I thought the weight and the height of your new 175cc Opposed Piston is not "confidential" information; it seems it is.
The 635cc PatOP Diesel prototype engine:
weighs (without the flywheel) less than 20Kg and has 500mm total height (for 128mm combined stroke).
It is a Diesel, it has 17:1 compression ratio and is overscavenged (1.34 scavenge ratio).
Despite your "long experience in the two-strokes", do you have something better to show?
By the way,
anybody, ANYBODY from around the world, who asked the blue-print (the CAD drawing) of the above prototype engine, he received it (together with information about the materials and methods used). Companies and individuals. No secrets.
Worth to note here: the Opposed Piston uniflow-scavenging Diesels keep the temperature of their exhaust ports and of their exhaust pistons substantially lower than the spark ignition uniflow-scavenging Opposed Piston engines.
Unless you run it on HCCI, or some other kind of lean (cold) burn (say, like the SkyActivX of Mazda), you will need a lot of cooling at the exhaust side (piston and cylinder) of your new design.
I don't need experience to see this.
As for the reliability of your 2-cylinder engine, I read for 15 hours without problems (at moderate revs and power, for its capacity).
If you think this is great, OK.
One more thing:
Please do not use again expressions like "shut up" and the similar. It costs nothing to be polite.
How many times do I need to show this manolis?
Here again, 25 years ago, 440cc, 9500 rpm, full load for some time, no seizures. It spent a good six months in this hull, until the owner wanted his boat back.
Opposed Piston, petrol, crank case charged, spark ignition, I have some experiance with this type of power unit.
My new 175 has similar innards, but like I said some new innovations to make it even better.
Weight of 175cc? not finished, but also I make no claims either.
Power, also no claims as I don't know yet. I'd be disappointed if I didnt see around 30HP @ 10 to 12 thousand revs.but that is pure speculation.
Size, 380mm tall. this is using a square bore and stroke on each piston crank assembly, no compromises in rod ratio at 100mm eye to eye .
Twostrokes that run short stroke, large bore suffer poor port / time / area.
84 x 30 is not very performance orientated, at all.
My twin cylinder aero engine has done more hours now as It is working prototype, not just a concept.
Last edited by uniflow on 04 Oct 2020, 11:34, edited 2 times in total.
The nazi development of V1 ramjet missile, reed valves in front, expansion chamber and a tapered exhaust.
With the correct proportions the system sustains itself and produces a thrust, this technology was transfered to the 2 stroke engine and it improved power output by large percentage.
Its the overlap of the timed ports, the reed valves and the expansion pipe working in harmony to produce the 'powerband'.
This is why we have the high outputs, sometimes the reed is a disc valve instead, but once timed correctly the powerbsnd still happens.
The Pattakon system seems to lack this scavenge at overlap without any expansion chamber, this technology was the domain of the Victa lawnmower of the 1950's.
I admire his talents, but its a long road to prove the world is wrong.
The nazi development of V1 ramjet missile, reed valves in front, expansion chamber and a tapered exhaust.
With the correct proportions the system sustains itself and produces a thrust, this technology was transfered to the 2 stroke engine and it improved power output by large percentage.
this is Wiki-age nonsense .....
the V1 wasn't a flying 'expansion chamber' (in the modern sense)
as I posted better a couple of years ago ....
pumpless cylinder charging via 'tuned-length exhaust' was Kadenacy's idea - Armstrong such stationary engines c.1928
the Americans (conveniently for patent disputes) found they had the same ideas
there's an owner's account of empirical pipe tuning by slip-joint manipulation in a 1929 boating magazine
(in the modern sense) the first expansion chamber appeared on the DKW 125 racer in 1953
then on the 250 and 350 handily for DKW's big go in the 1955 350 WC
here and I ask (again) .... having probably lost some tiny Gordon Blair plots once available on the interweb ....
is the mean exhaust pressure in the EC significantly above ambient ? (the purpose of the tiny tailpipe diameter ?)
btw all that stuff about the exhaust benefits of 3 cylinders appeared in a SAE paper Saab in the early 1960s
btw today's news to myself is that ......
a flat-crank 3 and conventional 3 would have about the same vibration
the rubber-mounted 3s (Suzukis and late non-750 Kawasakis) woudn't seem to be proper isolation systems
and that Scott 100+ years ago .... invented/made ....
the 180 deg twin ('chainbox' wide cylinder spacing) with very wide-spaced mounting lugs and torsionally stiff frame
and the deflector piston, and variable inlet and transfer timing, and 3 cylinder 750 and 1000cc
and that the 2 stroke Rotax seems to have been rather superceded by Hirth's Rotax-fit designs
Hirth also have a 2 stroke 'boxer'
BMW's 1800cc 'cruiser' 'boxer' seems useful to aviation
Last edited by Tommy Cookers on 04 Oct 2020, 13:37, edited 1 time in total.
So manolis, how is the pilot attached to the motor unit? Is he in some sort of parachute harness? Your prediction of 2g deceleration would imply so otherwise he will be very uncomfortable..... Early rock climbers who used a waist loop to tie themselves in were subject to suffocation while hanging after a fall as the loop pressed on their diaphragm and prevented breathing. I'm a climber and am familiar with climbing harness and hanging loads.
'Put up or shut up' is not an insult, it's an English idiomatic expression meaning prove it.
You write: "btw today's news to myself is that ......
a flat-crank 3 and conventional 3 would have about the same vibration"
The kind of their vibrations is substantially different.
The flat-crank 3 has a strong unbalanced inertia force, it also has a strange / asymmetrical inertia torque and uneven firing.
The conventional 3 has a strong unbalanced inertia moment (for the rest, it is near perfect).
Things get worse for the flat crank 3 in case they are two-stroke engines:
The two-stroke flat crank 3 fires per 180 crank degrees, with the one cylinder firing alone and with the other two cylinders firing simultaniously (and giving a two times stronger power pulse). The feeling will be close to a single cylinder.
The conventional 3 two-stroke has equal combustion pulses per 120 crank degrees.
With its lower inertia torque and the even and evenly spaced combustions, it gives the sense of turbine.
To "have about the same vibration", as you write, is not reasonable.
You write:
“'A very brief period' - in time.
Comparing an engines running at 80 rpm and 4000 rpm is hardly valid when the issue is charging time. The W has 50 times the time available to the Cox.”
Since the Wartsila X92 is a slow revving 2-stroke (yet it is not if you consider its piston speed (similarity); at 76rpm the mean piston speed is: 3.468*2*76/60=8.8m/sec),
125cc Turbo - Original TZR125 twostroke turbocharged by Boostbusters
Comment from Cooknasty300:
So how do you compensate for the scavenging effect of the 2 stroke? The sound wave pushes the unburned fuel back into the cylinder, but with a turbo, there would be a constant one-way vacuum which would disable this necessary effect in theory am I right?
and reply by Tyson James:
The pipe still works fine as the pressure wave is reflected back up the pipe like it is designed. The difference is with the turbo there is more exhaust backpressure as you are pushing a greater volume of air through the same size pipe then using it to drive the turbine wheel. If you watch the dyno pull when it spools up you see the exhaust pipe start stretching the springs at the manifold from the added pressure. So yes the intake charge blows in the chamber at a greater pressure but the exhaust pressure is also higher. 2 strokes love boost
End of Quote
Spot on where the turbocharger is located.
At 11,000rpm, the high revving small (50mm stroke) TZR125 has a mean piston of:
0.05*2*11,400/60=19m/sec, which is only double than the mean piston speed of the low revving Warsila X92 (by the way, at the 8.8m/sec mean piston speed the Wartsila X92 can work continuously at full load for weeks).
You also write:
“That 'post' running through the chamber wouldn't be my first choice either. But in Cox's defence, they are claiming excellent reliability/durability so presumably it doesn't impinge on those aspects.”
Suppose it is so, i.e. the Scotch Yoke of Cox engine offers excellent reliability.
Isn’t it strange that they don’t use it in a conventional 4-stroke engine (as CMC did a decade ago) replacing the typical “connecting-rod / wrist pin” mechanism?
Why to limit it to an unconventional design?
More reasonable is that they try to justify the increased friction and the reliability issues of their Scotch Yoke by the unquestionable compactness of the design. This is their basic advantage: a compact and lightweight design for outboard Diesels (not a design that offers better fuel efficiency).
You also write:
“Ricardo was of the view that the swirl necessary for CI combustion when achieved with a uniflow scavenging pattern left a core of residual exhaust products at the centre of the cylinder at high delivery ratios. The 'post' then is merely occupying what would be a dead zone anyway.”
The question is whether the unavoidable increase of the cylinder wall surface and the added sets of piston rings are justified by the decrease of the core of residual exhaust products "because the post occupies their place". But let me doubt.
The “cage” keeps the ring of the auxiliary piston in place all the time, and allows good scavenging everywhere.
Thanks
Manolis Pattakos
How is possible turbocharge a 2 stroke petrol engine carbureted? Exaust port and the fuel port are open at the same time. The fresh charge is not blow out through the exhaust port by the turbo boost?
silly old Laverda !
making and selling about 2000 3C machines with solid-mounted flat crank 1000cc and 1200cc engines
using terminology like 'feelings' and 'sense of a turbine' - that's what's not reasonable
IIRC, Laverda thought it was "reasonable" to use the same crank-building jigs as its flat-crank
750cc twins - as a manufacturing expedience measure - but later adopted the 'tri-star' 120`crank.
(Was the short service life of their cam/primary chains a result of 'abrupt' inertia torque impulses?)
Honda did use the 'heavy' centre conrod set-up on its production roadbike V3 250cc 2T machine.
"Well, we knocked the bastard off!"
Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).
You write: "How is possible turbocharge a 2 stroke petrol engine carbureted? Exaust port and the fuel port are open at the same time. The fresh charge is not blow out through the exhaust port by the turbo boost?"
Think the case you put a conventional carbureted 2-stroke to operate in a sealed room wherein the pressure is increased at 2 bars. It will double (or so) its power output.
The turbocharger does a similar job: it keeps both, the inlet and the exhaust pressure substantially higher than the ambient pressure.
If it is still confusing, think the case of a supercharged 2-stroke (say, a compressor feeds the inlet).
For instance, think the PatOP (post at top of this page) wherein the scavenge pump capacity is 850cc while the cylinder capacity is only 635cc (scavenge ratio: 850cc/635cc = 1.34).
It doesn't matter it is a Diesel. It could operate as a carbureted 2-stroke petrol, too.
Normally the exhaust ports close after the transfer ports.
So the surplus of air in the cylinder escapes through the exhaust (this is not bad if you think that the additional air, among others, cools down the exhaust piston crown and the exhaust ports on the cylinder).
But if you put a restriction / an obstacle at the end of the exhaust pipe, you can keep the pressure of the exhaust substantially higher than ambient (say, at 1.3 bar when the exhaust ports finally close). Yes, the scavenge pump will absorb more power from the crankshaft, however the trapped air in the cylinder will be much more than 635cc (nearly 850cc) and the power output will increase substantially.
Instead of the above restriction / obstacle, you can simply close the exhaust substantially earlier than the transfer (say, by phasing the intake and the exhaust of an Opposed Piston).
It is what the single piston PatATE two-stroke (at https://www.pattakon.com/pattakonPatATE.htm ) does:
In case of a supercharged carbureted petrol 2-stroke, the abovementioned restriction / obstacle is actually the turbine of the turbocharger.
You write:
". . . but later adopted the 'tri-star' 120`crank.
(Was the short service life of their cam/primary chains a result of 'abrupt' inertia torque impulses?)"
It seems it was: heavy inertia torque pulses combined with heavy combustion pulses.
See the plots in the reply to Tommy Cookers
.
