ESE's works engine tuner

[jonny quest]

Were combustion pressure and hot gasses burging off the lubrication on piston skirt?

That test definitely wasn't thought out very well. Pretty much a farce

[Pursang]

Were combustion pressure and hot gasses burging off the lubrication on piston skirt?

That test definitely wasn't thought out very well. Pretty much a farce

The pictures were hard to see, but more combustion marks on upper of Al than steel piston.
BUT, so many variables, Gaps, tapers, Cam, operating temps, etc.

The Military Industrial Complex provides grant money to conduct "interesting" experiments on 2T motorcycle engines.....
....and you call that a farce? Shame on you I want to know where to send the application.

"Busted" I don't really know that. Just cos it didn't work great this time, doesn't mean it can't eventually.
Like many of the MythBuster's experiments the result could be quite different with improved set-up & techniques.
(But possibly less Telegenic & less Blow ups)

Look at it this way...they tried some stuff and found out some things that worked better than others.
And they reported what they did and what they found.
Certainly pointing one possible way to low friction, hi reving, more powerful 2T racing engines.

If anybody was looking in that direction (forward?)

Cheers, Daryl


"First they tell you you're wrong, and they can prove it.
Then they tell you you're right, but it's not important.
Then they tell you it is important, but they knew it all along."
Charles Kettering.

[Hemi Makutu]

To be fair, Rotax have incorporated composite Fe/Al pistons/Fe bore coat in their hard running E-TEC Ski-Doo mills..

This is to support the ring lands while running on the edge of lean/low lube due to economy/emissions control needs..

[TZ350]

Were combustion pressure and hot gasses burning off the lubrication on the piston skirt?

Certainly one of the possibility's advanced in the study.

"Busted" I don't really know that. Just cos it didn't work great this time, doesn't mean it can't eventually.

Look at it this way...they tried some stuff and found out some things that worked better than others. And they reported what they did and what they found. Certainly pointing one possible way to low friction, hi revving, more powerful 2T racing engines.

If anybody was looking in that direction (forward?)

Yes, like you say I have had enough failed pistons of my own ....

These guys were paid to explore the ringless piston idea and publish their findings. Busted, well maybe or maybe not but they certainly put some effort into exploring the basic idea and arrived at a point where my interest in exploring ringless pistons for myself is certainly busted.

The idea was good, certainly cought my interest but I noted that even on the best runs the ringless piston did not make anywhere near the power of a conventional RM piston and ring and the setup was very fragile. They suggested improvements like a labyrinth seal instead of a ring but I suspect that after a lot of effort even the best ringless power wise will only come close to a conventional piston and ring.

I don't imagine I could do better than they did, so thanks to their efforts I now think it would not be worthwhile exploring ringless pistons myself but if anyone has the energy to make the effort, I am happy to do the dyno work for free.

Ringless Pistons ....... I am still struggling with my EFI 2T project.

[Hemi Makutu]

For a defunct technology (Wankel rotary piston engine) a fiddler has obtained nearly a US $ mil to play with..

http://www.businesswire.com/news/hom...Fuel-Efficient

Stupidity/lack of due diligence/kickbacks? Suspicious, sure, but whatever.. Trump might buy it..

Frankly, anyhow you cut it though , such a mill - fundamentally - cannot be 'eco'-trained..

Look at all the really big bucks companies who tried & failed, even Toyo Kogyo 'Mazda' had to flag it, 'ross of face' or no...

[Pursang]

My Mind is Open...my wallet is closed.

Cheers, Daryl

"First they tell you you're wrong, and they can prove it.
Then they tell you you're right, but it's not important.
Then they tell you it is important, but they knew it all along."
Charles Kettering.

[Hemi Makutu]

My Mind is Open...my wallet is closed.

Cheers, Daryl

"First they tell you you're wrong, and they can prove it.
Then they tell you you're right, but it's not important.
Then they tell you it is important, but they knew it all along."
Charles Kettering.

More than that useless lump of flim-flam... but only by 'an order of magnitude' - or so...

[Pursang]

No Apex Seals = No Piston Rings

from LiquidPiston on Vimeo.

[Hemi Makutu]

Unless they can get away with running it so lean/low powered - it makes no pressure/power/heat..

The fundamental epicycloid rotary piston issues with massive combustion chamber area/heat rejection are still there..

[Frits Overmars]

Used to be, Hemi, used to be. Now it's 24/7 all the time .

So that's 24/7 x 24/7 = 11.755

I was wondering if anyone would notice the pun. Glad you did .

Look at it this way...they tried some stuff and found out some things that worked better than others. And they reported what they did and what they found. Certainly pointing one possible way to low friction, hi reving, more powerful 2T racing engines. If anybody was looking in that direction (forward?)

How about looking back for a change? Then they might have found the rather more thorough research into ringless pistons carried out by the then-leading two-stroke company MZ around 1960. Their conclusion: it won't work.

That test definitely wasn't thought out very well. Pretty much a farce.

I'd say that's a pretty good summary Jonny. Among the various phrases that hurt my eye, this took the cake:

"The piston weight must match the stock aluminium piston weight to maintain the proper engine balance"

This has nothing to do with thermodynamics or gas dynamics; it's just plain simple mechanical engineering, or rather the lack of it.
Anyone with a basic understanding of reciprocating engines should know that lightening a piston in an engine without balance shaft, such as the Suzuki RM250 that was used for the test, will always reduce the inertia forces and improve the balance (unless you lighten the piston so much that the crank bobweights shift the balance factor to over 100%, which will be practically impossible to achieve).

No Apex Seals = No Piston Rings.

The LiquidPiston engine does use apex seals, Daryl. But they're not in the rotor tips, but stationary, in the housing, where they can be better cooled.
I had a discussion with the inventor a couple of years ago. The combustion takes place in a hemispheric chamber which is a huge improvement compared to a Wankel.
But then the exhaust gases are lead down through the rotor, heating it up asymmetrically, which spoils the idea for me.

[Pursang]

I was wondering if anyone would notice the pun. Glad you did (well, actually it's 11,755102 ). I do Engineering not Science.

How about looking back for a change? Then they might have found the rather more thorough research into ringless pistons carried out by the then-leading two-stroke company MZ around 1960. Their conclusion: it won't work.

Maybe, but what if MZ had decided to solve the issues and make it work, they might still be the leading two-stroke company.

There were a lot of things in 1960 that were impossible/implausible/impractical that we now benefit (or suffer) from everyday.

How many back then would have thought that a 125cc single could produce 50+ HP or a two-stroke engine could run effectively with the crankcase exposed to the intake 24/7?

Cheers, Daryl


"First they tell you you're wrong, and they can prove it.
Then they tell you you're right, but it's not important.
Then they tell you it is important, but they knew it all along."
Charles Kettering.

[lohring]

Here is a solution to that problem.https://s3.amazonaws.com/WEBPOSTS/KI...ston+trial.pdf

Don't need to worry about cross heads and linear piston movement.

Just make your own Ringless, Chrome plated, Steel pistons. Keep the revs over 5000.

Cheers, Daryl
[/I][/SIZE]

Ringless pistons have been around in small engines for a long time. They are superior to ringed pistons due to lower friction. They require a special fit and have the advantage that the methanol based fuels run at a lower temperature than gasoline. Very small engines (up to 1.5 cc) have been mass produced with steel pistons in steel cylinders. The most successful use high silicon aluminum pistons in chrome plated brass liners. This is called an ABC piston and liner. Chromed aluminum liners also work and that's called an AAC piston and liner. Those all work well up to around 15 cc. One manufacturer tried his AAC system on a 35 cc gasoline engine. That was a disaster and he went back to a ringed piston.

Lohring Miller

[TZ350]

Maybe, but what if MZ had decided to solve the issues and make it work.

How many back then would have thought that a 125cc single could produce 50+ HP or a two-stroke engine could run effectively with the crankcase exposed to the intake 24/7?

Cheers, Daryl

I am not sure if it was MZ but it was about that time, someone's disk valve 2T seized the disk in the open position during a dyno run. It was noted that it continued to make full power until the throttle was closed and the revs dropped so 24/7 has been known about for a long time. 24/7 has also been used in old 2T stationary engines where the engine is cranked up to speed and then inlet pipe resonance takes over and keeps it at a steady industrial like tickover suitable for generators, milking machines and pumps.

There are some things that are better acknowledged as being impossible. After a bit of a try most realize that you can't lift yourself up buy your shoe laces. But an enthusiast could buy better shoe laces and keep trying I suppose.

[Frits Overmars]

I am not sure if it was MZ but it was about that time, someone's disk valve 2T seized the disk in the open position during a dyno run. It was noted that it continued to make full power until the throttle was closed and the revs dropped so 24/7 has been known about for a long time.

It happened to me in 1973.

[husaberg]

I am not sure if it was MZ but it was about that time, someone's disk valve 2T seized the disk in the open position during a dyno run. It was noted that it continued to make full power until the throttle was closed and the revs dropped so 24/7 has been known about for a long time. 24/7 has also been used in old 2T stationary engines where the engine is cranked up to speed and then inlet pipe resonance takes over and keeps it at a steady industrial like tickover suitable for generators, milking machines and pumps.

There are some things that are better acknowledged as being impossible. After a bit of a try most realize that you can't lift yourself up buy your shoe laces. But an enthusiast could buy better shoe laces and keep trying I suppose.

It was MZ Rob, re the rigless pistons whoops i just noticed you were talking about the valve

but to be fair they had very little metalurgical expertise and were also not able to build decent forks or ignitions or spark plugs.
Pretty sure its mentioned in here, anyway i have posted about it previously.

Kaaden unsuccessfully tried ringless pistons. But his access to metallurgy was known to be poorer than the Japanese or Europeans. yet the Japanese and Euros never went this route either.
Your post there got me thinking about how one some of the tiny aero engines have no rings Secondly if anyone had ever tried a piston design with a Lab type combustion seal arranged of multiple grooved pockets.
Maybe with a better guided piston ring friction and the breaking of seal with tilting is not an issue and design can be different
I do however thing the limiting factor of high speeds breathing limitations was due to blowdown rather than total port area of the EX port. So it might be moot.

Cross heads change the angle to solely up and down they rid the thrust friction due to rod angularity.
That's why modern ringless Compressors use them as they can't allow the gas and the oil to mix otherwise they might explode.
.

Ringless pistons. Of course rings add friction, but the trade-off is that they also provide the proportional sealing of pressures, up to around 90 bar (1300 - 1400 psi) at all sorts of rubbing speeds and high temperatures, not a trivial task. Should they fail, as we’ve all seen with a stuck ring; blowby, loss of lubrication and death.
In a small engine, say a glow plug, one seemingly can get away with it, mainly due to viscous sealing because of the typically 20% oil quantity in methanol &/or nitro fuels, and possibly lower overall temperatures inherent in small engines due to the surface area to volume ratio effect providing a much greater heat transfer rate, at the expense of inherent lower overall thermal efficiencies.
Another thing that has been demonstrated, is that the crevice volume, formed between the bore and the top land above the ring, can result in trapped mixture, leading to unburnt HC emissions. This is why rings have been become higher up the piston. This is not so critical in a stratified charge running condition where, hopefully, only air or burnt gases enter and leave the crevice volume.
I am personally of the belief that a large percentage of the heat from the piston is transferred via the ring and rubbing contact of the ring land (the hottest part of the piston) against the bore. This effect is greatest at the TDC and BDC, where the piston land and ring area have the greatest residency time over the cycle. It is for this reason that cooling of the cylinder is best directed at the very top and also adjacent to the BDC area, usually within the transfer passage cup handles.
.

I think its interesting but a dead end, there is more pressing problems limiting a two stroke emissions etc.
interstingly reading about the Vdue Bimota it seems most of the problems it intitially had have been solved and traced to poor fuel mapping and leaky crankcases casting poor seal design and poor assembly detail.

Ed. Note December 2013 - Since writing this piece in 2012 I've learned that the main problem with the V-Due is improper crankcase sealing due to flaws in the crankcase castings, not simply a wonky fuel injection setup. You can fix a V-Due! Bob Steinbugler at Bimota Spirit offers newly manufactured crankcases that fix this issue and allow you to rebuild the V-Due into the screaming sport weapon it was meant to be. If only Bimota had known

Makes sense right?! Erratic power delivery with injection or carbs...
He has cast his own case halves to accept a proper beefy 2-stroke crank seal and offers them for sale separately or will rebuild your entire engine.

http://rideonboard.net/onboard-the-bimota-vdue/