Spinning an aluminum cowling

Ken Cook Sat Nov 22, 2014 8:42 am

Northeast PA has become quite cold. In the past week we went from the low 60's and plummeted to the low 20's with winds as much as 30 mph at times yielding what felt like 12 degrees. I work outside and for me this time of the year is most dreaded. However, it brings me back into the shop to finish a year long laundry list of what to do and things needed to be done. It also brings our club members together for some quality shop time and hamburger lunches. I'm very good at finishing builds that others have started and never finished. It becomes rewarding for me and also the builder who may have had that build sitting for 20 + years. That being said, I never seem to get a new build completed in a timely manner. One problem with older kits is that certain hard to find relics such as spun aluminum cowlings have gone missing. Consider these like decals as they're the complimenting touch to such desirable pieces. My son Shawn with the assistance of my friend Dan Banjock spun me some aluminum cowlings for my scratch built Cox powered C-47 twin. These are very special to me as the plane looked naked without those 'Gooney bird" cowls. Shawn did a wonderful job of providing me those. Dan has also made myself and others missing cowlings for such planes as the Sterling C-series kits. Dan has made several units for many cottage industry kit cutters. Currently Dan has made approx 20 more for a desired run which is shown in this video. It never ceases to amaze me of the things we do as modelers to achieve a certain level . Here's a neat video of Dan in action. Rich recently moved here from Portugal and he's responsible for our Philly Fliers Facebook page and videos. I can't thank Rich enough for his assistance and his overwhelming good sense of humor. https://www.facebook.com/video.php?v=761744223895714&set=vb.513140418756097&type=2&theater Ken

ian1954 Sat Nov 22, 2014 10:09 am

I liked watching the video. I have only ever "spun" brass and copper and that is far easier than aluminium.

I particular like the part where he took out the crease that was forming. Spinning that cowl is quite an effort and that amount of leverage must put a strain on the lathe.

I would not have thought of using beeswax as a lubricant but it makes sense using something that is sticky and pasty with a low melting point. It won't splatter everywhere.

Thanks for posting that video Ken, I like these informative snippets.

706jim Sat Nov 22, 2014 10:37 am

Interesting video. Any idea what the initial material thickness was or alloy used?

getback Sat Nov 22, 2014 11:33 am

YESS that was cool stuff seeing the forming taking place , good lathe work !! Eric

fredvon4 Sat Nov 22, 2014 11:58 am

Amazing the new things I learn almost every day here on CEF

Thanks Ken

Ken Cook Sat Nov 22, 2014 1:22 pm

Heat treated aluminum doesn't work due to work hardening and the piece starts to take shape and then explodes. I witnessed that early on. I don't have the exact specs on the aluminum or thickness, but I could get that and post tomorrow. Ian, if you noticed Dan was backing up the tool rest with the tail stock. Dan always makes that one part that sets his models apart from the rest. His OTS Galloping Comedian has formed aluminum wheel pants. He made the dies and had them welded. This was a tedious process as the aluminum was only .010" They were continuously welded. Afterwards, he filed the welds down and sanded and polished. No seams are visible. This took several attempts due to the welds breaking through. Here's a pic of that plane http://stunthanger.com/smf/index.php?action=gallery;sa=view;id=879 The cowling is the same cowling in the video. Wheel pants, cowling, and windshield surround were aluminum. Ken

KariFS Sat Nov 22, 2014 1:52 pm

Amazing work on both the cowling and the Galloping Comedian.

The cowling material must be something quite soft because it stretches so much in the process. This is definitely something that I would want to try someday.

I wonder if this could be done on a benchtop drill press? With the drill press "feed" movement and a sort of stationary pressing tool maybe? Although the radial forces involved would probably explode the bearings of my cheapo drill press. Maybe with copper, annealed a few times in between... Sorry, just thinkin' out loud Laughing

roddie Sat Nov 22, 2014 3:23 pm

That's thoroughly impressive! The man is certainly a craftsman. Sterling "Monocoupe's" and "Waco's" had beautiful cowlings.

Ken Cook Sat Nov 22, 2014 3:31 pm

The key to this is the maple mandrel under it. While the material appears soft, Dan is making this look quite easy. The material is really being heated with the stick and the beeswax provides the lubrication without setting the stick on fire. Wrinkles are constantly forming through this process. Without the mandrel and it being totally smooth, the transition to what you see wouldn't be possible. The mandrel was soaked thoroughly in thin ca and sanded smooth. Due to the heat and pressure being placed on it, the mandrel is certainly in need of repair. It has made approx 75 of these cowls. As Ian mentioned, there's a lot of stress being placed on the lathe. I highly doubt a tabletop drill press would be capable of such tasks due to it stalling and also smoking the bearings out due to unwanted side loads. Ken

1/2A Nut Sat Nov 22, 2014 4:16 pm

Back in the 90's I made a aluminum cowl with a hard wood mold and a mallet. I used a rolling machine to form the diameter then beat the front face lip over the mold worked great if you don't have a lathe. It was for an Eindecker so ok to have an opening at the bottom for the engine thus a C shape cowl.

I wonder if you could chuck up thin walled aluminum tube on both ends and press in the shape for a tuned pipe ending with the thin wall only at the apex of the pipe. Does anyone have a vid link for making solid aluminum tuned pipes?

pkrankow Sat Nov 22, 2014 4:21 pm

There is a lot of literature on metal spinning available. Some available for free download.
try this
http://archive.org/search.php?query=metal%20spinning

The basic concepts are not hard, create a plug, form the metal to the plug using a pusher tool of some type.

I haven't tried, and I have only read a little on the subject.

Phil

Ken Cook Sat Nov 22, 2014 5:50 pm

I had a nice chat with Dan this afternoon. Dan informed me that the material thickness is .032". The aluminum used is 1100-0. This is very soft aluminum with no hard straining or heat treating. Dan has tried this with various materials through the years and found this to work the best. I can say he's been at this for nearly 3 years now. The lathe rpm's was approx 1000. He's tried spinning faster but he usually ends up with extreme wrinkling or breaking towards the rear. Ken

706jim Sat Nov 22, 2014 7:14 pm

Thanks for the info. FWIW, it sounded like about 1000rpm.

And for 1/2a nut, I don't think a drill press would work very well for this process.

Side loading too much for the bearings.

**RknRusty** Sat Nov 22, 2014 8:49 pm

Isn't that the plane Dan lent to Matt Colan in Huntersville after Matt's Vector folded a wing in competition?
Not only talented, but generous too. Though I know he was very confident in Matt's ability to fly it.
Rusty

Ken Cook Sun Nov 23, 2014 3:51 am

Rusty, the Comedian is an OTS plane or it could also be flown in classic. The plane Dan lent to Matt was his Miss Suzie-Q P-51 Mustang racer. Dan and Mike Palko both built these at the same time which is a Bob Hunt lost foam wing design. Mike didn't finish his until years later. The interesting thing about the Mustang is that in order to save weight, no color is over top of another color. In other words, the checkerboards you see were all individually masked off and sprayed separately. THis is an amazing amount of work and it took almost 2 years to paint it. It looks pretty horrendous nowadays and it has literally thousands of flights on it. I know of only a handful of people who flew the plane. One being Windy Urtnowski who assisted Dan and Mike Palko. Bob Hunt flew it and my son also flew it. I haven't been so lucky nor would I take the chance in doing so. I was asked, but I know my limitations and I wouldn't compromise years worth of work to have 5 minutes of enjoyment. I'll pass and fly my own. Here's Dan's Mustang, I should say the RETURN of the Mustang after being in retirement for quite a few years. Power is a Randy Smith PA .61 on a Windy manufactured tuned pipe. https://www.facebook.com/PhillyFliersCL/photos/a.513142608755878.1073741825.513140418756097/712301858839951/?type=1&theater Ken

getback Sun Nov 23, 2014 8:34 am

Those are some Beautiful air planes , and a lot of dedication to your modeling hobby . Thanks Ken , Eric Very Happy

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