G’Day Dan,

This Wot is the mock up of the Commonwealth Aircraft Corporation (CAC) AA107 swing-wing supersonic jet trainer/light attack aircraft. Location is the Ballarat Air Museum.
Unfortunately, this Wot doesn’t quite fit the remit of Post #1

Only manned aircraft that have actually flown allowed, so no missiles/drones and no obscure unbuilt projects or flights of fancy.

, as it never proceeded beyond design/mock up stage, having being cancelled by the Australian Government on 22nd May 1970.

Some of my experiences over the years:

Spitfires have had some of the worst workmanship I have ever seen – “wavy” freehand drilled rivet lines on fuselages comes to mind straight off.

Jig drilling from the Curtiss factory – I have seen a Curtiss Tomahawk rudder parts match drilled almost perfectly with corresponding P-40N parts – probably close to 10,000 aircraft between them.

Most Japanese aircraft I have seen were beautifully made – especially the early stuff – built like gliders – very light and easy to mess up. I saw real pride in workmanship.

Ed, you need to get yourself a copy of Dan Whitney’s excellent book “Vee’s for Victory – The Story of the Allison V-1710 Aircraft Engine 1929-1948” ISBN 0-7643-0561-1. Every aviation petrol head should have a copy. 🙂

Paraphrasing from Dan’s book, the story is something like this:

Allison was contracted by the US military in the early 1920s to rebuild and test a high powered Liberty 12, with the goal of producing 570 bhp from what is normally a 425 bhp rated engine. Norm Gilman rebuilt the engine and ran it for 31 hours before the conrods failed, due to bearing failure. The problem was the original bronze bearing shells distorted under the heavy loads and temperature changes. Norm figured if he used a steel shell with a thin layer of bearing material on the bearing surface, it would be much stronger and stable. The next problem was getting the bronze or copper bearing material to stick to the steel shell. This was done by heating the steel shell to red hot, pouring the bearing material around it and then quickly quenching it to achieve the desired bonding and grain structure. Excess bearing material was then machined away. The secret was in the quenching process.
Allison rebuilt Liberty engines gained a reputation for greatly improved reliability, operating up to ten times longer between overhauls, mainly through the addition of the Gilman bearings.
Rolls Royce purchased a license for the copper lead steel bearing shells from Allison in the late 20s and had to pay a royalty for every bearing manufactured.
In 1935, Allison developed the silver lined bearing shells, initially casting them like the bronze/copper lead shells, before successfully being able to electroplate the silver onto the steel shell. The silver bearings were further improved by “flashing” a final layer of lead/indium onto the silver. The beauty of the electroplate process was that interchangeable bearing shells could be produced, eliminating the costly need to line bore them in the crankcases.
In my experience, it appears, however, Rolls Royce chose to stick with the copper/lead bearing shells in their Merlins, whereas the Packard produced Merlins went with the later silver shells.
Unfortunately, the silver content in the bearing shells caused a large number of Allison V-1710’s to “bite the dust” in the 70s when, I am lead to believe, the market price of silver was manipulated for nefarious reasons.

At the risk of drifting off the thread topic….

I am trying to figure out the logic of cast in copper (gunmetal?) bearings, replaced with removable bearing shells in RR Merlin.

The steel back bearing shells were invented by Norman Gilman and patented by the Allison Engineering Company (later bought out by General Motors) in the early twenties. After trying to come up with a number of solutions to bearing problems in their engines, Rolls Royce ended up obtaining a license from Allison for the steel backed bearing shell technology and paid a royalty on every engine for it (along with just about every other major engine manufacturer…:))

It’s a terrible shame that none have survived. 🙁

I would be looking into the materials used in the Canadian built Hurricanes and Bolingbrokes. I have been lead to believe there is a materials substitution list for British to American specs in existence for the Canadian Hurricane and Bolingbroke production. 🙂

Excellent news! Good to see recognition of his efforts. 🙂