My VAC Box iteration

So, I originally was following the black box thread and talking about my plans but then that thread got closed, so I thought that I would post my results here.

Around Christmas I decided that I needed to update my machine to incorporate a vacuum hold down. I just got tired of screwing everything down and all of the inconsistencies that come with screws. So I rebuilt my stand to allow for vacuum plumbing and sheet good storage underneath.

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Also I decided to go with a variation of the plenum from I believe one of Chris Brady's designs

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During this process I started searching for ideas to do this vacuum system cheaply and ran across the black box thread which discussed some ideas and most importantly vacuum motor options. This is what prompted me to order the LH7123.

Where my design differed is that I didn't like the idea of having a large vacuum box on the ground taking up space, so I decided to make my box a little more compact and just hang it off of the end of my table.

As usual I didn't do a great job taking photos to show all of the design, and I actually don't have a real 3D model to show you guys (I just drew it up in vcarve and used my brain to do the 3D part), so I will just do my best to describe it.

Basically there is a back plate that I can bolt to the end of my machine that faces the garage door, and corresponding holes in my stand that lead to 2" PVC pipes routed to the 4 zones in my table plenum. Each zone has a gate valve up under the table right behind where the vac box attaches.

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Back plate in place

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This was all routed out of 3/4" melamine that a friend sold me cheap b/c it was a maple wood grain patter that he no longer liked. I plan to paint it all in the end so it was a good deal.

I test fitted the back plate and all was well, so I glued up the vac box and glued it to the back plate. The vac box is 12" from back plate to the lid where the fan holes are located. Around 4" of the vac box is plenum that all of the motors will share which is also connected to the stand plumbing via PVC couplers which are cemented to the back side of the back plate. The remaining 8" is dedicated to the motor housing and lid.

Picture of the vac box plenum from above
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Vac box plenum side from the side showing the downward facing exhaust ports

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Vac box motor side showing insets for the motors and gaskits

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I didn't like the idea of having the long threaded rods, so I made some collars that I glued together for height and the top one has a threaded insert. There are all aligned via dowel pins.

Collars in place
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Motor in Place
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I liked how the collar design turned out, however using MDF for the collars turned out to be a bad idea. When I tightened the bolts to hold the motor down, the middle collar was pulled apart and came loose. I didn't feel like doing a complete redisign and didnt have any other type of wood available, so I just cut another set of collars and added 4 holes that I pushed a 3/8" dowel through from top to bottom. These additional dowels seem to be doing a good enough job of holding the MDF collars together, but I already have a better design in mind.

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Collars glued in, motor mounted and bolted to the stand.

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After it was bolted to the end of the stand I just had to run the 2" pvc to all of my zones. As I said before there are gate valves up under the table right behind the vac box back plate. They are out of the way, which is nice but you have to get down on your knees to operate them, so I might try and automate them with some actuators at some point, but for now they do the job.

I didn't take any pics of the under the table plumbing, but that's pretty standard. I used 2" PVC and the long curve 45 degree turns then used some toilet flange to connect to the table plenum.

Plumbing done, lid on. From some angles it looks like the box sticks out past the end of my table, but its actually flush.

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Reserved for Results.

So for the results...
I have still not cemented any joints, and I just have some wood scraps covering up the holes I made for future motor additions and my initial results are 7Hg at the table with a sheet of MDF on the bleeder board. Overall I am very happy with my results. Before I had finished this box I had a plain old shop vac piped into my plumbing and at best I would get 2-3Hg. So with over twice that amount, and with the additional CFM I would say that this was quite a large upgrade. I plan to rework the motor hold down collars and add an additional motor in the near future. I can't imagine I will ever need 4 of these motors, but I built it so I would have the option should I choose.

One question, has anyone taken a temperature reading from inside the motor box? I noticed mine was pretty warm after about 30 minutes.

More Pics...

Got tired of walking around and throwing individual switches so I made a switchpanel. First switch powers on machine, next is dust collection, followed by 2 switches for the vac box.
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Just a project done with the new vac.

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Thanks, hope this is helpful to someone!

Looks great-Gary's black box design has a fresh air intake valve to make sure some fresh air gets in to keep motors from getting too hot. If you don't you may want to check that part of his design out and implement it into yours

Quote:

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Originally Posted by bleeth

Looks great-Gary's black box design has a fresh air intake valve to make sure some fresh air gets in to keep motors from getting too hot. If you don't you may want to check that part of his design out and implement it into yours

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Yes, I saw the fresh air valve. I would imagine that my system has enough leakage right now to allow sufficient air flow, however I am kicking around the idea of just blowing some air through the motor compartment to keep everything cool in there since it is so small.

Highly advisable. Remember that the universal vac motors are designed to be sucking in room air and in your use there is no fresh air flow unless you make it happen. Under regular use guys normally get a couple few years out of them before they die. The hotter they are run the shorter they will live. The most up to date black box design was based on a couple prototypes and one of the key factors was airspace around them and fresh air cooling.

Looks good. I am getting 7 hg also with 2 motors, all zones open and full table covered with bleeder value opened a little. My machine doesn't run very much, but it was one heck of an upgrade. I built the conventional box design and blocked the other two holes so I can add 2 more motors down the road. But My thinking is once I burn these two up, I should have made enough money from it to upgrade to the Hurricane made by blackboxvac.com

My motors havent got over 120 degrees yet. But I havent run them for more than 15 minutes at a time, and its not summer yet.

Wish I had messed around with vac hold down years ago.

Dave

Just my 2 cents on vacuum hold down. My system isn't all that strong but it does hold sheet goods in place and also things like cardboard and plastic. I've used it many times by itself and in combination with clamps. The thing I really like about the vacuum is it flattens warped material that would be extremely difficult to cut accurately otherwise.