Global Scale Modeller

So my homemade paint booth is a failure, LOL! The exhaust fan just isn't strong enough to pull anything through. I'm thinking about getting a used range hood and trying again. My new desk setup didn't jive well with my first try anyway. I'll post pics as soon as I get a chance.

Anyone else use a homemade booth that would like to share their design?

chops1sc wrote:So my homemade paint booth is a failure, LOL! The exhaust fan just isn't strong enough to pull anything through. I'm thinking about getting a used range hood and trying again. My new desk setup didn't jive well with my first try anyway. I'll post pics as soon as I get a chance.

Anyone else use a homemade booth that would like to share their design?

http://www.intscalemodeller.com/viewtop ... 10&t=20269

scroll down to about half way.

Awesome! Thanks for the link. Great desk setup too!

can I ask you .... where does it Vent out ???

schweinhund227 wrote:can I ask you .... where does it Vent out ???

If you mean the bought one sitting on the new desk, I don't think it does. I cannot see any ducting.

digger303 wrote:

chops1sc wrote:So my homemade paint booth is a failure, LOL! The exhaust fan just isn't strong enough to pull anything through. I'm thinking about getting a used range hood and trying again. My new desk setup didn't jive well with my first try anyway. I'll post pics as soon as I get a chance.

Anyone else use a homemade booth that would like to share their design?

http://www.intscalemodeller.com/viewtop ... 10&t=20269

scroll down to about half way.

I wonder if the local hardware store will let me unscrew the back off there range hoods so I can inspect the motor fan set up...

digger303 wrote: I wonder if the local hardware store will let me unscrew the back off there range hoods so I can inspect the motor fan set up...

It's better to beg for forgiveness than to ask for permission!

chops1sc wrote:

digger303 wrote: I wonder if the local hardware store will let me unscrew the back off there range hoods so I can inspect the motor fan set up...

It's better to beg for forgiveness than to ask for permission!

I would consider this.... good compromise over CFM and Price !

http://www.homedepot.com/p/Quiet-Test-V ... /100490468

Got this as a project for my workspace in the new year

schweinhund227 wrote:I would consider this.... good compromise over CFM and Price !

http://www.homedepot.com/p/Quiet-Test-V ... /100490468

They say say this has a low speed motor, so I'm betting it is a double ended squirrel cage set up, Like a vehicle air conditioner.

I have a question that I have never had answered to my satisfaction. Some time ago there was a discussion about using fans with brushless motors which is not true of most of the exhaust fans I see mentioned. The reason given was that normal fans, especially when using enamels could present an explosion risk.

Is this of concern or not? Has anyone on here actually used a regular fan? Brushless motors add considerably to the cost. So if I can get away without that I could use a bathroom exhaust fan or range fan. That would be a lot cheaper.

Sorry for posting this twice, it had appeared that the first post had not worked and I can't delete posts from here.


Had a question for the group. I have heard many times that using non-brushless motors presents a fire/explosion risk, especially with enamels. Is this true? If so none of the fans I have seen discussed here are suitable. I have noticed it is also the reason some pro booths are so expensive, the motor is brushless and sealed. Both of which add considerably to the expense.

I would love to know for sure as saving me some money does not cover the associated costs of setting fire to my home. What do you all collectively think about this?

Cheers,

Bob

rbruceporter wrote:Sorry for posting this twice, it had appeared that the first post had not worked and I can't delete posts from here.


Had a question for the group. I have heard many times that using non-brushless motors presents a fire/explosion risk, especially with enamels. Is this true? If so none of the fans I have seen discussed here are suitable. I have noticed it is also the reason some pro booths are so expensive, the motor is brushless and sealed. Both of which add considerably to the expense.

I would love to know for sure as saving me some money does not cover the associated costs of setting fire to my home. What do you all collectively think about this?

Cheers,

Bob

Bob
Your question is a valid one and comes up any time the discussion of venting potentially volatile fumes arises and I am gonna give you my impression and opinions....others will sit on different sides of the fence with this issue.

The squirrel cage fans are purportedly the safest fan motors in moving dangerous fumes as the air flow does not pass directly through the motor, rather to its side. In North America, those motors are the type found in forced air furnaces.
Some guys use bathroom fans, range hood fans, computer fan motors etc etc that all flow air through the motor area itself thus the explosion risks. Sealed motor or not, it passes air through the motor.

Are risks present?? Yes.
Do people use unsafe motors and survive? Certainly
Are there many fires or explosions caused by hobby spray booths? Probably not many
Is the risk large? Likely not, but depends what you are spraying
Am I helpful? Certainly not, just more confusing
I have yet to see a discussion about making a spray booth withought this very issue brought up , sometimes with very strong opinions and heated debates

I have a squirrel cage motor from an old furnace that I am gonna try and hook up when I build my booth....hopefully it runs still.

I believe it to be a risk to be avoided. It should be noted that there are many potentially unsafe homemade spray booths out there. Why don't they all explode or catch fire you might ask. It comes down to this, the volatile liquid you are spraying has a certain set of parameters in which it will explode or ignite. The fuel to air ratio for this to happen is different for all volatile's or gases. Nothing will happen if you stay outside those limits. But if you don't anything can happen or nothing....it is a lottery I don't wish to win.
I will make a new booth later, but I will choose a sealed motor or like Scott has as the motor is remote from the fan. Take a look at the commercial peacemaker brand and that is all they use.

Thanks! digger303 and Dave both seem to be thinking as I am. Certainly the risk is probably low but not gone. I am especially worried about times when I am spraying thinner to clean the gun. I already turned my airbrush into a mini flamethrower once by spraying through a box fan to get the fumes away and that was outside.

My main worry is of course life and limb. On a related topic does anyone have any idea what CFM rating is needed in order to move enough air through say a 20x20x1 furnace filter?

After doing a little more research I am thinking this might be a better option.

rbruceporter wrote:Thanks! digger303 and Dave both seem to be thinking as I am. Certainly the risk is probably low but not gone. I am especially worried about times when I am spraying thinner to clean the gun. I already turned my airbrush into a mini flamethrower once by spraying through a box fan to get the fumes away and that was outside.

My main worry is of course life and limb. On a related topic does anyone have any idea what CFM rating is needed in order to move enough air through say a 20x20x1 furnace filter?

At a guess 280 as a minimum and 280-400 preferable.....there are complicated equations to work it all out, but as it isn't my field I don't won't to learn it.
I was using my spraybooth as a guide to that guess.

I found the OSHA calculations online, it is basically width times height by a factor equating to rated air movement for the fan in question. For volatiles such as thinners etc it comes out to about 300CFM for a booth opening of roughly 20X18 inches. A typical airbrush running at 30psi will generate critical volume of fumes to trigger flame from a spark after about 10 seconds of spraying at full bore according to their data sheets. As mentioned above however all manner of things need to line up before a fire actually occurs. Mainly the motor generating sparks and the airflow passing the vapors in sufficient density over the motor. Fire appears to be the predominate risk not explosion, as an explosion would require large volume of flammable vapors to have accumulated around the ignition source which of course is what an exhausted spray booth is designed to prevent.

So all in all I think as long as some attention is paid to exhausting a sufficient quantity of the vapor one would be safe provided your motor is not a spark generator!

Interestingly the health effects would be noticeable long before you generated a sufficient volume for an explosion, so as long as you are not feeling light headed or faint from the fumes you are probably not in danger of exploding!

rbruceporter wrote:I found the OSHA calculations online, it is basically width times height by a factor equating to rated air movement for the fan in question. For volatiles such as thinners etc it comes out to about 300CFM for a booth opening of roughly 20X18 inches. A typical airbrush running at 30psi will generate critical volume of fumes to trigger flame from a spark after about 10 seconds of spraying at full bore according to their data sheets. As mentioned above however all manner of things need to line up before a fire actually occurs. Mainly the motor generating sparks and the airflow passing the vapors in sufficient density over the motor. Fire appears to be the predominate risk not explosion, as an explosion would require large volume of flammable vapors to have accumulated around the ignition source which of course is what an exhausted spray booth is designed to prevent.

So all in all I think as long as some attention is paid to exhausting a sufficient quantity of the vapor one would be safe provided your motor is not a spark generator!

Interestingly the health effects would be noticeable long before you generated a sufficient volume for an explosion, so as long as you are not feeling light headed or faint from the fumes you are probably not in danger of exploding!

did you allow for friction losses in the ducting for at least 3m and allow for at least one 90 degree bend.

No I did not, as I mentioned these were off the cuff type just to get a general idea. The page I found was from a link in a thread on FineScale.com and was VERY detailed as to how to calculate all the variables, rapidly passed my ability to do the math in my head. Believe it or not there were factors such as the altitude of your location (air pressure), internal and external (vented) temperatures, and relative humidity. Leave it to OSHA to go way deep into detail.

chops1sc wrote:After doing a little more research I am thinking this might be a better option.

I had one of those and I found it really poor. Didn't shift much at all.

So I replaced it with one of my own designs!!!





It has one of these behind the filter.



I made the surround out of prespex for the extra light, but you could do it with cardboard.

Much cheaper than the purpose built extractor you are looking at and shifts 10 times the air.

Don't get me wrong it's not brilliant by a long way, if I'm pulling primer through my airbrush at full tilt it won't shift that (have to stop every few seconds to let the fan catch up), but normal painting duty and cleaning the airbrush is fine.

chops1sc wrote:After doing a little more research I am thinking this might be a better option.

I have a similiar one...it looks exactly the same. It is only just doing the job, but once the filter pad gets a little clogged it battles. I removed one of the filter pads and that improved it. I vent to the outside so I could if I want use no filter at all. Also if the air flow from your airbrush bounces off the kit or your hand. The booth is not strong enough to capture it.
If the benchvents weren't so expensive for me I would buy one of those.

rbruceporter wrote:No I did not, as I mentioned these were off the cuff type just to get a general idea. The page I found was from a link in a thread on FineScale.com and was VERY detailed as to how to calculate all the variables, rapidly passed my ability to do the math in my head. Believe it or not there were factors such as the altitude of your location (air pressure), internal and external (vented) temperatures, and relative humidity. Leave it to OSHA to go way deep into detail.

yeah I didn't either which is why I took a stab at it....I gota nose bleed even thinking about it. I just got lazy and looked at what the spec's are for something like a benchvent

chops1sc wrote:After doing a little more research I am thinking this might be a better option.

Perfect ! Great price to !!!

As I was cleaning my setup I thought that I'd take a couple of pictures to show you what I have done.



That is the basic thing going, it vents to the outside via the original exit point on the fan housing, then that goes into a snug piece of tubing about 6 inches long which is in turn fitted snugly into the whole through the side of the shed.



And in closeup.

You can see the pull cord on the side as I mounted it sideways to make it easier to pull.

At the other end of the hole is a manual louver screen and the fan has a louver screen which opens and closes when you switch it off and on.

Looks great! Thank you for sharing! I'm still on the hunt for something. Right now I have a window fan with a filter in front of it. I don't spray any oil-based paints or rattle cans so I'm only concerned about the overspray at the moment.

Love it! My biggest obstacle to overcome is venting to outside. For right now I open a window a crack and stick the hose out but I am working on a more permanent solution.

The motor and fan is the heart and key to any booth and that is the biggest problem in actually building your own. I hope you have many happy hours with new booth.

I totally applaud all the home built stuff; that plexiglass one is gorgeous
Blowing fumes straight through the fan doesn't make sense to me
I am going to get the group build spray booth for my airbrush.....interested to see what THAT motor is like

Being a hvac mechanic, I have a couple of overkill exhaust fans sitting on the shelf in the shed at home.... now when I mean over kill these things are designed to pull 300litres a second.... might possibly suck the model off the stand if I used one of those...

Nice work on the booth. Plexy gives such a neat tidy finish. Im looking to re-build the shroud around my existing extractor

well done