Pratt & Whitney and Briggs & Stratton…..Briggs & Stratton on the left! 😉

…did you mean MY piston…

Good morning. Yes, I was wondering.

I’ve had a rummage around in my garage and have found two other American radial pistons that I can’t positively identify. Both are something like 5.75 inches in diameter and are of broadly similar design but with significant differences. I’ll post some photographs later.

Here is one of the unknown radial pistons. It has a diameter of 5.735 inches (5.75 nominal) and has an unusual domed crown; the domed part only about two-thirds of the diameter of the piston and rising out of an otherwise flat top.

Poland had wanted independent status for its Air Force as it did not want to see its personnel distributed throughout the RAF. Its intention was that the PAF would return home able to defend the Polish government. When it came to negotiating with the British it was is size and money that counted not any legal complications over International recognition…

Thank you for taking the trouble to post such a long and interesting reply. It seems many of my preconceptions about Polish squadrons in the RAF (or rather under RAF operational control I should say) were totally wrong.

The West never recognised the DDR but that never stopped it having an Army, Navy and Air Force.

Yes, but then the DDR had East Germany to operate those forces from; it may not have been recognised by the West but its possession was undisputed. The situation with the Polish government in exile, and its forces, was different after the war, that is after the new British government recognised communist Poland.

Therein lies the problem; one country, two governments…..and Britain recognised the government in possession of the country (and the one with the backing of the Soviets).

Before the Soviet Union and the USA entered the war, Polish Armed Forces constituted about 20 to 25 per cent of the forces available to Britain.

Surely there must be some caveat that applies to this statement. I know Britain experienced some dark times during the war but I’m sure that at no time did Polish forces account for 20% – 25% of the total ‘available to Britain’. Even in terms of air forces alone I’m sure Polish forces didn’t account for 20% – 25% of the RAF.

…your R1830, which is exactly the same as mine…

Can you do a quick measurement of the diameter of your piston?

I will have to get round to digging out all my American radial pistons and properly identify them! 😀

I bought Leo McKinstry’s ‘Spitfire’ paperback in a remaindered bookshop to read on a camping holiday (usually a one-way trip for any book) and I was pleasantly surprised by the detail that it went into. I’m no Spitfire expert so I’d welcome a review from some knowledgeable person who has read it.

…a photo of the inside of the flat top piston please.

I think the flat topped one is an R-1830 piston so it should be the same as the inside as the R-1830 photograph that I posted (which is also flat topped but I’ll admit it doesn’t look it because of the way I took the photograph).

There are some differences with my R-1830 piston such as the ring-groove spacing and the bottom of the skirt being slightly longer on the thrust faces (mine is flat all round). I think I’m right in saying that not all the pistons in a single R-1830 are the same; the pistons on the master rods are different…..maybe?

An R-1830 piston is one of the smaller ‘big’ (:confused:)American radial piston engines with a nominal bore of 5.5 inches (measured my piston at 5.4770 inches) but of course there are 14 cylinders to the 9 cylinders of the R-1820.

I’m sure you know this but the ‘1830’ refers to the engines capacity in cubic-inches and the ‘R’ for radial; this being a common naming system for all American aero-engines of the period.