New plenum concept

[carter_beck]

I am in the process of building a vacuum table based on two Imperial vacuum motors working in parallel. Like some others here, I am not too fond of the heat issues which go with pumps in series.

I want to build a multi-purpose plenum board with fixed vac openings. The following modification of the usual four or five zone table has occured to me (perhaps inspired by Stan's card valve 9-15. Imagine a 4 x8 table with parallel zones running the entire length of say the short axis. These zones could be subdivided 3/8 square strips of HMWPE milled into the table before the grid is cut. The could then be optionally slid out a fraction to cut vacuum to unneeded areas?

any thoughts?

Sorry, no CAD drawing yet.

[tuck]

http://i50.photobucket.com/albums/f332/Superfan52/FinalSolution.jpg

[beacon14]

Business still slow up there, Mark?

[tuck]

It's gettin' a little better, David. Had a decent week and next week looks crazy.

[beacon14]

Carter, not sure from your description exactly what you are proposing.

[carter_beck]

david,

sorry, i need to do a CAD drawing when i get time. but let me try again.

i am suggesting that sliding 3/8" square rods of say polyethylene be inlayed, but not glued, into the plenum. they can slide, say a half inch. the rods are perpendicular to the zones of the grid. the plenum grid is then milled. by sliding the rods one can cut of areas of the grid distal to the vacuum source because the channels don't line up. One can therefore concentrate the vacuum to a small portion of the grid.

does that make sense?

[Gary Campbell]

Carter...
You can accomplish the same thing, and possibly allow for irregular shapes by using Allstar round gasket material placed directly in the plenum grooves. Here is a pic showing a rectangle around the vacuum outlet and gauge port.

7424
Gary

[billp]

If you could slide these plastic rods easily you probably wouldn't have much of a vacuum seal. Even a fraction of an inch gap multiplied over the length of the rod(s) will add up to significant leakage...
If they did NOT slide easily the process would be a PIA...

[Gary Campbell]

Carter...
I have reread all your posts and now have a better idea of your plenum design. First let me say that I should be the LAST person that uses the phrase "Don't reinvent the wheel"!.

There are possibly thousands before us that have gone thru the same problems. What is out there now is the product of many ingenious persons, coupled with "standard practice" and of course, value engineering. My 4 head system and PVC table were aimed at changes I wanted to make to test some of the "standard practice" options to see if improvements could be made. Some worked out very well, and the others, well, seemed like a good idea at the time. Your 3/8" square stips may fall into that category. Zone valves will work to effectively seal off an area of the table, at least to the size of zone you cut. The strips will be more prone to leakage and harder to use.

Now that I have actually used my system for a year, I am trying out some ideas for a new design to go along with a larger regen blower when I can afford it. I am going to use my existing vac heads to test, as the results will be more pronounced with lower flow. Here are the areas that may benefit from minor improvements, with the hope that a few of them combined will yield a measurable improvement.

Plenum:
instead of a grid of grooves, try leaving an inch or smaller square every few inches to support the bleeder. the more open area the better.
I am looking at 6 approx. 24" by 32" zones as this size works better with the table brace layout and shortens the distance from the vac port to corner to around 18" max.

Manifold:
I will be looking at upsizing and streamlining the most commonly used zone valving system to improve flow. I will use a 3" manifold pipe down the bottom center of the table, using a cross to mount a pair of vac motors and then use wyes and 45's to go to each vac outlet.(maybe even more crosses) There will be a 3" knife valve in the manifold to allow use of either 2 or 4 motors.
I plan on using a stainless blade knife valve glued directly to the port on the table bottom. valve handles can be extended with steel rod to the table side or front for convenience. a long sweep 90 out of the bottom of the valve and less than a foot of pipe to the wye.

This approach uses less than 5' each of 2" and 3" pipe and should perform fairly well. A 90 degree el has the resistance of between 7 and 12 feet of straight pipe. If you add that amount for every 90 to the amount of pipe in a typical system, its starts to be a long pipe that we are trying to make a small vacuum motor draw thru.

If any of these sound good to you, work on them and report back. I will add more as work on it.
Gary