Supermarine Spiteful Merlin?

[BarnOwlLover2]

Hi. I got the itch to look back into World War II era aircraft again. I do have a question or two about the Supermarine Spiteful. I did look for a thread where I might have asked about this topic. However, the probable best fit is nearly a decade old, and I don't know if necroposting is frowned upon or not.

Anyways, my question is that on the Old Machine Press website that the Spiteful was designed to use some version of the Rolls-Royce Merlin two stage supercharged engine. This was apparently in case there was difficulties or production shortfalls for the originally intended Griffon 60 series and later engines. Of course, all Spitefuls were Griffon 60/80/100 series powered, so there was no Merlin version built.

My questions are, what versions of the Merlin would've been looked at if it's true that the Merlin was seen as a possible alternative? And if so, what would the advantages/disadvantages of such a fitting be?

 

[Foo Fighter]

IMHO, the 133 or 134 type Merlin. Similar power rating.

 

[steelpillow]

The last production version of the Merlin was the 13x series which came in the four different combinations of left-and right-handed and high- and low-altitude versions for the DH Hornet. So this or a derivative of it, which was no doubt on the drawing board, would have been in mind.

Its principal advantage would have been that it worked, since the assumption is that the Griffon variant had not and would not.

The Merlin's upper profile is higher, so maintaining the pilot's view over the nose would have meant either mounting it lower so the nose bulged down underneath, or raising the cockpit unnecessarily high for the Griffon. Its thrust line is also higher, affecting the pitch trim change with power, and stalling characteristics among other things. This would have been reduced if the Merlin were lowered, otherwise pilots would have just got used to it; the difference was not a major issue with the Spitfire's handling. The final solution would have affected the mximum diameter of the propeller to maintain ground clearance, an issue which on the Spit led to the Griffons' growing an extra blade to make up for their smaller diameter.

The Merlin also had a higher specific power output in terms of bang per pound weight than the Griffon and consequently was not as heavy, so it would have needed balancing in pitch. If that was done by moving it forwards a little, then this would make the nose longer and the tail fin would also need to be larger, i.e. oversize for the Griffon. Alternatively, the Spitfire made significant use of counterweights in the tail to accommodate all its various engines; but since the Spit was designed for the Merlin and later adapted to the Griffon, while the Spiteful was the other way round, the ingots would go in the nose with the Merlin.

Then of course there are simple physical things like provision for fitting a different mounting frame, for any extra service lines through the firewall and space allowances for varying ancillary items.

But all that would not have been worked out in detail, it would just have been in the back of the designer's mind, to try and not rule out the Merlin conversion altogether.

 

[kitnut617]

You could add the Merlin 140 to the list, this was a contra-prop engine of 2,080hp and two of them powered the Short Sturgeon.

 

[royabulgaf]

The Spiteful/Seafang already raised the cockpit a few inches compared to the Spit, so that was no issue.

 

[BarnOwlLover2]

Also found this on another forum, talks about the Merlin 100 engines at the end. All Merlin 100s are similar to the Merlin 130s aside from using updraft carb/supercharger intakes.

http://www.wwiiaircraftperformance.org/Aircraft_Engines_of_the_World_Rolls-Royce_Merlin.pdf

 

[steelpillow]

You could add the Merlin 140 to the list, this was a contra-prop engine of 2,080hp and two of them powered the Short Sturgeon.

According to Wikipedia the contra-prop was adopted for much the same reason as the Griffon, to reduce overall diameter. It had been tried on a regular Spit and found to offer no thrust advantage over the lighter-weight single prop.
The other reason was torque cancellation, as these high-power engines were becoming a right handful (or is that left? ). Presumably the Sturgeon followed the Hornet in having opposite-handed 140s?
And where does the 140 fit in the Merlin family? That Wikipedia article does not mention it.

 

[Hood]

And where does the 140 fit in the Merlin family? That Wikipedia article does not mention it.

Alec Lumsden's entry from British Piston Engines:
Merlin 140, 1,725hp. This was a special, two-speed, two-stage Merlin, designed for the Short Sturgeon. It featured a shunt-flow and a Coffman starter. It had a L.H/R.H. counter-rotating propeller drive with a reduction gear ratio of .512:1. Rating RM.14SM. 57 built at Derby 1947-1948
Aircraft: Short S.A.1 Sturgeon I

So presumably sits within the Merlin 100/102/130/150 (later 620)/300 family.