Merlin 266 Trial Data?

[Shortways]

I am researching the Merlin 266 in combination with the Spitfire Mk.XVI. When checking the internet or books, the only mention ever made is that it is sort of a carbon copy of the Merlin 66, but built by Packard and with the same performance.

It does however have a few differences:
1. Reduction Ratio of 0.479 (in stead of the 66's 0.477)
2. Supercharger Gear Change altitudes MS > FS @ 11,000ft & FS > MS @ 10,000ft (in stead of 66 : 14,000ft & 12,500ft)

I would like to know the reasons of this and am also wondering if there are any performance trial data around, like graphs or tables?

Thanks

 

[Simon Thomas]

There is a bit of info in this thread that gives a hint or two, but no answers.

Were surviving early Merlins rebuilt and upgraded?

I had never noticed this before, from 'The Merlin in Perspective" RRHT: It's worth reading re this topic, as it includes the whole of life partnership RR had to keep the Merlin operational, such as defect investigation, modifications, repairs etc.

ww2aircraft.net

 

[Engineman]

Hi,
The RRHT book "The Merlin in Perspective" gives a fair amount of information on the R-R / Packard Merlins. Originally, the possible USA production deals went through stages of options but the Packard arrangement bore the first fruit of US Merlin production. The general aim was to produce virtually identical production but, the particular needs of Packard production and pragmatic solution of design / production problems saw differences in some parts. Rolls-Royce and Packard worked to identify the parts of each Merlin that were interchangeable and they amounted to most of the engines components. The interchangeable parts were listed in spare parts guides. Differences in updates to engines also saw different standard engines produced.
For the Merlin 266, which was produced for the Spit XVI, it is generally known that the 2-Stage, 2-Speed supercharger drive used by Packard on their production was the epicyclic type, the prop reduction gear was .479 which would use a different gearset to the UK .477, the prop splines would be a UK spec and the Magneto's might have been UK type.
The difference in supercharger gear ratio's may have been different, possibly to suit Packard production, or even by UK request. Who knows? You would need to find the original specification documents to find out more.

Cheers

Eng

 

[Bretoal2]

Merlin engines built in England throughout their production run retained the two-speed supercharger drive originally developed for the Kestrel, which was based on Farman patents. The design employed two sets of "standard" gears: a single one for the first speed and a double (paired) set for the second.

As previously mentioned, Packard rejected this system for industrial reasons and introduced its own design based on epicyclic gearing.

Inevitably, this meant that the exact same gear ratios could not be replicated. A difference that was reflected in the engines' critical altitudes.

 

[Shortways]

There is a bit of info in this thread that gives a hint or two, but no answers.

Were surviving early Merlins rebuilt and upgraded?

I had never noticed this before, from 'The Merlin in Perspective" RRHT: It's worth reading re this topic, as it includes the whole of life partnership RR had to keep the Merlin operational, such as defect investigation, modifications, repairs etc.

ww2aircraft.net

Hi Thomas, Thanks very much. Yes this was the only topic I could find as well. I didn't want to append my question to it and hi-jack the subject. Cheers

 

[Shortways]

Hi,
The RRHT book "The Merlin in Perspective" gives a fair amount of information on the R-R / Packard Merlins. Originally, the possible USA production deals went through stages of options but the Packard arrangement bore the first fruit of US Merlin production. The general aim was to produce virtually identical production but, the particular needs of Packard production and pragmatic solution of design / production problems saw differences in some parts. Rolls-Royce and Packard worked to identify the parts of each Merlin that were interchangeable and they amounted to most of the engines components. The interchangeable parts were listed in spare parts guides. Differences in updates to engines also saw different standard engines produced.
For the Merlin 266, which was produced for the Spit XVI, it is generally known that the 2-Stage, 2-Speed supercharger drive used by Packard on their production was the epicyclic type, the prop reduction gear was .479 which would use a different gearset to the UK .477, the prop splines would be a UK spec and the Magneto's might have been UK type.
The difference in supercharger gear ratio's may have been different, possibly to suit Packard production, or even by UK request. Who knows? You would need to find the original specification documents to find out more.

Cheers

Eng

Hi Eng, Wow that's a lot of useful information. I think I'll buy the book indeed. Although I still need to finish "The Horse Power Race" . Thanks a lot for this very thorough reply. Greets Edwin

 

[Shortways]

Merlin engines built in England throughout their production run retained the two-speed supercharger drive originally developed for the Kestrel, which was based on Farman patents. The design employed two sets of "standard" gears: a single one for the first speed and a double (paired) set for the second.

As previously mentioned, Packard rejected this system for industrial reasons and introduced its own design based on epicyclic gearing.

Inevitably, this meant that the exact same gear ratios could not be replicated. A difference that was reflected in the engines' critical altitudes.

Aaand … you stuck it in the goal! Farman gears vs Packard Epicyclic. That gave me some good search criteria. Very nice. Thanks very much.

 

[Engineman]

Inevitably, this meant that the exact same gear ratios could not be replicated. A difference that was reflected in the engines' critical altitudes.

Is it true that the Packard double-layshaft 2-Speed supercharger drive really was impossible to construct with Merlin 66 ratios or, was it more of an easy fix with a gearset that Packard were already producing or, actually a requested specification by the British?

Eng

 

[Shortways]

Is it true that the Packard double-layshaft 2-Speed supercharger drive really was impossible to construct with Merlin 66 ratios or, was it more of an easy fix with a gearset that Packard were already producing or, actually a requested specification by the British?

Eng

Yes the second "good enough" option seems very likely doesn't it?

Edit:
I found the following and noticed the V-1650 have a .479 ratio as well. So I guess "convenience" seems more than likely.

Packard V-S Drive