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Post by Roger on Jul 19, 2020 20:26:38 GMT
I shot blasted and sprayed primer on these on both sides with the AirBrush but wasn't happy it was wet enough as it was being applied. So I shot blasted them again, and this is my first attempt with the bigger Spray gun. I tried it on some cardboard and then some sheet metal to get a handle on what effect the controls had. Compared to the AirBrush, the paint plume particle size seems much larger, and I thought it wasn't going to be any good. However, making sure it was wet allowed it to flatten out. 20200719_211348 by Roger Froud, on Flickr I don't know what this gun is, or what the jet size is, so I decided to buy this from eBay which gives me two sizes of HVLP gun and a regulator for a very low price. I'll still be using the AirBrush for all the detailed small stuff, it's brilliant for that. Anything bigger than say 50mm x 50mm I reckon I'm better off using something bigger. I'm sure it's possible to use an AirBrush for larger surfaces, but I think it would take me way too many failed attempts to figure out how to do it.
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Post by chris vine on Jul 20, 2020 9:47:18 GMT
Hi Roger,
You are definitely making progress now! For these larger surfaces you just have to get the paint on fast enough for it to flow out before going tacky or even just a bit more viscous. I don't see how an airbrush can possibly do this, especially with the viscous coach enamels we tend to use.
When painting the gloss on Bongo, the pressure was quite low (20 psi I think), but it was with an hvlp gun. The droplet size was quite large but they pulled out flat perfectly. The bigger droplets have the advantage that they tend to fly in straight lines and don't get deflected by the air current. So they are better at getting into corners.
The higher the pressure, the smaller the droplets so that less paint goes onto the surface.
Chris.
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Post by Roger on Jul 20, 2020 10:29:29 GMT
Hi Roger, You are definitely making progress now! For these larger surfaces you just have to get the paint on fast enough for it to flow out before going tacky or even just a bit more viscous. I don't see how an airbrush can possibly do this, especially with the viscous coach enamels we tend to use. When painting the gloss on Bongo, the pressure was quite low (20 psi I think), but it was with an hvlp gun. The droplet size was quite large but they pulled out flat perfectly. The bigger droplets have the advantage that they tend to fly in straight lines and don't get deflected by the air current. So they are better at getting into corners. The higher the pressure, the smaller the droplets so that less paint goes onto the surface. Chris. Hi Chris, Hopefully when the new guns arrive, I'll be able to find something that works well on these larger parts. Out of interest, I've contacted Badger to see if they will tell me what the thread and angle is for the nozzle on the AirBrush. I think it's M5.5 x 0.35, so I've modelled it with a view to making a nozzle that doesn't have that shaped cone. The idea is to have a parallel end so I can fit any shape of diffuser I like, or none at all. I probably don't need to bother now, but it would be interesting to see if it could be made to work with a much bigger plume without the blobbing problem.
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Post by 92220 on Jul 20, 2020 12:11:31 GMT
Hi Roger.
I found a spare Badger Airbrush nozzle yesterday. If I can work out what thread it has, I'll make up a threaded jig and try machining off the nozzle cup, just to see how it effects the spray pattern. If it can be done without spoiling the maximum spray cone, It will get over the problem of paint build-up, and blobbing, in the nozzle cup.
Bob.
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Post by Roger on Jul 20, 2020 14:56:12 GMT
Hi Roger. I found a spare Badger Airbrush nozzle yesterday. If I can work out what thread it has, I'll make up a threaded jig and try machining off the nozzle cup, just to see how it effects the spray pattern. If it can be done without spoiling the maximum spray cone, It will get over the problem of paint build-up, and blobbing, in the nozzle cup. Bob. Hi Bob, That would be most interesting. I'm pretty sure it's going to be a Metric thread since the inlet thread for the air fitting is. I think it's M5.5 x 0.35 but you'd probably have to screw cut one to check it, because the thread is so short it's almost impossible to check with thread guages.
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Post by Roger on Jul 20, 2020 15:37:45 GMT
I wasn't confident about picking out the detail on these with the large spray gun, so I thought I'd just spray around the covers and along the edge with the Airbrush... 20200720_143515 by Roger Froud, on Flickr ... then finish it off with the large spray gun. That worked out really well. 20200720_150617 by Roger Froud, on Flickr I very tentatively shot blasted the Brass backhead cladding from a distance, and only gently. I blasted both sides, not that the back really needs painting, but I thought it would be more likely to remain flat if I gave both sides the same treatment. I think this would all bend like a banana if I aggressively blasted it, especially on those very thin side plates. I couldn't see how it would be possible to get paint deep into those washout recesses with the large spray gun, so again, I used the AirBrush for all of this. I'll give it a really thin coat of Black enamel the same way so that I can be sure to get into them, and also into the cutouts that represent the gaps between the plates. Once I've got those looking black, I'll use the big gun to cover the rest and just treat it as if they weren't there. 20200720_142702 by Roger Froud, on Flickr I shot blasted these gently again and repainted them just like I did the first time. Again, this is a job that's easily done with the AirBrush. I turned them all four ways to make sure I'd got all of the edges covered. I'll paint these Black with the AirBrush too. 20200720_150652 by Roger Froud, on Flickr There were a couple of runs on the Black paint on this, so I decided it was easier to just shot blast it back to bare metal and start again. I sprayed it with the AirBrush which is probably what I'll used for the enamel too. 20200720_150704 by Roger Froud, on Flickr
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Post by 92220 on Jul 21, 2020 12:15:40 GMT
Hi Roger.
You are not going to believe it but I've put that spare nozzle in such a safe place I can't find it at the moment!! I will. I can't screwcut metric threads with my gearbox so I will make up a collet to hold the OD of the thread when I find it!). It doesn't even matter if it's not running concentric, as long as it is square to the face. I'll let you know how it goes.
Bob.
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Post by andyhigham on Jul 21, 2020 12:21:39 GMT
It may be an imperial thread 72tpi?. Badger are American
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Post by Roger on Jul 21, 2020 13:34:09 GMT
Hi Roger. You are not going to believe it but I've put that spare nozzle in such a safe place I can't find it at the moment!! I will. I can't screwcut metric threads with my gearbox so I will make up a collet to hold the OD of the thread when I find it!). It doesn't even matter if it's not running concentric, as long as it is square to the face. I'll let you know how it goes. Bob. Hi Bob, If you turn a part of the front section to be parallel, you can then add any shape you want to it if you want to experiment some more. I think Delrin or even PTFE would be a possible candidate material, or of course I could 3D print something if I do this too.
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Post by Roger on Jul 21, 2020 13:35:03 GMT
It may be an imperial thread 72tpi?. Badger are American This is true, but they made the inlet air feed Metric Fine, so it's just as likely to be Metric.
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Post by Roger on Jul 21, 2020 20:07:06 GMT
I thought I'd share the way I've settled on for using the Shot Blasting Cabinet. I built the tiled cover way for the sideway a few years ago because I got sick of getting wet going in and out of the workshop. This provides a shower resistant area where I can leave the door open to let out the heat the compressor, freeze drier and vacuum make. Yes, it's right in the way, but being on wheels I can just move it to one side to get in and out. The key thing is that I can quickly and easily connect the compressor, vacuum and power and work in the dry. It's also tucked away a little so that the noise is somewhat muffled. 20200721_203013 by Roger Froud, on Flickr Anyway, I've now shot blasted the boiler cladding to get off the Holts Grey Primer I'd put on there to stop it rusting. That's a sod to get off with Wet & Dry, but it comes off really easily with blasting. I cleaned up the outside of the washouts with Acetone and they're now fitted with Loctite 620 high temperature retainer. I'll shot blast it again lightly when that's fully cured tomorrow. 20200721_202715 by Roger Froud, on Flickr They look pretty deep from the outside, but they're actually quite shallow. 20200721_205400 by Roger Froud, on Flickr I've also re-worked around the edges of the 1501 header plate because I could see some engraving artifacts around the edges of the numbers at the top and bottom. That showed quite badly when it was painted a glossy black. I hadn't noticed it before.
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Post by Roger on Jul 22, 2020 9:23:16 GMT
I lightly shot blasted this so it wouldn't distort, especially on those thin edges. It's probably not necessary to paint the unseen Brass parts, but I think it might help paint adhesion on the edges where the paint forms a film right around the edge from inside to out. It might also prevent verdigris since this might get damp in service. I sprayed this with the large gun... 20200722_100533 by Roger Froud, on Flickr ... as was this, and for the same reason... 20200722_100522 by Roger Froud, on Flickr ... and also the inside of the boiler cladding. However, those washouts are much easier to paint up close and personal from every angle with the AirBrush without applying too much paint, so that's what I've used here. I've left the outside bare until that's all dry because I want to mount it on the spit for the rest of the paint job. 20200722_100527 by Roger Froud, on Flickr I'll be using the AirBrush for a light coat on all of the Black Enamel work where there is fine detail like this as a first coat. I won't attempt to cover more than what I've done here, it's just to make absolutely sure that when I spray with the large gun, the deepest parts of the detail will already have been painted so it won't matter if the top coat doesn't get everywhere.
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Post by silverfox on Jul 22, 2020 12:19:02 GMT
Roger, What medium do you use for blasting?
Ron
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Post by Roger on Jul 22, 2020 13:58:29 GMT
Roger, What medium do you use for blasting? Ron Hi Ron, I bought this from eBay , the 150-250 grit glass bead size. It works really well, getting through difficult deposits but without leaving too rough a finish. It's ideal for painting afterwards, but too coarse if you wanted to finish the surface to a shine by hand.
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Post by Roger on Jul 22, 2020 20:36:39 GMT
Here's the boiler cladding firmly clamped to the spit, ready for spraying. 20200722_211231 by Roger Froud, on Flickr And here is the smaller of the two spray guns which arrived today. This looks exactly the size I need, it's a shade smaller than the one I borrowed. It came with a regulator and pressure gauge, although the pressure gauge went up to 160PSI which is absurd. I swapped it with one that goes up to 60PSI. I had a play with the controls to see what they all did and check what happened to the pressure. I concluded that it was probably best to leave the main air supply screw on the bottom wide open and set the air delivery with the pressure alone. The control above my thumb is for the shaping air. That robs the main jet of air as you open it, so you have to balance this with the air pressure to get the right amount of delivery with the desired shape. Hopefully with a bit of experience, I'll be able to set that by spraying onto a sheet of paper to see the shape and how it's covering. At least with the pressure gauge and the dial on the side, it ought to be easy to replicate the settings. Anyway, I'm very impressed with the quality, it's amazing how they make them so cheaply. I suppose they just steal the designs and don't need to support an R&D team. Let's hope it works as well as it looks. 20200722_211917 by Roger Froud, on Flickr
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JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,912
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Post by JonL on Jul 23, 2020 8:38:57 GMT
Being a newbie at this I've not seen a gun mounted regulator before. Doesn't it make it unwieldy?
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Post by Roger on Jul 23, 2020 9:46:46 GMT
Being a newbie at this I've not seen a gun mounted regulator before. Doesn't it make it unwieldy? Good question. I don't think so, it still feels ok when I handle it. It is necessary to clamp it in the orientation shown so that the gauge and control knobs don't get in the way of your wrist. I'm hopefully going to give it a try later on today, so we'll see.
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Post by delaplume on Jul 23, 2020 17:08:22 GMT
Hi Roger, Here's mine that I bought at a Classic Motorcycle Autojumble in Malvern not so long ago..............Just the gun and instructions, no gauge etc.. I've yet to make use of it as the aerosol tins meet most of my needs......As you say it's a good quality item at little cost ( Just over a tenner albeit inside a showground )... so I'll be interested in your findings.... Cheers, Alan..
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kipford
Statesman
Building a Don Young 5" Gauge Aspinall Class 27
Posts: 566
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Post by kipford on Jul 23, 2020 18:02:49 GMT
Roger Why do you need the pressure regulator on the gun? Once I have a gun set up I normally don't change the pressure and if I do I just stop spraying and adjust it. Mount it further up stream where it will not effect the action of your hand on the gun. From first hand experience can guarantee it makes the job more difficult. Dave
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Post by Roger on Jul 23, 2020 21:24:32 GMT
Roger Why do you need the pressure regulator on the gun? Once I have a gun set up I normally don't change the pressure and if I do I just stop spraying and adjust it. Mount it further up stream where it will not effect the action of your hand on the gun. From first hand experience can guarantee it makes the job more difficult. Dave Hi Dave, The idea is to reduce the variation you get at the gun. It's not my idea, it's what they show with the instructions and Chris Vine shows this in his book too. I've tried it just now, and I didn't find an issue with it at all. Maybe there are some situations where it makes life more difficult, but at the moment I don't see the need to change it. Perhaps on cars, where you have to get inside a wheel arch it might present problems, but here it's all external use without obstructions. I've just left the main air screw wide open and used the regulator to set the pressure to get the desired delivery.
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