2 stroke thread (with occasional F1 relevance!)

[autogyro]

If F1 has been the peak of IC engine development then the regulations allowing only poppet valves must have been the main thing that has kept the concept of ice development firmly in the pre-war era.
For four valves per cylinder that would of course be the 1914 18 war.

[J.A.W.]

Indeed, development potential can be shown by comparing the final single cylinder 500cc G.P. Manx Norton..
.. ( itself a source of F1-tech for Vanwall).. & the final single cylinder 125cc 2-stroke Aprilia G.P. bikes..

Both were capable of a reliable, rideable output of ~55hp, via a 6-speed gearbox..
& both were breathing through a fairly similar sized carb..

[J.A.W.]

2-strokes are - sadly - currently banned for G.P. power units, bike or car..

The G.P. 125s were replaced by Moto 3 250cc 4Ts,
& the G.P. 250s were replaced by 600cc 4Ts (which have not bettered the lap times/speeds)..

[gruntguru]

Here is an interesting high-efficiency 2-stroke turbo-diesel design (2.2Ltr/1000hp) done by Garrett for NASA
~20 years ago - as an alternative to gas-turbines for military helicopters..

http://ntrs.nasa.gov/archive/nasa/casi. ... 001160.pdf

Nice link JAW. I am going to re-post it in the "Formula one 1.6L V6 turbo engine formula" thread. Of particular interest is the high pressure ratios selected for the turbomachinery with no detriment to BSFC.

[uniflow]

2-strokes are - sadly - currently banned for G.P. power units, bike or car..

The G.P. 125s were replaced by Moto 3 250cc 4Ts,
& the G.P. 250s were replaced by 600cc 4Ts (which have not bettered the lap times/speeds)..

A sad fact. There are alternatives but no manufacturer in their right mind would look at developing a twostroke. EFI, direct injection has been shown to work but still has it's problems. Thankfully there is nothing stopping development from the back yard and I think you will find there are many ideas still bubbling away in the back ground.
I used to enjoy watching the 125's but not interested in the 250 ( heavily regulated ) fourstrokes.

[J.A.W.]

Rotax is one, & Hirth is another..
& the logic is inescapable.. http://www.hirth-motoren.de/en/2-stroke-logic.html
(Love your work though, Uniflow).

[J.A.W.]

Here's a considered view on the subject of current 2-stroke potential from Kevin Cameron..

http://www.cycleworld.com/2014/02/07/as ... reetbikes/

[J.A.W.]

& more from Cycleworld, http://www.cycleworld.com/2012/08/13/tw ... urrection/

KTM have been evidently sitting on 'ready-to-go' 2T DFI emissions compliant bikes for some time..
Even to the extent of buying Husqvarna from BMW, when they announced they were ready to release one..

[gruntguru]

This thread raises an interesting question. Now that F1 is all about turbo compound engines and maximising thermal efficiency, is it still valid to mandate a four-stroke ICE? If the formula was opened up to two-strokes, would they become the weapon of choice? There is certainly no immediate power advantage. The only route to increased power is increased thermal efficiency and any advantage here would be incremental at best. Of course the two-stroke core would be simpler, lighter and smaller - offering cost, packaging and performance advantages.

If turbo-compounding and direct injection are the future, the drawbacks of two-strokes fade and they become the "core" of choice.

[FW17]

interestingly the Rolls Royce 2 stroke experimental engine ran with a sleeve valve and AFR of 15-23:1 direct fuel engine.......

[J.A.W.]

Well G-G, a cluey Pommy aero-engineer named Stanley Hooker came to that conclusion ~70 years ago..
He reckoned that.. " 4-strokes = 1 power stroke, & 3 to wear the bloody engine out".

[J.A.W.]

& it was another aero-engineer of the era, Walter Kaaden.. ..while working on Hitler's missiles..
.. who realized that the 2-stroke mill was an ideal method of harnessing the pulse jet harmonic pump..
..to recip/shaft/geared power output.. too..

[autogyro]

The problem with a two stroke light aero engine is that to keep the propeller speed below 4000 rpm requires the engine to be geared down.
This results in negating the weight saving and introducing a gear set which is difficult to prevent backlash vibration at low rpm.
The Wallis AG has been flown on practically all engines available. Flat twins, flat fours, rotaries, inline two strokes etc.
We even cut off two cylinders from a flat four RR to make a flat twin from it.
Hewland built a one off engine as did Weslake just for the Wallis.
There was a crank case supercharged cross two stroke from Italy, subaru flat fours and various VW based air cooled flat fours.
The McCullock flat twin target drone engine of 60 hp was the best all rounder.
The aircraft held over 20 world records at one time.
So I have had a little experience in this field.
I wanted to build an all electric W116 to achieve the first operational all electric rotor craft.
My idea for an ideal engine would be two stroke with only two moving parts.
Cant say anymore.

[J.A.W.]

The problem with a two stroke light aero engine is that to keep the propeller speed below 4000 rpm requires the engine to be geared down.
This results in negating the weight saving and introducing a gear set which is difficult to prevent backlash vibration at low rpm.
The Wallis AG has been flown on practically all engines available. Flat twins, flat fours, rotaries, inline two strokes etc.
We even cut off two cylinders from a flat four RR to make a flat twin from it.
Hewland built a one off engine as did Weslake just for the Wallis.
There was a crank case supercharged cross two stroke from Italy, subaru flat fours and various VW based air cooled flat fours.
The McCullock flat twin target drone engine of 60 hp was the best all rounder.
The aircraft held over 20 world records at one time.
So I have had a little experience in this field.
I wanted to build an all electric W116 to achieve the first operational all electric rotor craft.
My idea for an ideal engine would be two stroke with only two moving parts.
Cant say anymore.

I'd suggest you check out the Patakon work done by Manolis, he has some innovative answers to your issues..

[uniflow]

Autogyro, here is a twostroke gyro engine for you.