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What material are the engine cowls of the Handley Page Hampden made from?


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Hey all

 

Just wondering what material the engine cowls of the Handley Page Hampden were made from, the bit right at the front?

 

Thanks in advance.

 

 

Image as reference -

 

Handley_Page_Hampden_in_the_air.jpg

 

Edited by RobL
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The collector ring changed colour, due to heat staining, during use, as most any engine exhaust piping will. 

 

This drawing shows where the heat staining appeared on the ring:

 

48919735002_f74495d697_b.jpg

 

 

 

Chris

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On 3/7/2021 at 10:39 AM, BS_w said:

the front ring was the exhaust collector made in stainless steel  

"stainless steel" means that it can corrode and will corrode, but much slower then normal, black steel. Especially in contact with chlorides (so flying at low level over sea) it becomes rusty.  On the other hand, heating it up makes it blueish, so depended on conditions it goes rusty (red-brown) with blue hue sometimes.

Regards

J-W

 

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There are a lot of variation in stainless steel, with various combinations added to the basic steel. I've looked for, but couldn't find the exact material that the collector rings were made of, but I'm sure I've read somewhere, years ago, that it wasn't stainless steel, or at least not the shiny stuff most of use are familiar with.

 

 

 

Chris

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On 3/7/2021 at 8:40 PM, dogsbody said:

The collector ring changed colour, due to heat staining, during use, as most any engine exhaust piping will. 

 

This drawing shows where the heat staining appeared on the ring:

 

48919735002_f74495d697_b.jpg

 

 

 

Chris

Wow, thanks for those diagrams! Are they directly Hampden-related (if so, I think I may want that publication...), or generic? Especially that "lip" variant, that explains a lot.

 

BTW, not Hampden-related, but collector-ring-on-boxtop-stuff: On the Airfix SM 79, the cowlings look like (painted) white-red- white, while they actually show natural-discoloured-natural material (always assuming the arrangement was similar).

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37 minutes ago, tempestfan said:

Wow, thanks for those diagrams! Are they directly Hampden-related (if so, I think I may want that publication...), or generic? Especially that "lip" variant, that explains a lot.

 

BTW, not Hampden-related, but collector-ring-on-boxtop-stuff: On the Airfix SM 79, the cowlings look like (painted) white-red- white, while they actually show natural-discoloured-natural material (always assuming the arrangement was similar).

The exhaust collector ring shown features on most of the Bristol engines, and can be seen on many different aircraft types that used the Pegasus.  Bristol  Hercules  engines also used on many aircraft had the same feature.  Interestingly the Italian SM 79  is also quoted, The Alfa Romeo engines used on this aircraft were basically licence built Pegasus engines! (licence was granted pre war).

 

Selwyn

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31 minutes ago, tempestfan said:

Wow, thanks for those diagrams! Are they directly Hampden-related (if so, I think I may want that publication...), or generic? Especially that "lip" variant, that explains a lot.

 

BTW, not Hampden-related, but collector-ring-on-boxtop-stuff: On the Airfix SM 79, the cowlings look like (painted) white-red- white, while they actually show natural-discoloured-natural material (always assuming the arrangement was similar).

 

 

The left-hand drawing would be the one for a Hampden. The right-hand one is for Hercules collectors, especially those used on night-flying aircraft. The extra baffle allowed air to move over the outer surface of the collector, cooling it a bit and lessening the glow of the hot metal, which enemy nightfighters could see. The outer part of the ring was also overpainted with a black stove enamel type of paint to hide the glow even more.

 

 

 

Chris

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Here are some photos of the collector rings from Hercules engines.

 

Wartime production:

 

46345661462_6bbf39bfe0_b.jpg

 

 

 

And some much later ones, awaiting restoration for use on museum display.

 

31457116917_fe7dd133b3_b.jpg

 

 

 

 

 

Chris

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There are a few comments scattered in various WIPs here that confirm the ring should not be painted bronze. I normally go for nebulous aluminium/black/dark earth/bronze concoctions, making sure I look at a colour picture such as this one of the RAFM Bolingbroke I took many moons ago.

 

23945506017_541a583dae_c.jpg

 

As you can see, there is definitely a brown tinge of sorts there.

 

Trevor

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^^ That is how I went to work on the Hampden in my signature.

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6 hours ago, dogsbody said:

or at least not the shiny stuff most of use are familiar with.

 

Only shiny if polished - like cutlery, etc.  Otherwise, it is generally brighter than mild steel, but not inherently shiny.

 

I don't really understand the reference earlier to stainless not being resistant to chlorides, as this is pretty much exactly what SS was designed to be resistant to.  Its the reason why the majority of marine fittings (hand rails etc) are often made from SS.  Obviously there are different grades of SS with higher/lower chromium content and other qualities, but the overall objective (ie anti corrosion) remains the same.

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Some modern flying collectors. These were not necessarily made of the same material as originally used, but it does show what the heat will do.

 

49527464918_f8774d5b56_b.jpg

 

49527975216_f8b45fac40_c.jpg

 

49527464873_d1babc6077_c.jpg

 

49495131047_36fea8b0e9_c.jpg

 

49494412868_a114212d76_c.jpg

 

 

 

 

 

 

Chris

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I guess there should be quite the market for Exhaust Collector Ring Discoloured Steel paint. 
Should we invent a lacquer or acrylic for that? :P


 

 

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6 minutes ago, alt-92 said:

I guess there should be quite the market for Exhaust Collector Ring Discoloured Steel paint. 
Should we invent a lacquer or acrylic for that? :P


 

 

I personally paint the rings base colour steel and do some home made washes of clear varnish with a slight tint of brown or blue paint to get the effect I want, then a bit of silver around the inner edge.

 

Selwyn

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7 hours ago, dogsbody said:

There are a lot of variation in stainless steel, with various combinations added to the basic steel. I've looked for, but couldn't find the exact material that the collector rings were made of, but I'm sure I've read somewhere, years ago, that it wasn't stainless steel, or at least not the shiny stuff most of use are familiar with.

 

 

 

Chris

It's a nickel alloy called Inconel. It may or may not have a ferrus content.

 

https://en.wikipedia.org/wiki/Inconel

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10 hours ago, 303sqn said:

It's a nickel alloy called Inconel. It may or may not have a ferrus content.

 

https://en.wikipedia.org/wiki/Inconel

Definitely not Inconel, it's development is 20 years too late.

Inconel is developed in the 1940's specifically for gas turbine development 

Aero engine exhaust collector rings had been in common use in the 1920's

The material used appears to be an alloy steel, most likely with a high chromium content to resist heat and corrosion, so some form of stainless steel but a bit more specialist than that in your cutlery draw.

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IIRC it's plated steel, I think the post where I first saw the drawing said what exactly and I'll try to find it when I get home

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Curtiss and NAA used for exhaust collector, stack & dampener
"stl steel : 57-136-9"
"stl steel : 57-180-3"
"stn. stl. : AN-QQ-757 & AN-WW-858"
"corros. res. steel sheet. : AN-QQ-757 & AN-WW-858"

 

I no found for british equivalent,

 

RR manual Merlin 66 to 85 indicates "steel sheet pressed"

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1 hour ago, rossm said:

IIRC it's plated steel, I think the post where I first saw the drawing said what exactly and I'll try to find it when I get home

 

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If anyone out there has access to that Ian Huntley article, in the November 1985 Scale Aircraft Modelling issue, I would really like to have a nicely scanned copy. The one I have had for a number of years now wasn't scanned that clearly and is hard to read.

 

 

 

 

Chris

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It appears that inconel was used for British wartime aircraft exhausts if not those of other nations.

 

According to extracts from ‘The Design and Development of Exhaust Systems for Rolls Royce Engines’ RR Ltd, Hucknall Aerodrome May 1943’ (contained within the thread linked below) Rolls Royce used it exclusively for their exhaust manifolds although wartime shortages of nickel later necessitated the use of metals with lower nickel content.

 

As to the Hampden and it’s Bristol Pegasus engines I am unable to further assist. It is possible that the Filton museum may be able to help as and when they re-open:

 

https://aerospacebristol.org/

 

The following linked thread contains the report extracts referred to above and very useful technical comment on the use and types of alloys used for exhaust manifolds of different types, including an extract from an British analysis of the Japanese Sakae engine. (Metallurgical Examination of a Japanese Sakae 21 Aircraft Engine (1944).’):

 

https://www.key.aero/forum/historic-aviation/143045-historic-aviation-metallurgy-exhausts

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It's going to be a 18-8 stainless steel the way it discolours in the area indicated. It might be 'staybrite', it was used in the aerospace industry.

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5 hours ago, dogsbody said:

If anyone out there has access to that Ian Huntley article, in the November 1985 Scale Aircraft Modelling issue, I would really like to have a nicely scanned copy. The one I have had for a number of years now wasn't scanned that clearly and is hard to read.

 

 

 

 

Chris

 

 

I've got it!

 

Thanks to @rossm for supplying me with not just one, but two Huntley articles!

 

 

Thanks, Ross!

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