Round engine question

[Shay]

Are the Cyclinder Jugs made of Aluminum or Steel?

Thanks

Shay
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Semper Fortis

[jcw]

that depends....... both...

[bdk]

Typically the heads are aluminum with high temp steel inserts for the valve seats while the cylinder barrels are steel and are screwed and shrunk into the heads.

[Shay]

Ok then my next question.

If the Jugs are steel then how are they coated to protect them from rusting? Is it just paint or are they treated.

Also does anyone know if rust, over time, reduces the cooling efficiency of the Cyclinder?

Shay
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Semper Fortis

[thundergull pilot]

A lot of the large radial engine cylinders have a finned alumnin cooling muff swaged on to the steel cylinder. Carl

[famvburg]

Rust on the inside of a steel cylinder can be a problem, tho.

Ok then my next question.

If the Jugs are steel then how are they coated to protect them from rusting? Is it just paint or are they treated.

Also does anyone know if rust, over time, reduces the cooling efficiency of the Cyclinder?

Shay
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Semper Fortis

[Craig]

Pratt & Whitney radials had a "plasma" type spray coating applied to the cylinders when they were new. I don't recall the exact name for it, but it coated the exposed steel surfaces of the cylinders, and protected them from rusting. It was aluminum colored. During overhaul, this coating was blasted off, and was replaced with paint, usually black. Therefore, a new Pratt & Whitney radial would have silver colored cylinders, and an overhauled one would have black. When we restored our R-2800, we blasted the cylinders with Arm & Hammer baking soda, and we were able to leave the original spray coating intact.

Craig

[Shay]

Thanks guys.

The reason I ask is that I have a Air Cooled engine and the barrels are rusted. During rebuild I want to treat the barrels to keep the rust at bay and allow them to transfer heat optimally.

I don't want to paint them....it'll only last so long and the rust will come back. And since it's a coating on top of the iron it will decrease the heat transfer to some degree.

First, after blasting the barrels, I was thinking of trying a method of Black Oxide "Bluing". Seems promising. It chemically alters the iron resisting rust while adding nothing to the volume of the iron.

The plasma coating is interesting though I would like to hear about it if anyone knows more.

Thanks

Shay
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Semper Fortis

[Craig]

Shay,

If I remember correctly, Pratt & Whitney may have called this spray process "aluminizing", maybe. I will look through my engine manuals and see what I can find. Your best bet may be to check with after-market aircraft overhaul shops. I researched this myself a while back, and recall that all overhaul shops just use paint on the cylinders. Check out the engine restoration section of our website, (although the site is under re-construction). We have demos of the baking soda process on the site.

Craig

[bdk]

I researched this myself a while back, and recall that all overhaul shops just use paint on the cylinders.

Aero Engines aluminized the cylinders when they overhauled my T-6 engine...

[engguy]

So is that an aircraft engine? And is it going to be used in an aircraft?
There is a paint called zero rust. It is very good stuff, it may do what you want. And if it is painted there should be no problem with the heat transfer issue you are concerned about. Look at most old automotive radiators, they are painted and seem to accomplish their jobs just fine.

[warbirdcrew]

Pratt & Whitney radials had a "plasma" type spray coating applied to the cylinders when they were new.

I could be wrong, but I believe it is called Cermachrome. We had this done with the engines on our Hu-16 and ran into big problems when it started to flake off and get caught in the oil screens. We had to send one whole engine and a couple of cylinders off the other back so they could fix it.

-WC

[skymstr02]

I think that he's referring to the cylinder fins on the outside of the cylinder, not the bore.

[sdennison]

The process is called "metallizing" and involves flame sprayed aluminum coating. This process goes back to the 30's. My grandfather started a flame spraying business that stemmed from his work at AO Smith Company here in Milwaukee. He was spraying steel beer barrels with zinc for corosion resisitance.

The process involves sand blasting the outside of the cylinders and then when clean, the aluminum is sprayed onto the outside. The gun feeds an aluminum wire into it where it is melted by an oxy-acetylene flame and then sprayed in a molten condition using compressed air. The molten particles then bond to the rough sand blasted surface giving the corosion protection desired. Plasma spraying is the same concept but much more high tech and usually with very exotic coatings.

I am sure that there are many metallizing shops around the country that have experience spraying aircraft cylinders. Ranger engine rebuild manuals even describe how this process is done.

Hope this helps.

[SaxMan]

A slightly related question. When people say that an engine is "Zero Timed", what exactly does that entail? Is that automotive equivalent of using the same engine block, but putting in new pistons, crank, valvetrain, etc...i.e. a remanufactured engine?