2 stroke thread (with occasional F1 relevance!)

[J.A.W.]

Vulture sure sank deeply out of contention W, just as every X-type R-R mill did..
& regardless of the correct dimensional parameter particulars, it effectively orphaned the Tornado airframe..

[J.A.W.]

Hello J.A.W.

For some reason your posts are published with one or two days delay.


You write:
“. . . repeating the claim of lower S-V oil consumption”

The specific lube consumption of the Sleeve valve airplane engines was about half than that of the poppet valve airplane engines of that era.

But we talk for extreme specific lube consumptions: about 5gr/kWh for the sleeves (0.008lb/HP/Hour), and 9gr/kWh (0.0015lb/HP/Hour) for the poppet valve engines.

Supposing a specific fuel consumption of 250gr/kWh (32% BTE), the oil-fuel ratio is 1:50 in the sleeve valve aero engines and 1:28 in the poppet valve aero engines.

Such a specific lube consumption fits with 2-stoke engines (the modern giant 2-stroke marine engines run on specific lube consumption of 0.7gr/kWh, i.e. seven times lower than in the old sleeve valve 4-stroke aero engines.

In order sleeve valves to be used in a modern car / motorcycle engine, it is required a control mechanism to keep the oil from escaping to the exhaust and from getting into the combustion chamber degrading the combustion and increasing the emissions (MIT, http://www.pattakon.com/tempman/Lubrica ... Diesel.pdf )...

Thanks
Manolis Pattakos

To be fair Manolis, & as you well know, engines set to fly have a markedly different set of design parameters to contend with..

Those big easy-going marine units are not going to approach the Napier Sabre 7's final take-off rated specific output -weight/power of 0.33Kg/hp, ( does any currently rated 4T GA piston engine ?).
& even the Sabre's 1,750 hp cruise rating offered 205g/hp/hr - 6g/hp/hr for fuel-oil consumption, not bad for a 'fighter' mill..
( Sabre 7 figures from Wilkinson, 1947)

Even the venerable Detroit Diesel 2T mill is available in significant higher states of tune/boost for high performance duties,
- albeit at the price of proportionately increased consumption, including <TBO..

[wuzak]

Vulture sure sank deeply out of contention W, just as every X-type R-R mill did..
& regardless of the correct dimensional parameter particulars, it effectively orphaned the Tornado airframe..

Only the Vulture was seriously considered for production.

The Exe was too small. Similar in capacity to the Kestrel/Peregrine, but quite a deal heavier.

Apparently a liquid cooled version of the Exe was made, but not to a flight standard, so only tested on the bench.

The Pennine was intended for the after war civilian market, but as it was started late it was dropped in favour of gas turbines.

The Eagle XVI was the earliest X-type engine Rolls-Royce did. It was also not a flight worthy engine, and was preferred by Royce over the F (the Kestrel) but not the airframe manufacturers, so only the one was built.

Given the resources tipped into the Sabre project during the early years of WW2 to make it viable (ie getting production sorted) the Vulture could have been completely sorted.

But Rolls-Royce didn't have those resources available, and suspended development of all engines bar the Merlin for a time during 1940. Including the Griffon. And with the Tornado the only possible recipient of the Vulture going forward, the Manchester to Lancaster decision having already been taken, it would have been illogical to continue with production beyond immediate needs (completing Manchester production).

The Tornado airframe was hardly "an orphan", given that the Tornado and Typhoon differed mainly in the engine bay area.

[J.A.W.]

Well, W, I'd have to call the sole 1-off production Tornado an 'orphan' - by any manner of means..
& as Manolis has described, the R-R X-designs looked promising on paper, but wouldn't/didn't fundamentally work out in metal.
( viz: "4 different geometries" in the one recip' unit - all conspiring to cause catastrophic crankshaft conniptions..)

Pragmatist boss of R-R, Hines, to his credit, saw this & wisely concentrated on the development of their basically effective, if old-fashioned V12 units.

The Sabre design was sound, as shown from its 1940 type test at 2,200hp, production issues were another matter altogether,
& cannot be fairly conflated with its design merits as such, from a technical standpoint.

[manolis]

Hello.

At the http://www.pattakon.com/pattakonPatRoVa.htm they have been added these two animations:





The angular size (duration) of the exhaust port and of the inlet port on the rotary valve are by far larger than the angular size (“duration”) of the cylinder-head-port (which, by the way, serves both: the exhaust and the intake).
The valve lift profile turns from triangular with soft “ramps” to trapezoidal with abrupt opening and closing “ramps”.

Bore: 80mm
Stroke:70mm
Con-rod center-to-center: 125mm (=1.8*stroke)
Displacement: 350cc per cylinder

Cylinder head port area: 2*6.5=13cm2

According the following diagram / plot:



with f1=40, f2=25, f3=75 and f4=85 degrees (measured on the rotary valve):

exhaust duration: 230 crank degrees

inlet duration: 250 crank degrees

overlap: 30 crank degrees

“sealed” duration (from the closing of the inlet to the opening of the exhaust): 270 crank degrees.


The port areas and the timing can be by far more “racing” for higher than extreme revs; in such a case, a racing underneath mechanism (crankshaft, con-rod, piston, cylinder, crankcase) is required capable to stand the punishment.

Thoughts?

Objections?

Thanks
Manolis Pattakos

[FW17]

Manolis

Have you tried the pre-chamber jet ignition lean burn on 2 strokes?

[manolis]

Hello FW17.

You write:
"Have you tried the pre-chamber jet ignition lean burn on 2 strokes?"

No.
On the other hand, one can consinder the 2-stroke Diesels as "pre-chamber" jet ignition lean burn.


Here is one more animation of the 4-stroke PatRoVa:



Its architecture and its combustion chamber seem ideal for applying the F1 "pre-chamber jet ignition lean burn".

By the way, a free breathing 4-stroke capable to operate at really high revs can make a lot of power; more than a conventional 2-stroke of similar design / capacity, without the "issues" of the conventional 2-strokes.

Thanks
Manolis Pattakos

[J.A.W.]

By the way, a free breathing 4-stroke capable to operate at really high revs can make a lot of power; more than a conventional 2-stroke of similar design / capacity, without the "issues" of the conventional 2-strokes.

Thanks
Manolis Pattakos

Actually Manolis,
You've got that about face, since for a N/A 4-stroke of the same displacement to even attempt at being competitive, it MUST be capable of operation at "really high revs".. ( & thus with "issues" of very expensively robust construction) - to come anywhere near2T outputs, power-wise.

& even Honda, after spending many years & much money, could not get a defacto 'V8' 4T - to win in 500cc G.P. Championship racing,
- so while they did get promising peak power figures on dyno-runs, it proved both unrideable & unreliable - in racing for real..

As for unconventional, whatever happened to the 'Ryger'? That claimed 70hp from a 125cc 2T single..

Luc, where are you - Luc?

[Tommy Cookers]

we now know that the NR500 suffered far more than eg a reed-valve or disc-valve 2 stroke from .......
lack of the modern fast-burning type fuel and suitable fuel injection
lack of the modern fly-by-wire type relationship between twistgrip and throttle plate for shaping response
and from noise limits .....
affecting a 4 stroke (multi-camshaft and megaphone) far more than the 2 stroke (whose expansion chambers want tailpipe restriction anyway)

but which Honda engine designer would have had the guts to forecast this outcome to the policy-makers ?

Honda were then in a displacement-efficiency competition
but 2 stroke fans should consider that now Moto GP rewards fuel-efficiency, not displacement-efficiency


btw despite unequal piston motion the Vulture and Exe had no crankshaft-torsion problem (the only Exe engine flew hundreds of hours)
similarly so the Lion/Sea Lion, the Lorraine-Dietrich/Isotta-Fraschini W18s (incl. marine versions), also Farman and Hispano W12s ?
and Rocchi's Life F35 W12 F1 engine of 1990 had master/slave rods
as does apparently a development of the Isotta-Fraschini in production by CRM Motori Marini, a W18 54 litre turbocharged diesel
and engines with equal motion had such problems eg the original Liberty, and the DH Gipsy 6s (weird firing order, and six 3rd order dampers)
current Continental flat 6s have 6th order dampers and some also 4.5th order - presumably Lycomings are the similarly equipped

but there will anyway be torsional etc vibration design issues from driving the aircraft load system ie propellor or rotor
ok the X4 2 stroke might be no more difficult in this regard than eg the conventional 4 stroke flat 6 cylinder or radial 7 cylinder ?

[Brian Coat]

Pragmatist boss of R-R, Hines, to his credit, saw this & wisely concentrated on the development of their basically effective, if old-fashioned V12 units.

Hives?

He must have been a very special type of tactician who was able to stick with and develop the "tried and tested" then soon after ... switch everything to a *brand new* technology.

[Brian Coat]

Hi

Rotary valve 4 stroke random thoughts ...

common port - gas reversal/ gas exchange effects, residuals esp. part load, charge heating/detonation?

valve - coolant passage packaging, crevices/HCs, sealing/distortion?

These are not "nails in the coffin" but they are "boxes to tick"?

[J.A.W.]

Pragmatist boss of R-R, Hines, to his credit, saw this & wisely concentrated on the development of their basically effective, if old-fashioned V12 units.

Hives?

He must have been a very special type of tactician who was able to stick with and develop the "tried and tested" then soon after ... switch everything to a *brand new* technology.

Hives.. yes ta Brian, that typo had me scratching..

& if by 'tactician' - you mean 'ruthless business tycoon' - then yes, Hives snaffled up Whittle's gas-turbine quick-smart..
..after he'd done every industrial/commercial 'dirty trick' in the book, to dominate the piston engine scene, even in wartime..

[J.A.W.]

we now know that the NR500 suffered far more than eg a reed-valve or disc-valve 2 stroke from .......
lack of the modern fast-burning type fuel and suitable fuel injection
lack of the modern fly-by-wire type relationship between twistgrip and throttle plate for shaping response
and from noise limits .....
affecting a 4 stroke (multi-camshaft and megaphone) far more than the 2 stroke (whose expansion chambers want tailpipe restriction anyway)

but which Honda engine designer would have had the guts to forecast this outcome to the policy-makers ?

Honda were then in a displacement-efficiency competition
but 2 stroke fans should consider that now Moto GP rewards fuel-efficiency, not displacement-efficiency


btw despite unequal piston motion the Vulture and Exe had no crankshaft-torsion problem (the only Exe engine flew hundreds of hours)
similarly so the Lion/Sea Lion, the Lorraine-Dietrich/Isotta-Fraschini W18s (incl. marine versions), also Farman and Hispano W12s ?
and Rocchi's Life F35 W12 F1 engine of 1990 had master/slave rods
as does apparently a development of the Isotta-Fraschini in production by CRM Motori Marini, a W18 54 litre turbocharged diesel
and engines with equal motion had such problems eg the original Liberty, and the DH Gipsy 6s (weird firing order, and six 3rd order dampers)
current Continental flat 6s have 6th order dampers and some also 4.5th order - presumably Lycomings are the similarly equipped

but there will anyway be torsional etc vibration design issues from driving the aircraft load system ie propellor or rotor
ok the X4 2 stroke might be no more difficult in this regard than eg the conventional 4 stroke flat 6 cylinder or radial 7 cylinder ?

T-C, Honda research had shown that ultra-high rpm 4Ts were not particularly fuel sensitive,
& it was the 2T machines that suffered when leaded fuels were banned from GP racing.

It is true that 2T race engines remained race-rideable at very high specific outputs, due to naturally
inherent characteristics such as low rotational inertia, giving excellent response to throttle modulation.

The 4Ts require a huge suite of electronic aids to assist the rider, & this season the econo-dumbdown ECU
has been the cause of difficulties.. including blow-ups of very expensive engines.

The triple bank broad-arrow arrangement aero-mills such as the Napier Lion, did not suffer the 'herky-jerky' motion issues
that bedeviled the X-types, due to the 'magic' of the prime 3 at work, mayhaps?

& did the R-R Exe pass a type-test, or was it a pampered experimental hack for its "hundreds of hours" of flight?

[wuzak]

The triple bank broad-arrow arrangement aero-mills such as the Napier Lion, did not suffer the 'herky-jerky' motion issues that bedeviled the X-types, due to the 'magic' of the prime 3 at work, mayhaps?

& did the R-R Exe pass a type-test, or was it a pampered experimental hack for its "hundreds of hours" of flight?

Are you making things up again?

What are these "herky-jerky motion issues" that plagued X-24s?

I have seen no mention of that as an issue with the Vulture - the most produced X-type of the period. And the Vulture did have issues in its 6 year program.

Problems such as cavitation in the coolant pumps, solved with a balance pipe, relative motion between crankcase halves, solved with dowels and the failure of the big end bearing and the master rod, the biggest problem that faced the Vulture. No mention of crankshaft failures (early Griffons had some crankshaft failures).

And no mention of "herky-jerky motion issues". So I'm not sure that the Lion had any advantage in this area.

And yes, the Exe would have to have gone through a type test to gain flight status.

[wuzak]

Hives.. yes ta Brian, that typo had me scratching..

& if by 'tactician' - you mean 'ruthless business tycoon' - then yes, Hives snaffled up Whittle's gas-turbine quick-smart..
..after he'd done every industrial/commercial 'dirty trick' in the book, to dominate the piston engine scene, even in wartime..

What exactly were these "dirty tricks".

Not running a company into the ground (as was done by Napier)?
Having the best available engine when it was needed most? The Hercules wasn't ready, and the earlier Bristol radials weren't suitable/powerful enough for the fighter types needed for the BoB. And what were Napier's available engines for the BoB - the Rapier and Dagger.
Hiring a mathematician and aerodynamicist to work on supercharger development?
Not giving away their secrets (ie giving the supercharger designs to competitors)?
Having a good relationship with the Air Ministry?

Rolls-Royce dominated the piston engine business in WW2 because they had a good product, the Merlin, which they relentlessly developed and improved and it was the go to engine for most British airframe manufacturers of WW2.

Regarding Rolls-Royce taking over jets, Rover was having a tough time in development and in dealing with Whittle - Rover's engine department and Whittle often didn't see eye-to-eye. Rolls-Royce swapped tank engine production (the Rolls-Royce Meteor), which was right up Rover's alley, and took over the turbine business. The deal was done over dinner and a handshake.

But Rolls-Royce had made moves towards gas turbine development earlier. They hired AA Griffith in 1939. AA Griffith had written a paper on the design of an axial compressor gas turbine in 1926, using aerodynamic principles, and proposed a design of a turbo-prop.

It was AA Griffith that Whittle sent his calculations for review. Griffith found some errors, but was also critical of Whittle's concept.

As for being pragmatic, Hives sought to discontinue the projects for the Vulture, the Exe, the Peregrine and the Crecy so that his team may concentrate on developing the Griffon and, more importantly, the Merlin.

Meanwhile, Napier built a jewel of an engine that was, frankly, a bit player in WW2. It was too late, like the Griffon, to be built in large production numbers in shadow factories and under licence. The development of the engine nearly bankrupted Napier, which narrowly escaped the government's preferred option - a take-over by Rolls-Royce.

But imagine what might have been with the Sabre if it had Rolls-Royce resources behind it and Hives driving the program.

Napier also had help from the government. The government had some grinding machines diverted from Pratt and Whitney to Napier. The government forced Bristol to give up production secrets for the sleeve valves - secrets they had developed over 10+ years at enormous expense - to save the Sabre program.