Twin Series Parallel Vac Motor Setup

[Gary Campbell]

I picked up 2 of the 220V 3 stage vac motors from Ward at Lighthouse and finally got them assembled on my series/parallel valve assembly.

For those of us that have access to 220v power in our shops, this system gives pretty good performance and draws 12 amps (both running) during most cutting operations.

I tested them in both parallel and series and results are:
Parallel max Hg 9.9 max CFM 175
Series max Hg 16.5 max CFM 95

The valve uses a lexan slide valve sealed by o rings to switch from series to parallel. There are also micro switches that allow indicator lights to show which mode is operating.
Here are a couple pics:

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and a pic of the test rig:

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Gary

[ed_lang]

Gary,

Looks like you have the right tools to test for flow.

Do you (or anyone) know how much air can be moved through Trupan at 3/4" and then down to 1/4"?

Also has anyone experimented with different size grooves in the plenum and just how much effect that has on the efficiency of the system?

[cabnet636]

gary, i have ordered a sheet of phenolic to cut a new vacuum plenum and so far the best consensus
is to get as nuch air flow as i can and round the grooves, i too would like to hear more on this

jim

[Gary Campbell]

Ed...
As soon as I get them mounted to the table, I am going to make a cover for the zone and test cfm thru various materials. The down side of my gauge is that I get inconsistant results under 50cfm due to guage extremeties. I may not get an exact number, but more or less by fractions should be evident. I will post when complete.

james...
I will also be cutting larger and different designs into the spoilboard to see if it makes a difference. As it will be a couple weeks in the future, you may want to go ahead with one of the tried and true designs. You can always hog a little more out. I doubt I will find any magic. I think that by far the largest difference I have seen in cutting conditions is using twin motors in air parallel configuration.
Gary

[ed_lang]

Thanks Gary, I am in the position to replace my Trupan spoilboard this week and this would be a good time to recut the plenum if a better design should show up. There has been a lot of talk around this shop about 2" pipe not allowing all the CFM that 2 to 4 motors could pull at once. Seems that no matter how good the plenum design is, you are always forcing all of the air past a 2" hole in the table. Maybe going to one large zone, with multiple holes would allow better under spoilboard air flow to take place. I may experiment with one 4'X 8' zone with four holes each feeding one motor. Without knowing how much CFM can be pulled through the Trupan, it is impossible to calculate how many motors you would need to obtain 100% flow rate on the full sheet. Since my machine is working great, I need something to think about! We also talk about the shape, size and depth of the pattern cut into the plenum and how that makes a difference in air flow. Everyone agrees that in a perfect world with no leaks, there would not be any air flow.... but then we all want to hold the little parts and cut them out without a skin.

[Gary Campbell]

Ed...
Harold Weber sent me an awesome flow characteristics chart, as it applies to our vac piping and plenums. I think he said it was going to the Wiki also. During cutting operations, which should keep cfm under 100, there is no problem with 2" pipe. 2 motors might be slightly restricted at open flow, but again, during normal cutting, should be fine. The case where 2" pipe would have a performance loss would be in using it for a manifold using 3 or more motors, going to 3 or more zones. Branches off the manifold can be 2", but the manifold should be at least 3".

Here is what I can tell you from my incomplete testing:
The 3/8" dia. 5/16" deep groves in my table restrict air to the extremeties when flowing over 40cfm. This has caused hold down to fail.

That installing a fairly substantial chamfer from the vertical pipe to the horizontal plenum may be the most significant improvement we all can make over the OEM vac grid. A simple 45 degree chamfer about 3/4" deep should work fine.

THere are a few more little tweaks, but they are small percentage improvements.
Gary

[Gary Campbell]

After running these particular motors for an extended time, I am not happy about the heat generated in both the aluminum transfer pipe and the downwind motor. Looks like if I cant cut it with 10"Hg, I get out the clamps.

A side benefit is I get to eliminate the plumbing.
Gary

[Gary Campbell]

After running all the tests I could think of on the vac motors in parallel and series, both above and below the spoilboard, here are some of the useful numbers. (pages of useless available upon request)

The mfgr. published performance charts are basically right on the money for the Ametek motors. The 3 or 4% difference my readings were off were both high and low, most likely a result of my unscientific setup and not alway glueing the pipes together.

When running 2 motors in parallel:
Max CFM = 1.75 X single motor (thru 2" pipe)
Max vacuum = max as listed for single

When running in series:
Max CFM = 1.1 X single motor
Max Vacuum = 1.6 X single motor

Both configurations were tested using 1/4" thru 2" orifices as per the Ametek performance charts and returned numbers that equals the ratios above.

How this applies to my system, and maybe yours, is: Upgrading to the higher vacuum 3 stage motors gives us an addition 2 inHg. in cutting operations. (5.1" to 6.9") Adding a second vac motor in parallel adds another 2inHg. (8.9")
Note: Average flow (leakage) during our testing has been from 20 to 30 cfm in 1 zone. This is the equivalent of a 1/2" hole in a pipe for a 2' by 4' Trupan zone.

This chart id mfgr data but within .4inHg at all cfm ratings. The gray area represents the minimum and maximum cfm we found PER ZONE. The left edge represents around 50CFM leakage and the right 10. 10 is about as tight as we could mask off a 2 by 4 piece of Trupan. 50 is the equivalent of ten 10" slots cut into a 12" square. Most of our normal cutting falls in between the 2 (the proverbial gray area) Until I can get a funtional intercooler for the series funtion, I can only wish I had that much vacuum.

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Gary

[Brady Watson]

An intercooler from a Ford PowerStroke Diesel is cheap & fairly efficient (air to air)...The only downside of adding an intercooler is that you might give up 1-2" of pressure in doing so. This is at least what happens on boosted cars (turbo or supercharged) and what I've experienced on my turbo cars when adding an intercooler. A straight aluminum tube with ribs machined into it may be enough to lower the air charge temperature to function as an IC. Whether or not it is worth investing in is up to you...At some point one must question where to stop on a budget system & just bite the bullet & get something better suited to the task at hand (after you've made your $$$ on the budget system to afford the industrial one)

Nice work on the data. Thanks for sharing.

-B

[Gary Campbell]

Brady...
I looked into the intercoolers, and there seems to be many that would work for this. With our shop ambient being close to 90 these days, even with a fan attached, I wonder if I would get as much cooling as I would like when cutting for extended periods of time.

I heartily agree on the budget system. I was following the seed you planted on the 9-15 with this. I opted for the 240 volt version as they draw a little less amperage. I think the small percentage performance increase of these motors is due to the higher efficiency of the 240V.

I have always said I want a 15HP+ regen. And purchasing one is within our budget. The cost of 3 phase run to our leased building or the 30HP VFD or phase converter kills the deal every time. Our days in this building may be shortened due to Ownership change, our next is sure to have 3 ph. power.

I do want to note that the testing I did was NOT on the Imperial motors on the 9-15 Threads. These are Ametek motors that have slightly higher vac numbers (10%) and a similar cost in a 240V version.

We are going to replace our existing 7" max motors with these 10" units and install 2 of them to allow parallel operation in our "Zone 1". This will give us the option of increased flow advantage, even if confined to a 2' by 4' area. We can add a 2nd motor to the other zones if needed.

Since I have to redo the plenum to allow full coverage for a dual Z that is coming, I am going to do some testing on plenum designs with a flowmeter to see if anything pops off the page as an advantage.

Brady, thanks for the info and reality check.
Gary

[Brady Watson]

All good stuff Gary...Research pays off


-B

[dana_swift]

Gary- if you need three phase, look up "pony motors" to generate three phase artificially. They are cheap and do the job very nicely. I know several shops around here using them. If you end up having to move, just take it with you, and then you can work with a standard 240v feed wherever you end up.

D

[Gary Campbell]

Dana...
I have been doing some homework on these phase converters. I havn't heard of "pony motors", but I am sure that they fall into one of the 3 categories I've resarched: VFD's, Static phase converters, and rotary phase converters.

As far as I can tell, the minimum upsize requirement for a single/three phase converter is 1.7 to one. That puts the VFD or converter, whether static or rotary at or near 30HP for a 15HP regen. Even at eBay prices they are stout.

This also means the addition of a 60-70 amp circuit. We havn't been very kind to our power loads as it is.

Unless some magic comes along, we will stay with the Ameteks until we have access to 3 phase. With close to 10" max, these new motors are actually pretty good, and I was happy with the old ones.
Gary

[Gary Campbell]

A little more data. Zone 1 with the 117123 motor installed. (listed on lighthouse ent. website as the 240V version of the Imperial motor comonly known as the "9-15") Zone 2 with our original 116296 motor installed. This is the motor that was spec'd by Grainger as the Euro (240V) Fein equivalent) specs match that published for the Fein Turbo lll. I believe that the Fein publishes the motor specs rather than real data thru the hose for their vacs. Due to altitude and plumbing, most users do not get the full 6.92 inHg to their manifolds.

Pieces cut THRU in 3/4" Birch ply with 1/4" Mort. Comp. Bit over 2 zones:

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Vacuum in 2 zones before and after, note difference in gauge readings.

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Keep in mind that the actual vacuum on TOP of the spoilboard will be 2 to 2.5 inHg less than shown on my plenum gauges.

Side note... to make sure normal cutting conditions are maintained... spoilboard is trashed: Surfacing the spoilboard will net .5 to 1 inHg higher in plenum ....1 to 1.5 inHg higher on TOP of spoilboard.

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Next, we will move the single 117123 to zone 2 and install 2 in parallel in zone 1.

Gary