revised vacuum motor enclosure, a sneak preview.

[michael_schwartz]

I didn't like the original setup I had made a month ago so I decided to discard it. I opted to do something a bit nicer, but I had to obtain various parts which has taken a couple of weeks.

My priorities were to enclose the motors to provide a degree of protection should they burn up, and to also enclose the electrical connections so they are not exposed.

I decided to use a NEMA type 1 enclosure because they are readily available, and economical. They are also designed for uses, where allot of things could go wrong, inside of them. The enclosure which which is 12x24x24 14 gauge steel is a bit large. I had originally planned to use something smaller but I opted to spend another $50.00 to have a lot more room to work, and a greater volume of air, for heat dissipation. I added 2 louvered vents. I may separate the cooling intake and exhaust with a piece of 3/8" PVC. The blower exhaust is going to get plumbed out the back of the cabinet.

I am looking into fabricating some metal work, to bolt the enclosure to. Right now I have it set on the floor, so that I can start playing with the plumbing configuration.

I milled a piece of 1.30" type 1 PVC to act as a motor mount, and flange.

I must have milled the holes for the PVC pipe to within about .001 since I got a nice tight friction fit. No need to glue, or to seal the short stubs of pipe. I am really amazed by the accuracy that can be achieved with my PRS Standard.

I should have this up and running later next week and I will post a detailed write up.

14614
The pvc flange

14615
pvc flange, with stubs of pipe, friction fit.

14616
side of enclosure, with double beads of silicone around
the knock outs prior to the installation of the flange.

14617
inside of enclosure, with motor gaskets. I temporarily installed some shorter bolts
in the holes for the threaded rod the motors get mounted to, while the
silicone dries.


14618

The enclosure will be raised up about 2.5"-3" off the floor and I am planning on fabricating some metal work to support it. Right now I have it sitting on the floor, so I can layout all my plumbing. On the side you can see the beginnings of the manifold, with a pair of 2" PVC swing check valves.

[garyc]

"I may separate the cooling intake and exhaust with a piece of 3/8" PVC."

Michael...
If you do not separate them, and provide relatively unrestricted air flow for both to the outside of the box, you will most certainly burn up those motors.

[knight_toolworks]

don't forget a separate air intake. that's the most important. piping out the exaust makes life easier.

[michael_schwartz]

I will definitely separate the intake air then. I have a plan to pipe the heated exhaust from the blowers out the back.

[knight_toolworks]

4" pvc pipe usually fits right over the top of the motors. well the thin walled drainage type does.

[michael_schwartz]

I have a piece of 3/8" x 12 x 48 PVC I will use to create a partition to separate the intake side, from exhaust. I may have to duct the air a couple of inches, or I may be able to just machine holes that fit the top of the motors.

I also recall finding that a piece of metal flex duct I had was almost an exact fit. I threw it out for some reason. I will probably go with something larger though to avoid un necessary resistance, and just machine a ring/adapter to fit over the top of the motor.

The surface area of the smaller louvered vent does exceed the combined intake surface area of both motors. The larger vent on what will be the intake side is almost twice as big. I will think about adding a third vent to the exhaust side just in case.

I oriented the motors so it will be easy to plumb the exhaust from the turbine straight out the back of the enclosure with a rubber coupling, and 1.5" PVC pipe. I will probably make my own mufflers.

I still need to scrounge up some parts that I can't get locally. I will run up to home depot in the morning to see what I can find.

[michael_schwartz]

Today I fabricated a metal frame to support the enclosure and had my friend weld it together. I used 1 inch square, steel tubing bought as a 24 foot length, for about $30.00. I haven't bolted it to the table yet, but I am going to work on that in the morning. I primed it with automotive primer, and painted it with a few coats of Rustoleum (navy blue), which is a somewhat close to Shopbot Blue. I think Brady pointed that out at one time or another.


Last night I cut the knock outs in the back of the enclosure for the exhaust from the blowers. By accident I found that the pair of of 2" rubber pipe couplings I had were the perfect length, and also acted as their own grommet to cover up the slightly oversized knock out holes.

I have a plan to separate the intake/cooling air, and I am going to work on that tomorrow.

[michael_schwartz]

I bolted the support frame to the table this morning, and then I made a divider to separate the intake side, of the cooling fan on the motors, from 3/8" type 1 PVC. I used 4" flexible dryer ducting, which gave plenty of room for error. I need to machine a pvc ring to fit over the top of the motor, to act as an an adapter.

Last I heard my electrician is coming tomorrow. Then I will move on to finishing all the plumbing, and start work on my spoil board.

I will post some better quality pictures of everything when I have the time. For now these will have to suffice.

[michael_schwartz]

I do have a question. I read that Lighthouse Enterprises recommends allowing roughly 1/4" leakage per motor. I am thinking of drilling a pair of holes in my plumbing, but that would end up amounting to additional vacuum loss when you introduce leakage into the spoil board. Or maybe it is an insignificant amount. I am not sure.

I am wondering what approach people have taken to accomplish this.

[michael_schwartz]

I cut a pair of PVC doughnuts from 3/8" grey type 1 PVC to slip over the top of the motors. The outer diameter, is sized for the 4" flex duct. Disregard the cut quality on the PVC. I rarely mill plastics so I had to make due with the tooling I had on hand.

[garyc]

Michael...
The 1/4" diameter hole (per motor) will ensure that if you do happen to have a "sealed tight" condition, that enough air will circulate to cool the vanes. If you wish, you could install a properly sized vacuum check valve to open when vacuum is .5 inHg less than max. That way no leaks during normal usage and peace of mind that you are not overheating the pumps.

[michael_schwartz]

I like the idea of a relief valve. The two 1/4" holes would add up to be about a 20 CFM loss according to motor curves.

I took a look at the valves intended for regenerative blowers, and they appear to cost more than just adding a third motor to make up for any losses, so spending that kind of money would be overkill.

I don't know of these proportional relief valves would be worth trying. The 3/4" valve I linked to below is rated for up to 54 CFM of flow, and the smaller 3/8" valve which costs much less is rated up to 15 CFM. Both state that they are rated for 0-30" of vacuum. I would assume those flow rates are at a much higher vacuum though, so maybe they wouldn't allow enough airflow.

http://www.cdivalve.com/products/relief/relief.htm
http://www.grainger.com/Grainger/CDI-CONTROL-DEVICES-VacuumPressure-Relief-5Z765?Pid=search

If this would require too much engineering or trial and error drilling a pair of 1/4" holes might just be the way to go.

[garyc]

Michael...
Use the one rated for 54 cfm and place a restrictor down stream that is 5/16 diameter. (equals 1/4" X 2)

On your 1st link, the "VR" series would work the best

[michael_schwartz]

I will give it a try then. The first link is the manufactures page for the valve sold by granger.

Thanks.

[knight_toolworks]

that's a good idea ordered them they are only 8.00

[michael_schwartz]

The one I am going to try is $35.00 I saw one for $9.00 from grainger, but it is only rated for 0-2 CFM.

[michael_schwartz]

I drove up to Grainger and picked up the relief valve. I think I have driven about 200 miles this week to pick up parts for this project. I bought the 3/4" VR75-100 ($35.00)

I couldn't find an appropriate fitting, and I don't have the time to track one down so I made may own 5/16 restrictor by placing a washer in one of the fittings.
I chose not to prime, and glue the fittings with pvc cement, using silicone instead so I can have some hope of reusing them if I reconfigure things later. .

Edit*

I put this together from the plumbing section at home depot. I could have done it much easier with a 2" to 3/4" reducer "Grainger #2PMH6", as per Brady Waton's suggestion, on the next page. Then I would probably use brass fittings to go from 3/4" to 5/16", and back up to 3/4". Then again I put this together for about $5.00



I suppose the restrictor is a good idea should the valve, ever become stuck open, so the flow is limited to the maximum you would want.

[knight_toolworks]

I ordered one too. mcmaster had it for 27.00 and shipping would be less but they did not have any flow info on it. I found a 2" t with a 3/4" top so that made it easy. nut now that I reidid my pipe I have solved some leaks and my two boxes now have a 2" vac difference. so I will have to put another check valve on the 120 motors.
I almost toasted a motor with this wacky plugged up thing that just happened.

[michael_schwartz]

I saw that too. I wasn't sure, but they could be the same. The valve I bought is the CDI VR75. Grainger adds the - 100 on, their website.

[michael_schwartz]

I also used the same 1.5" slip male, to 1/2" threaded female reducer to connect the barbed hose fitting, for my vacuum gauge.

I have also done this by drilling, and tapping pvc end caps in the past, but I can't find my NPT taps.

I put this in another post to get around the 5 picture limit.

[Brady Watson]

Grainger #2PMH6

2" X 3/4" bushing

-B

[michael_schwartz]

Nice find. I updated my previous post to include that.

[Brady Watson]

Look for a white one if you can...I only did a quick search. You can use the gray PVC although it may look out of place in your system...or spray it white :D

-B

[michael_schwartz]

My priority now is just minimizing the number of elbows, so I can finish the plumbing.