:

1600/220=7,545 amperes per second.
1Ls=2.11888 CFM where 53ls = 112,30064 CFM per engine, or 14,03 per Amperes.

Adding to eight engines: 898,40 CFM. I calculating an engine operating simultaneously set loss of 20% to 25% efficiency.

It may be in the house of 700 CFM disregarding
side pressure of the friction variables, for example turbulence generated in contact with the passage to the pressure side.

Excluding mathematics, the rest is theory, what the experts think about my placements my calculations are correct.


http://www.convertunits.com/from/L/s/to ... oot/minute

[damunk]

http://www.ebay.co.uk/itm/381256596982? ... EBIDX%3AIT

The above motor looks really interesting.
Two stage motor.
Low wattage @ 240v
Ametek

edit:
An even cheaper one below but this is numatic.
http://www.ebay.co.uk/itm/Double-2-Stag ... 1348659511

http://www.ebay.co.uk/itm/Double-2-Stag ... 487dd2cbbb
This one is stated as a ametek brand 18250rpm - they all look the same to me but the brands are different.

[Tony]

Hotz,
By my numbers that will give you 112 CFM x 8 motors = 898 CFM.
You won't quite reach that in practice, but something well over 700 CFM should definitely be possible.
But its also 14 Amps x 8 motors or 112 very scary total amps.

Just for fun, I worked out it would cost me about $11.00 in electricity (26.9Kw x 41c) per hour to run those motors flat out where I am.
Its an excellent example of why even slightly more efficient motors are well worth the trouble finding.

Damunk,
Nothing there to link to any performance curves, so no way of knowing how much air or amps those motors will reach when run against 44 inches of back pressure.