Preserving polished aluminum

On Friday, August 4, 2017 at 10:33:54 AM UTC-4, Ashevilliot wrote:
On Thursday, August 3, 2017 at 11:45:43 PM UTC-4, John B. wrote:
On Thu, 3 Aug 2017 17:55:06 -0700 (PDT), Ashevilliot
wrote:

On Monday, July 31, 2017 at 5:01:29 AM UTC-4, John B. wrote:
On Mon, 31 Jul 2017 15:46:41 +1000, James
wrote:

On 31/07/17 12:54, John B. wrote:


The alodine I have used to coat aircraft parts gave a yellowish tint
to the finished part. I guess it was designed as a preservative, not a
beautifier :-)



Both form a barrier to further corrosion, but alodine is a conductive
coating where as anodized is insulative. Also alodine is easy to
scratch, where as anodized finish is harder.

Alodine is available in different colours, IIRC.

Ah, I didn't know that. I never actually used it a great deal but back
then it was a yellowish and rather thin liquid that we dipped or
painted any raw machined aluminum things we made with.

I'll research it a bit more. If there is a clear version then it would
probably work well.
--
Cheers,

John B.



I have an old airplane with some magnesium alloys like aileron hinges
which are exposed to the environment. Left untreated, they corrode
like crazy too.

Interesting. What aircraft? I would have thought that the extra cost
of magnesium would preclude its use for something like hinges.
--
Cheers,

John B.

The hinge is an alloy, not pure magnesium. There are three on each wing.. These alloys add lightness, even better than aluminum. I bought a few spares a decade or so ago after one of my hinges broke because of corrosion. $2 apiece from an old bush pilot in upstate New York. The spares I treated with a chemical wash, probably a chromic acid solution, manufactured for the purpose. Then I painted with chromate paint, another coating to hedge against corrosion.

The aircraft is a '46 Taylorcraft manufactured in Alliance, Ohio.

Lots of aircraft and aircraft engines have magnesium parts. Some of the old VW crankcases were castings of magnesium. You can take drill filings and burn them. They make spectacular hot fires.

I have rebuilt recip aircraft engines in which the oil sump and the rear accessory case (for oil pump and magnetos) were magnesium castings. They are beautiful parts but quite delicate when you're wrenching on them.

http://www.univair.com/taylorcraft/v...hinge-bracket/

Take a look at the bronze bushings.

Yes, if you buy these parts new, they are quite expensive. This hinge is elongated to permit the "up" aileron's leading edge to protrude down into the airstream and cause a corresponding drag when the draggy "down" aileron (which is lifting that wing) is actuated. It's quite a neat idea, learned long before WWII of course, to decrease yaw and foster coordinated flight when the aircraft is in a turn. You also have to step on the rudder pedals in a turn. And keep the ball centered. These are called "Frise" ailerons, probably named after some aero engineer named "Frise." [Yep it was a Brit engineer who invented them. I just looked it up.]

Now you guys all go out and get some flight instruction, or just learn on your own like Orville and Wilbur and Cale did. More fun than anything else you can do with your clothes on.

Great old aero engineer Nick Jones once told me that NASCAR champ, Cale Yarborough, bought himself a Piper Cub (also designed by C. G. Taylor, btw) and checked himself out in it that afternoon. The next day he checked out a couple of his buddies in it. Some people are just naturals at flying. If you're good on a bike, you can fly! Plant the tailwheel first on landing and don't ground loop it.

Well, fellers, I'm a gittin' old and fergitful. The bracket is magnesium, but the hinge with the hinge pin fitting, and a press-in bronze bushing, is steel. I went and looked mine up and looked at them stashed lovingly in the basement.

And the Frise aileron was invented with the intention to reduce stick (or yoke) forces in a turn. The longer the wing, and the faster the aircraft, the greater the stick forces. Of course, a Taylorcraft (with a 36' wing) is a pussycat to fly, although its airfoil is not as forgiving as a Cub's. I had an old bushplane instructor tell me once that he'd start a student on a Cub and once he had a few hours soloing he'd put the student in a Taylorcraft, which is a little faster and tends to float on landing. This prank would scare the hell out of a student because while the Cub will come down quickly when landing, a Taylorcraft will continue wanting to fly and the student will almost run out of runway.