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Glove Box Style Paint Booth (Fully Enclosed)


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#1 Miatatom

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Posted 03 June 2013 - 03:42 PM

Well, I've finished the glove box/paint booth and thought I'd share what I've done. I was hoping to keep the cost around $100 but that was a pipe dream. It wound up being about $240. The size is 2' deep by 3' wide.

 

Attached File  gb1.jpg   40.99KB   78 downloads

 

I mounted an air filter I had left over from 1:1 work in line with the air regulator. The on/off switch is located next to it. The hose connects through the bottom of the booth on the right side.

 

Attached File  gb0.jpg   25KB   83 downloads

 

The air filter is from WM. I mounted it on the top.

 

Attached File  gb4.jpg   31.31KB   71 downloads

 

The exhaust port in the bottom is a plumbing piece as are the flanges I used to mount the gloves to the front. I'm using the gloves that veterinarians use for birthing calves. Nice and thin, but one size fits all so they're loose on my hands. To get them to fit tight, I put a vinyl glove on over each one.

 

Attached File  gb2.jpg   28.08KB   65 downloads

 

The exhaust is 3” all the way. I used 3” I. D./3” O.D. automotive fittings in order to be able to connect and disconnect things quickly.

 

Attached File  gb6.jpg   29.16KB   55 downloads

 

The hose from the booth connects to a 3” O. D. section mounted in the wall.

 

Attached File  gb7.jpg   16.98KB   49 downloads

 

Here's the exhaust fan/power supply and hoses all hooked up on the other side of the wall.

 

Attached File  gb8.jpg   51.88KB   57 downloads

 

I mounted it on an old kitchen chair. The exhaust fan is a 100 CFM bilge pump which is safe for combustible fumes. My brother in law gave me the power supply. He works on computers for a living.

 

Attached File  gb10.jpg   46.52KB   59 downloads

 

The hose goes from the pump to a device I fabricated. It fits under the garage door and will keep the critters out at the bottom (wifes requirement). Again I used some 3” O. D.

 

Attached File  gb11.jpg   49.66KB   51 downloads

 

Attached File  gb13.jpg   36.38KB   39 downloads

 

The whole thing can be connected and ready to paint in less than 5 minutes.

 

No nasty fumes and no respirator needed. I've used it once and there was no junk in the paint job. Now I've just got to learn to paint! :rolleyes:

 



#2 1930fordpickup

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Posted 03 June 2013 - 04:22 PM

Wow .



#3 Cato

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Posted 03 June 2013 - 04:25 PM

Your place is immaculate Tom. Thanks for sharing many novel ideas.



#4 Miatatom

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Posted 04 June 2013 - 06:06 PM

Thanks for the feedback guys. I'll post some pics of the whole place in another thread soon. The room is 12' x 24' so I've got plenty of space.



#5 Skip

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Posted 05 June 2013 - 07:31 PM

Your bilge blower is the best non-commercially built spray booth idea that's come up on this forum, it's specifically designed to exhaust flammable vapors out of an enclosed area. As long as it pushes / pills enough air to do the job it's a great idea!
Thanks

#6 Miatatom

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Posted 05 June 2013 - 09:11 PM

Thank you very much for the compliment. I calculated the number of complete air changes per minute which would be 12 cu. ft. / 100 cfm which equals one air change every .12 minutes or one every 7.2 seconds. My first test paint job was using MM lacquer. Got some orange peel so I'll try to get just a little closer or slow down or whatever it takes. :D Trying again tomorrow. We'll see how it goes.



#7 ScaleDale

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Posted 06 June 2013 - 06:01 AM

Very interesting design. A closed system is the best defense against dust. Flow rate is important, and I'm impress with the application of math in dealing with this. When I built my open faced booth I watch a bunch of videos on-line and got a kick out of a dude from another model forum who had to rebuild his half way through because his fan was under powered.

Here's the link to the article I used for mine. I have 4 60 cfm computer fans in mine.

http://modelpaint.tr....com/booth2.htm

Dale

#8 Miatatom

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Posted 06 June 2013 - 04:51 PM

I had used computer fans in another experiment that failed. Not because of the fans though.

 

The reason for a complete closed system was the dust issue. Seemed like there was always some junk in my paint jobs and I was never satisfied with them. I used to work at a nuclear weapons plant and spent many hours working in glove boxes so I just proceeded with that design in mind.

 

I need to find some larger flanges for the front arm ports. The biggest plumbing flange I could find was 5". Makes for some limited movement. I'll find something that'll work. Maybe someone will have a suggestion. That's where I came up with the veterinarian gloves. Someone suggested them and they're ideal. Cheap, fairly durable and thin enough to allow for some feel when air brushing.



#9 LOBBS

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Posted 16 June 2013 - 11:44 AM

While I can appreciate the design and execution of the box, the 100 CFM bilge pump is greatly underpowered to properly clear the space even with its downdraft layout. The industry standard is 100 CFM for every square foot of area that the fan has to clear.  For your 2' x 3' box you would need a minimum of a 600 CFM blower even before you began adding the exhaust ductwork. The sheer length of flexible 3" hose you're using would add a great deal of airflow resistance. Not trying to step on any toes, it's about safety.

 

I've attached an article that Klaus Raddatz released years ago about building your own booth and how to properly calculate which motor is required for the size of the box and the attached duct work.

 

http://www.mediafire...6wffygg65u98eo6



#10 Miatatom

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Posted 16 June 2013 - 02:46 PM

The 100 cfm seems to be working fine. I've painted in it 5 or 6 times so far and the inside stays clear without any sort of foggy condition. In fact, I decided to install a false floor above the exhaust vent in the bottom of the booth. I'm using lacquer paint and I was having problems with the paint drying before it got to the model and felt like I actually had too much flow. Your guideline of 100cfm/sq. ft. would mean I'd need a 1200 cfm fan. Since the enclosure is only 12 cu. ft., that would be a complete air change every 0.6 seconds. That sounds like a lot.



#11 LOBBS

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Posted 16 June 2013 - 05:55 PM

I can only hope for your safety that the 100 CFM rating listed for your bilge pump is given at an extremely high static pressure and that it's airflow abilities within your system (possibly lower SP) are much higher. The flow rate for this application is not a cubic calculation or the "air changes" that you keep referring to. It is quite simply the square area (in your case 2' x 3' or 6 sq ft) by the desired face velocity or FPM. Because your booth is a downdraft booth you can safely maintain a minimum of 50 FPM which would require at least 300 cfm blower (6 sq ft x 50 FPM) at the static pressure of your total system. Again your bilge pump, given its original application, may be able to support 300 cfm at a relatively low static pressure.

 

The biggest issue that I see with your setup is that your pump is already questionable and you are using, quite frankly, the worst possible solution for your ducting with those long sections of flexible 3" duct.  3" ducting is already fairly restrictive and the flexible type is around 3 times worse than that. That combination would produce an extremely high static pressure and it is very likely that your pump is not even producing anything close to the advertised 100 cfm. It is all in the article that I posted and Klaus has been a very respected member of the modeling community for a long, long time. With a sealed system like you've built, it is possible that you could be filling a confined space with an excess of volatile solvents (an explosion hazard) and your best warning device (the ole nose) is taken out of the equation.

 

I've built three booths using Klaus' instructions and they have all served me well for years with no incidences.  The only reason I've built as many as I have is to improve on the materials in which they were originally constructed in (spare wood->MDF->sheetmetal) or to tweak minor things that I wanted to add to the previous generation.

 

Please give the article that Klaus published years ago a read and do the best that you can to verify that you have sufficient "oomph" in your system to safely exhaust the fumes.


Edited by LOBBS, 16 June 2013 - 05:57 PM.


#12 Miatatom

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Posted 19 June 2013 - 01:41 PM

Thanks for the feedback, Kyle. I took the time to really study the article in the link you suggested. I've already moved the lights. My booth is all wood with a glass window. Since the biggest safety concern is explosions, eliminating all sources of sparks should remove that hazard. Is there something I'm not taking into account with that reasoning?

 

As for the flexible ducting, I can see that it's very restrictive but I've got to have a system that can be taken apart and stored. I'm going to study that situation more and may be able to come up with something.



#13 LOBBS

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Posted 19 June 2013 - 04:27 PM

Absolutely no fault to that logic. As I said before, I think it's a brilliant design. Safety is the top priority and if you can eliminate the ignition risks and ensure that your system can keep the box cleared of fumes you are golden.

#14 Aaronw

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Posted 20 June 2013 - 07:50 AM

While I can appreciate the design and execution of the box, the 100 CFM bilge pump is greatly underpowered to properly clear the space even with its downdraft layout. The industry standard is 100 CFM for every square foot of area that the fan has to clear.  For your 2' x 3' box you would need a minimum of a 600 CFM blower even before you began adding the exhaust ductwork. The sheer length of flexible 3" hose you're using would add a great deal of airflow resistance. Not trying to step on any toes, it's about safety.

 

I've attached an article that Klaus Raddatz released years ago about building your own booth and how to properly calculate which motor is required for the size of the box and the attached duct work.

 

http://www.mediafire...6wffygg65u98eo6

 

You've miss read what the sq ft relates to. It is not the size of the working area, it is the size of the opening. It may seem a trivial difference but has to do with the velocity of the air not simply movement, both are moving 100 cfm but the larger opening allows for slower moving air and areas of little movement.

 

If a closed 2x3 ft working area only has a 14" x 20" opening (fairly standard size filter) then you are looking at 1.9 sq ft, not 6. 1.9 x 50 (downdraft) would put the 100 cfm fan at the appropriate size.

 

I would be concerned that the 3" ducting is inadequate though and could be restricting the blower from seeing its full potential. I picked up a section of 6" metal flex duct at Home Depot, it is cheap, easy to use and provides for very little friction loss. 

 

Here is an easy to use online airflow calculator. If you use it you will see that the 3" duct has 4x the restriction of a 4" duct and 30x the restriction of a 6" duct.

 

http://www.engineeri...loss-d_444.html



#15 Aaronw

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Posted 20 June 2013 - 08:04 AM

Thanks for the feedback, Kyle. I took the time to really study the article in the link you suggested. I've already moved the lights. My booth is all wood with a glass window. Since the biggest safety concern is explosions, eliminating all sources of sparks should remove that hazard. Is there something I'm not taking into account with that reasoning?

 

As for the flexible ducting, I can see that it's very restrictive but I've got to have a system that can be taken apart and stored. I'm going to study that situation more and may be able to come up with something.

 

Everybody gets hung up on looking for ignition sources. The #1 priority should be on avoiding a flammable atmosphere in the first place (keeping the vapors to lean to burn). This is really why most people get away with a homemade booth using a bathroom fan or other "inappropriate" vent fan. They have adequate ventilation so never reach the lower explosive limits of the paint vapors. The only paint booth fire that I have seen posted with details, involved an individual using a shop vac for the blower. The cannister makes for an excellent bomb by collecting the vapors until they reach a level that will support combustion.

 

I advocate using an appropriate fan, but as long as the fan selected provides adequate ventilation there is minimal danger from using the wrong fan. Obviously the right fan and adequate ventilation is a better choice.



#16 Miatatom

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Posted 20 June 2013 - 02:23 PM

 

You've miss read what the sq ft relates to. It is not the size of the working area, it is the size of the opening. It may seem a trivial difference but has to do with the velocity of the air not simply movement, both are moving 100 cfm but the larger opening allows for slower moving air and areas of little movement.

 

If a closed 2x3 ft working area only has a 14" x 20" opening (fairly standard size filter) then you are looking at 1.9 sq ft, not 6. 1.9 x 50 (downdraft) would put the 100 cfm fan at the appropriate size.

 

I would be concerned that the 3" ducting is inadequate though and could be restricting the blower from seeing its full potential. I picked up a section of 6" metal flex duct at Home Depot, it is cheap, easy to use and provides for very little friction loss. 

 

Here is an easy to use online airflow calculator. If you use it you will see that the 3" duct has 4x the restriction of a 4" duct and 30x the restriction of a 6" duct.

 

http://www.engineeri...loss-d_444.html

 

Thanks for the info. It makes a lot of sense. I wasn't sure if I had the right size fan, but visually, there never was any sort of fogging of the interior while spraying. That led me to believe that I was in the ballpark.

 

My painting technique is a work in progress but I've recently moved to lacquer paint and really like it. I apply 3 or 4 mist coats and 2 or 3 wet coats. I wait about 5 minutes between mist coats and about 10 between wet coats. . There's never a lot of continuous spraying and the booth stays clear.



#17 LOBBS

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Posted 20 June 2013 - 02:51 PM

You've miss read what the sq ft relates to. It is not the size of the working area, it is the size of the opening. It may seem a trivial difference but has to do with the velocity of the air not simply movement, both are moving 100 cfm but the larger opening allows for slower moving air and areas of little movement.
 
If a closed 2x3 ft working area only has a 14" x 20" opening (fairly standard size filter) then you are looking at 1.9 sq ft, not 6. 1.9 x 50 (downdraft) would put the 100 cfm fan at the appropriate size.
 
I would be concerned that the 3" ducting is inadequate though and could be restricting the blower from seeing its full potential. I picked up a section of 6" metal flex duct at Home Depot, it is cheap, easy to use and provides for very little friction loss. 
 
Here is an easy to use online airflow calculator. If you use it you will see that the 3" duct has 4x the restriction of a 4" duct and 30x the restriction of a 6" duct.
 
http://www.engineeri...loss-d_444.html


I will respectfully disagree with that logic. Greatly exaggerated to make my point, following the method you stated, one could in theory properly exhaust a full-size 8' x 10' x 8' room through a 1' x 6" filter with a 25 CFM fan as that combination would have a proper rate of flow at the filter. There is no respect to the area being cleared and outside of the immediate area of the fan the pull would be virtually non-existent.

I have read and re-read Klaus' article many times over the years and have exchanged communications with him several times. In his guide, he always refers to the square area of the box dimensions when calculating the first portion of the flow needs.

#18 Aaronw

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Posted 20 June 2013 - 04:51 PM

I will respectfully disagree with that logic. Greatly exaggerated to make my point, following the method you stated, one could in theory properly exhaust a full-size 8' x 10' x 8' room through a 1' x 6" filter with a 25 CFM fan as that combination would have a proper rate of flow at the filter. There is no respect to the area being cleared and outside of the immediate area of the fan the pull would be virtually non-existent.

I have read and re-read Klaus' article many times over the years and have exchanged communications with him several times. In his guide, he always refers to the square area of the box dimensions when calculating the first portion of the flow needs.

 

I actually used the same article when building my booth and it worked out great.

 

Something to ponder, he never takes cubic feet into account. Using his formula a booth 2 ft x 3 ft x 3 ft (18 cu ft) and a booth 2 ft x 3 ft x 10 ft (60 cu ft) will both recommend a blower of 300 cfm (down draft) or 600 cfm (cross draft).

 

Try an experiment with your own booth, get a large piece of cardboard and cut a hole 1/2 the size of your current booths opening. You will feel a dramatic increase in the velocity of the air entering the booth, it may even suck the paint right into the filter making it hard to actually paint the model. 

 

Your exagerated example would be ineffective no doubt, but the actual opening does play an important part. I'm not an aerodynamic engineer so I can't tell you where that point is.  


Edited by Aaronw, 20 June 2013 - 04:52 PM.


#19 Danger

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Posted 21 June 2013 - 09:43 AM

The movement of airflow is measured by the size of the openings the air flows through, not the size of the box. With the closed system the only incoming air is through the airbrush. He doesn't have an opening of 2x3 ft.

 

I too have read Klaus' website and built 2 of my own paint booths. All of his examples show the incopming air coming through the large open front.

 

As long as the air is being sucked out as fast as it is entering, he should be good.

 

I would highly recommend either a larger smooth hose or a shorter run to increase efficiency.

 

Danger



#20 LOBBS

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Posted 21 June 2013 - 11:40 AM

Yes, Klaus is using the angled-face 18" x 24" opening dimensions in his calculation which is correct. But, the point you both have missed is that the actual cross-sectional area of his booth is around 17" x 24". So when the air leaves the opening of the face and enters the body of the booth the airflow is actually slightly accelerated by being forced through the smaller area. By calculating for the slightly larger opening you can ensure that the column of air through the booth maintains a sufficient velocity. Air is not empty space. It is full of molecules that have to be treated like a fluid where motion is concerned. So in the case of a booth you have to move all (or a great deal) of the molecules that are in the space between the fan and the opening. In the case of this booth, you have exactly the opposite scenario of Klaus' example. You have an extremely small opening and a large cross-sectional area. Once the air passes through the inlet filter into the box, it will decelerate rapidly as the molecules coming in have to fill the much larger column of the booth. That 100 cfm fan has to move all (or a great deal of) of the molecules in that 2' x 3' column before it can exact a draw on the smaller inlet. To actually obtain 50 fpm at the fan in this case of the enclosed booth, the air may have to hit the inlet filter at nearly 100 fpm to overcome the inherent deceleration of hitting such a large working column.

If you want an example, take a drink with a straw from a glass and see how easily it pulls. Next take the large end of a funnel and put it over your face and try to take the same sip with the same effort. It's not going to happen.

The straw has the same inlet and working area so it is relatively simple to draw your column of fluid through it. The funnel has the same roughly the inlet size as the straw but a much larger working column and as such requires a great deal more pull to achieve the same effect.

Quite simply put, you have to maintain the rate of flow through the largest cross-sectional area of the column of air. It does not matter whether that is the opening (as it is with the angled opening of Klaus' example) or the large working area of the booth in this thread. On the exhaust side or second part of the equation, the ducting is so much smaller than the area being vented that the molecules of air can get stacked upon each other and create a back pressure. So in picking a fan you have to have enough pull to maintain velocity on the inlet side and overcome back pressure on the exhaust side.

Edited by LOBBS, 21 June 2013 - 12:12 PM.