Flowbench capacity - Motor capacity

[gofaster]

I am currently using a SF-110 bench with SF's Motor Controller and Flowcom, and Performance Trends Port Flow Analyzer v3.0 software. It's a nice unit the way it set up now. It's a good tool for small valve heads and "street heads", but when I get into the big valve "race heads", I have to go to 3" depression to get anything and that doesn't tell me much.

I am gatherig materials to build a new MSD/Mercdog
style bench. My goals are:
To be able to pull 45" vertical through a 3" orifice at 75% or better on the inclined manometer.
To have the capacity to flow test the pro stock heads and have useful results.
Be able to test manifolds, carbs, and air cleaners.
To have enough capacity to add Joe Mondello's Wet Flow Conversion Kit for the SF-600

I signed up for a cabinet making class at the local adult ed. center so I can have access to all the wood working tools I could possibly need, plus I'll have some professionsl guidance.

Here's what I am using:
At the Cabinet making instructors recommendation, the bench will be made from 3/4" Baltic Plywood that is ten ply with no voids. Very strong stuff!
Two Dwyer 60" vertical manometers, one for Pitot tubes, one for depression
Dwyer 246 inclined manometer with "0% to 100%" scale
(The Dwyer pieces are special order, and have a delivery date of Oct 15th or sooner)
Audie Flow Pro Software, Data Aquisition, and Depression Control
Ten Ametek 116297-00 motors rated for 123 CFM through a 2" orifice (these are the same motors that Superflow uses in their benches)

Here's where I could use a little help from our more experienced and educated members:
I tried to figure out if I'm on the right track, but I don't understand the formula:
C*(3.14d2/4)[(2g(P)pH20)/(12pair)]^1/2*(60/144)
I got booted out of school in 1969 and I don't remember seeing the symbols * and ^ in my math clases. I bought a book on fluid dynamics, and there again, the math leaves me scratching my head wondering what I'm looking at.
Thanks to posts on this forum, I know I have to raise the test plate, and put a diffuser between the test opening and the orifice plate, and thats about where I'm at with it now.
This project has started to get expensive, and I sincerely want to do it right.
Any help or suggestions form the members will be greatly appreciated.

[Thomas Vaught]

I have looked at a lot of the "Blue Benches" over the years and to the best of my recollection they have traditionally used the Ametek 115923 Vacuum motor. This is a two staged ball bearing unit.

The motor is a 110 volt motor that they have wired in series with a second vacuum motor so they can run on 220 volt power.

Good luck with your project and let us know how the Audie controller/
other parts work out with your unit.

Tom V.

ps I would not worry so much about the math. Several members have
created excellent excel spread sheets that will do all of the math for you very easity with minimal inputs on your part. I would suggest looking for one of the posts that have the link to the spread sheets.

[gofaster]

I want to thank Larry for sending me some spread sheets.

Thomas Vaught posted that I have the wrong motors, I should have the 2-stage motors, #115923.

I looked up the specs on that motor, and besides being 2-stage, the only other difference is the "Max Air Watts" rating.

My motors are 227 air watts, and the 2-stage units are 447 air watts. I don't have a clue what that means. They both flow similar cfm's on a 2" orifice. The 1-stage is rated 123cfm, and the 2-stage is rated 122cfm. Before I go any farther, I'll need to find out what the significance of the air watt rating is. I don't want to proceed with motors that won't handle the job I want to do.

The reason I used these motors is that when my SF-110 bench caught fire due to an internal electrical problem, I assumed I smoked the motors and ordered 2 more from SuperFlow. They sent me 116297-00's. I figured to reduce my down time by getting the motors on their way while I pulled the bench apart. Anyhow, I got into the bench and found out the motors were fine, the problem was a loose electrical connection that was getting hot, and with air being pulled through the bench, it was quickly burning through the inside panel.

If anybody can educate me to the significance of the "Air Watts Rating", I would truly appreciate it. If it means buying more motors, then that's what I'll do. I already have what I consider a lot of money in this project, and I want to do it right. Even if it means getting more motors.

Thanks, Thomas Vaught, for your reply.

[bruce]

Here is a previous discussion on air watts:



If you haven't already, do a search and make sure you specify from "the beginning" there has been alot of past discussion on motor selection. Should be able to find some good info.

[gofaster]

Thanks Bruce,
I went to that link and used the calculations there. It looks like the single stage motor will pull 68.9 cfm, and the 2-stage will pull 135 cfm. That confused me because the motors are both rated within one cfm of each other @ 2" orifice. I dug deeper for more info on the motors and found out that at vacuum (H2O sealed), the 1-stage motor is rated at 60.6" and the 2-stage motor is rated at 100.4".
I am thinking that Air Watts are something like a power and torque factor in engines.
Through a 2" orifice they have similar cfm ratings, but as the restriction to flow increases, the 1 stage motor shows less ability to do work.
I thought I researched the forum thoroughly before I posted, but it's obvious that I missed the mark.
Tomorrow I'll call my supplier (Grainger) and see if I can exchange the 116297-00 motors for some 115923's. The 2-stage motors cost $35 more apiece. That would be better than buying a whole new batch of motors outright!

Thanks for your help.

[Thomas Vaught]

The early 110 benches may have had the motors you described but the SF 300/ SF600/ SF 1200 I have looked at, all used the 923 motors.

Hope it works out for you.

Tom V.

[gofaster]

This is getting very interesting! I checked around on the internet, and found this site. It supports the formula that "2seater" posted, It has an explanation of "air watts" and performance graphs of various vacmotors that are commonly used in whole house cleaning systems. If anyone is interested, here is a link:
Thanks for all of your help. I think I would have been very disappointed in the performance of my bench if I had not received your help!

[Sups]

so then what is the better method of measurement? I tested the equation out on a vacuum motor listed in grainger and the CFM conversion from air flow watts was smaller than the listed CFM.

[gofaster]

I'm not an educated person so I may not word this right. This is how I interpret this information. CFM only tells you how much air a motor can move. Air Watts tells what the motor can move through a restriction.
For an example, I took the specs out of Grainger's catalog for the 115923 (Grainger item #4M903) and the 116297-00 (Grainger item #2M203), and used the formula to determine what the waterlift (H2O") would be at a 2" orifice.
Air watts = (cfm x H2O)/8.5
To get H2O":
AW/cfm = [(cfm x H2O")/8.5]/cfm
AW/cfm =H2O"/8.5
(AW/cfm) x 8.5 =H2O"
The 116297-00 specs are: AW = 227, cfm = 123 @ 2" orifice, so:
(227/123) x 8.5 = 15.7" (rounded off to nearest tenth of an inch)
In other words, this motor will pull 15.7" of water on your manometer at a 2" orifice
The 115923 specs are: AW = 447, cfm = 122 @ 2" orifice, so:
(447/122) x 8.5 = 31.1"
This motor pulls 31.1" at a 2" orifice.
I take it to mean that the motors with a higher air watt rating will permit me to flow test heads at a greater depression than the motors with the lower air watt rating. That is where I'm trying to go with my new flowbench project.
I hope this helps you.