Warbird Information Exchange

Hello group. First timer newbie here. Warbirds are not normally my area, more into the civil biplane stuff. But I do find the study of large recip engines fascinating and the pinnacle of precision and complexity in large recips are Aero engines Thus I pose a question which I haven't been too successful at resolving. I have searched past posts but have seen nothing.

Regarding the Rolls Merlin engine. When installed in Hurricanes, Spits and Lancs, etc. These used Dowty Rotol propellers no? As such, did the UK built (even those by Ford Motor Company of UK) Merlins have a crankshaft spline other than SAE? Did the British employ crankshaft splines of their own design?
I believe the Packard Merlins had SAE #50 (as the Ham Standard prop is an XXD50 indicating an SAE #50 hub). Is this an alteration the US made to their liscense from RR?
This poses a real interesting logistics problem....

The "crankshaft" itself did not have the propellor driving spline. The prop shaft had that spline and they were either the #50 US type of spline or the #51 Rotol spline. To change types of props, change reduction gear and prop shaft sets.

Hello & Welcome Wheels up

Packard produced a licensed adapted version for both the American & British Govs and adapted it for mass production.

I've found this website a great resource for engine research:
http://www.enginehistory.org/index.php

i'm sure one of the engine builders here will give you am answer soon

edit: someone has

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Vintage Warbird & German WWII galleries @ http://zeeat.spaces.live.com/

The propeller spline is on the out put shaft that is geared to the crankshaft. It is similar to what most all large radial engines have, a gear reduction to reduce the rotational speed of the propeller as compaired to the engine crankshaft speed. If those old props turn too fast meaning over supersonic speed they would loose their effciency. So basicly there is a "transmission of sorts" on the nose of the engine.

In what manner does it pose a logistics problem? Could you explain what you mean?

Ooops there folks...a bit of a brain fart! I meant the PSRU shaft not crank.
Well, if indeed there are Uk engines with a UK spline and US engines with a US spline there is no QEC between RAF and USAAC units. True? Not that that scenario would ever arise but in wartime conditions anything is possible.

I think the answer to your question is very simple. Packard built engines under license from Rolls for the US airplanes while Rolls built engine's for the British airplanes. Not only were the prop shafts differant, but there were also other items such as connections and linkages that were differant as well.

Sparrow

It just seems a tad odd that there could be a UK squadron and a US group 5 miles apart utilizing essentially the same engine yet they would be wise not to share parts. Not much different from ammunition or other minor bits. But when one looks at the various other lend lease ships (C47's and other "heavies") you could perform virtual QEC's regardless of operator. Not exactly apples to apples, as these other ships were suppied as complete aircraft, but it is a bit of an odd example. It shows that when the US liscensed that engine there was no intention of supplying cores or engines....it would appear to be, shall we say..purpose built. The UK had a lack of confidence in the US ability to successfully produce this item and they likely weren't interested initially in "polluting" their stocks with the "inferior" US examples.

i wouldn't say that was the case Wheels up. Packard version rolled out their first Merlins in 1942 (IIRC).. by then the RR Merlins had already proven themselves in the B0B 1940... which is also when Packard first reached an agreement to produce the engines. It was decided that the engine would have to be adapted for mass production and would be supplied to both the British & American Gov. The Packard built Merlin was finally used in the British aircrafts (spits/hurri/lancs) in the final 3 years of the war so by then the USAF and the RAF were using the same engine in all new planes.

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Vintage Warbird & German WWII galleries @ http://zeeat.spaces.live.com/

Ahh! Then the US did build UK spec'd engines?
So Packard would have built both types of prop interfaces (the British never used Ham Std in their Merlin applications did they?), superchargers, etc?
Not likely the UK was building US spec'd engine tho'. Not much point in that.
If this is true, it would appear that Packard's challenge to tool up and ramp up production of an engine, with which they had no experience (they were out of the aero engine business for a few years by that time), and produce it in both US (SAE, standard pipe threads, etc) and UK (BSPT, Rotol spline, ignition products,etc) versions, was indeed monumental. And to accomplish production status in a matter of, what, 18 months? Remarkable!
While the Packard folks were not exactly dim witted (they were quite capable), still RR must have been very cooperative handing over documentation. A testament to both builders wanting to excell.

IIRC, a universal spline was developed for UK engines at some point during the war.

Early Spitfires and Hurricanes used de Havilland props which were built under license from Hamilton Standard. No idea what spline they had
though.

Did the Packard Merlin use US pipe threads? I know the rest of the engine was built using UK threads and I think I read a few years ago that Packard made their own taps and dies owing to a shortage of production capacity elsewhere in the US.

What ammunition did the US and UK share? US used .30-06 and the UK used .303 for rifle/machine gun ammunition for instance.

Sort of. Certain versions of Hurricanes, Spitfires and Lancasters had the Packard built engines which were different dash numbers from the P-51 engines (no intercooler for one) but still utilized the US splines, magnetos, etc. The Spitfire Mk.XVI was similar to the Mk.IX except for its Packard Merlin engine.

http://www.fantasyofflight.com/aircraftpages/spitfire.htm

Also:

BDK, the Spitfires that used the Packard, ie XVI, did have an intercooler I am pretty sure, just like the 2 stage Rolls in the IX, etc. If you look at the prop shaft you can tell which engine it is. Rolls has a lot of narrower splines, perhaps 20, and the Packard fewer thicker ones, perhapsa dozen. When Packard produced the Merlin, of course they change a few things and had some problems. Eventually the busg began to be worked out and by the end of the war the Packard version was a good engine as it certainly was in the Mustang, RCAF Lancs, etc. I have flown both, sort of glad I have a Rolls, but if I didn't know I might not notice any difference.

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Bill Greenwood
Spitfire N308WK

Britain started using the .5 Browning in Spitfires et al later in the war, but yes, generally RAF was .303 - later 20mm cannon as well. In the Pacific, US and British ammunition disparity caused problems for the Commonwealth air forces etc.

As to the prop-hub spline, I'm not qualified. The CanCar Canadian Hurricanes were fitted with Hamilton Standard props, after IIRC the first few had DH type. Early Merlins were upgraded, including adding the oil pitch change mechanism, IIRC.

As Wheels-up said, the licence / liscense production of the Merlin was an amazing achievement by Packard and RR, both, and was, in a very real sense, a war-winner.

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James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com

I suppose that my staement could be read that way but it was not meant to be....more like it would be unwise to share ammunition between RAF and USAAC units. Obviously, in rifle caliber we loved the 1/2incher whislt the Britsh pretty much stood fast with the .303....but they also were fond of cannons (20MM) where we simply put on more fifties!!



So to recapitulate.... IF Packard Merlins were used in RAF ships they were essentially building US and UK application powerplants thus the following statement is untrue?


This is obviously a complicated and obscure subject! Either way, one can see the logistics issue this all provides when under wartime conditions. Forget about gasloline, oil, tires, bullets and bombs, and even pilots for that matter......take care of those guys and gals in procurement! To get the right part( and that goes for complete assemblies as engines and props) to the right place at the right time...remarkable they flew at all! After reading this thread one would have to imagine the parts books stacked to the ceiling at some dank base, while the requisition officer hovers over the manual and hopes he writes down the correct number!