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[andyn]

Sorry if I offend, I don't mean to, but it appears you aren't listening, even I can tell you this is madness.

The advise of everyone here is not to use it, PLEASE DON'T USE IT, you would probably be better off not using a box at all, and that's not adviseable either.

I was lucky, I was given a box, but it's well worth buying one.

Andy

[Bee]

Interesting. It never ocurred to me that a hobbyist would actually consider buying a special booth rather than knocking up a quick bit of plastic sheet as required. However I can see the attraction if only I had the room. Your set up looks ok to mee though not sure how I'd fit a 4 ft boat in there.

 From picture 6 it looks like there is an arrow showing direction of air flow out the back of the box and down the duct. Surely it was never the intention to blow the fumes inwards into your face, so why bother with a filter? You are not producing industrial quantities of effluent.  The whole idea is to whoooosh the fumes out. Unless you decided to point the spray straight at the motor the vapour concentration would be very low so not a problem even if it weren't a shaded pole induction motor see picture 4, - the kind that doesn't make sparks anyway. Vaccum cleaner motors are different because they need to go hell for leather and make a racket. All small domestic fans will be induction types but if you get a bit bigger as is being suggested they will also have starters that do produce a single spark one second after turn on.
If you are still put off you could mount the fan in the other side of your shed pointing IN -  it would then get far more use ase a cooling fan on hot days, and provided the rest of the shed is airtight all the air will still go out through your box. I think RM suggests that.
Although American screw light bulbs can be made to produce sparks unlike nice safe British bayonets I would have gone with Reade Models suggestion of external light just 'cos it's cheaper to move one of my anglepoise lamps over temporarily. The older Fluorescent light starters also do produce a spark on turn on only.
Personnaly I spray outside but if there is no wind to clear the fumes have an 18 in centrifugal driven by a 1.5HP sealed motor - woodworker extraction type. I have to issue a tornado warning before turning that on !

[Reade Models]

I just know you chaps will condemn me to death for this one...Stavros, do your worst.

Stavros is busy on another thread so I'll do it...

Nobody will blame you for experimenting, and risk killing yourself - providing they are all a safe distance away!  The important thing to understand is that gases/vapours and sparks from electrics/motors DO NOT MIX.  Fans and vapours in combination are LETHAL.

Unless you've ever been mixed up in a real explosion, you can't begin to imagine how truly terrifying they are....

I've been involved in a few, in the early 70's I was on deck of the Liverpool ferry in Belfast harbour immediately opposite a large building that was blown up, got thrown back against the bulkhead when it went off in front of me.  Another IRA bomb outside a cinema in Birmingham a year later - blew the windows out of my hotel bedroom.  I'd wallked right past the bomb a short while earlier.  I was working in Manchester on the Saturday morning that they blew up the Arndale Centre.  In Feb this year we had a gas explosion in our caravan which caused major damage and scattered parts of the flue over a 150 yard radius.

My only interest in contributing to this thread is to try to get EVERYBODY who reads it to act responsibly, and be very careful.  DON'T MESS WITH FUMES AND FANS  The last thing that any of us want is to see is somebody badly injured - or worse.

Malc

[The long Build]

 Malc , from your last post do you come with a health warning, It seems that its not safe to be around you..

[Reade Models]

Me? Safe as houses...(said he, not wishing to tempt fate).

It's the ones that didn't make it that you needed to keep well away from   

Malc

[sheerline]

Blimey Malc, you're in more danger going about your daily business than I have ever been whilst experimenting!

[warspite]

Since they didnt make it, there no point in keeping away from them - unless there decomposing gases are a danger 

Heres a point - most, if not all, paint extraction booths consist of a box with a plenum attached, covering the passage from the box to the plenum is a matt of filter media to entrap the larger particules of paint, most lighting is kept external and passes through the perspex windows (may need to be replaced over time to keep the illumination up to acceptable levels).

Now, connected to the plenum is a duct system, in which a Bifurcated flow fan is fitted, this ensures that the motor is not in the airstream, some in the past have used vee belted axials, where the impeller is on a shaft, which is pulley driven to the outside to the motor sited on the outside of the casing, the pulley arrangement is enclosed in a box with bearings to hold the impeller shaft.

It may not have occurred to anyone yet but this arrangement is used quite extensively in Model Boating.



A BOW THRUSTER   

Dont have the fan motor in the duct, make it a bow thruster and save the effort of building a bif or vee belt axial, for all our sanity

[Reade Models]

Hi Warspite

You are absolutely correct.

My earlier suggestion to Salty in America was based on the concept of pushing fresh air into the booth and not sucking volatile fumes through the fan, but a bifurcated fan system would do the same job providing the motor is sited well away from fumes in a non-hazardous area. Other electrics moved to a safe area outside the booth.

All this talk of 12V fans and screw-in light bulbs is a nonsense (no disrespect to previous contributors).  Screw in light bulbs are just as perfectly capable of generating a spark as bayonet types - as is a 12V fan - just try shorting a 12V battery to see the sort of effects you can get...What is forgotten is that even a dangerous system can work well - until a fault develops.  Good design caters for the fault situations as well as normal operation.

In industry, intrinsically safe circuits are mostly 24V DC (analogue 4-20mA or digital on/off), but the available power in the part of the circuit located in the hazardous area is limited with zener barriers (Google Pepperl+Fuchs) to the point where the circuit is incapable of generating a spark - it's handy actually, because if you're commissioning (as I often do) or maintaining instrumentation in these areas, you can quite happily do it 'live'.  All of these circuits and the drawings for them are fully certified by the way, and nobody is allowed to work on them unless qualified and authorised to do so.

The first principle of locating electrical circuits in hazardous areas is DON'T - unless you really have to.  Only then, firstly resort to intrinsically safe circuits before looking at other methods.  If power is needed, flame proof/explosion proof/sand filled equipment is often specified. Explosion proof equipment is heavily built - not to withstand an explosion, but to allow large mating surfaces which prevent 'flame paths' of volatiles approaching the ignition sources inside.

Sorry to have bored you with this lot... I shouldn't bring work home.

Malc

[warspite]

So what do you think of the bow thruster idea, as long as the motor is quite a distance away to prevent leaking / localised gases from effecting the motor

[Reade Models]

I'll be installing one soon in my 54 inch long French harbour tug - thought I'd turbocharge the little blighter and see if I can get it to do wheelies.

Malc

[tigertiger]

Unless you've ever been mixed up in a real explosion, you can't begin to imagine how truly terrifying they are....

I've been involved in a few, in the early 70's I was on deck of the Liverpool ferry in Belfast harbour immediately opposite a large building that was blown up, got thrown back against the bulkhead when it went off in front of me.  Another IRA bomb outside a cinema in Birmingham a year later - blew the windows out of my hotel bedroom.  I'd wallked right past the bomb a short while earlier.  I was working in Manchester on the Saturday morning that they blew up the Arndale Centre.  In Feb this year we had a gas explosion in our caravan which caused major damage and scattered parts of the flue over a 150 yard radius.

Malc Reade, the Kate Aide of model boating.
If you see him coming, run 

[Reade Models]

OK - that's you stuffed for the figures competition...

Malc


For the Tech-Heads amongst you:
http://www.pepperl-fuchs.co.uk/cps/rde/xbcr/great_britain/ATEX_Poster_ENG.pdf

[tigertiger]

OK - that's you stuffed for the figures competition...

Malc

Hey I don't mind.
But Steamboatphil will be bricking it next show.

[salty Nscaler]

Good Morning All, sorry for the time lag be we are a few time zones apart.I have read all your input and I do thank you all I'm going to try and cover all bases in one shot.The fan motor is a in-line duct fan and will both blow and draw air depends on how you mount it,Yes I know the danger but I find it hard to think that ever person that models is using the proper type.I goggled " home made spray booths and found over 10,000 sites ans yes I know it does not make it right and all list warning about building them,it was not built for shooting paint on my first tug it is way to small I'll shoot that either outside or at my friends shop who is a welder and yes he's has a "real" spray booth.I like the thing about the bow thruster but I can't even find a RC boat club over here close to where I live so I'm sort  of on my own, and yes I've been blown up myself happen in Edzell,Scotland 1985 I really didn't think I would have opened a can of worms here just wanted to share and yes my tug is ordered and now I'm waiting for it to get here
Larry

[Martin (Admin)]

Hi
I used a free cooker hood that was being throw away.
Boxed in and lead outside worth it weight in gold.
If using spray cans put a filter in front and be ready for
a shock at the amount of paint it collects.

Dave

That sounds an excellent idea!

[Billyruffian]

As my main hobby is the building of guitars I can say that the finish of choice is still nitrocellulose lacquer.  If you are spraying this stuff you most definitely need an explosion proof fan and spark arresting electrics.  Without them you are on borrowed time.  You may get away with an ordinary fan IF the motor is not in the path of the fumes and if you are using ordinary motors then you would need a squirrel cage blower so that the motor is far enough away from the fumes.

I am experimenting with some of the waterbourne finishes and they have come a long way towards replicating the nitro finish although the end result is not as hard as nitro.  With this stuff you will get away with ordinary fans.

I have the added difficulty of maintaining humidity - which is a guitar builders worst emeny - plus maintaing temp at around 68 deg F. although this has more effect on finishing than building.

A dehumidifier works well with a properly insulated shed but the heating is still a problem particularly with regard to cost

[Les]

When I built my spray booth I used a 12volt fan from a marine chandlers .

These bilge extractors are used to remove the volatile and explosive fumes generated by fuel or leaking gas cylinders from the bilges of small boats, the 12v supply is from sealed lead acid batteries which are always to hand.  The fan is approx 4" diameter means you can use the ducting from a tumbler drier to pipe the flow outside.

My spray booth is collapsible to save space when not in use and the sides top and cover (to keep the dust off after finishing) are all made of perspex so no need for internal lighting. TAt the back of the spray booth, forming the front the plenum chamber is cooker hood material to act as a filter. But after using it for quite a while it is noticible that the pipework is discoloured by the spray. Evidently the filter material is not good enough but shows the extractor is working OK and as I really only use oil based paints the system must be working as I'm still here and haven't disappeared in a cloud of of smoke - yet!

Les Jones 

[salty Nscaler]

Hi Les, Sounds like you have a great set up there, I was playing with the idea of Plexiglas but never follwed Thur on,I have been checking the both the duct and fan and have yet to find any paint spray on any surface and there is no paint resdue on the rear of the filter as of yet.
Larry

[boatmadman]

Les,

Any chance of a pic of your spray booth?

Ian

[Les]

Hi Ian,

I hope that the attached photos help.

The overall size of the box closed is 600mm x 470mm x 150. When open the booth is about 585mm wide x 520mm High and 500mm deep. The overall sizes were decided by the depth of the bench and storage space. It is made of 6mm MDF and 6mm Perspex. Most of the materials I had to hand and only bought the piano hinges. These had to be modified by drilling out the holes to suit the M4 countersunk bolts and then countersinking the piano hinge by hitting the bolt into the hole with a backing piece drilled and countersunk, this should be visible in one of the photos.

Other photos show:-

The box packed away for storage.

The fan, the “elbow” was made using some of the ducting; the photo inside the ducting shows the paint residue which means the filter media is not working that well. I think I’ll have to find some of the paper type material used in proper car spray booths. 

The sequence of putting it together.

The front lid is in two pieces which fold back on top of the box when spraying.

At each side there is a butterfly bolt which screws into the Perspex and holds it all rigid

A short section of aluminium angle to hold the side in place, there are actually two pieces to sandwich the side the top when it is in place

The base of the right hand side Perspex has been lifted up by 6mm so that when it folds down it lies on top of the left hand side.

The top double hinge was necessary to make enough space in the box for the bits to fold into.

Its doing me very nicely at the moment the only thing is it’s never big enough to do the hulls of models so they still have to be done elsewhere either the garage or outside. One small thing that I did realise before I built this spray booth is that the larger the area behind the object being sprayed the higher the volume of air/spray you must extract, guideline figures can be found on the net. My Attwood fan seemed to be just about capable of the area I decided on.

I hope this helps.

Les

[Hagar]

So my cardboard box with a plastic bag over it is ok then?

[Bartapuss]

Hi Les,

You unit look the business any chance you could produce a plan of you unit for the rest of us to copy??

[Umi_Ryuzuki]

It's a brushless motor isn't it?
There shouldn't be any sparks...