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overspray


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#1 alarmstrong

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Posted 20 November 2012 - 05:11 AM

what is the deal with overspraying the undercarriages on model cars? i can possibly understand 70's era and before cars maybe having some overspray issues but in todays robot controlled spray booths it doesnt seem likely to have an issue with this. i have looked at some of the new cars like the camaro undercarriages and have not seen any instance of overspray on them. am i being too anal?

#2 plowboy

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Posted 20 November 2012 - 05:19 AM

Some people do seem to get carried away with over spray on the chassis' even on cars that did have it. But, you are right in that there was very little over spray on later years and it is practically non existent (if not entirely) on current cars back to the nineties.

#3 Erik Smith

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Posted 20 November 2012 - 06:13 AM

Could replicate a recent Maaco paint job.

It's just research, or lack of, that leads to using overspray when it is not needed.

#4 Luc Janssens

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Posted 20 November 2012 - 06:30 AM

what is the deal with overspraying the undercarriages on model cars? i can possibly understand 70's era and before cars maybe having some overspray issues but in todays robot controlled spray booths it doesnt seem likely to have an issue with this. i have looked at some of the new cars like the camaro undercarriages and have not seen any instance of overspray on them. am i being too anal?


There are still humans in the spray booths, to paint areas, where it would be costly or to difficult to program a robot or tool special "hold open" devices which do not hinder the paint process.
Bodies are painted on skids and there will be overspray on the chassis near the rocker panels, the rest (front or rear section of the car) is covered up by fr & rr facias, wheel wells are ether covered by a black paint (to hide the primer) and black plastic fenderliners...

#5 Fat Brian

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Posted 20 November 2012 - 06:36 AM

To replicate it correctly you have to think about what is being done to the full size car. The spray pattern of the guns used to paint a car produce a spray that it 6 to 12 inches wide. When painting areas like the lower drip rail of the car you would not expect to see overspray getting on more the very edge of the underside of the car, no more than the 6 to 12 inches of the spray pattern. The rear wheel wells tend to pick up more paint since you have a surface only a foot or so behind the surface being painted that is facing the same direction as the surface being painted. You get almost full coverage on the vertical surface of the inner rear fender but much less on the flat upper areas. It also depends on what parts were installed when the body was painted, this is where research comes into play.

#6 dmk

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Posted 20 November 2012 - 12:03 PM

I'd love to see examples of what factory overspray looks like on original 1:1 cars.

I've been looking for pictures and haven't found any examples other than some restorer's idea of what overspray should look like (which may or may not be accurate).

#7 MrObsessive

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Posted 20 November 2012 - 02:27 PM

Here's the undercarriage of my '06 Magnum wagon when I did the overspray. I happened to stumble upon a then new Charger off the 'net (possible off eBay Motors) and saved the pic. Yes, it can be difficult to find chassis shots of newer cars. Even more difficult is to find an undercarriage shot of a vintage racer! :o

Posted Image
Posted Image
Posted Image

As you can see there is some overspray..........not an overkill amount like you might see on an over-restored car, but some just the same.

#8 slusher

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Posted 20 November 2012 - 02:45 PM

l use semi gloss black on my chassis, but it really varies with the builder and what he likes....

#9 Fat Brian

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Posted 20 November 2012 - 03:20 PM

The pics Bill posted illustrate my point, the highest concentration of overspray is within the outer most 6 to 12 inches of the chassis and parts installed later have none on them. This is where research is crucial in doing correct factory stock model. For a custom or even a restomod classic stuff like this doesn't matter but for factory stock it is huge.

#10 Art Anderson

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Posted 21 November 2012 - 07:13 PM

The overspray on the underside of car bodies in the 50's through the 70's or early 80's came about because of factory practice in the days before robotic spray painting (and when the vast majority of American cars were built body-on-frame).

In June 1960, as a 15yr old, just out of school for the summer (finished my Sophomore year in High School), I took a trip (earned by selling subscriptions to the Indianapolis Star as a paper boy) to St Louis, Missouri. During that week in St Louis, one of the highlights was a tour of the Chevrolet Assembly Plant, which then was the largest, highest production automobile assembly line in the world. There we kids got to watch a new 1960 Chevy being built, all the way from a bare frame, and for the purposes of this discussion, the body itself go from bare sheet metal stampings to painted and trimmed, to a finished car.

The group of paperboys I was with followed a '60 Impala convertible on both lines (body, and final assembly), and it was where the body shell was painted that this description comes from: We didn't get to see the body shell being welded up (Chevrolet certainly didn't want to shell out for a bunch of kids getting their eyes damaged from watching welding without goggles or welder's shields!), but saw the raw body shell go through painting. The body shell (1960 Impala Convertible) was lowered onto a heavy cart, which positioned it about 2 feet above the factory floor, on iron wheels, and pushed by hand into the paint room. There, a team of three workers attacked it with ordinary spray guns, each hooked to a double set of hoses, one for the Roman Red Dupont acrylic lacquer, one for compressed air), Two painters sprayed the sides (one worker painted the firewall, a second the rear panel and underside of the trunk lid) while a third worker sprayed all the upper surfaces. The two painters spraying the body sides and ends, as they worked, ducked down with their spray guns, and sprayed the bottom sides of the rocker panels (on that era of Chevy, the rocker panels are about 4" wide, and about 2" below the underside of the floor pan) to get color coverage there. That step alone meant overspray along the outer edges of the floor pan, memory telling me that the overspray extended perhaps 8" in from the sides of the bottom of the body shell, as well as across the front of the toe board at the bottom of the firewall (no such overspray at the back, as the rear splash apron was not installed at this point in assembly). Chevrolet, at this plant at least, used red oxide primer, which was applied by dipping the entire body shell into a huge vat of primer--this was not sprayed on!. Within mere minutes, the body was pushed to a conveyor, which carried it into a long baking oven (LOTS of infrared light bulbs, in a long tunnel), which process took a good 20 minutes or so to traverse, during which time we were shown the masking and second color paint steps while our convertible was being baked dry.

Fast forward to June 1970: I got a call at work one morning that my newly ordered 1970 Barracuda was being delivered to Fireproof Garage in downtown Lafayette. As I was the assistant manager at Weber's Hobby Shop then (plastic model and HO model trains buyer, among other things), I hustled over to the dealership (2 blocks south) in time to see my Barracuda on the haulaway. I clearly remember seeing the overspray on the bottom of that car as well--pretty much as it would have been on that Chevy body back 10 years earlier (Rally Red over grey primer), so little had changed in factory practice).

Now, when I watched my 1990 Plymouth Grand Voyager being prepped for me at Twin City Dodge-Chrysler-Plymouth in April of that year, I first saw that car on a lift during prep--the entire underside was a nicely finished in the darker metallic blue as the lower body sides, evidence I suspect, of robotic painting, so there was no color overspray on the bottom of that unibody.

But in any event, the overspray on the underside of those earlier body-on-frame cars wasn't much more than 6-8 inches in from the sides, NEVER reached up into the rear wheel wells due to the lower, skirted wheel arches in the rear, and NEVER on the frame rails (as all this was done before the body was delivered to the body drop area).

Art

#11 truckaddict

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Posted 21 November 2012 - 09:11 PM

up here in the great white north many of our cars have an undercoat applied to them so there is zero overspray visable. instead there is a thick black substance that never fully dries.

#12 dmk

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Posted 22 November 2012 - 10:15 AM

Thanks for the pic of that Daytona Charger. Pics like that are hard to find.

#13 Scott - Elm City Hobbies

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Posted 23 November 2012 - 06:25 AM

Considering in modern car manufacturing, the bodies are sprayed separately from the rest of the vehicle....the should be no overspray of body color on the underside of the chassis.

Only time you would get overspray on the chassis is if the car was later custom painted, where obviously they aren't likely to take the body off the chassis to do it.

#14 dmk

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Posted 23 November 2012 - 03:24 PM

Now when you guys say "chassis", do you really mean frame?

Aside from some trucks, most cars are unibody these days and don't have frames separate from the body.

Edited by dmk, 23 November 2012 - 03:26 PM.


#15 Junkman

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Posted 24 November 2012 - 05:05 PM

In Europe body on frame construction was pretty much gone in the 1950s, with few exceptions. The monocoque bodies were usually dipped in primer tanks, then painted inside out, up and under. So even if you remove the pretty customary undercoating, you will find paint. Usually, even the engine bays are painted body colour, but on cars with metallic paint often lack the clearcoat.
To use overspray on a model of a European unibody car would be just plain wrong.