My vac project, updates.

[michael_schwartz]

I will be updating this thread over the next week or two as this project progresses. Hopefully with something more than sketches in the next couple of days.

I chose to use two LH6765-13 3 stage 120 volt vacuum motors that are rated at 106 CFM each (maximum) and 140" h20 sealed, which is roughly 10" HG. They should arrive in a couple of days.

I will be setting up two table zones or ports as I should say since I do plan on using "Brady Vac" plenums, machined from Trupan Ultralight MDF, rather than a dedicated plenum. I decided not to attach the motors to the bottom of the spoil board since I do want to be able to concentrate both motors on a smaller fixture, at the front of the table when necessary.

The current configuration I plan to use has a single ball valve, and two 90 degree elbows. The ball valve is used to close off the rear port. The front will always be left open. The motors are going to be attached directly to a plywood, or melamine box which is divided by a check valve, inspired by Garry Campbell's black box setup.

The goal behind the check valve is to automatically seal off the other half of the box when I only want to run a single motor, on the front zone. This could be done with a ball valve, but I want something automatic.

I also plan to be able to add 1-2 additional motors at a later date if I feel its necessary. The plumbing could also be reconfigured to allow for a manifold for a multi zone plenum.

For the electrical controls my electrician is going to setup a 6"x6"x4" steel enclosure with two switches, fuse blocks, and a knock out for a panel mounted vacuum gauge. I chose to add fuses to have some kind of thermal protection at an amperage closer to that of the motors, rather than relying on the breakers for the 20 amp circuits.

[Brady Watson]

Looks like you are on your way to designing a nice system. You might want to add a couple of air filters to the box. The plenum will work for most of the filtration, but some particles invariably get sucked into the motor. It adds a little insurance for those 'whoops!' days.

-B

[michael_schwartz]

I am thinking about adding a mesh or screen to protect the motors from chunks of debris, or large dust particles. I may also add pleated filters but I am not sure how much damage limited amounts of fine dust would do.

[michael_schwartz]

After some reading I am going to add 2 cartridge style shop vac filters, for a total cost of $20.00, and expand the box to accommodate them.

[Brady Watson]

The impeller to housing clearances are pretty tight on these motors, so I would definitely look into using an automotive or ShopVac type cylindrical filter on the inlet. Since you are building a box, It is super easy to add. Just use 3 or 4 allthread rods and a disc topper to lightly compress/seal the filter over the intake hole. A 4" inlet is big enough to allow full CFM of all 4 motors without restriction.

-B

[Rob Gunn]

Wondering about recommendations for a vacuum gauge to install on my vac table that I am building. Rob Gunn

[michael_schwartz]

I am ordering the following gauge from http://www.mcmaster.com/
4002K25

I have a nicer glycerin filled gauge on my Venturi pump that I use with my vacuum bag, but I am going to give this one a try.

[michael_schwartz]

this is the other gauge I have, which is probably nicer, and costs about the same. However they don't supply a bracket to mount it in a panel.

http://www.veneersupplies.com/products/Vacuum-Gauge---Heavy-Duty-14-NPT.html

[Brady Watson]

I've been getting my vac gauges from Summit Racing (http://www.summitracing.com/parts/SUM-G3125/)

-B

[curtiss]

So again, 10 in of Hg means.... you have how many PSI pushing down on your material???..... and what is the theoretical maximum you can achieve at sea level ?

[Brady Watson]

Perfect vacuum @ sea level is 29.92 Hg", which equals 14.7 psi

10 Hg" / 29.92 Hg" = 0.334

0.334 * 14.7 psi = 4.91 psi

-------------

1 Hg" = approx 13.6 H2O"

So... 150 H2O" / 13.6 = 11.03 Hg"

-B

[michael_schwartz]

I ordered 6 sheets of Trupan ultralight today.

If anybody in the northeast is having a hard time finding this contact Atlantic Plywood. They sell everything you could ever want, and they are more than willing to work with small shops. I just ordered about 30 sheets of various materials from them and their prices are quite reasonable.

[michael_schwartz]

I finally got around to cutting the box for my vacuum motors.

I had originally planned to use baltic (russian) birch and I was going to name it the "peoples box" to be sarcastic. I ended up using black melamine to keep the costs under control.

The motors will get bolted onto baltic birch motor mounts which will get bolted onto the box. I did this so that I can switch to different motors if I need.

The design changed a bit from the my original plan. I am still going to use 2 motors, to start. I may upgrade to 4 in the future. The box is still going to have a check valve, and I am going to add a plexiglass window so I can see it in action, and troubleshoot without taking it apart. I will probably add some internal gussets to reinforce things. I don't want the box to implode when I put it under vacuum.

I will likely build an enclosure to go around the motors with ducted intake air, air and exhaust. I will add some kind of a filtered baffle for the intake air.

The pictures were taken with my phone. I am going to work on assembling the boxes tomorrow, and I will take some better pictures soon.

[michael_schwartz]

I got the box sealed up well enough to hold 8.5-9.5" of mercury with the back taped on. That is at about 900-1000 feet above sea level. I have done some additional caulking since, and I will check again. Sadly I learned over tightening the bolts on these motors with a cordless drill on fast speed is a bad idea. As a result I have to replace one of my motors. Don't make this same mistake.

Disregard the dark amber shellac I used to seal the baltic birch. Gives stuff a nice ugly 1960's look.

I might get around to working on my spoil board later in the week. I have changed my mind and I am going to go with a permanent 4 zone plenum with 2" knife valves.

My current spoil board is so riddled with holes, and broken screws that I can't even really surface it much more than another .01 I am going to switch to sacrificial fixtures for when I need to hold stuff down with screws.

[knight_toolworks]

You only need the bolts tight enough to keep the motors from twisting when they turn on. but you can make that motor work Just make a wooden collar that fits over the motor and extends far enough to screw through down into the mounting surface.

[michael_schwartz]

I managed to crush the housing for the turbine on that motor, so its as good as scrap. The replacement should be here in a few days.

I agree that with the gaskets they don't need to be tight at all.

I am going to try these knife gates. They were about $16 each.

http://stores.drainageproducts.us/-strse-623/Valterra-knife-gate-valves/Detail.bok

[Brady Watson]

Nice find on the cheap gate valves. Let me know how they work. I'll be re-doing my own system soon...Although I am thinking of throwing some actuators on the gate valves so that I can just flip a switch. The 2" ball valves can be a bear to turn some days. I think there is a possibility that vacuum sucks the ball valves dry of all lubrication...not positive, but it sure seems that way after a while.

-B

[michael_schwartz]

I took a look at the ball valves at home depot and I gave up trying to turn the 2" valves because I didn't want to make a scene. They also cost more than the knife valves I ordered.

The 1.5" valves aren't nearly as bad. I bought one to to use as a takeoff, or as a port to connect a shop vac in a pinch.

I ordered 5 of the knife valves. 4 for the table zones, and an extra to use to release the vacuum, or as a port that I can connect to a fixture with flexible pvc.

[michael_schwartz]

I currently have the check valve working reasonably well.


I made this box too large and complicated. I am going to get it up and running as a proof of concept, and then use what I have learned to make something better.

For revision 2.0 I want to ditch the box, and just use PVC pipe to accomplish the same thing. I am trying to scavenge a large steel enclosure to house everything.