Spray painting with SCUBA...

[Fibonacci]

Working through some lockdown projects, one being restoring a 1980's vintage road bike with a rare 63cm XL sized frame... worth spending the time to get it right.

Stripped off all the paint, and carefully hand rubbed back to bare steel... but how to refinish it without having to resort to rattle cans?

They say 'necessity is the motherhood of invention'... was stuck in lockdown for 112 days and being restricted to within 5km of home meant I couldn't borrow my mate's air compressor

Eyeing my two 15L SCUBA tanks... both full... hmmm.

Patched up a hose by cutting the end off an old LP hose and crimping it onto a 250psi air tool hose fitted with a standard Nitto QD connector. Old Aqualung unbalanced piston reg pressed into service reduced tank pressure to ~125psi, secondary inline adjustable regulator at the gun got it to 30psi.

Back of the envelope calculations said a 15L 240 BAR fill should get me around 12 mins air with the gun fully open at 277L/min... but of course painting a bike frame is very different to a car panel, lots of short bursts and angle changes. One 15L tank was just enough for 2 coats of etch primer and 3 coats primer surfacer. The other one handled 4 colour coats with 20 BAR left after cleaning the gun.

Zinc rich etch primer first coat in state-of-the-art spray booth

Top coats done, colour is 70's vintage Land Rover Series 2A Marine Blue

Reg iced up even in 20C ambient temperatures with longer spray bursts on top coats!

Now for the re-assembly... in keeping with the vintage style I have sourced and rebuilt a classic Sturmey Archer AW 3 speed hub, currently being built into a wheel using 27" Velocity alloy rims

 

[lowwall]

Nice.

You know what's even nicer on this style of bike? When the lugs are a different color

Edit for our Antipodean friends: colour

 

[MikeinCA]

Nice paint job! Gonna be a tall beauty!

 

[happy-diver]

Sturmey Archer AW 3 speed hub

Ha ha ha ha ha the best of the best

Magnificent! Magnificent!

and it still iced up with blasts at 30psi interesting

I was using car spare wheels and air brushes in the 70s and a million trips to the servo
the vacuum cleaner flyspray gun worked ok for cars
but I liked rattle guns purple and green metallic, not in the same can for pushys man!

 

[Fibonacci]

Big fan of the AW, very reliable indestructo hub!
I got so bored in lockdown I 3D CAD modelled the entire thing... and yes the gear teeth do have involute curves

 

[happy-diver]

Yeah right genius

I was always fascinated by the little chain and adjustment was so simple, never pulled one apart

Huge wooden knobbed gearstick on the main bar
Had to get a little one for the butterfly bars to fit the paper round horse
and the girls


Magnificent! Magnificent! Magnificent!

 

[eyeballgummy]

Hi mate, I really enjoyed your story of spraypainting using scuba cylinders. I want to do the same, maybe even hook a few together for more volume. So did you get 12 minutes of air on each of those 15 litre tanks u recon? What was the maths? I have 4 alloy tanks.

 

[jellycatsdad]

What gun were you using - “true” HVLP(SATA, Iwata), Harbor Freight “HVLP”, compliant reduced pressure(SATA also makes these) or just a standard spray gun? I need to paint some car wheels soon.

 

[Fibonacci]

Hi been away interstate sorting out my Dads estate, gear is at home so will check details like spray gun type and L/M or CFM soon as I can…

 

[Fibonacci]

OK back in town and can get you the correct details:

Spray gun
DeVilbiss FLG-G5-14 spray gun
1.4mm nozzle
Air Inlet Pressure: 1.6 bar (23 psi)
Air Consumption: only 9.8 cfm 277l/min
DeVilbiss FLG5 gravity feeds a general-purpose spray gun for a wide range of automotive materials and coatings.

• An all-metal construction includes a high-grade aluminium drop-forged gun body.
• The FLG5 employs compliant technology, ensuring low overspray and reduced consumption.
• Proven DeVilbiss controls and a light, smooth trigger action.

Suitable for solvent and water-based materials.

Supply valve
DeVilbiss HAV-501-B Air Adjusting Valve
Fits neatly in-line at the gun air inlet
Can increase or decrease working pressure right at the gun
Calibrated up to 11 Bar (160 psi)

SCUBA regulator
Aqualung old unbalanced piston regulator (previously used in the garage for tyre inflation and blowing off parts!) with IP at 9 BAR (130psi)
I'm not sure of the L/min it could deliver at that IP but it couldn't handle steady periods delivering maximum air volume and frequently iced up or stuttered. OK for a bike frame but not for bigger items like a wheel or car panel.

If I was doing it again I would look for a reg capable of delivering very high volumes at a lower IP.
I have a couple of Poseidon XStream Deep first stages laying about that may get pressed into service soon... these are upstream balanced diaphragm regs that can deliver >4000L/min at 8.5 BAR (123psi but could be adjusted lower) which should be sufficient for larger jobs without icing up!

SCUBA tanks
Faber 15L at 240 BAR
Leaving 50 BAR reserve 15 x 190= 2850L
Max air consumption of the FLG5 gun is 277L/min so 2850/277= 10.3 mins wide open (assuming the reg can deliver that volume)
Cutting back air delivery at the gun to ~200L/min 2850/200 = 14.3 mins
Cutting back air delivery at the gun to ~150L/min 2850/150 = 19 mins
Time will vary depending on the type of gun you have and what you are spraying, but these times are reasonably accurate in real world applications.

If you are using smaller 12L tanks or multiple tanks manifolded, just redo the numbers as above to get an approximate run time for your spray gun!
Have fun