2 stroke thread (with occasional F1 relevance!)

[uniflow]

S-250.. did you not read the G.W. 'Aeroplane' article where it states Ricardo..

"... met his goal, Astoundingly he managed to coax 219hp/litre & a BMEP of 325lbs/in".
&,
"Finally, it can be said that the Crecy was ahead of its time."

Apparently not, since that directly contradicts your assertion..

I did actually put the 1st quote in a fairly recent post, but it seems you didn't get it..
Likewise the apropos comments on the Crecy oil system by Uniflow..

Why very large piston aero-engines have not been designed for decades - is pretty self evident..
& as previously stated, current technology would deal to the Crecy issues you claim as crushing design faults..

I suggest you spend a bit of time reading some of the real data in this thread prior..

Such as the ~1000-hp 2.3ltr 2-stroke turbo-compound V6 designed for NASA by Garrett as a helo mill..

Just because someone designed it doesnt mean it was ever built and made to work or ever could have. Nasa gave up their G.A.P. general aviation propolsion program in the 90s after they realized they were even worse at designing aircraft engines than they were at designing space shuttles. Mention a 2.3 litre 1000hp 2 stroke to any engineer in the automotive or aviation field today and he will probably ask you politely to take your hand out of your pants.

Well, not having my hand in my pants, I belive with todays twostroke tec that 1000HP from 2.3L is indeed possible.
( dubious calculations and all ), if a 125 can produce 55HP. then a 2,25L ( 18 cylinders ) will produce 990HP, 10HP produced by the last 50cc. So there is your 1000HP 2.3L twostroke ( at 13500 RPM ), now fly on that.
J.A.W, imagine that sound, 18 chambers on song, Imagine the fuel consumption.

[J.A.W.]

The link to the professionally researched 1,000hp Garrett design is on page 5 of this thread..
..if S-250 could get his "hand out of " - his - "pants", stop blowing "red hot air" & read it..

Dunno if 18 cylinders would work together so well Uniflow , but an H-24 ( Napier Sabre-like layout) could be a bit of fun..
..a naturally aspirated 1320hp 3.0litre.. .. & 24 exhaust pipes would be a splendid bit of design work too..

No wonder they were banned.. ..too bloody good for N/A 4-strokes to compete with..

[uniflow]

The link to the professionally researched 1,000hp Garrett design is on page 5 of this thread..
..if S-250 could get his "hand out of " - his - "pants", stop blowing "red hot air" & read it..

Dunno if 18 cylinders would work together so well Uniflow , but an H-24 ( Napier Sabre-like layout) could be a bit of fun..
..a naturally aspirated 1320hp 3.0litre.. .. & 24 exhaust pipes would be a splendid bit of design work too..

No wonder they were banned.. ..too bloody good for N/A 4-strokes to compete with..

Throttle cables could be a bit of a birds nest.

[J.A.W.]

Yeah..

I run a few 2-stroke triples that have 4-1 cables ( 3 carbs + oil pump regulator) & they work fine..

Fly by wire.. electronic control.. ..aint it though.. these days..

[gruntguru]

The next reasonable question: if the sealing with the ring-less sleeve valve is good and the relative friction/wear low, why this technology was never used to eliminate the piston rings in normal size engines?

A few ideas,
1. Higher surface speed, so a lot of viscous friction, energy, loss, heating.
2. Heat flow to piston crown is uneven. Maintaining exact circularity difficult.
3. Sleeve valve is a hollow cylinder so can flex to circular shape. Piston crown is a filled disc.

[J.A.W.]

@ Manolis..

Here's what Kevin Cameron reckons re: rings..

http://www.cycleworld.com/2013/12/05/as ... nder-wall/


The sleeve valve combustion chamber design was free from the need to accommodate poppet valves,
& their various associated issues & concerns, so were freely optimised..
.. for efficient burn shape/sparkplug placement/strength/cooling & etc matters..

[smoker250]

S-250.. did you not read the G.W. 'Aeroplane' article where it states Ricardo..

"... met his goal, Astoundingly he managed to coax 219hp/litre & a BMEP of 325lbs/in".
&,
"Finally, it can be said that the Crecy was ahead of its time."

Apparently not, since that directly contradicts your assertion..

I did actually put the 1st quote in a fairly recent post, but it seems you didn't get it..
Likewise the apropos comments on the Crecy oil system by Uniflow..

Why very large piston aero-engines have not been designed for decades - is pretty self evident..
& as previously stated, current technology would deal to the Crecy issues you claim as crushing design faults..

I suggest you spend a bit of time reading some of the real data in this thread prior..

Such as the ~1000-hp 2.3ltr 2-stroke turbo-compound V6 designed for NASA by Garrett as a helo mill..

Just because someone designed it doesnt mean it was ever built and made to work or ever could have. Nasa gave up their G.A.P. general aviation propolsion program in the 90s after they realized they were even worse at designing aircraft engines than they were at designing space shuttles. Mention a 2.3 litre 1000hp 2 stroke to any engineer in the automotive or aviation field today and he will probably ask you politely to take your hand out of your pants.

Well, not having my hand in my pants, I belive with todays twostroke tec that 1000HP from 2.3L is indeed possible.
( dubious calculations and all ), if a 125 can produce 55HP. then a 2,25L ( 18 cylinders ) will produce 990HP, 10HP produced by the last 50cc. So there is your 1000HP 2.3L twostroke ( at 13500 RPM ), now fly on that.
J.A.W, imagine that sound, 18 chambers on song, Imagine the fuel consumption.

Uniflow is technically correct, you probably could just about wring 55 hp out of a 125 and so if you joined 18 of them together you might just be lucky enough to get 1000 hp before the whole thing shat itself. Maybe a project for when you've finished your uniflow engine.
If your talking about an aircraft engine capable of running 2000hrs before overhaul and using 200grams/kw/hr then your all dreaming. Can't you guys tell the difference between a design study on paper and proven hardware. At least they based it on something sound like the Nomad not the dead end Crecy. Actually NASA did build a 200 hp flat four uniflow (Valves) two-stroke aircraft diesel in conjunction with TCM and even some help from Detroit Diesel but it was eventually shelved as being too troublesome.
TCM is now the world leader in aero diesels, all 4 stroke.

[J.A.W.]

Again S-250, a bit of preliminary research might be helpful before issuing yet more spurious opinions..

Still no meaningful quotes or links to support your assertions either.. too bad.. .. & who is "dreaming" eh?

55hp from G.P. 125 racing motorcycles as a repeatedly reliable & tractable output - is fact..

& have you still not bothered to read - the 1,000hp V6 2-stroke NASA helo mill proposal - done by Garrett?

Nah, didn't think so.. ..otherwise you could've quoted their comments about the Crecy.. (..as if..)..

[smoker250]

Again S-250, a bit of preliminary research might be helpful before issuing yet more spurious opinions..

Still no meaningful quotes or links to support your assertions either.. too bad.. .. & who is "dreaming" eh?

55hp from G.P. 125 racing motorcycles as a repeatedly reliable & tractable output - is fact..

& have you still not bothered to read - the 1,000hp V6 2-stroke NASA helo mill proposal - done by Garrett?

Nah, didn't think so..

I did take a quick read through, it was as you said a proposal, a design study, full of theoretical calculations and assumptions. was it acted upon, I guess not, no one seems to have built one that I know of. I suspect, since it used the same slipper bearings as the Nomad, that NASA's G.A.P. diesel I mentioned may have been influenced by that or similar study. In any case there is not much said about the Gap program these days, because it was such a total failure. Nothing wrong with Garrett, doesnt mean theyre infallible. As for NASA, their record of designing and operating the space shuttle is nothing short of criminal.
Until someone proves in actual hardware that the open sleeve concept is feasible my opinion will remain that it was not.
I am always open to more information so if someone can dig up information on whether the Crecy was intercooled or not and whether it had iron sleeves in the aluminiuim block, or any other information that adds to the discussion. I did say at the beginning that it might have been better if he kept it as a diesel. Ricardo might have been clever but looking at the combustion chamber he used in the E65, if he used that in the Crecy then no wonder he had problems.

[J.A.W.]

S-250.. you "suspect" after a "quick read".. yeah right.. ..as if it was all "red hot air"..
More likely, vested interests, not too dissimilar to those which sealed the fate of the Napier Nomad, were responsible..

& given certain oddly convergent similarities between current F1 mills & the Garrett proposal for NASA..
It certainly seems reasonable to assume it was read & understood by the guys responsible for those reg's..

Again as to the value of your "opinion".. ..you provide no evidence - that it represents anything of significant worth..

[smoker250]

S-250.. you "suspect" after a "quick read".. yeah right.. ..as if it was all "red hot air"..
More likely, vested interests, not too dissimilar to those which sealed the fate of the Napier Nomad, were responsible..

& given certain oddly convergent similarities between current F1 mills & the Garrett proposal for NASA..
It certainly seems reasonable to assume it was read & understood by the guys responsible for those reg's..

Again as to the value of your "opinion".. ..you provide no evidence - that it represents anything of significant worth..

Yes JAW you may be right there, vested interests killed off the Nomad.....communists probably, that bloody Putin I bet.
They had to you see JAW because they knew that if the Garrett proposal was correct, then the Nomad at 41 litres would soon be capable 41,000 hp, and if the americans ever got the idea to stick those in tanks, why they woudlnt even need tracks, they would be able to fly, and the poor comrades at the Chelyabinsk Tractor factory, busy screwing together T34s, would probably all lose their jobs, and possibly their heads. You might be onto something there JAW. Vested interests might be why the Crecy program failed do you think? A communist spy at Rolls Royce, chucking a spanner in the works. Maybe thats why they kept blowing up all ther time.

[J.A.W.]

S-250, now you are just getting silly.. tantamount to trolling, certainly..

Since - in fact - the NASA report actually states the issues, but obviously you missed that,
..or "think" your "opinion" is somehow of more value..

& do give the sarcastic stuff a rest too, can't you - eh?

Of course the turbine makers do not want their expensive, thirsty, inefficient units
replaced by 2-stroke diesel-punk 'throwback' ICE units, & will lobby to prevent it..

Hell, they even got them into M1 tanks!
But you cant buy a showroom production gas turbine car either - can you..

& why do you imagine 2-strokes are specifically banned in F1 & Moto G.P.?

[manolis]

Hello.

Thank you Gruntgugu and J.A.W. for your technical replies to my questions.

I think it would be more interesting a “strictly technical discussion” than a controversy about “who knows everything” (as the discussion turns to be now).

I put a few proposals for unconventional / “promising” two-strokes (for instance the PatRE rotary engine (it has some characteristics of the 2-strokes) and the tilting valve OPRE engine, etc).
Well?
What are their disadvantages you see?
Can they run at extreme revs?
Can they provide more power, reliably?

Thanks
Manolis Pattakos

[riff_raff]

.....Of course the turbine makers do not want their expensive, thirsty, inefficient units
replaced by 2-stroke diesel-punk 'throwback' ICE units, & will lobby to prevent it.......

All of the aeroengine companies that were building recip engines later switched to turbine engines, including RR, Napier, P&W, Allison, BMW, and even Garrett still mostly builds turbine engines. So I can't see any conspiracy there.

You should also remember that the new generation of large turbofan engines, with PRs exceeding 50, have extremely low SFC rates. And no recip engine could possibly come close to matching them when all factors are considered, including thrust/weight.

[J.A.W.]

r-r.. just what have your notions of "conspiracy" got to do with it?

It is, in reality - commercial interest, which is far more deadly..

& of course - giant high speed turbofans are best for jet airliners & such..

But if you'd bothered to read the NASA/Garrett design proposal for a helo mill, you'd see..
..that in smaller applications - from cars to (slower airspeed) aircraft to tanks.. ..gas turbines are..
.. significantly less efficient, more costly, & offer lower performance parameters accordingly..

However, legalistic 'liability' issues clearly constrain new developments, as vested interests do in military modes.

& why are giant 2 -strokes used in cargo ships & giant turbines are not?
Costs..

& Manolis, all the best with your innovative designs, I'd really like to see some running,
& well supported by some big buck investment/sponsorship, that lesser designers have received..