2 stroke thread (with occasional F1 relevance!)

[J.A.W.]

R-R seemed to traditionally be - a tad skimpy on their conrods, T-C.

Routledge, ( designer of the successful Napier Lion, which ran triple banks of 4, using a master/slave conrod set-up)
found the big R-R V12 Buzzard a bit flimsy in its 'knife & fork' bottom end - when developing the type R race mill,
& so reverted to the Lion-type M/S arrangement (still as a V12 though, of course)..

The R-R Vulture X-24 was a failure, ( as were all their X-mills, it appears)..
.. but whether due to those 'skimpy' R-R conrods, or for harmonics reasons.. ( maybe both?)..

Even today, the R-R Merlins raced at Reno are fitted with the more substantial Allison V12 conrods,
& this was after a number of needful R-R factory improvements made during wartime power developments..

Anyhow, back to topic, as an example of current 2T R&D.. http://www.iffitech.com

[manolis]

Hello J.A.W.

You write:
“Anyhow, back to topic, as an example of current 2T R&D.. http://www.iffitech.com”

Quote from the above link of iffi tech:

Iffi Technologies was engaged by Martin Aircraft to enhance the performance and reliability of their existing V4 2-stroke prototype engine, which was created by a previous team.
We redesigned and remade the crankcases, cylinder head retention system, cylinder heads, cylinder head covers, compression ratio, ignition system, crankshafts, pistons, ACG area, inlet manifolds and exhaust system to achieve the
performance and reliability goals required by the client. In the areas where aspects of the base design could not be corrected, a monitoring schedule was established and components were “lifed” accordingly. Our developments increased the engine stiffness and system performance, and enabled Martin Aircraft to achieve their company goals within their prototype phase.

End of Quote


Until recently in Martin JetPack they were using the abovementioned V-4 two-stroke engine, and they were proud of it.
2,000cc, 200PS, water-cooled, 60Kp (130lb) heavy.
Maximum speed: 74Km/h (45mph)
Cruise speed: 56 Km/h (35mph)
Range maximum: 50Km (30mi)

At take off this engine together with the required fuel (and it requires a lot of fuel) weighs about 100Kp (220lb).



Too heavy, too thirsty, too complicated, too expensive.


Now things have changed. The above engine is phased out, and they decided to use a Wankel Rotary.


Quote from Martin Jetpack official site:

“Martin Aircraft Secures Supply of Newly Developed Engines
Martin Aircraft Company Limited (Martin Aircraft) (ASX: MJP) is pleased to announce that it has entered into an agreement with UK based Gilo Industries Group Limited for the supply of its advanced rotary engines from its wholly owned subsidiary Rotron Power Limited.
As described in our prospectus and recent announcements,Martin Aircraft is moving away from the custom designed and built two stroke V4 engine presently used on Martin Jetpack test aircraft. The company never planned for this engine to be its commercial engine solution and therefore in June 2015 the company began to investigate other options. Following an engine study, Martin Aircraft selected the Rotron rotary engine and consequently is not proceeding at this stage with either the 2 stroke or 4 stroke engine concept design. The Rotron rotary engine reflects a completely new approach to vertical take-off and landing (VTOL) propulsion both in manned and unmanned air vehicle (UAV) operations by redefining the relationship between size, performance, efficiency and reliability. It delivers a higher power-to-weight ratio when compared to any other specific engine while remaining small, lightweight and reliable with almost zero vibration. This makes it an ideal power plant for the Martin Jetpack range of aircraft, including both Manned and UAV models.”

End of quote

It seems in Martin Jetpack they have plenty of money to spend before realizing that their project has several fundamental flaws. And that they have way better choices for their propulsion unit.

A 2,000cc Cross-Radial aircooled heavily turbocharged direct injection Diesel PatAT engine:



(animation at http://www.pattakon.com/PatAT/PatAT_Cross_Radial_1.gif )

can provide easily and reliably some 50% more power than the V-4 of Marin JetPack (the 2,000cc 4-in-line BMW turbocharged di Diesels provide some 200PS, and they are 4-stroke engines) with less than half specific fuel consumption, with nearly half weight, with true free-of-vibrations operation, with low specific-lube-consumption etc, etc.

Think also about the manufacturing cost of the PatAT Cross-Radial.

Thanks
Manolis Pattakos

[J.A.W.]

Indeed Manolis,
I am curious to know whether a British Gov't subsidy is at play there - in the choice of a rotary piston mill, too.

Actually though, I was more interested in your view of the IFFI ( unfortunate choice for a business name , perhaps)
'patented' 2T piston design - which seeks to avoid having its rings bulge into the open cylinder ports..

[manolis]

Hello J.A.W.

The Wankel Rotary of Rotron, which is the new propulsion unit of Martin Jetpack, is not a lightweight engine if it is taken under account the required fuel.

It also has a short TBO.

Besides, after 50 years of evolution Mazda phased out their Wankel Rotary.

Do I miss something?



You write:
“Actually though, I was more interested in your view of the IFFI ( unfortunate choice for a business name , perhaps) 'patented' 2T piston design - which seeks to avoid having its rings bulge into the open cylinder ports..”

It’s a smart idea.

The added complication is justified in case of racing use.

It was filed a patent application in the USPTO (11/916,865, filed July 1, 2008, inventor: Denver Lawson), but it never ended with the granting of a patent (it was rejected as anticipated by two older US patents).

Thanks
Manolis Pattakos

[J.A.W.]

Here is an interesting attempt at an F1 2T design.. by Harold Clisby..
..with the cylinders arranged in a pattern that would've doubtless attracted backing, in late `30s Germany..

http://www.collingrovehillclimb.com.au/haroldclisby/

[manolis]

Hello J.A.W.

The basic module:



of the multicylinder Harold Clisby F1 2-stroke engine of your link comprises four complete single cylinder engines:



and five bevel gears (one per crankshaft and one on the power shaft).

A significant part of the power provided by each single cylinder is consumed in the transmission (and on the required bearings and thrust bearings).

Excluding the modularity of Clisby’s architecture (a 3lt engine needs 6 basic modules, with each basic module comprising 4 complete single cylinders sharing a center bevel gear on the power shaft), I can’t see other advantages.

Talking for multicylinders, the characteristics (specific power, reliability, cooling, compactness, vibration-free, flow capacity etc) of a 4-stroke even-firing, 8-cylinder 2-row cross-radial engine with PatRoVa cylinder heads fit with aero engines:









The crankshaft has two crankpins at 0 and 135 degrees. Each crankpin drives four pistons.

There is no way a rotary valve to hit on the respective piston crowns (overall reliability).

In case the timing belt of the one row of cylinders falls apart, the other row of cylinders remains functional (safe landing). Compare the case with a poppet valve aero engine.


More about the PatRoVa rotary valve at http://www.pattakon.com/pattakonPatRoVa.htm

Thanks
Manolis Pattakos

[gruntguru]

. . . . but - its a 4 stroke!

[J.A.W.]

. . . . but - its a 4 stroke!

Yes..
& AFAIR, 4T radials all run odd-numbered cylinder layouts - per bank - for firing order purposes?

[manolis]

Hello Gruntguru.

Yes it is a 4 stroke, as most airplane engines.

Actually it is more than “4-stroke” if you consider:

the flow capacity,
the unlimited rev limit of the cylinder heads,
the lubricant-free cylinder heads,
the cooling of the cylinder heads,
the efficient scavenging of the combustion chamber during the overlap (no short-circuit between the neighboring intake and exhaust poppet valves),
the compact combustion chamber during combustion,
the considerably higher compression ratio (there are no hot sports into the combustion chamber during the combustion)
the combustion chamber shape fitting, among others, with the lean burn used lately in the F1 and with direct injection wherein the injector shoots the spark plug,
the friction free operation,
the elimination of the inertia and of the impact loads,
etc.


A few weeks ago, in the http://www.douglas-self.com/MUSEUM/POWE ... alveIC.htm (Rotary-Valve Internal Combustion Engine) it was added a line for the PatRoVa rotary valve:

“Another contemporary concept is the PatRoVa rotary valve. Like the Cross design it balances out the forces acting on the rotating valve

I tried a few times to explain to the author that his:
“Like the Cross design it balances out the forces acting on the rotating valve”
is as wrong as it gets, but unsuccessfully.
However it is quite simple: when you have a high or extreme pressure into the combustion chamber, a Cross rotary valve (either with the “reaction bridge” of Cross, or without it) and the bearings whereon the Cross rotary valve abuts, receive a huge force (equal to the area of the window towards the combustion chamber times the pressure) that causes flexing / deformation of the parts, leakage, friction, scuffing etc.


A good characteristic of the Wankel rotary engine for aviation applications is the progressive reduction of the power in case of seizure. Nothing to do with the TBO.
Even with broken or destroyed apex rings, a Wankel rotary can operate at high revs like a turbine.

The above good characteristic of the Wankel rotary is met in the PatRoVa rotary valve, too, wherein there is no case of valve – piston collision. Even in case of severe scuffing, the power of the PatRoVa drops progressively giving the chance for a safe landing.

In comparison, when a poppet valve, or a pushrod, or a rocker arm, or a valve spring, or a cam-lobe of a Rotax airplane engine:



or of a UL390i airplane engine:



fails, a sudden engine stall is possible (valve – piston collision, piston holed, parts into the crankcase, broken connecting rods, holed crankcase etc).
Even if the airplane lands, the engine will need replacement.





On the other hand,

a single-row 2-stoke PatAT Cross-Radial turbocharged Diesel is another approach having its own characteristics / advantages for aviation applications:



However, like the PatRoVa it is unconventional and needs to be put to the tests.

Thanks
Manolis Pattakos

[gruntguru]

Hello Gruntguru.

Yes it is a 4 stroke, as most airplane engines.

But this is the "2 stroke thread".

[manolis]

Hello Gruntguru.

You write:
But this is the "2 stroke thread"


This is why the Cross Radial 2-stroke turbocharged Diesel PatAT was at the bottom as an alternative solution to the PatRoVa 4-stroke Radial.


On the other hand, the PatRoVa seems capable to bridge the gap of specific power between the 2-strokes and the 4-strokes, keeping the good characteristics of both schools.

For instance, the Panigale 1199 Superleggera (60.8mm stroke, 112mm bore, 200PS at 11,500, red line at 12,500rpm (the most expensive motorcycle in the world) puts the Desmodromic valvetrain of Ducati at its limit.

What if the bore was increased at 120mm (the Panigale 1299 has 116mm bore), the stroke was decreased at 50mm (1,130cc capacity) and the desmodromic cylinder heads were replaced by PatRoVa ones of higher flow capacity?

For the same mean piston speed, the red line goes from the current 12,500rpm at 15,000rpm. And if the underneath mechanism (crankcase, crankshaft, connecting rods, pistons) can stand a little more revs (the cylinder heads can operate at way higher revs, say at 25,000rpm) a power of 220PS per liter seems attainable.



Thanks
Manolis Pattakos

[matt21]

could be fun to watch:



http://suter500.com/isle-of-man-tt/

[Andres125sx]

2 stroke 500cc bike for Isle of Man???

OMG some people need a doctor ungently!

[J.A.W.]

2 stroke 500cc bike for Isle of Man???

OMG some people need a doctor ungently!

Somehow I doubt that Yamaha would let "The Doctor" race there, on anything..

& FYI Bruce Anstey got the 'classic' lap record at the IoM last year - on a 2T YZR 500 @ a 200+ km/h - average speed..

[wuzak]

. . . . but - its a 4 stroke!

Yes..
& AFAIR, 4T radials all run odd-numbered cylinder layouts - per bank - for firing order purposes?

Not all, but generally speaking, yes.

By "firing order purposes" I assume you mean even firing intervals?

For example, if you take a 7 cylinder radial the firing order would be:
1, 3, 5, 7, 2, 4, 6.

This gives even firing, each cylinder firing after two revolutions of the crankshaft.

A 6 cylinder would be:
1, 3, 5, 6, 2, 4 or 1, 3, 5, 2, 4, 6.

Either way there is one point with a shorter interval and one where there is a longer interval.

Alternatively, it could be arranged as for the Jumo 222, where pairs of cylinders fire to mimic a 3 cylinder radial.
That is,
1, 2, 5, 6, 3, 4.