Nick, while you visit can you ask if drawings and material specifications for the Bristol Jupiter still exist and are accessible? Thanks, Ed

Adrian, it is definitely the Mosquito forward armour plate, with the four clips for the ammo boxes on yours. It is on its side, missing the little fold down door. If you google images of Mosquito you will soon find it in exploded diagrams of the day or in some of the restoration photos from NZ. A yellow dot on this plate signified armour. Is yours from Australia? The way to tell is if there are red backs attached!

Forward plate

Adrian,

This is not a drawing but the actual forward armour plate that the ammo boxes were attached to.
What sort of information do you need, ie dimensions ?
Are you doing a CAD model or something else?

[ATTACH=CONFIG]245125[/ATTACH]

Can you attach an image showing the exact armour plates for Nav’s position you are after to help resolve your query.
This plate is from Australia. Many farmers saved these plates to cut up for use as the points in ploughs.
It is a manganese alloy steel that work hardens.
Ed

Alertken, I enjoy your posts. They are more densely packed with facts than a morning muesli drawn into a black hole! I have to use a fork to pick through it all, but every bit is a good feed. Thanks.

So why strip each engine after initial build ? Welcome to the world of adverse tolerance stack up.

Now you will have the tolerance variation on everything, dimensions, materials, coatings, treatments and assembly. Each one of these has numerous sub categories I.e dimensions includes length, diameter, squareness, parallelism, flatness, concentricity, and more… Just one part, with one parameter at top acceptable tolerance is not a problem but get a number of these at the top limits and you maybe lucky and spot the assembly won’t go together but it could assemble with gaps critical for function being significantly compromised so will wear very rapidly or even crack.

When a complex assembly is designed it’s assumed all parts are in the middle of the tolerance range. Although you’re supposed to consider permutations of tolerance, in reality it’s massively time consuming on technical resources.

A great explanation, thank you.

Tear down

I seriously doubt that every new Napier Sabre was stripped and rebuilt as a matter of routine after ‘running-in’; although it could identify, presumably, a very small number of engines with problems it would not make economic sense and, to me, would introduce another potential source of problems.

I wish we had some statistics to get a better handle on this.

CD, there is a superb, contemporary, 4 part serial on youtube by Hall Scott which deals with ‘tear down’ inspection after initial test run :

https://www.youtube.com/watch?v=Wdpg16jeKYU

It is worth watching the whole presentation to appreciate the care taken in the construction of these engines, used in PT and Fairmile boats, landing craft and other applications. I once had a 700 HP Hall Scott V12 Defender, which is now in a Fairmile restoration project, and it was a magnificently built engine. I originally bought it as a Mother’s Day present for the missus, at an auction that happened to be conducted on the day…she took it silently and I lived in ‘icing conditions’ until it was sold on to fund a family holiday. Wimmin!:)

The key point in the film is that tear down and re assembly is done by Inspectors rather than usual line staff, a prudent control measure, and the tear down is partial, seeking to identify obvious points that may develop into field failure.

I can think of quite a few issues that would warrant a ‘tear down’ after an initial test :

1. Within the thousands of components and human interactions assembling these into a finished product, it is statistically probable that incorrectly dimensioned parts may be incorporated, eg one oversize crankshaft bearing shell half out of a set, that might allow the crankshaft to turn but would cause obvious wear. This is a personal experience with one auto engine.
2. Under wartime production pressure, there would not be the opportunity to ‘lap in’ components that today’s engine builder, dealing with a rare and expensive engine, might invest the time in to ensure no issues with correct clearances between articulating parts. This is the ‘running in ‘ period, when this is accomplished by ‘careful’ field operation. With shipping space at a premium, say to Guadalcanal, sailors dying to transfer goods across the Pacific, soldiers desperate for food and ammunition, why would you risk shipping a unserviceable engine?
3. How much would German manufacturers have given, to have the luxury of a tear down, to discover all the bits of rags shoved down fuel lines by slave labourers in their factories?

To bring this thread to a more scholarly tone I submit a cockpit photo of OEM Afghan Hind cockpit :

[ATTACH=CONFIG]243815[/ATTACH]

[ATTACH=CONFIG]243828[/ATTACH]

Then Shuttleworth Afghan Hind, with remnant Farsi script on the camera exposure counter mount :

[ATTACH=CONFIG]243816[/ATTACH]

[ATTACH=CONFIG]243817[/ATTACH]

Very little seems to be known about RAAF Hinds in service, that is Royal Afghanistan Air Force Hinds. Recent politics have pushed many Afghan Hazaras out into the world, and the stories of historical persecution of this significant minority percolates out into wider appreciation. Much of the current topography of Afghani politics aligns along these historical rivers. I understand that much of the Sunni-Pashtun-Taliban-Pakistan thing is one bank of this river and the other is occupied by Shiite Hazara and Tajiks and odds and sods. I also understand that the Kingdom of Afghanistan and its military up to the late 70’s was a Pashtun construct and the Hazaras got the rough end of the stick during this time. So I wonder if the RAAF was a Pashtun construct and most of the work of the Afghan Hinds in the 50’s and 60’s was in strafing Hazaras and Tajiks. The good news for the Hazaras is that the Gilman bearings in the Rolls Royce Kestrel conrod big ends were unobtainable and so the bazaar smiths of Kabaul resorted to machining out the worn copper lead bearing lining and replacing it with white metal, giving 40 hours of engine life instead of the original 480 hours. So the RAAF Hinds, let alone the Hazaras, were probably preserved by unserviceability.

Another thought is on the fact that Hart biplanes never had dust filters on the intakes. You would think that dust and herdsmen riding horses and playing polo with goat carcasses around the aerodrome would result in all sorts of matter being sucked into the carburettors. Interestingly a 1942 report from the Australian RAAF on Hawker Australian Demons and other types subject to dust on rough and ready made airfields indicated that this was not a problem with RR Kestrels, more so with American radials and later engine types. It may have been a form of serendipity that airflow over the cowling of the Hart type biplanes pushed dust laden air aside or it may have simply been that partial supercharging and a cruder, lower compression engine made allowances for conditions that would disable higher performance aircraft.

Some evidence shows that Indian Hart biplanes were supplied to Afghanistan, and no doubt spares, while they lasted. I wonder if in this mix Indian trained ‘mercenary’ pilots were engaged to operate or train the Afghan RAAF?

I CAMM to the conclusion that BIPLANE broken old records on a topic for which my HARTBEES some folk just want to be CURSE-TROLLS. (4)