Tractorsport Flowbench Forum Archive

Posted: **Sat Apr 30, 2005 11:05 pm**

I was going through my notes on my bench and lost the specs on my vacc motors

I went to the Ametek site and looked up the motors PN116309-00 and ran in circles lol
Anyhow what is the conversion formula again to go from a higher test pressure to a lower.
The motors are rated at 112 cfm @ 63" h2o or 190 air watts On a 2" hole

i am thinking that it was about 33cfm @ 28"
Thanks
John

Posted: **Sun May 01, 2005 9:49 am**

SQR(New "wc/Old "wc) * CFM

Posted: **Sun May 01, 2005 2:23 pm**

Thanks Mouse
If im doing the formula correctly then each motor flows
49.77777777777777777 @ 28
and if i mult. that by 8 motors I get a total of 398.2222222 @ 28

Right ??

Thanks
John

Posted: **Sun May 01, 2005 2:28 pm**

Playing with theorys then the biggest orifice I should need in the bench would only have to flow 400 cfm.

Posted: **Sun May 01, 2005 8:59 pm**

You cannot assume any sort of fixed relationship between developed blower pressure and available flow, every blower has a different shaped curve.

Some blowers can be throttled right down to zero flow and the pressure hardly changes. In others the developed pressure will reach a high maximum at zero flow. It all depends......

Posted: **Sun May 01, 2005 11:45 pm**

Let me re-iterate that...

New CFM = SQR(New "wc/Old "wc) * Old CFM

What is a air watt? Is that like an electrical watt.. volt * amps? Or in this case pressure * cfm?

John

Posted: **Mon May 02, 2005 1:48 am**

Posted: **Mon May 02, 2005 9:59 am**

John, The 112cfm @ 63"wc does not make sense to me. That is a lot of air power. It must mean 112 cfm maximum flow rate (probably at 1"wc or less) and 63"wc max pressure (probably at 1 cfm or less). But if you state 112cfm @ 63"wc through a 1" orifice, then the equation applies.

John

Posted: **Mon May 02, 2005 11:57 am**

The specs for that motor show the flow performance thru a 3/4" orifice is 43.9cfm @33.7"wc. Max airflow is 112cfm and max(sealed-no flow) vacuum is 63".

The formula mouse quoted is for converting flow thru a fixed orifice or port, not for calculating vacuum motor output. The vacuum motor performance curve is the ONLY way to know what flow it will have at a given depression. With a specific vacuum motor, the higher the vacuum the lower the flow.

In this case the specs show 43.9cfm @ 33.7"wc and that should be close to the vacuum you will need depending on your other flowbench losses. It will probably require a little more motor vacuum than 33.7" to get 28" vacuum on a head at higher flows. I would figure on around 40cfm per motor. These motors are single stage impellers and most use 2 stage. Single stage motors would probably work better for lower vacuum. Without the full flow/vacuum curve of the motor you can't say for sure.

Rick

Posted: **Mon May 02, 2005 1:14 pm**

Rick thanks for the explination.
Mouse im posting a link to the motors i am running. Hopefully that will help explain my confusion.
Again Thanks for all the help
John

I finally found a pdf on the motor heres the link

if im reading correctly @29" it flows 55 cfm through a .875 hole

Posted: **Mon May 02, 2005 1:31 pm**

Sorry forgot to add.
I am just trying to make sure on the number of motors i need to have enough vacc to pull 400 cfm @28

Posted: **Mon May 02, 2005 1:53 pm**

Here is a link to the AmetekLamb product page. On the left of that page is Download links. Click on PDF Product Bulletin for the design curve for that motor.

Remember you need more than the 28" from your motors to get to 28" on the port. Add the orifice drop @ 100% flow (less for a pitot bench) and a few more inches for other restrictions in the flow path.

Rick

That Link doesn't work very well, here is the performance curve for your motor.

Posted: **Tue May 03, 2005 11:34 pm**

thanks rick360.
Now all i need to do is verify how many motors will sufice to pull 400 cfm at 28". Im figuring on 8 total.
PS with 360 at the end of your nic Is that for ford 360 or mopar 360 or something else? Just courious
John

Posted: **Tue May 03, 2005 11:46 pm**

Posted: **Wed May 04, 2005 3:33 am**

The motors are from a MSD bench copy I built a fiew years back. Still have the bench and 8 motors I was planning on redoing the bench from scratch and reuse all the motors and meters off the old bench. Kinda a hobby project that has turned to necessity. The bench I used to have access to is no longer in service (bench owner sold it without telling me) :angry:
so now im pressed to redo the MSD clone.

Tractorsport Flowbench Forum Archive

Mouse or any of the other math wizzards