Gravity can be your friend -- Paint dolly

The Achilles' Heel of Luthiery
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kencierp

Gravity can be your friend -- Paint dolly

Post by kencierp »

This is a fixture I designed (at least in my head) a long time ago --- my finishing projects are getting backed up so I had to take action and build the darn thing. As some might know in my past life I worked for GM -- a lesson learned as far as paint application, was to work with and in some cases “take advantage of gravity”. These days large scale spray operations are almost all electrostatic in nature, a peocess which pretty much defies gravity by electrically charging the paint and the target object so that the coating is actually attracted to the part – not unlike magnets in concept. In the old time facilities most spray booths were a downdraft (waterfall) set-ups, even to the extent that a porous grate covered a tunnel, which ran the length of the booth – air was drawn from the ceiling and pulled down to the floor by the exhaust system. While these booths did not direct every molecule of paint to the desired surface, they did serve to control the over spray and prevent it from landing in an undesirable location.

This downdraft concept is now the heart of my finishing system --- not in the picture is my explosion proof exhaust fan – the intake is placed at the base of this paint dolly literally on the floor --- sucking the air down --- stray over spray quickly follows.

Gravity helps in another way in the process – the finish is applied to the horizontal surface, so its not like trying to get the coating to stick to a wall evenly, but rather laying it on the deck and letting gravity help it flow out even and level. (No drips) Watching our painters flawlessly spray the “huge” old Cadillac hoods made it clear why horizontal was better than vertical.

If I ever get to finish my guitar construction publication I will include the dimensions for this dolly. Its fairly simple to build, the rotating trunnion is just a couple of disks fastened to spacers there’s two locking knobs, one to capture the mortise mounted holding detail that is bolted to the guitar body and another to lock the trunnion in the desired attitude. It’s on casters – note too, there’s no reason one could not apply finish in this manner just by taking the work outdoors – no exhaust required – just good old gravity.
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Last edited by kencierp on Thu Aug 05, 2010 1:32 pm, edited 2 times in total.
kencierp

Re: Gravity can be your friend -- Paint dolly

Post by kencierp »

More dolly pictures
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tippie53
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Re: Gravity can be your friend -- Paint dolly

Post by tippie53 »

nice and useful device
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
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Darryl Young
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Re: Gravity can be your friend -- Paint dolly

Post by Darryl Young »

That looks like a nice setup Ken. Does the drum have wood-to-wood contact or something else? Does it rotate fairly easy? I guess the handle mounted in the neck hole slides in and out of the drum? If so, I assume you spray the top of the guitar (and maybe the bottom) to spray while those surfaces are flat then slip the handle in the drum and finish the rest of the guitar?
Slacker......
kencierp

Re: Gravity can be your friend -- Paint dolly

Post by kencierp »

Yes the drum is wood to wood and yes it moves freely that why there's locking knob.

Not understanding the rest of your question -- the mortise mounting detail is fastened to the guitar, placed in the trunnion, locked with the knob ---- rotate to the disired plane -- so all surfaces can be sprayed while in the most horizontal attitude, actually this fixture could be used for brushed application as well.
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