Was the Hispano-Suiza 12Y the worst ≥25L V-12 of WW2?

[Shortround6]

Was it the supercharger or the supercharger drive or the fuel injection system?

You could use either Packard or RR engines as spare parts to overhaul each others basic engines. Difference were pretty much external (accessories like pumps)

 

[Simon Thomas]

I agree with TM06, the 12Y wasn't a truly bad engine. It did have some good qualities.

The valve actuating and adjustment is light, robust and simple. The supercharger discharge ducting cross sectional area appears to be quite a bit larger than its contemporaries. The head to block sealing is not an issue, being cast in one piece.

On the other hand, the two valve design might have been fine in 1932 but was inadequate within a few years. The yardstick for supercharger design in the mid 30's is the Merlin, and every other supercharger falls short. The 12Y falling particularly short.

I can't work out if the six carburettors after the supercharger was better or worse than one large carb before the supercharger. Maintenance on six carbs would have been tedious. The cooling effect of fuel evaporation might be argued either way, possibly the carbs after might give a nett overall increase in cooling? The six separate carbs would no doubt be heavier than one large carb.

description_12Y31

 

[Shortround6]

the 12Y wasn't a truly bad engine. It did have some good qualities.

It did but it had hit a dead end.
To make more power (around 1000hp depending on altitude) it needed two things.
1. a stronger bottom end, crankshaft and crankcase.
2. a better top end, more valves/increased air flow.

Fix both and you have a new engine, VK-107 or Saurer or Hispano 12Z.

 

[Admiral Beez]

You could use either Packard or RR engines as spare parts to overhaul each others basic engines.

That's handy. Not like my old Triumph motorcycle that used Whitworth threads and fasteners that were incompatible with North American specs and tools.

 

[MIflyer]

Some sources say that believe that the Soviet AM-30 V-12's were based on the Hisso 12Y but the Soviets said they were based on the BMW V1 and the VK series were based on the 12Y. The VK-105 was 2147 Cu In and produced 1100 HP, and that was better than the 1940 12Y 860 HP. The VK-107 was 2075 cu in and produced 1600 HP, but at 1655 lb weighed far more than the 12Y's 1000 lb.

 

[Shortround6]

Some sources say that believe that the Soviet AM-30 V-12's were based on the Hisso 12Y but the Soviets said they were based on the BMW V1 and the VK series were based on the 12Y. The VK-105 was 2147 Cu In and produced 1100 HP, and that was better than the 1940 12Y 860 HP. The VK-107 was 2075 cu in and produced 1600 HP, but at 1655 lb weighed far more than the 12Y's 1000 lb.

The VK-105 got 3 valve heads instead of two valve, had a beefed up bottom end and had the 2mm smaller bore.

"Based on" does not mean you can take a 12Y and turn it into a VK-105 with some spare parts. The M-100(VK-100) was pretty much a 12Y.

 

[bf109xxl]

Some sources say that believe that the Soviet AM-30 V-12's were based on the Hisso 12Y but the Soviets said they were based on the BMW V1

Mikulin's engines starting from the AM-34 can be considered as an independent design - there is almost nothing left from their progenitors (BMW VI).

 

[MIflyer]

Herschel Smith points out that if the AM-30 was based on that BMW then they took a welded block engine and turned it into a cast block engine, which is an even bigger design divergence than the 12Y and the VK.

Big question is: Which WWII V-12 engines WERE NOT ultimately based on the Curtiss D-12 Conqueror?

 

[bf109xxl]

Herschel Smith points out that if the AM-30 was based on that BMW then they took a welded block engine and turned it into a cast block engine, which is an even bigger design divergence than the 12Y and the VK.

There were no "AM-30" prior to AM-34. M-17 was a licensed copy of the BMW VI.

 

[Engineman]

Was it the supercharger or the supercharger drive or the fuel injection system?

You could use either Packard or RR engines as spare parts to overhaul each others basic engines. Difference were pretty much external (accessories like pumps)

The Japanese versions of the DB V-12 engines were really quite re-engineered in detail. The Fuel injection system is listed as not being a copy of the Bosch PZ12 type, but a locally designed and built type. This may have been a choice by the Japanese, as I cannot imagine Bosch refusing an RLM directive.

Rolls-Royce built Merlin, Packard built Merlin and V-1650 engines did have differences, sometimes quite major. The Magneto's and accessories were American specification but there were some major differences. The supercharger drive was a different type of mechanism completely, the Packard engines always had a Bendix Stromberg pressure carburettor (and very late with Simmonds FI) that was immune to negative-G, the early Packard Merlins had their own design of detachable heads (changing later to the RR type), propeller shafts had splines etc for American props and reduction gears could have slight ratio differences. Beyond that, the modification states of the Packard engines could lag the UK production.
That said, the majority of parts in the same build-state engines were identical and so, interchangable.

Eng

 

[wuzak]

The Japanese versions of the DB V-12 engines were really quite re-engineered in detail. The Fuel injection system is listed as not being a copy of the Bosch PZ12 type, but a locally designed and built type. This may have been a choice by the Japanese, as I cannot imagine Bosch refusing an RLM directive.

Rolls-Royce built Merlin, Packard built Merlin and V-1650 engines did have differences, sometimes quite major. The Magneto's and accessories were American specification but there were some major differences. The supercharger drive was a different type of mechanism completely, the Packard engines always had a Bendix Stromberg pressure carburettor (and very late with Simmonds FI) that was immune to negative-G, the early Packard Merlins had their own design of detachable heads (changing later to the RR type), propeller shafts had splines etc for American props and reduction gears could have slight ratio differences. Beyond that, the modification states of the Packard engines could lag the UK production.
That said, the majority of parts in the same build-state engines were identical and so, interchangable.

Eng

2 stage Packard Merlins had a different supercharger drive from Rolls-Royce, the single stage engines had the same design.

The detachable heads were Rolls-Royce design, but had different connections for the cooling water and oil, IIRC. They changed that to the Rolls-Royce system later.

As many Packard Merlins, or more, were built for British aircraft as were for American aircraft. These had the British standard splines.

 

[Engineman]

2 stage Packard Merlins had a different supercharger drive from Rolls-Royce, the single stage engines had the same design.

The detachable heads were Rolls-Royce design, but had different connections for the cooling water and oil, IIRC. They changed that to the Rolls-Royce system later.

As many Packard Merlins, or more, were built for British aircraft as were for American aircraft. These had the British standard splines.

All Packard Merlins had the Epicyclic 2-speed supercharger drive, Rolls-Royce 2-speed engines had the Farman type 2-speed drive.
The initial Packard engines had the Packard designed two-piece block with external coolant transfer on the Merlin 28. Later, that was changed to the RR style transfer ferrule two-piece block for their Merlin 38 onwards.

Eng

Edit. Further research on my part has shown that, contrary to much written information, the single stage, 2-speed Packard Merlin and V-1650-1 engines did have the Farman supercharger drive.

 

[Engineman]

Herschel Smith points out that if the AM-30 was based on that BMW then they took a welded block engine and turned it into a cast block engine, which is an even bigger design divergence than the 12Y and the VK.

Big question is: Which WWII V-12 engines WERE NOT ultimately based on the Curtiss D-12 Conqueror?

Or really based on the Hisso, or ..?
Truth is, they all developed with the technology. I would say the D-12 was a successful engine of it's time that perhaps first embodied the cleaner design and layout that became
classic for the upright V-12. However, some might say it just followed the H-S concept.
I do like it and it's clean lines. But the cylinders are not fantastic, really a watercooled "poultice-head" design.

Eng

 

[Reluctant Poster]

Or really based on the Hisso, or ..?
Truth is, they all developed with the technology. I would say the D-12 was a successful engine of it's time that perhaps first embodied the cleaner design and layout that became
classic for the upright V-12. However, some might say it just followed the H-S concept.
I do like it and it's clean lines. But the cylinders are not fantastic, really a watercooled "poultice-head" design.

Eng

If the Kestrel is a copy of the D-12 every American V-8 since 1949 is a copy of the Oldsmobile Rocket. They are peas in a pod compared to the differences between a Kestrel and a D-12. Virtually all American V-8s are 90 degree OHV with a camshaft in the valley of a cast iron block. This brings us to the first major difference between the Kestrel and the D-12. The Kestrel is SOHC while the D-12 is DOHC. When they were transcribing the drawings apparently Rolls Royce missed 2 camshafts. How they made it work with this major omission is a mystery. RR also cast the head as a unit with the block overlooking the separate head used by Curtiss. They further compounded the error by using an open cylinder liner instead of a closed one. Another puzzling feature is the long bolts used by the Kestrel to tie the upper deck to the crankcase instead of using the cylinder block to take the firing loads. At the bottom end RR got confused and accidentally got the drawings mixed up with the Condor using fork and blade connecting rods instead of the D-12s articulated rods. Finally RR added the complexity of a geared propeller drive rather than the sleek simplicity of the D-12s direct drive. This error meant that the Kestrel had to turn at much higher rpm. It as a tribute to the designers of the D-12 that the Kestrel could withstand the greater stresses imposed by the higher rotational velocity. RR did a very poor job in copying the D-12.

I am of course being sarcastic, but the reality is that they are very difference engines even in exterior appearance. In fact nothing on the D-12 is actually ground breaking. Most of its features had already been incorporated in Packard and Millers earlier V-12s among others.

 

[marathag]

Basically the 12Y was about the same as RR keeping the Buzzard engine of 1928 and improving it the least amount possible until 1940 and still being able to sell it and then wonder why everyone else had passed them by.

Would have made a decent tank engine for the British, than relying on the far older Liberty. Even cut that 2240 cubic inches down to a V8 of 1494 cubic inches, that would be a 400ishHP class engine for land use

 

[Shortround6]

Buzzard

• Bore: 6 in (152.4 mm)
• Stroke: 6.6 in (167.6 mm)
• Displacement: 2,239.3 in3​ (36.7 L)
• Length: 75.7 in (1,923 mm)
• Width: 30.6 in (777 mm)
• Height: 44.4 in (1,128 mm)
• Dry weight: 1,140 lb (517 kg)

H-S 12Y

• Bore: 150 mm (5.9 in)
• Stroke: 170 mm (6.69 in)
• Displacement: 36 L (2,197 cu in)
• Length: 2,137 mm (84.3 in)
• Width: 764 mm (29.9 in)
• Height: 945 mm (37 in)
• Dry weight: 492 kg (1,085 lb)

Buzzard used 4 valves per cylinder instead of 2 like H-S did.

H-S didn't really improve much of anything until 1939 at which point it is simply too late.

 

[Shortround6]

To kind of show where the 12Y was.

12Y-45....................920hp/4200 meters Szydlowsky-Planiol (SP) supercharger
12Y-49....................910hp/5200 meters Szydlowsky-Planiol (SP) supercharger + variable ignition timing
RR Pergrine..........885hp/4570meters.

 

[Reluctant Poster]

All Packard Merlins had the Epicyclic 2-speed supercharger drive, Rolls-Royce 2-speed engines had the Farman type 2-speed drive.
The initial Packard engines had the Packard designed two-piece block with external coolant transfer on the Merlin 28. Later, that was changed to the RR style transfer ferrule two-piece block for their Merlin 38 onwards.

Eng

Jerry Wells article "The Packard Merlin Supercharger Drive Mechanism for Two-Stage Engines" in Torque Meter Volume 1 Number 4 Fall 2002 clearly shows that the Packard drive was NOT a true epicyclic. It starts with:
"The Packard designed supercharger drive for the two stage Merlin engines is often described as "epicyclic" but this is quite erroneous. It was in fact basically a conventional compound spur gear step up mechanism consisting of three sets of paired gears equally spaced around the impeller/crankshaft center line axis.
….For those familiar with the British built Merlin this arrangement is exactly the as that on the single stage Merlin engines."

Basically there is a layshaft within a layshaft connected by a planetary gear set. In low gear the inner layshaft is locked out and the power flow from the engine to impeller is the same as the single stage Merlin via spur gears. In high gear the planetary set is engaged with the power flowing through the planetary gear set to dive the outer layshaft at a higher rpm.

The single stage Packard used the same the Farman drive as the Rolls Royce Merlins.

 

[ThomasP]

FWIW

There is a detailed word description of the workings of the Merlin/V-1650 2-stage/2-speed supercharger drive on the Thunderboats website:

"Rolls-Royce Merlin/V1650 Engine"

It begins about 2/3 of the way down the page.

 

[ThomasP]

My understanding is that to have an epicyclic gear system you need to have a ring gear as well as the sun and planetary gears. If you look in the Merlin SC gear drive cut-aways below you can see that there is no ring gear, and the 'planetary' gears do not rotate around the 'sun' gear.

Merlin XX SC gear drive

Merlin 60 series SC gear drive

An epicyclic gear drive looks like this:

The sun gear is the yellow one in the center, the planetary gears are the blue ones rotating around the sun gear, and the ring gear is the stationary red one.

As I mention above, there does not appear to be a ring gear in the Merlin SC gear drives, and the 'planetary' gears are fixed(?) relative to the SC housing and so cannot rotate around the 'sun' gear.

[edited]