radial vs inline vs naiper h-pattern

[MiTasol]

DeHavilland used magnesium in the Gipsy Major series of engines, and I understand in the Gipsy Queen and six series as well. The top cover and rear case was Mg.

The Gypsy Major engine I have has an Al alloy crankcase but agree that they used Mg in many of the secondary castings. Same with the six and Queen. Although the top cover is attached to the crankcase it is not primary structure and, as I read his comment, the OP was discussing primary structure rather than covers and secondary structure.

I'm curious which engine type can take the most damage and make it home my guess would be to say the V and H pattens wouldn't make it if they took any damage if a merlin or db601 takes a .30 in or .50 into the block i wouldn't say it would make it home.

What he is calling the block is the crankcase and, in the case of an inline, cylinder banks. Being a newbie he is not aware how inlines like the Allison and Merlin were built. He is thinking that the crankcase and cylinder blocks are a single unit with removable heads like on a vehicle instead of separate components with the head integral with the cylinders like on an aircraft. Give him time and he will learn.

 

[MiTasol]

Weren't the cylinder barrels steel?

Yes the barrels are steel but the heads are Al alloy.

 

[MiTasol]

Eh?

Cast aluminium is cast aluminium. According to my metallurgy textbook, cast iron is anywhere between 2 and 6.67% carbon. 6.67% carbon makes it a mineral called cementite Fe3C, not a metal at all. Apparently, 2.5 to 4% is normal. They don't heat treat it for higher strength. They might anneal it to relieve stresses.

Pure aluminium, most commercial aluminium, the 3000 and most 5000 series alloys cannot be heat treated to increase strength but ALL the structural alloys used in aircraft have a multitude of heat treatments, the vast majority of which are to increase strength.

The attached is from a USN training pub dated 1945 that gives you the basics of the time. 17 is now 2017, 24 is now 2024, 53 is now 5053 and 61 is now 6061. 7075 was just coming into use outside of Japan where it was developed.

Not covered are the many different quenching systems that all produce distinct differences in properties which is why you now find alloys with a heat treat codes like 351. Also not covered are processes like taking annealed alloy, normalizing it then quenching it to -40C before working it instead of working it first then normalizing it.

A modern heat treat primer for aircraft alloys is far longer and very boring even when you need to know the process.

 

[pbehn]

Pure aluminium, most commercial aluminium, the 3000 and most 5000 series alloys cannot be heat treated to increase strength but ALL the structural alloys used in aircraft have a multitude of heat treatments, the vast majority of which are to increase strength.

The attached is from a USN training pub dated 1945 that gives you the basics of the time. 17 is now 2017, 24 is now 2024, 53 is now 5053 and 61 is now 6061. 7075 was just coming into use outside of Japan where it was developed.

Not covered are the many different quenching systems that all produce distinct differences in properties which is why you now find alloys with a heat treat codes like 351. Also not covered are processes like taking annealed alloy, normalizing it then quenching it to -40C before working it instead of working it first then normalizing it.

A modern heat treat primer for aircraft alloys is far longer and very boring even when you need to know the process.

I gave up (again) when pure elements were being compared to alloys, and materials with yield properties were compared to those without. Some cannot grasp the idea that materials dont have a yield value even when shown a table with no yield value quoted, it has happened before here. I could also add that while steels are supposedly an alloy of carbon and iron, some steels have almost no carbon in them like 0.03% they can have up to 28%Chrome and 5% Nickel, these steels do have a "carbon equivalent" which is quoted in the material specification. Cast irons are not necessarily cast material, and what is called "quenching" on carbon steels is called "solution heat treatment" on stainless steels. Temperatures which normalise carbon steels can sensitise stainless steel and so on and so forth, which I am sure you know but others dont.

 

[Deleted member 68059]

Weren't the cylinder barrels steel?

Only the thin liner.

 

[gumbyk]

Only the thin liner.

No, the whole barrel was steel, with an al alloy head threaded onto it, for air-cooled engines.

 

[nuuumannn]

Not covered are the many different quenching systems that all produce distinct differences in properties which is why you now find alloys with a heat treat codes like 351. Also not covered are processes like taking annealed alloy, normalizing it then quenching it to -40C before working it instead of working it first then normalizing it.

This all brings back all that stuff I had to learn when sitting my engineering papers... Completely useless to a Ramp Tramp!

 

[Deleted member 68059]

No, the whole barrel was steel, with an al alloy head threaded onto it, for air-cooled engines.

Sorry in the case of the earlier R-1820 and R-2600 you`re quite right they were steel.

 

[MiTasol]

Only the thin liner.

Actually that only applies to some of the liquid cooled engines in aviation. Many of those have a steel barrel (called liner) clamped by, but otherwise not touching, the water jacket.

The air cooled engine usually have a steel barrel incorporating steel fins machined in and then an Al alloy head either screwed and shrunk on (most common) or bolted on.

 

[MiTasol]

This all brings back all that stuff I had to learn when sitting my engineering papers... Completely useless to a Ramp Tramp!

Like the copper content of 2024 which is totally irrelevant because there is nothing you can do to change that part from 2025 to 7075 or any other alloy.

 

[Deleted member 68059]

Actually that only applies to some of the liquid cooled engines in aviation. Many of those have a steel barrel (called liner) clamped by, but otherwise not touching, the water jacket.

The air cooled engine usually have a steel barrel incorporating steel fins machined in and then an Al alloy head either screwed and shrunk on (most common) or bolted on.
View attachment 652457

The Hercules in the photo you show, for example, does NOT have a steel barrel. Its an aluminium forging. The sleeve inside is steel.

The R-2800 also does not. The head is aluminium and also the mid-level fins are aluminium shrunk onto the steel liner underneath.

 

[nuuumannn]

Like the copper content of 2024 which is totally irrelevant because there is nothing you can do to change that part from 2025 to 7075 or any other alloy.

The thing I remember the most to do with the alloy was when making new brackets and stuff out of 2024 and the surface was scratched through filing into shape, was the alodine process, either through alodine pens or a dipping bath, which we had out the back of the workshop, before painting.

A mate of mine equated the word "alodine" with the film The Dictator, whose name was Aladeen and of course being a dictator sought to replace certain words in his language with the word "Aladeen", so we used to make jokes about the fact we were going to "aladeen" the part we had just made... Yeah, night shift will do that to you...

 

[msxyz]

Generally speaking, the only parts of an engine which need to be made of a wear resistant material are those which are subject to friction. Different materials have different mechanical properties, sometimes they're good in one respect but bad in another, i.e. magnesium alloys employed in engines are rigid but not ductile and not very elastic therefore they're good for the crankcase/basement where maximum rigidity is desired. Heads can be made of lightweight aluminium alloys because they need to dissipate heat and be tolerant of thermal stresses without cracking (in this they're superior than most steel alloys and also lighter) and so on...

Italians WW2 engines also generally employed a lot of magnesium and other lightweight alloys; the large Piaggio P.XII engine, for example, (18 cylinders, 53 liters, 1.4m diameter and 1.7m long) weighted only 850kg

 

[Lefa]

Here is some model made by Cadmatic. CAD Models