Gary,
I had to look it up and check myself on this as I didn't want to tell someone
the wrong thing to do. It shows the same as I'm speaking of which is measuring
how far the water has moved up the tube (open side). This is on page 15-13 in
the 1991 ARRL Handbook I'm referencing. If you measured the length of the
movement at the chassis end and the open air end, you would have a measurement
X2 as you would be adding this same movement amount to itself. Really, what it
is, is the height the water will travel against the downward force of the
atmospheric air pressure. it's like having two air cylinders in series. If you
push the piston rod of cylinder A in 2 inches, the rod of cylinder B will move
out 2 inches against a certain pressure. The amount of force it took to move
this that far is what is of interest. We used to measure this the same way on
the vacuum systems for those roof bolters we built at JH Fletchers. There you
measured it at the filter to see the back pressure. Except
here it was a negative pressure.
Quote;
"The pressure differential between the air passage and the atmospheric pressure
is measured with a device called a manometer. The manometer is nothing more
than a piece of clear tubing open at both ends and fashioned in the shape of a
U. It is temporarily connected to the chassis and removed after the
measurements are completed. As shown in the diagrams, a small amount of water
is placed in the tube. At figure 15A the blower is off and the water will seek
its own level because the air pressure (atmospheric pressure) is the same at
both ends of the manometer tube. At B the blower is on (socket tube and chimney
in place) and the pressure difference in terms of inches of water is measured.
For most applications, a standard scale can be used for the measurement, and
the results will be sufficiently accurate".
Here's some tubes with the CFM and back pressure reccomended;
3-500Z 13 cfm, 0.13 inches
4CX250R 6.6 cfm, 0.50 inches
4CX300A 7.2 cfm, 0.58 in.
4CX350A 7.8 cfm, 1.2 in.
4CX1000A 25 cfm, 0.2 in.
4CX1500, 8860, 8874 8.6 cfm, 0.37 in.
Best,
Will
*********** REPLY SEPARATOR ***********
On 5/23/06 at 11:25 PM Gary Schafer wrote:
>Will,
>
>To read pressure you measure the difference between the water levels in
>each
>part of the tube when the blower is on. The part of the tube that is
>connected to the amp will get pushed down and the other side of the "J"
>will
>get pushed up. It is the difference between these two sides that is the
>measurement.
>
>With the blower off the water level in each part of the tube will be equal
>height to the other.
>
>What you are describing is only measuring one side of the tube. That will
>only give you 1/2 the inches.
>
>73
>Gary K4FMX
>
>
>> -----Original Message-----
>> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
>> Behalf Of Will Matney
>> Sent: Tuesday, May 23, 2006 11:07 PM
>> To: amps@contesting.com
>> Subject: Re: [Amps] Alpha 91b fan/blower motor
>>
>> Gary,
>>
>> The pressure on the outside is the low pressure and the pressure in the
>> chassis is the high. With the blower off, that's the low pressure or room
>> pressure where the water is settled. The difference between low and high
>> shows the back pressure. The low side though, I don't understand what
>your
>> saying? I always checked them the same as the set ups shown in the
>> handbooks showing the same setup using the tubing. Are you counting the
>> pressure above the chassis as the low pressure? It should be the same as
>> the outside pressure unless the cabinet is not ventilated well enough. On
>> most Alpha photos I've seen the tubes chimney runs right to the top and
>> out the vents. You could check it that way but in reality it should be
>the
>> same, especially if it set up that way. I doubt that perf metal will hold
>> back the outgoing air flow very much. Now if above the chassis wasn't
>> ventillated very good to the outside where it caused a restriction to
>> flow, then yes, the above chassis would be used I
>> would think.
>>
>> What most have been doing with the high speed blowers is cutting the
>speed
>> back with a rheostat. Then if the temperature gets so hot, a thermostat
>> shorts out the rheostat and full voltage is applied to the motor. In his
>> case, my guess he has a fan already slow enough, and I'm afraid may be
>too
>> slow.
>>
>> Best,
>>
>> Will
>>
>> *********** REPLY SEPARATOR ***********
>>
>> On 5/23/06 at 10:41 PM Gary Schafer wrote:
>>
>> >You want to read the difference in water level between the high and low
>> >side
>> >to obtain inches of pressure. Not the difference from no pressure to
>> >pressure.
>> >
>> >Speed will have the greatest effect on pressure under load.
>> >
>> >73
>> >Gary K4FMX
>> >
>> >> -----Original Message-----
>> >> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]
>> On
>> >> Behalf Of Will Matney
>> >> Sent: Tuesday, May 23, 2006 10:11 PM
>> >> To: amps@contesting.com
>> >> Subject: Re: [Amps] Alpha 91b fan/blower motor
>> >>
>> >> Bob,
>> >>
>> >> Had they removed the label on the old motor where you couldn't see
>what
>> >> the RPM and HP was? The RPM is what makes the flow or speed of the air
>> >> throught the amp. The pressure is created by the size of the blower
>> wheel
>> >> which in turn sets the motors HP. The pressure is one of the most
>> >> important things and that may be something you have to check. You can
>> >> check this by using a clear rubber tube filled with some water. One
>end
>> >of
>> >> the tubing will be hooked to a fitting that goes into the chassis
>where
>> >> the blower goes into. Let it loop down under the chassis so it will
>> hold
>> >> water in it. The other end is supported up higher where the whole
>thing
>> >> will look like a big J so you see a water level in it. The high end is
>> >> also left open. Turn the blower on and pressurize the chassis. The
>> water
>> >> will move up in the tubing. Make a mark at the water level both
>> >> pressureized and unpressureized. Then measure the distance to see how
>> may
>> >> inches it moved. This will give the back pressure in inches rea
>> >> ding, and can be used to check against the tables in the tube specs
>as
>> >to
>> >> be the right amount or not. If it's correct (matches), you'll have the
>> >> correct pressure and flow. I think there's some charts in the ARRL
>> >> Handbooks too. If you have to drill a whole to do the test, simply
>plug
>> >it
>> >> up when your done.
>> >>
>> >> Best,
>> >>
>> >> Will
>> >>
>> >> *********** REPLY SEPARATOR ***********
>> >>
>> >> On 5/23/06 at 9:47 PM KR4DA wrote:
>> >>
>> >> >I recieved the fan today.
>> >> >BUT the SPECS on the label say RPM 1100 and HP 1/500
>> >> >
>> >> >The web page says RPM 3000 and HP 1/200
>> >> >
>> >> >I hooked the fan to the NEW motor and WOW I don't think 3000 RPM
>> >> >would be GOOD.
>> >> >The fan spinning on the NEW motor does put out a nice flow of air.
>> >> >At 3000 RPM it would really be spinning.. my gut feeling is that 3000
>> >rpm
>> >> >is to fast.
>> >> >
>> >> >
>> >> >Geees I wish I could get an answear on WHAT THE RPM SPEED IS IN THE
>> 91B.
>> >> >I AM CONFUSED NOW AND IT PROBABLY ISN'T 3000 RPM AS WAS I
>> >> >WAS LED to believe and TOLD to me by ALPHA.
>> >> >Who the heck knows about these amps???????????????????????????
>> >> >or should I say really knows about blower motors and needs for
>> cooling.
>> >> >
>> >> >I also posted this to the ALPHA GROUP 2 weeks ago on YAHOO ...
>> LOL...no
>> >> >responce.
>> >> >
>> >> >
>> >> >
>> >> >KR4DA wrote:
>> >> >
>> >> >>
>> >> >>The motor currently in MY 91B is labeled as:
>> >> >>BOMAX type b-jc 50/60hz .64amp 301-6623.
>> >> >>Bomax seems to be out of business.
>> >> >>But web page is up but no refernce to this number.
>> >> >>
>> >> >>Anyone have suggestion for replacement???
>> >> >>
>> >> >>
>> >> >>I do not know how critical it is but there are on the web at
>> >emotorstore
>> >> >>c frame open motors CLOSE to the same specs.
>> >> >>
>> >> >>Plate thickness 16.6cm
>> >> >>shaft deminison .186 x 2in
>> >> >>115v .64a CW rpm 3000
>> >>
>> >>http://www.emotorstore.com/productdetail.asp_Q_catID_E_6_A_subCatID_E_
>> >> >>251_A_productID_E_402_A_skuID_E_25484
>> >> >>has this part do you think I would it be ok to USE IT???
>> >> >>
>> >> >>I don't blame anyone but really think a person derserves better
>> >> >>communication from ALPHA on getting this fan.
>> >> >>This AMP cost me $2,748 in April 1997 that was alot of money to me.
>> >> >>And now cannot use it for HOW LONG???? until I get a motor.
>> >> >>
>> >> >>Frustrated Bob KR4DA
>> >> >>
>> >> >>
>> >> >>
>> >> >
>> >> >--
>> >> >Bob
>> >> >Vmoa chat list -> http://autos.groups.yahoo.com/group/vmoachat/
>> >> >Vmoa tech list home -> http://autos.groups.yahoo.com/group/vmoatech/
>> >> >
>> >> >
>> >> >Middleburg Fl (South Jacksonville)
>> >> >ICQ 13912841
>> >> >Web Page http://bellsouthpwp.net/k/r/kr4da
>> >> >
>> >> >Visit the FDXPG at http://www.geocities.com/w4wx1/
>> >> >
>> >> >Ham Radio Calls: KR4DA FG/KR4DA J79DA HK0/KR4DA
>> >> >
>> >> >Motorcycles CBMMA #4
>> >> >1977 XS750D 1J7008405
>> >> >1997 Vmax12J VMOA #504
>> >> >
>> >> >
>> >> >
>> >> >_______________________________________________
>> >> >Amps mailing list
>> >> >Amps@contesting.com
>> >> >http://lists.contesting.com/mailman/listinfo/amps
>> >>
>> >>
>> >>
>> >> _______________________________________________
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>> >
>> >
>> >_______________________________________________
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>>
>>
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