Cast & stamped cowl grills on eBay

[Larry Lyons]

Re: Cast & stamped cowl grills on eBay

I got my castings from Mike, thank you Mike! As for the clear coat we will use, I will have to tell you later, (don't know) but I can say it will be a commercial grade. Very toxic, not the stuff for us armatures, but not rocket science either. (with a nod of the head to Hank) Just find a good quality body shop, (if you drive by and see hot rods or custom bikes sitting outside you have struck gold) as they use several different coatings from several different manufactures, what you get will differ according to what that body shop uses but these coating are designed for outdoor use even more sever then what we will give it. (salt, rock chips, etc.)
Larry

[Pearson]

Re: Cast & stamped cowl grills on eBay

Robert,

If you are going to spray clear over your polished aluminum, wipe it down with Tolulene a couple of times first. Use a clean rag each time and give it a few minutes between wipings. If you get any fish eye stop spraying imediately and wash off anything you have sprayed. Fisheye means you didn't wipe it down well enough.

I suggest clear coating with clear polyurethane on a warm day. Turn the paint volume way down so that you are just putting on a fine mist. Then control the amount you put on by how fast you move the gun. It only takes a very thin coat to protect the polished look. If you put a thick coat on, it has a greater chance of peeling off later.

[wmfife]

Re: Cast & stamped cowl grills on eBay

'41 cowl grille castings arrived today via UPS. (-TKS Hank! ..End of a long search...)

(Using soft wood pads, clamped first grille into vise. Inserted coarse brass wire wheel into ye olde power drill. Began polishing first grille - )
...Rough cast becomes BRIGHT METAL in thirty seconds! ALL bright in just at one minute! Ready for the "after" pic!

@Larry - What is supposed to be hard about this? This is history. World War Two hadn't even started for the U.S. when this (rough) casting was made! ...I just improved it! (I LOVE NOS parts..)

(Wait till you see this white-faced oil pressure gage...) - On a wood-grained panel. (...Hey ...It's a Deluxe.) Why not get it right.

(I love being part of history. Especially the part before I was born...)

[Hank Jarrett]

Re: Cast & stamped cowl grills on eBay

Hey Bill, how about a little more detail on how you did the polish job. You actually used a coarse brass rotary brush on cast aluminum and it worked? I would have never even thought of that! I have some rough cast aluminum parts and planned to start with files and sanding blocks followed by fiber polishing wheels. Any pictures or part numbers for the wire wheel? How fast did you spin it? Pressure?
We want more!
Hank

[wmfife]

Re: Cast & stamped cowl grills on eBay

Hank,

I didn't use any set speed. My drill is an old Black & Decker corded with a variable speed trigger. I had it pretty near max maybe 75% and just used a light pressure and sweeping motion, all under a good light. It's all pretty intuitive. You just knock off the dark sand cast surface untill you see bright underneath. This is supposed to be hard? I know and a Bumblebee isn't supposed to fly. (Maybe I should go back to getting paid to do this stuff...)

The wheel was a 4" Task Force® Coarse Wire Wheel Brush w/ ¼" shank. Has "4500 RPM Max" stamped on it but this is an old drill and I would estimate I got it to maybe half that at best.

Both it and the Fine are brass bristle though nothing on the package says so. You want what? Part #? Not sure that's the same but the item # says 179894; the fine is #179895.

Picked these up at Harbor Freight Tools but pretty sure any hardware chain sells 'em. -Lowe's, Home Despot, Wal-Mart Imports, etc.

This was a lot easier than doing the stamped ones because these hold up better. Of course I only used a 3" polishing wheel and compound on those and no vise. I have 3" steel bristle wheels but don't really want to apply them to the aluminum. The smaller spaces between the grill bars may require another shopping trip to get a 3" one in brass, then out comes the steel wool. At this writing I've only gone over the upper surfaces & what else I could reach, not the finer areas.

I clamped it (the one with the wing cut off) along the inner edge (next to the prop hub) using two 3/4" wide strips of 1/8" trim wood for pads. This vise is probably older than the plane, smooth jaws about 2½" wide though 3"-3½" might work better. It's mounted vertically on a sawhorse because I can reach the work better when it's held straight up @ waist height not flat at chest height (and my old workbench got thrown out). Details, details...

Will keep you advised. What did you use on yours?

[Hank Jarrett]

Re: Cast & stamped cowl grills on eBay

This is EXACTLY what I was interested in. The process details make all the difference between success and a ruined part.

My grills on my plane were actually finished parts but looked bad with one having a broken "wing". Before I got the replacement, complete one, I bought a set of rough cast ones. I have never bothered smoothing them out and polishing them since I found an unbroken one.

The surface condition of the ones I am using now was poor so I painted them (after lots of experiments to fins a paint that looked like polished aluminum). They look good from 5' or through a spinning prop, but I want to put the polished ones on some day. Since I am making "fake" side trim that has to be painted I will stay with them till I find a full set of original side trim. At least the grills and side trim will match.

Anybody know what the effect of brass bits driven into the aluminum casting is? One reason I hadn't thought of using a wire brush was I was afraid to hit the aluminum with another metal and didn't think an aluminum brush was good for much more than throwing little aluminum wires all over the garage!

Hank

Going to Harbor Freight tonight!

[wmfife]

Re: Cast & stamped cowl grills on eBay

Anybody know what the effect of brass bits driven into the aluminum casting is? - H.J.

I don't for sure but think it would be no worse than using a steel metal file or steel wool. You have to use the same net force to get the job done. Those just take longer and use harder metal. (Driven into- ?) Let me get my microscope. I'll get back with you on that.

Remember we're removing metal not adding it. And hardened aluminum alloy is a close second in hardness to copper alloy aka brass which unlike Al alloys does not use steel. ...I don't see anything out of the ordinary under a 3X diopter but fine scratches. Will keep looking..

(The cyl heads on my Lyc. have evolved from using paper to copper to aluminum gaskets. Aluminum is softer than copper but not by that much depending which scale you use.)

Bill

[Larry Lyons]

Re: Cast & stamped cowl grills on eBay

I guess I will have to see a pic or two, please! The wire brush will polish to a point but does it level out the surounding area? I am very interested in what you are saying as sanding alone is work! I can see it shining up the piece but making it smooth is a question I still have. The piece I have done looks like chrome plating, like you see on fancy motorcycles but is only aluminum. Larry

[Howard Wilson]

Re: Cast & stamped cowl grills on eBay

I'll bet that Hank has a S.E.M. with an X-ray backscatter detector at work. That would tell you the ratio of metals imbedded in the aluminum.

[Hank Jarrett]

Re: Cast & stamped cowl grills on eBay

I DID have access to an SEM in my old job and it was really fun to look at things like this. Unfortunately the facility is closed down and I don't have access any more.

What I did most of the time was examine fracture surfaces for fatigue striations after component failures. When we worked stress corrosion fractures we would look for embedded materials in the fracture origin that started the corrosion. The corrosion products would strain the surface of the base material beyond the elastic limit and that was the crack starting point.

I doubt these grills will have that problem since they are castings and have so many microscopic inclusions already. They would just be really fun to look at. Under SEM a casting looks like a jig saw puzzle of little cracked parts interlocked with each other. A forging looks like tiny crystals all aligned locked together. You can actually see the grain in the metal. That's why you don't see many castings on airplanes.

I probably spent way too much time hanging around the lab, but hey, ANY excuse to play with the fun equipment.

Hank

[Howard Wilson]

Re: Cast & stamped cowl grills on eBay

Hmmm, Sounds kinda like the lab stuff I did a hundred years ago. Still have the pics of fly eyes and ant mouths. Those were just for practice while waiting for something interesting to fail......

[Larry Lyons]

Re: Cast & stamped cowl grills on eBay

One complaint about the cast grills is porosity! I found out on the first one, that if I work too long to get rid of one two more show up next door!
Larry

[wmfife]

Re: Cast & stamped cowl grills on eBay

"The wire brush will polish to a point but does it level out the surounding area?" - L.L.

I hear what you're saying Larry and the short answer: No. It can't do that. My next question may well be: Do you really want to?

Looking closely at mine I see a very subtle undulating pattern on the surface that follows the grill bars, that is, for whatever reason there is a very gentle "dip" at each bar where the trim strip crosses. I would guess (with my high-school chemistry expertise-) that some heat-sinking occurred when the piece cooled and that manifested itself in selective shrinkage at the cross-bars. So I have to ask myself: "do I want to rub that out?"

- Or would I be erasing history by doing so?

Opinions are welcome. -Beyond that, to further answer your question, I see no surrounding areas that need leveling out. Beyond smoothing and polishing, this first test grill looks fine to me.

All this especially considering I am faced with using JB Weld, sheet aluminum and trim wood to decorate the cowl and complete the illusion of a *new* plane vintage 1941. ..I have tricks. But will they all work? (@ Hank: What do you think of my SNJ proposal? I have seen this metal finish and the effect leaves paint on the pad. You have to see it. All I can say.)

Finally - is this the SEM club? "I DID have access to an SEM in my old job and it was really fun.." - H.J.
That was the first thing I saw first day on the job. OK, I guess the Republicans are right about raising taxes. Government facilities have way too much money. But do they have to spend it ALL on blowing stuff up? We at least weren't about that. Polluters were out of control then and things have just gotten worse.

OK enough outa me. What were we saying? Oh yes Aluminum. Soft and softer. How to tell the difference. Looks like I'm stuck with what I've got. These are coming along. And they beat whatever is in second place. In any case - no regrets. It's the way they were made and we can either take 'em or leave 'em. '41's are still flying with them so I guess the test of time has been passed..? Onward -

[mikeg]

Re: Cast & stamped cowl grills on eBay

This is EXACTLY what I was interested in. The process details make all the difference between success and a ruined part.

My grills on my plane were actually finished parts but looked bad with one having a broken "wing". Before I got the replacement, complete one, I bought a set of rough cast ones. I have never bothered smoothing them out and polishing them since I found an unbroken one.

The surface condition of the ones I am using now was poor so I painted them (after lots of experiments to fins a paint that looked like polished aluminum). They look good from 5' or through a spinning prop, but I want to put the polished ones on some day. Since I am making "fake" side trim that has to be painted I will stay with them till I find a full set of original side trim. At least the grills and side trim will match.

Anybody know what the effect of brass bits driven into the aluminum casting is? One reason I hadn't thought of using a wire brush was I was afraid to hit the aluminum with another metal and didn't think an aluminum brush was good for much more than throwing little aluminum wires all over the garage!

Hank

Going to Harbor Freight tonight!

Hank,
Which of your grills is broken. I have some grills. See my "part for sale" list.
Mike

[Hank Jarrett]

Re: Cast & stamped cowl grills on eBay

I always thought of the SEM as the least bad form of "blowing stuff up"!

I haven't tried SNJ yet but I haven't had much luck with the buffing metal paints before. They didn't exist back when I was deep into models years ago. I think it would be great if I was able to afford the time to practice and learn to do it right.

I don't know how durable it is but I did learn a good trick when I was refinishing some wheels for an antique car project years ago. They were originally a factory applied bare aluminum paint and I used Rustolium Aluminum sprayed on to get a close match. Looked GREAT, but wasn't durable enough for wheels. Next I repainted and sealed them with Hobby Poxy clear. The trick is to VERY LIGHTLY tint the epoxy with a little blue epoxy. That keeps the clear coat from yellowing in the sun. Worked great!

HAnk