Re: Blower vs. Sucker Gap - Was RE: Aspirated Gap (fwd)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Mddeming-at-aol-dot-com>

In a message dated 3/26/01 10:14:48 AM Eastern Standard Time, 
tesla-at-pupman-dot-com writes: 



>
> Original poster: "Yurtle Turtle by way of Terry Fritz <twftesla-at-uswest-dot-net>" 
> <yurtle_t-at-yahoo-dot-com> 
>
> Preliminary findings of my blower vs. shop vac gap 
> airflow testing: 
>
> I just hooked a fuel pump gauge up to my shop vac and 
> then to my blower. This is a very cheap and poorly 
> constructed gauge; however it is capable of measuring 
> vacuum and pressure. I hooked up my shop vac to the 
> gauge and it pulled 3.5 inches of mercury. My blower 
> only pushed .5 inches of mercury. This isn't too 
> surprising to me, as the blower is designed for lots 
> of cfm, not lots of pressure. However, this doesn't 
> tell the whole story. cfm vs. pressure is a curve. I 
> simply measured pressure at no cfm, or shutoff. 
>
> This would be easier to resolve if I had a shop vac 
> that allows a hose to be connected to either the 
> suction side or the blower side. I may try to borrow 
> one, and assume the cfm is the same whether blowing or 
> sucking; probably a decent initial assumption. To make 
> the suction side exactly equal the blower side, I 
> could hook up one gap to the suction hose, and hook up 
> a hose and identical gap to the blower side. This 
> would insure identical cfm on both gaps. For 
> comparison, I wouldn't have to swap out the gaps, only 
> the hoses. 



Snip - - - 
Hi All, 
Alternative #1 
Here's a poor man's air flow meter from way back when. (It worked at P.S.134 
in 1957) 
1. Get a surplus round weather balloon (10-16ft rated diameter) 
2. Attach it to exhaust side of vac/blower 
3. Inflate for 15, 30, 60 sec. etc., in seperate runs. 
4. measure diameter at end of each run. 
5. As long as diam < 80% rated diameter, P(interior) ~ P(atmos) and it should 
not load the blower significantly. 
6.Check with manometer gauge. 
7. Using V=4/3 x pi x (D/2)^3 and V(1at)=P(int)V(int)/P(1at) 
8. Plot V vs P and extrapolate back to P(1at) (this corrects for any 
"loading") 

Alternative #2: 

1. Scrounge a small orifice-type meter (not bellows type) from local gas 
company or liberate from mech. eng. lab. . 
2. Also scrounge a copy of AGA-3 manual from same place. 
3. Measure inlet P and differential across orifice. Can be used on suct. or 
dischg. 
4. Flow rate ~k x P1 x sqrt(deltaP). Value of "k" is from tables in manual. 

Sparks without flames, 
Matt D.