240 volt vacuum motors - fan search.

[ivanhoew]

so looked into the vfd, one on ebay at 60 quid but only does up to about 3hp .bummer ,so may end up using my single phase 3hp motor and seeing if 1480 rpm does absolutely anything at all this means my fan would be doing half the rpm so about 4600 so it may not make any pressure to speak of .
time will tell !!!

[riga team]

[Tony]

Anatolij,

That looks like a very well made and interesting blower you have there. It is difficult to estimate what the results will be, but from my own testing I can make some guesses as to what might happen.

The sixteen inch rotor looks very well made, and the straight vanes will not have any significant bending loads likely to cause failure. It would be fairly easy to enlarge the entry eye on the casing slightly to increase flow. The biggest limitation that I can see is the very restrictive outlet area. All the air has to flow through that very small outlet. That is going to cause a large pressure drop at higher flows and restrict airflow capacity.

I would expect at lower flow with that large diameter rotor it will be quite easy to get some fairly high pressure, but my guess is that as flow increases, the developed pressure will fall of fairly quickly. But if your cylinder head ports are roughly the same size or smaller than that outlet it should make a very useful flow bench blower. It is just not going to be able to generate many hundreds of CFM.

As a rough guide my first blower has an outlet of 5.94 square inches and was rated at 300 CFM at 2850 Rpm. (18" rotor 3.5" eye so it is fairly similar)

My second blower has an outlet area of 9.625 square inches and is rated at around 400 CFM at 2850 Rpm. (18" rotor 4.0" eye)

Your blower has a 3.75 square inch outlet so expect perhaps 170 CFM at 2850 Rpm. That is just a guess. Doubling the Rpm will almost double that flow but not quite.

[Tony]

Ivanhoew,

I went through all this myself about thirty years ago trying to run a three phase motor from two phases. It was I that did the rope trick !! It just would not start from stationary by itself, but once turning would gather speed and eventually run. I tried capacitors, all sorts of weird things. Later I had three phase connected to the house, and all that fun and drama has long since faded from my memory.

Save yourself a lot of trouble and investigate the possibility of getting genuine three phase power hooked up. The next best thing is a variable speed drive, but three or perhaps four horsepower will be the largest single phase VSD you will be able to find. But you can run a much higher power three phase VSD from single phase but it must be de-rated. The only problem is the massive single phase load. Your fusebox and house wiring may burst into flames. Six Hp is probably about thirty amps single phase, which must be getting pretty close to the practical maximum.

Regardless of what you end up with, any flow bench is going to be very power hungry, and using multiple vacuum cleaner motors is not a solution to that. A three phase system and large single blower with VSD is going to be more efficient, have much better air control characteristics, be a lot quieter, and be much more long term reliable.

[riga team]

Thanks TONY! I can easily increase an aperture of an input on 4 ". I shall clean backlashes up to minimum.So I wish to try: nevertheless 8 motors Cost more

Anatolij

[ivanhoew]

thanks tony , i was looking at a 4 hp single ph motor ,that was 16 amps . i can get them for about 150 to 200 pounds ,the other option is a vfd and use it on the 5hp motor i allready have on the fan which i imagine would be about 4kw with all the efficiency losses thruogh the vfd and the motor i imagine a flow of 5 to 6 kw ,a bit less than my 8.5 kw shower uses ,does this make sense tony ,also can you tell me if this motor was a 5hp one running at 9600rpm and so on is it poss to guess its boost pressure ,and what the drop would be if i used it with a 1480 motor insterad of a 2800 one ?
thakns for yuor help so far ,this is a godsend of a forum for my situation .
regards robert.

[riga team]

[Tony]

[larrycavan]

Tony,

Is there some small blower setup that will fit inside a flowbench?

Everything I've seen pictures of in this thread is really oversized. I don't know. Maybe thats just the way it has to be to get the performace required?????

Or is there a good way to install pairs of motors in series and keep them cool at the same time?

I've been toying with the idea of 16 motors setup in 8 pairs in series. Even using the 1234 cheap motors the suction and cfm capacity should be quite good.

In a series connection like that, which would be the hotter of the two motors? Would it be the inner motor that has no immediate heat dispersement path except through the second motor....or would it be the rear motor that is receiving already heated air from the first motor....

Don't mean to hijack the thread....just anothe twist to the blower discussion...

Larry C

[riga team]

Tony,

Is there some small blower setup that will fit inside a flowbench?

Everything I've seen pictures of in this thread is really oversized. I don't know. Maybe thats just the way it has to be to get the performace required??

Or is there a good way to install pairs of motors in series and keep them cool at the same time?

I've been toying with the idea of 16 motors setup in 8 pairs in series. Even using the 1234 cheap motors the suction and cfm capacity should be quite good.

In a series connection like that, which would be the hotter of the two motors? Would it be the inner motor that has no immediate heat dispersement path except through the second motor....or would it be the rear motor that is receiving already heated air from the first motor....

Don't mean to hijack the thread....just anothe twist to the blower discussion...

Larry C Owing to a forum I have gone deep to studying of streams and vacuum. Now ideas in hearing: two following one after another chambers of vacuum: why do not use? So I see strengthening depression on the weak motor. We shall consider......?
Anatolij

We too consider it. Opinions ordinary: two consecutive motors should double vacuum..... Here a minus in complication of a design: and how will lead itself the second number of motors? 10 motors are a minimum 70 AMP currents a current of start. 1 collector the motor 10-15 HP. for blower 35-40 amp here I am inclined to TONY, it in a place should be more silent than less details. Constant search..

[Tony]

Larry, Anatolij,

I cannot help feeling that using many small motors is not the best way to do this, but it is really a matter of personal preference.

Vacuum cleaner motors come in various types, some already have two rotors fitted in series one behind the other, whereas others only have one rotor. The two stage units can develop much higher pressures, as you would expect.

The most compact system possible would probably be a centrifugal supercharger driven by a three phase motor. These can easily generate several pounds per square inch pressure, at many hundreds of CFM, vastly more air than would ever be needed, and possibly occupy only a couple of cubic feet.

Even a very large turbocharger compressor would probably work, but driving it to the very high Rpm required would be far from easy.

There is no real reason why the blower itself needs to be very small. Much easier to keep the diameter large and the Rpm low enough to be directly driven by a high power induction motor. An 18" or 24" rotor only needs to run up to 5,000 Rpm or less to generate perhaps fifty inches. A four inch rotor would need to go to perhaps 25,000 Rpm to 30,000 Rpm to achieve the same sort of pressures. That creates a lot more problems with bearings, balance, and belt speeds.

A 36 inch diameter rotor would run straight off the end of a 2,850 Rpm motor and provide fifty to fifty five inches of solid pressure at massive flow. The rotor for it could be home made too. That would be far easier than trying to drive something small at extremely high Rpm.

The blower does not really need to be fitted inside the flow bench, it can be on wheels and sit beside the bench and be connected with some large pipework. Or even be located behind a wall for silent operation.

I realise that is the exact opposite direction in which you want to go, but after switching from multiple vacuum cleaner motors to a single large blower, I would never go back.

Robert,

I just tried running my VSD on one phase only and struck a serious problem. Although it should in theory work, the microprocessor does not like seeing any missing incoming phases and shut down the unit. I fear this may be an insurmountable obstacle for most microprocessor controlled VSDs these days, and is something I had not considered. These units are very smart, and have very comprehensive inbuilt protection. That seems to have killed the idea, sorry.

[ivanhoew]

[color=#000000]well thats very kind of you to try tony ,i was looking at those variable frequency drives ,that appear to offer as you say a change to dc then back to a 3 ph output with a pad on the front with the up and down arrows for rpm ,but it woulds appear trhat they only go up to about 2hp for single phase .at least thats whati have found so far ,my next thought is an inverter as one would use for chANGING 1 PH TO 3 PH ,with out a speed control just a throttle valve on the inlet adjustable for area like a big butterfly valve,from what iv read this would also mean that my powr consumption would drop at the lower flows so costing me less in my power bill !,i have found a 3hp sinlge ph motor new for

[larrycavan]

In a series connection of vacuum motors , which would be the hotter of the two motors? Would it be the inner motor that has no immediate heat dispersement path except through the second motor....or would it be the rear motor that is receiving already heated air from the first motor....

[riga team]

Yes! Yes! To TONE! You completely confirm mine a sight: blower outside of a premise it is silence:it is supper (my working computer with passive radiators and especially small rpm the fan) I''m very appreciate it. I shall check up my blower, results I shall declare: also I see a way to raise a stream. The drawing I shall publish tomorrow . thank*s TONY. Anatolij

[Thomas Vaught]

I have a friend who built a flow bench over 10 years ago and used a roots type blower.

He mounted the blower in a shed on the outside of his workshop/ dyno building.

He used PVC pipe (4") to plumb the blower.

(He had three phase power available in his shop).

By controlling two "Three way" air valves he could set the test pressure to any value he wanted. The Bench was an orifice plate design, much like the SF 1200 bench and used stoppers.
Manometer was a 246 dwyer.

Very quiet bench and the only noise you heard was the port.

Tom V.