Hercules Engined Fighters

[tomo pauk]

not necessarily in July 1939 the Poles ordered the Hercules for the PZL.53 obviously with the war starting only a couple of months afterwards the Plane never went into production but if the order had been made a couple of months earlier in the same order the Poles also planned ordered a modification to the Taurus that pushed it to 1,145hp for the PZL 50b although it wasn't due for delivery until October 1939 and when the war started only a handful (1 completed + 6 almost finished) of Pre-production PLZ 50a's (using Bristol Mercury VII) had been completed . If the war had broken out in September 1940 not 39 the Poles expected to have 300 modern fighters mainly PZL 50bs and PZL 53's if these fighters had seen service it is likely that more attention would have been paid by the British.

It is a bit of an unnecessary trouble to sift through a post where the capitalization and punctuation is very sparsely used.
Just saying.

 

[Shortround6]

If the war had broken out in September 1940 not 39 the Poles expected to have 300 modern fighters mainly PZL 50bs and PZL 53's

Expected to have and actually having them are two different things.
The British expected to have a more Beauforts in service 1940 and expected better performance and reliability than they got in 1940.
Same with the early Hercules engines.
The problems with manufacture had not reached the higher levels they would later reach when the Poles were making their plans.
Bristol did straighten things out and the Hercules became a reliable (and later very reliable) engine but 1939-40 was not that time.

 

[southjn1982]

Expected to have and actually having them are two different things.
The British expected to have a more Beauforts in service 1940 and expected better performance and reliability than they got in 1940.
Same with the early Hercules engines.
The problems with manufacture had not reached the higher levels they would later reach when the Poles were making their plans.
Bristol did straighten things out and the Hercules became a reliable (and later very reliable) engine but 1939-40 was not that time.

The Poles were planning on making the engines themselves they already produced the Mercury under licence and had made successful modifications. As for the Hercules and Taurus the modifications they were planning to make and had been ordered for the test engines that were to be made by Bristol and delivered in October 39 were the ones that Bristol eventually copied and made that made the engines in question significantly more reliable, so it likely that the Polish built ones wouldn't have had a lot of the same issues as they had already isolated several of the problems and came up with a solution.

 

[Shortround6]

Would have been nice if they told the British so that Bristol could have fixed their own engines instead of killing crewmen due engine failures.
You said they did but it took well over a year for Taurus to get straightened out.
Bristol had problems keeping the sleeve valves round on production engines. Never heard of a solution coming from Poland.
Not saying that the Poles didn't solve something/s.
Just that the Bristol engines were not really serviceable engines for a lot of 1940. They were used but at cost (lost planes and crew).
Taurus had problems over heating. That was never truly solved.
Rating the engine at 3500ft is not really solving the problem. A 1130hp engine at 3500ft is worth around 905hp at 13500ft. You might was well leave the Mercury engine in the fighter.
Especially as the Taurus needed 100 or 100/130 fuel to reach the 1130hp figure.
Taurus faded as an all purpose engine and turned into a torpedo plane engine (special purpose), the high altitude (14,500ft) version disappeared and never came back.

Hercules engines had problems in 1939 and into 1940.
Hercules development was often a story in improved cooling. You can't make (or at least use) more power if you can't keep the engine cool and it seems Bristol had a problem with this. The heat path for a sleeve valve engine was not the same as a poppet valve engine (you have the extra oil/sliding surface between the inside of the cylinder and the cylinder fins a

Please note the area at the top of the cutaway cylinder.
1. getting airflow down into the head where the spark plugs are is difficult. Yes there were baffles.
2. there is not a lot of fin area on head outside of the central hole.
3. The sleeve reciprocates/oscillates in that few inches at the top of the sleeve "well" meaning you have an intermittent path for the heat to reach the upper part (higher than the ports) of the cylinder wall and fins.

Like other radial engine makers, it was a constant battle to improve the cooling of the cylinders and heads and a constant improvement/enlargement of fin area per cylinder.
This was in addition to what other improvements had to be made.
Bristol may have over promised.

 

[tomo pauk]

The Poles were planning on making the engines themselves they already produced the Mercury under licence and had made successful modifications. As for the Hercules and Taurus the modifications they were planning to make and had been ordered for the test engines that were to be made by Bristol and delivered in October 39 were the ones that Bristol eventually copied and made that made the engines in question significantly more reliable, so it likely that the Polish built ones wouldn't have had a lot of the same issues as they had already isolated several of the problems and came up with a solution.

Think you're over-selling the Poles here.

 

[Snautzer01]

Think you're over-selling the Poles here.

Because ? Overselling? As to what?
They broke enigma. In those days i think they would have tinkered the hell out of any engine they could have laid their hands on and done better.

 

[tomo pauk]

Because ? Overselling? As to what?
They broke enigma. In those days i think they would have tinkered the hell out of any engine they could have laid their hands on and done better.

Let me repost:

Think you're over-selling the Poles here.

"Here" is the keyword. There is no Enigma here.
Your last sentence is also over-selling the Poles.

 

[Snautzer01]

Let me repost. As to crack the most secret computer in the world at that time it would have taken more then luck. Schools, education etc.
In all fronts.

You are selling short.

 

[tomo pauk]

Let me repost. As to crack the most secret computer in the world at that time it would have taken more then luck. Schools, education etc.
In all fronts.

You are selling short.

What is the track record of Polish engineers, between the wars, in improving the engine AB from the foreign company XY before that company itself improved the engine in question?

 

[Shortround6]

I am going with Bristol over sold the Sleeve valve engines and the Poles didn't realize how much it was going to take to straighten out everything.
That or Bristol threw the Polish solutions in the rubbish bin and tried to use their own solution/s.

The whole Taurus thing needed some explaining. Any decent engine designer (or buyer) should have seen the whole idea was rubbish.
Take your base line engine......Mercury VIII 24.9 liters running at 2750rpm and get 840hp at 14,000-15,000ft
Look at your goal Taurus ............25.4 liters and try to get even 1050 hp at the same altitude. If everything was the same basic theory says you need about 3440rpm. (that doesn't take into account the whopping extra 500cc displacement.)

The most I have seen for the Taurus is 3300rpm and the actual engines in service ran 3100rpm.

Basic engine theory says the frictional losses go up with the square of the speed. going from 2750 to 3300rpm means 44% more friction....except
basic engine theory says 80% of your friction comes from the pistons (and rings) sliding up and down the cylinder walls. Taurus has 17% more wall area than the Mercury.
Yes the Taurus uses a high compression ratio, The Taurus uses a bit more boost (about 1 more pound).
And we have the ....................long drum roll............................................................SLEEVE VALVE.......to give higher volumetric efficiency!!!!!
Even if you drop down to 3100rpm you still have 27% more friction.

The Taurus was blind hole.

 

[tomo pauk]

The whole Taurus thing needed some explaining. Any decent engine designer (or buyer) should have seen the whole idea was rubbish.
Take your base line engine......Mercury VIII 24.9 liters running at 2750rpm and get 840hp at 14,000-15,000ft
Look at your goal Taurus ............25.4 liters and try to get even 1050 hp at the same altitude. If everything was the same basic theory says you need about 3440rpm. (that doesn't take into account the whopping extra 500cc displacement.)

Install a 2-speed S/C drive on a Mercury, and it should cover all the needs for a compact and light engine with good overall power. On 100 oct, it will do a bit more than 1000 HP for take-off, and still be 300 lbs lighter than the Taurus. Also more reliable, earlier available, and cheaper and easier to make.

 

[southjn1982]

What is the track record of Polish engineers, between the wars, in improving the engine AB from the foreign company XY before that company itself improved the engine in question?

They had a very good record of tinkering with engines in the interwar years as well as continuously producing competitive designs in many fields of aeronautics form passanger planes like the PZL 44 WIcher to which was very comparable to the Lockheed Electra the PZL 37 which was a very effective light bomber throughout the 1930s PZL were one of Europes great producers influencing many others the Gull-Wing is often called the "Polish-Wing" as they developed it. In the interwar years PZL had a stellar reputation for not modifying and improving engines they licenced from the UK and France although they showed a preference for Bristol Engines from the UK and normally went for Gnome-Rhone or Hispano-Suiza from the French. Quite a few Aircraft projects around Europe during the war like the IAR81 are direct dependents of Polish designs it is a real pity so little is written in English about what PZL were up to but Cynk, Jerzy B. Jastrząb ujawniony and Gruszczyński, Jerzy. Jastrząb nie zdążył are both great

 

[southjn1982]

According to the Poles they did tell Bristol but they were ignored of over a year

 

[southjn1982]

According to the Poles they did tell Bristol but they were ignored of over a year as for high altitude performance the Poles didn't think they needed it they knew that the Germans didn't really have a strategic bomber force and were gearing up mainly to counter Stukas and German tactical assets and they rightly or wrongly assumed that if they were massacring the Stuka's that were hardly great climbers taking 12mins to get to 12,000 feet the Germans would be forced to fly lower thus dragging the Germans down in many ways this is exactly what the Soviets did to the Luftwaffe.

 

[tomo pauk]

They had a very good record of tinkering with engines in the interwar years as well as continuously producing competitive designs in many fields of aeronautics form passanger planes like the PZL 44 WIcher to which was very comparable to the Lockheed Electra the PZL 37 which was a very effective light bomber throughout the 1930s PZL were one of Europes great producers influencing many others the Gull-Wing is often called the "Polish-Wing" as they developed it. In the interwar years PZL had a stellar reputation for not modifying and improving engines they licenced from the UK and France although they showed a preference for Bristol Engines from the UK and normally went for Gnome-Rhone or Hispano-Suiza from the French. Quite a few Aircraft projects around Europe during the war like the IAR81 are direct dependents of Polish designs it is a real pity so little is written in English about what PZL were up to but Cynk, Jerzy B. Jastrząb ujawniony and Gruszczyński, Jerzy. Jastrząb nie zdążył are both great

Thank you for the feedback.
BTW - the Bristol engines were main engines in use the Polish airforce, not the g&R, let alone the H-S.
I'm still at loss on the topic of this:

What is the track record of Polish engineers, between the wars, in improving the engine AB from the foreign company XY before that company itself improved the engine in question?

According to the Poles they did tell Bristol but they were ignored of over a year

Do you know what they were talking, what was the engine in question, and when that communication took place?

 

[southjn1982]

Thank you for the feedback.
BTW - the Bristol engines were main engines in use the Polish airforce, not the g&R, let alone the H-S.
I'm still at loss on the topic of this:




Do you know what they were talking, what was the engine in question, and when that communication took place?

While they were using the Taurus on the PZL 50b they believed the PZL 53 that was to use the Hercules had greater development potential and thus they paid great attention to it and most of the design alterations where for the Hercules that was to be delivered to their specifications in October 39 several of the Polish engineers did escape and according to their testimonies spent a lot of 1940-41 being ignored by British colleagues who thought they knew better in many ways it parralled the way a lot of Polish pilots were treated early in the VOB just it took longer for the Engineers to be listened to it has been stated that it was the skill of the Polish Pilots and the Free Polish Navy that was instrumental in changing British attitudes and allowing for them to be listened to more after all the Mine-detector used by Monty etc in 42-43 is a direct copy of the ones the Polish introduced in 1938. As for the Polish Airforce the Poles used engines GR engines on several planes such as the PZL 24 an upgraded version of the PZL 11 that was exported to several European countries. The PZL 43, 45 and 48 all used G-R engines (along with several others) they tended to go for a variant of the GR 14 series. The PZL 56 was to use the Hispano-Suiza 12Y as was the PZL 54. The Polish were also exploring using the Gnome Rhone 14R-4 as a backup engine in case the Hercules modifications didn't work as well as actively trying to licence the Hispano-Suiza 12Z which they had been paying close attention to the development of.

 

[Shortround6]

One of the problems with the early Hercules was the already mentioned problem that the sleeves would go out of round very quickly which lead to excessive oil consumption at best.
Now running out of oil is bad.
However it sometimes lead to the oil fouling the spark plugs which could lead to the engine misfiring or missing (not running on all cylinders) which means less power and more vibration. Sometimes the engine quit.
Sometimes the sleeve would seize and snap the sleeve drive. Engine stays running (badly) on 13 cylinders. That depends on where in the sleeve drive system something broke.

Not saying there not other problems but until they get the sleeve thing sorted out the Hercules was a problematic engine. It was this "secret" to getting the sleeve valves round that had to pried out of Bristol practically at gun or bayonet point (sarcasm) in order to save Napier and the Sabre engine. Bristol had figured it out, by accident so the story goes (maybe it was a polish employee, they never disclose his name in all of the stories) but the fact they had done so (without knowing how) was known to the air ministry in 1942.
It is mainly the early (1939-40) use of Hercules engines in "what-ifs" that I object to (and the drag, you are not going to get Fw 190 cowls out of Bristol in 1939-40 without a visit by Dr. Who.)

 

[tomo pauk]

While they were using the Taurus on the PZL 50b

Believing that just because they planned to use Taurus on their fighter automatically gives them technical expertise to debug and fix that engine is really a tall order.

in October 39 several of the Polish engineers did escape and according to their testimonies spent a lot of 1940-41 being ignored by British colleagues who thought they knew better

Have these engineers had the specific skillset to debug the Taurus?

As for the Polish Airforce the Poles used engines GR engines on several planes such as the PZL 24 an upgraded version of the PZL 11 that was exported to several European countries.

Main engines in use by PAF were still Bristol types, the prototypes, planned aircraft and export models nothwithstanding.
Note that what "Polish AF used" is a very different thing from what "Poland exported".

 

[Steve Hnz]

I can't help but think the answer to this is why did they bother with the whole family of sleeve valved engines to begin with. In the USA, P & W were building twin row radials (P & W R-1830) from the early 1930s which were little more than single row engines back to back. If Bristol management had pulled their heads out of their sleeve valved backsides, we could could have had Double Mercuries & Double Pegasuses (Pegasi ?) years before the Taurus & Hercules. A 14 cylinder version of a 885 hp Mercury should have been good for just short of 1400hp. In the nose of something like a developed F5/34, you might have had something that would have been very useful. In Italy Alfa Romeo tried to do it with a double Jupiter as the AR 135. It wasn't that successful but I've little doubt that had Bristol done it with their resources it could have been made to work, earlier & more reliably than they managed with their fixation on sleeves.