Packard built vs RR built Merlin engine differences?

[P-38 fan]

Just curious about what differences there are between the Packard built Merlins and the RR Merlins. Just an engineer's curiosity (as there's minimal chance I'd ever be able to afford anything with this powerplant). One thing that has always got my curiosity was the choice of bolts/nuts/fasteners. Obviously we in the US use SAE type bolts/threads, but it's my impression that the British had their own bolt specs (the bolt type name escapes me at the moment). I was wondering if Packard converted their tooling to use the same fastener configuration as the British, or if Packard engines used SAE bolts in their construction.

I've searched around on the web for information, but have struck out so far.

Thanks for any info.
Mike

[VikingsBoss]

The Hangar 11 Team in the UK have just back-engined their Spitfire PR XI (PL965) from a Packard Merlin 266 to a RR Merlin 70 as originally fitted. A recent magazine article mentions the main differences being in the engine ancilliaries. Packard apparently made several mods to the engine to ease the manufacturing process and produce greater reliability. An example given is that Packard simplified the blower assembly, removing the separate 'kettle' tank which housed the intercooler coolant resevoir and made it integral with the intercooler matrix housing. All this had to be reverse engineered when retro fitting the Merlin 70.

Regret they didn't mention the bolts!

[Red Tail]

Just curious about what differences there are between the Packard built Merlins and the RR Merlins. Just an engineer's curiosity (as there's minimal chance I'd ever be able to afford anything with this powerplant). One thing that has always got my curiosity was the choice of bolts/nuts/fasteners. Obviously we in the US use SAE type bolts/threads, but it's my impression that the British had their own bolt specs (the bolt type name escapes me at the moment). I was wondering if Packard converted their tooling to use the same fastener configuration as the British, or if Packard engines used SAE bolts in their construction.

I've searched around on the web for information, but have struck out so far.

Thanks for any info.
Mike

The Packard build units used BS just like the RR units.

John
CC Red Tail

[agent86]

Just curious about what differences there are between the Packard built Merlins and the RR Merlins. Just an engineer's curiosity (as there's minimal chance I'd ever be able to afford anything with this powerplant). One thing that has always got my curiosity was the choice of bolts/nuts/fasteners. Obviously we in the US use SAE type bolts/threads, but it's my impression that the British had their own bolt specs (the bolt type name escapes me at the moment). I was wondering if Packard converted their tooling to use the same fastener configuration as the British, or if Packard engines used SAE bolts in their construction.

I've searched around on the web for information, but have struck out so far.

Thanks for any info.
Mike

The Packard build units used BS just like the RR units.

John
CC Red Tail

The brit fasteners are known as "Whitworth,Wentworth? used to have a full set of wrenches,Taps and Dies for repairing old Brit cars.

[agent86]

I'm thinking the quality of the US metalurgy might have been better. its easier to smelt high quality metals when you dont have bombs dropping through your foundry roof and dont have to rely on ship loads of raw material.

[51fixer]

Just curious about what differences there are between the Packard built Merlins and the RR Merlins. Just an engineer's curiosity (as there's minimal chance I'd ever be able to afford anything with this powerplant). One thing that has always got my curiosity was the choice of bolts/nuts/fasteners. Obviously we in the US use SAE type bolts/threads, but it's my impression that the British had their own bolt specs (the bolt type name escapes me at the moment). I was wondering if Packard converted their tooling to use the same fastener configuration as the British, or if Packard engines used SAE bolts in their construction.

I've searched around on the web for information, but have struck out so far.

Thanks for any info.
Mike

Its a loaded question.
RR design evolved over time so even within RR produced examples there are many changes.
The Brits use a different spline on their prop hubs so a US Prop uses SAE 50 or 60 Spline design. So US and RR engines have different Prop Shafts.
Early Merlins used a Float Type Carb, Americans used a Bendix Pressure carb, Later RR used a version of a Pressure Carb but called it Fuel Injection. So on an American Packard you had an adapter for a US Fuel pump.
The front of the nose under the prop shaft had a V drive. On american versions on the left side was the prop gov, american made, and on the right was a vacuum pump for the instruments and to pressurize fuel tanks. The Brits had Vacuum pumps that were a copy pretty much of the American pumps. Unsure if the base is any different or the drive interface. I really don't know what Prop Gov was used on the RR engines. Much later RR engines had a different gov setup.
About the only thing with SAE threads on Packard engines is the Cuno oil filter on the R/H side by the oil regulator and on a couple of the adapters to American accessories.
Packard engineered some improvements, RR used some.
I believe US paid RR $5k an engine in royalty costs. With the P-82 that is why they went with GM after the war ended. At least one reason.

[51fixer]

Just curious about what differences there are between the Packard built Merlins and the RR Merlins. Just an engineer's curiosity (as there's minimal chance I'd ever be able to afford anything with this powerplant). One thing that has always got my curiosity was the choice of bolts/nuts/fasteners. Obviously we in the US use SAE type bolts/threads, but it's my impression that the British had their own bolt specs (the bolt type name escapes me at the moment). I was wondering if Packard converted their tooling to use the same fastener configuration as the British, or if Packard engines used SAE bolts in their construction.

I've searched around on the web for information, but have struck out so far.

Thanks for any info.
Mike

The Packard build units used BS just like the RR units.

John
CC Red Tail

The brit fasteners are known as "Whitworth,Wentworth? used to have a full set of wrenches,Taps and Dies for repairing old Brit cars.

Actually there are several types of British fastener types. I have wrenches with BA, BS and Wentworth. There is also British Pipe Threads so there is more than just Wentworth.
I forget all the in and outs but BS is British Standard. Wentworth is Wentworth. And BA is just out of reach at the moment.
Differences have to do with thread angle and pitch, ect.
A 2 BA is a 10-32 but with a different angle on the threads.
I remember Frank Sanders using a 10-32 tap on the nutplates for the wing fairings on their 2 seat Seafury way back when so he would install American Screws.

[Mudge]

WOW...Keep it up troops. This is why WIX is what it is.

Mudge the educable

[Richard W.]

I read in one of the Ian Allen "Lancaster At War" volumes that each Packard Merlin was crated at the factory with it's own set of very nice tools for servicing the engine.

One of the British aircraft mechanics wrote that they were often short on good tools, so there was a heated competition to be the first one to get to the US tool sets to claim them.

[agent86]

My experience with crazy Brit fastners is limited to Whitworth. They have their own Thread pitch,angle and the bolt heads are close,not quite close enough to substitute SAE wrenches.some will ,most wont. Had a Set as I said of ancient wrences taps and dies. used to charge other shops to borrow the set,so they could restore or repair old Brit cars.someone finally stole it from me

Last edited by agent86 on Sat Jun 18, 2011 3:32 am, edited 2 times in total.

[Red Tail]

This page is full of handy reference material I refer to often. http://www.britishfasteners.com/threads/index.html

John

[Sopwith]

My experience with crazy Brit fastners is limited to Wentworth. They have their own Thread pitch,angle and the bolt heads are close,not quite close enough to substitute SAE wrenches.some will ,most wont. Had a Set as I said of ancient wrences taps and dies. used to charge other shops to borrow the set,so they could restore or repair old Brit cars.someone finally stole it from me

Actually it is not Wentworth it is Whitworth,incidently they were the first to standardise thread size, allowing for interchangeable nuts and bolts,prior to this all threads were nonstandard,so Whitworth opened the door to mass production worldwide.

[old iron]

I will bet that the RR-powered units had better hood ornaments.

[P-38 fan]

I will bet that the RR-powered units had better hood ornaments.

Well, that goes without saying.

[The Inspector]

Agent 86,

if British fasteners drive you nuts, by all means donot decide to restore an International Harvester of any kind, whether a 'tater torquer or pickup as they had their own, unique bolt sizes and thread pitches too, it kept the farmers coming back into the dealership instead of going to 'FREDS HARDWARE' and generated repeat business, but now that binder is long gone, you'd have to go to a specialty bolt and screw store to get direct replacements.

And try working on a MERLIN sitting in a cradle on a finger pier @ a lakeside race site like Detroit or Guntersville and your boat is in the next heat.

P.S. don't take on a VINCENT BLACK SHADOW motorcycle either