PTS Flowbench Forum

olympiadis wrote:
What do you think best? One, two, or three stage blowers?
..and are there any vacuum motors rated for continuous use and high temps?

The important thing to realize is that a vacuum cleaner normally operates with almost blocked flow.
A very high suction pressure at low flow is what pulls the grit out of your carpet.
This is why they compound two or three stages on a single shaft to get the highest possible suction pressure from a given electric motor.

A flow bench application is rather different. We will be pulling a large volume of air at only moderate pressures, typically around 44 inches of total suction pressure.
The ideal flow bench blower would have a very flat pressure versus flow curve.
The "perfect" flow bench blower would generate 44 inches of vacuum over the entire flow range without the need for any adjustment !

The more peaky the flow curve, the more touchy it becomes to set and hold a constant test pressure, so three stage vacuum motors are never used.

Most of us are limited by how much mains power is available, and so choosing the most efficient vacuum motor becomes an important consideration.
More CFM out for fewer amps in, is always a bonus, and that plus the initial cash cost should be your guide.

So try and find vacuum motors that have the highest efficiency at around 44 inches, that is CFM out per amp of mains current going in. This is more likely to be a single stage, and sometimes a two stage vacuum motor, never a three stage.

Unfortunately all these vacuum cleaner motors run at very high rpm, with a very high power density, and are made to a price with planned obsolescence in mind...
That does not seem to be a serious problem, just design your flow bench with very easy motor access, and maybe initially buy a couple of spare motors of the identical type.
Later you will be glad you did.

Tony wrote:Most of us are limited by how much mains power is available, and so choosing the most efficient vacuum motor becomes an important consideration.
More CFM out for fewer amps in, is always a bonus, and that plus the initial cash cost should be your guide.

This is the number 1 criteria.

As far as doubles and singles, it depends on the manufacturer. Ametek doubles have better specs than their singles, and Domel makes singles that have better specs than their doubles and the big Ametek doubles.

Do these better specs translate into better performance?
as in being heavily loaded without overheating?

I'm pretty sure my most time-intensive work on the bench will be developing valve seats, which is at very low
valve lifts and very high depression, - so would load the motors heavily.

That's why I am considering 3-stage and 220v vacuum motors, in hopes that they will handle
heavy loading better by design.

I'm also guessing that when you're using the motors to blow for exhaust work they will heat up
much quicker.
I'd rather not have to worry about trying to work in a hurry in order to avoid overheating.

Normally a higher voltage at reduced amps will allow a device to run cooler and more efficiently, - often handling loads better.
Is this the case with the vacuum motors?

The motors will have a much easier life than in a vacuum cleaner.

A vacuum cleaner always runs at full mains voltage, very high vacuum, with almost totally blocked flow, that means limited cooling air through the motor.

In a flow bench the motor voltage will be reduced to set the required test pressure, and even at zero valve lift the motor temperature will be much lower because you don't need to apply full motor voltage to reach the required test pressure at zero flow.

Almost everyone uses vacuum motors in their flow bench, including the high dollar commercial flow benches.
It is proven to work, and ordinary vacuum motors have a quite acceptable reliability and lifetime.

They still sometimes blow up spectacularly, but that has proven not to be a significant limitation compared to favorable cost and convenience of using them.

The main disadvantage is motor noise, but even with a silent larger lower rpm centrifugal blower, air roar is still going to kick up quite a bit of noise flat out.

1960FL wrote:Salt, lets see if Bruce can move your post to a new thread.
PS update us on your reasoning for gas power...

Rick: I wasn't ready for a new thread yet. As a newbie I have weeks of time coming up to speed on the forum before I ask questions or add some value. Just had a single question about power source as I start down this path. The title of this thread fit my situation perfectly and I didn't think my single question would start a turf war or thread drift. I will go away now and let Mr. olympiadis have his very own personal thread.

saltfever wrote:

1960FL wrote:Salt, lets see if Bruce can move your post to a new thread.
PS update us on your reasoning for gas power...

Rick: I wasn't ready for a new thread yet. As a newbie I have weeks of time coming up to speed on the forum before I ask questions or add some value. Just had a single question about power source as I start down this path. The title of this thread fit my situation perfectly and I didn't think my single question would start a turf war or thread drift. I will go away now and let Mr. olympiadis have his very own personal thread.

It's all good, I split off your question into a new thread as you saw and you can ask questions as you go along not a problem for me There is no time limit on threads here as you can see some have been going on since the early times, some pop back up after months or even years . . .

olympiadis wrote:Do these better specs translate into better performance?
as in being heavily loaded without overheating?

I'm pretty sure my most time-intensive work on the bench will be developing valve seats, which is at very low
valve lifts and very high depression, - so would load the motors heavily.

That's why I am considering 3-stage and 220v vacuum motors, in hopes that they will handle
heavy loading better by design.

I'm also guessing that when you're using the motors to blow for exhaust work they will heat up
much quicker.
I'd rather not have to worry about trying to work in a hurry in order to avoid overheating.

Normally a higher voltage at reduced amps will allow a device to run cooler and more efficiently, - often handling loads better.
Is this the case with the vacuum motors?

Have I got this right, you don't care about performance of the motor, nor power supply problems, nor the massive cost of a 3 stage, just that it doesn't get hot. I for one, and probably everyone else, would put that very low on the list.

You probably haven't run a flowbench, and that's probably why you are concerned with heat, but a flowbench is an intermittently run appliance, ie, run for a minute, and then shut off for a considerable time while you do porting and adjustments.

My experience with Ametek motors is that you don't run them hotter than 110ºF. We have had 3 failures, but only after the guages on the SF110 reached 120ºF-ish, and that only happened on really hot days.

For the cost of a 3 stage you could buy 2 singles or doubles, and have double the capacity, and that is why no one would consider it.

Took two heads to get tested.
Man tried to test head on SF600.
Bench got hot, he turned into an ass, took my money and told me to leave because he wasn't going to run the machine anymore.
Took heads to second shop with similar SF600. This one also got hot which stretched out my wait time to half a day, and the operator also got frustrated and just wanted to take my money and let me leave.

Going through 15 lift stations on two ports was more than it could handle and I consider that ridiculous, and hence
it is a very important factor to consider.


I'm not going to be doing porting, then only check at one lift and shut it down. That's dumb.
....

(deleted)

Another factor is that actual vacuums like my shop vac DO have a separate cooling fan for the motor, UNLIKE these flow-through vacuum motors that operate in their own hot air, so I don't think that's a fair comparison.

If nobody here really knows much about vacuum motors that's fine. I'll figure it out myself over time.


Also, having a separate thread for individuals isn't about a turf-war. It's about getting the best answers to your particular question. My suggestion to make another thread was for your benefit, not mine.

I keep my flowbench in a controlled environment. When the bench is running the air conditioner is set about 74*F. Haven't had a problem with overheating.
Ray

olympiadis wrote:Took two heads to get tested.
Man tried to test head on SF600.
Bench got hot, he turned into an ass, took my money and told me to leave because he wasn't going to run the machine anymore.
Took heads to second shop with similar SF600. This one also got hot which stretched out my wait time to half a day, and the operator also got frustrated and just wanted to take my money and let me leave.

Going through 15 lift stations on two ports was more than it could handle and I consider that ridiculous, and hence
it is a very important factor to consider.


I'm not going to be doing porting, then only check at one lift and shut it down. That's dumb.
....

(deleted)

Another factor is that actual vacuums like my shop vac DO have a separate cooling fan for the motor, UNLIKE these flow-through vacuum motors that operate in their own hot air, so I don't think that's a fair comparison.

If nobody here really knows much about vacuum motors that's fine. I'll figure it out myself over time.


Also, having a separate thread for individuals isn't about a turf-war. It's about getting the best answers to your particular question. My suggestion to make another thread was for your benefit, not mine.

When I first started playing with the PTS style of bench I did not have all the vacuum motors but I wanted to get it up and running. I built just the chamber side of the flow bench and plumbed in two big shop vacuums into it. On a small block chevy that is pulling a lot of cfm it will hold 12" of H2O at .700" lift.

If I am getting this correctly you are wanting to test only at low lifts? On my 2.05" intake at the lower lift, .050" .100", it will pull 40" H2O. So why don't you just build the chamber side like I did and put shop vacuums hooked to it. Problem solved.

John