Build the perfect water cooled engine

[wuzak]

The outer diameter of the annular radiator of the Jumo 213 DB 603 was substantially smaller than the outer diameter of the cowling of the BMW 801. The cowling of the 801 was designed as a tight fit anyway, installation employing fan to cover the cooling issues because of such a fit IIRC.

They still had to fit up to the same firewall as the BMW 801 QEC.

 

[wuzak]

I received a reply from the RRHT about the Vulture. The main question about was the overall dimensions of the Vulture, which are:

Length overall - 87.625in/2226mm.
Width overall - 35.8in/909mm.
Height overall - 42.175in/1071mm.
Weight - 2450lb/1111kg

5-6in/127-152mm wider than a Merlin and about 2in/51mm taller.

I also enquired as to the veracity of statements I had seen that the Vulture had reached 3000hp on test before its cancellation. The reply was:

I have not been able to find anything to substantiate that the Vultureattained 3000hp on occasions but the Vulture V is known to have reached 2500hp, and it is possible that, under the right conditions of test, 3000hpwas achieved.

If 2500hp was achieved in late 1941/early 1942 before it was cancelled, then it would still have been around 1000hp more than the Merlin at the time, and on par with the Sabre at that time.

 

[tomo pauk]

They still had to fit up to the same firewall as the BMW 801 QEC.

Actually, the hull-end of the engine bearer had to fit to the hull attachment points.
The reduction of the firewall dimensions would've dictated a substantial hull redesign, probably with reduction of ammo capacity - not worth of it.

If 2500hp was achieved in late 1941/early 1942 before it was cancelled, then it would still have been around 1000hp more than the Merlin at the time, and on par with the Sabre at that time.

Even better than Sabre

 

[wuzak]

Even better than Sabre

More compact (width x height) too, albeit longer.

 

[Tartle]

The snuggest nacelle around a Merlin is the de Havilland Hornet design... details here.
There is also a sideview of the Peregrine... 4 blocks of which formed the first Vulture.

 

[johnbr]

According to the designer the rez in it was dumped was it cost more to make so it got the axe from RLM.

 

[Shortround6]

If 2500hp was achieved in late 1941/early 1942 before it was cancelled, then it would still have been around 1000hp more than the Merlin at the time, and on par with the Sabre at that time.

It rather depends on the test. The Merlin had done about 1800hp in 1938? for the "speed Spitfire". A large number of engines have hit some rather high power levels for a few minutes at a time but passing a type test at those power levels or even a test to "OK" an "emergency" rating can be rather different. For example while the US limited WEP to 5 minutes in service the test engine had to survive 7 1/2 hours at that power level, 5 minutes at a time.

Please remember that the Vulture HAD passed a type test at 1845hp 3000rpm at 5,000ft and 1800hp for take-off at 3200rpm and we know how that turned out in service. Maybe the MK V would have been OK but just because an engine hits a power level on a test stand does not mean that engine can go into service at that rating. The P&W R-1340 (AT-6 engine) had hit over 900hp back in the early thirties for a few moments (and survived) but P&W never rated the engine at more than 600hp.

 

[Shortround6]

The snuggest nacelle around a Merlin is the de Havilland Hornet design... details here.
There is also a sideview of the Peregrine... 4 blocks of which formed the first Vulture.

There is some dispute about that. Some sources claim that the Vulture used more spacing between the cylinders to allow for using Merlin sized pistons at a later dated. "IF" this is true the Vulture blocks would have to a minimum of 2 in longer from the center of the first cylinder to the center of the last cylinder. assuming equal cylinder wall thickness and no increase in depth of the water jacket/passages between cylinders.

 

[wuzak]

The snuggest nacelle around a Merlin is the de Havilland Hornet design... details here.
There is also a sideview of the Peregrine... 4 blocks of which formed the first Vulture.

There is some dispute about that. Some sources claim that the Vulture used more spacing between the cylinders to allow for using Merlin sized pistons at a later dated. "IF" this is true the Vulture blocks would have to a minimum of 2 in longer from the center of the first cylinder to the center of the last cylinder. assuming equal cylinder wall thickness and no increase in depth of the water jacket/passages between cylinders.

The Vulture had wider bore spacings than the Peregrine/Kestrel, but not the same as the Merlin's. I understand that Merlin bores could have been used, if so desired.

 

[wuzak]

It rather depends on the test. The Merlin had done about 1800hp in 1938? for the "speed Spitfire". A large number of engines have hit some rather high power levels for a few minutes at a time but passing a type test at those power levels or even a test to "OK" an "emergency" rating can be rather different. For example while the US limited WEP to 5 minutes in service the test engine had to survive 7 1/2 hours at that power level, 5 minutes at a time.

Please remember that the Vulture HAD passed a type test at 1845hp 3000rpm at 5,000ft and 1800hp for take-off at 3200rpm and we know how that turned out in service. Maybe the MK V would have been OK but just because an engine hits a power level on a test stand does not mean that engine can go into service at that rating. The P&W R-1340 (AT-6 engine) had hit over 900hp back in the early thirties for a few moments (and survived) but P&W never rated the engine at more than 600hp.

We also know that the Vulture was put into service before it was ready, and that it was detuned to pass the type test, and further detuned in service because of the myriad of reliability issues. However, most, if not all, of these were fixed at the time of the engine's cancellation, but not early enough for engines in service.

It is true that we do not know the circumstances of the engine(s) that reached 2500hp. We do know, however that the kW/l at 2500hp were about 7% better than the Merlin XX on 100 grade fuel, and about 5% less than the later 70 series engines.

 

[wuzak]

Bore spacings of some of RR's production piston engines

Vulture – 6.1in
Kestrel/Peregrine – 5.625in
Merlin – 6.075in
Griffon – 6.9in

Interesting that the Kestrel/Peregrine had a bore spacing 0.625in (15.875mm) wider than the bore, the Merlin 0.675in (17.145mm) and the Griffon 0.9in (22.86mm). I am guessing that is due to the extra thickness required in the wall lining of the larger bores.

Interesting that the bore spacing alone makes the Griffon 4.125in (104.775mm) longer, yet the two stage two speed Griffon 65 is some 7.7in (195.58mm) shorter overall than the two stage two speed Merlin 61. Amazing packaging effort.