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Toroidal Opposed Piston Engine
3

Toroidal Opposed Piston Engine

RE: Toroidal Opposed Piston Engine

And the advantage is supposed to be.

Obviously not lower manufacturing cost.

I don't see a possibility for less friction.

There is no weight or heat loss from a cylinder head, but there seems to be a lot more cylinder block.

Regards
Pat
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RE: Toroidal Opposed Piston Engine

Fun with CAD or another example of someone with more CAD skills than real life practical experience.

How do you oil those downward facing pistons?
How much power loss does reversing that large piston assembly cause?
How would you ensure the block and piston assembly both expand at the same rate so the piston stays centered in the bore?
How could you even manufacture the thing given typical machining tolerances?

And these are the big problem I thought of with just one look at that thing. Maybe we should make a game of finding all the weaknesses in these CAD engines?
 

RE: Toroidal Opposed Piston Engine

(OP)
Obviously not lower manufacturing cost.?
==>Please explain.
I don't see a possibility for less friction.
==> There is no explosion-force hitting the pistons against the cilinderwalls. No friction, no wear.
How do you oil those downward facing pistons?
==> Study Junkers or Commer if you rotate the engine 90 degrees.
How could you even manufacture the thing given typical machining tolerances?
==> Has been done for the Wolff-patent recently.
How would you ensure the block and piston assembly both expand at the same rate so the piston stays centered in the bore?
==> these are wet cylinders




etc : sorry for my basic english.

etc..
 

RE: Toroidal Opposed Piston Engine

(OP)
... but there seems to be a lot more cylinder block.

Compare the volumes of the cylinder en pistons with the volumes of all the mechanical parts to convert the thermal energy in a rotatable mechanical energy of an opposed piston Junkers, a opposed piston Commer ( TS3), of any other single piston four-stroke with valves.
 

RE: Toroidal Opposed Piston Engine

Franky,

   I hope I live to see the day you put these skeptics in their place by actually producing one one of those winky smile

RE: Toroidal Opposed Piston Engine

Quote:

==> you are so funny for an electricien.

Build one and make it run and it's superior to all other working engines. Then you'll have the last laugh.

You've got pistons on both sides of the block. You're showing them left and right but suggesting run them top and bottom. Top and bottom leave the bottom ones with the middle of the bore lower than the starts of the bore meaning oil that gets in the cylinder will not drain out. The only way I see around this oiling problem is to stand it on end.

You've got extra pivots and links and more mass you are reversing with each piston stroke compared to a typical production engine. So, why will this design have lower losses than current production engines? Trading a little piston friction for more bearing friction and more inertia losses due to changing the direction of moving mass isn't a win.

 

RE: Toroidal Opposed Piston Engine

(OP)
I have a company myself. We develop and build machines, 25 years already.

My company is "perhaps fun with CAD or another example of someone with more CAD skills than real life practical experience-as you wrote."

The second generation engine is being build. This one is open source as a warm-up.

Still haven't studied Junkers or the Napier-Deltic or the Rootes Commer TS3 , haven't you. Doesnt matter in what angle the cilinders are.  Google is waiting for you.

There is no litle pistonfriction, there is NO piston friction except for the seals ofcourse. Pistons and beams are fixed and therefore not hitting the cylinderwalls. Ceramic producers will love this. I prefere greasing joints.Everybody does.

I thought this was a forum for engineers, my mistake.

 

RE: Toroidal Opposed Piston Engine

Your pistons have skirts. Why waste the metal if they don't touch anything.

You also have 3 cranks and a gear drive system.

Some of the pistons will retain oil. Not an insurmountable problem, but far from ideal

By the way this forum is for engineers who behave in a professional manner. Spitting the dummy when someone questions your statements of alleged fact is unacceptable conduct, as is promoting snake oil. At this stage you are borderline on both counts.

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
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RE: Toroidal Opposed Piston Engine

How do you machine a toroidal cylinder bore with acceptable accuracy and surface finish to allow proper piston ring seal? I'm not saying it can't be done - just that I haven't seen how it can be done.

Even piston rings are normally designed to work in cylindrical cylinders, not toroidal cylinders. The local shape of the piston rings has to match the curvature of the "cylinder" so piston ring orientation would have to be maintained. Not impossible, just another thing to think about. I'm not sure how you would make piston rings with a locally convex shape on one side and a locally concave shape on the other side, or whether ignoring this would have any repercussions (I tend to suspect that it would).

Normal cylinder boring and honing equipment only works with cylinders - not toroids.

I should note that Wankel engines also have an odd shape to them - but it is only an odd shape in two dimensions. The apex seals are straight. Those sure had their own set of sealing and oil consumption headaches.

I don't get the claim that there is "no" piston friction. It's got crankshafts and con-rods (which impose a side load on *something*) just like a normal engine. If you solidly guide the pistons so that they are "not hitting the cylinder walls" I guarantee that your engine is going to seize due to differing thermal expansion of the various components unless excessive clearances are provided for ... or you design in some "give".

Piston-porting is always associated with at least *some* loss of lubricant oil out of the ports. Detroit Diesel gave up on piston ported two-strokes largely because of this - and those were "normal" piston and crankshaft engines without the additional headaches of having toroidal cylinders and pistons. Oil out the exhaust or into the combustion chamber is a no-no due to emission regulations.

What combustion system is proposed here? You can't use a normal diesel engine central injector and piston bowl. You can use spark ignition but the spark plug would be at the side of the chamber - not ideal. Again, not saying it can't be done, just that it's another set of things to think about. Poor combustion chamber design means poor efficiency and emissions if you get this wrong.

Opposed-piston concept with this scavenging and combustion concept are possible to achieve using normal cylindrical cylinders and pistons so that you only have to overcome the emission and combustion headaches without additionally having to overcome the difficulty of machining.

I've taken apart and modified and rebuilt my share of "normal" four-stroke piston engines in my own workshop and I have a reasonable understanding of why a good many things in a normal engine are the way they are. Have you done that?

RE: Toroidal Opposed Piston Engine

Junkers or the Napier-Deltic or the Rootes Commer TS3

And what is the current production state of these engines?

Your video claims "based on proven opposed piston technology for fuel economy and low emmisions ratings". Where are these current opposed piston engines that have good fuel economy and low emmissions? Remember, production engines are proven designs. Concept engines are not proven designs.

It appears you're claiming the piston and the large pivot arm is one piece. It will be extremely difficult to have a production line machine the block and piston assembly so they mate properly. Then, the expansion rate from the pivot point to the bore center line will be different for the block and for the piston assembly. This will cause the engine to scuff or seize the pistons when the engine temperature changes. You'll likely want to run at most 0.002" clearance between the piston and the bore so there is very little tolerance for error and for varying temperature expansion rates in this assembly.

I believe you will need some form of connecting rod between your piston and that pivoting arm if you expect it to work. You lose your frictionless advantage with a connecting rod. Once you add a connecting rod there is no point in making that extremely difficult to machine toroidal bore.

You posted a link to an CAD engine concept and expected some kind of response. There are a lot of very difficult issues for you to overcome if you expect the design to work. I personally don't feel this CAD design will ever reach production. You don't have to agree with my opinion.
 

RE: Toroidal Opposed Piston Engine

(OP)
@patprimmer : i am the one with with more CAD skills than real life practical experience, remember ?

@brianpeterson : this conversation looks promissing.

how to machine? There is a you-tube film of someone remanufacturing the wollf-patent.  http://www.youtube.com/watch?v=cSOzSKxtWzg ( all his movies or quit interesting conserning toroidal engines ). Have no idea if he honed it.
I myself used for the second enginetype vonkerosion ( don't know if that is the correct english word )in prehardned cylinders, no need for honing.

Wankel in NSU and MAzda : i know the tipseal problems. The pistons in the TROPE are locally cilindrical for the pistonseals with ring fixation for the scavengingports.
I also thought having compressionloss ( convex-concave )but it seems ok. The second engine is having variable compression , because i'm working on HCCI, but that's another item.

Free piston. There is no force ( explosionpressure multiplied with the surface , quite a lot ) slamming the piston against the wall as soon as the piston has left BDP. If you have opened a engine you will noticed the elliptical wear bigger at the top to less at the bottom. fig : http://www1.learningbox.nl/mobikit/attachments/Zuiger/zuigers.jpg  The swingbeam with the fixed pistons have a momentum around the central shaft and are pulling also at that central shaft. All the forces are situated in the rotanting and pivotating ( what a word ) joints.

Loss of lubricant oil out of the ports. Agree. Therefore i prefer quasi vertical cylinders with the cooler inletpistons at the top with reduced lubrification . Pistons being free helps a lot. Not like a Junkers, there is no oil dripping on the back of the upper pistons because these shafts and those cylinders are not vertically lined up, because of the toroidal shape. Eventually leaking oil from the upper pistons can be burnt, bottom leak from the outletpistons is no problem, as you mentioned.

These were usefull remarks. Greetz.

RE: Toroidal Opposed Piston Engine

I think that from now on we should talk in these forums only about the positive aspects of these oddball designs, and avoid any discussion of the negatives.  Let those who would invest in them learn from experience where the problems lie.  
 

RE: Toroidal Opposed Piston Engine

(OP)
@LionelHutz

Maybe a email to Bill Gates  ? http://www.greencarreports.com/blog/1047122_bill-gates-backs-ecomotors-new-opoc-engine-with-23-5-million-investment

There is still a lightweight opposed piston airplaine engine. Two-sroke diesel, fueleconomy and great power to weight.
http://www.dair.co.uk/

Nobody says it's easy. The easiest stuff is already being thought of. Vonkerosion is a beautifull techniek that wasn't available in the early day's of combustion engines. The sleeves of the cylinders for the swingbeams able to pass by helped the erosionhead going deep to the point were the cilinderwall collisioned with the erosionshaft. Hope you understand what i mean, English is not my native language.
 

RE: Toroidal Opposed Piston Engine

We have had a complete revolution in diesel FIE during my (short, ~25 year) career, plus one or two dead ends.  Who's to say that the basic mechanical design that implements an Otto/Diesel cycle can't change?

The garage/CAD inventors should be praised.  Unless they start syphoning government funding.

- Steve

RE: Toroidal Opposed Piston Engine

(OP)
the copper erosionhead is a ball-shape offourse.

RE: Toroidal Opposed Piston Engine

@steve - yeah, but the need for (and benefit of) ever higher injection pressures and better control of timing has been apparent nearly the whole time.  Few out there in the engine world are saying "boy if I only had a piston that went in circles, I could meet my customers' and regulators' needs so much better!"

 

RE: Toroidal Opposed Piston Engine

"boy if I only had a piston that went in circles, I could meet my customers' and regulators' needs so much better!"

... I was parked next to an RX8 this morning.  His pistons go round in circles.

 

- Steve

RE: Toroidal Opposed Piston Engine

yeah... and what an improvement, eh?

RE: Toroidal Opposed Piston Engine

Playing devil's advocate of course, although the horns don't really suit me.

The real verification of a novel mechanical design would be when it gets banned from motor racing.  Like the Wankel effectively did from both car and bike series.  However, racing is mainly power/weight, not practicality.

- Steve

RE: Toroidal Opposed Piston Engine

I believe by "erosion" you are talking about a process such as EDM. Keep in mind that EDM is a "slow" process, which generally implies an "expensive" process. Machining is a "fast" process.

I don't agree with only talking about the positive aspects. Discussion with others results in asking questions that one may not have thought of otherwise. Inventors tend to be overly focused on the merits of their own design and not think about the real world problems that they are going to encounter. If the discussion results in the inventor accounting for whatever the problem or issue is, and then making a better design, that's a good outcome. If the discussion results in the idea being abandoned, then perhaps saving someone the cost of building something that doesn't work can be a good thing, too ... Back to the matter at hand.

I don't know enough about surface finish achievable by EDM to state whether proper piston seal is possible without honing. I do know that a mirror finish will have poor results in terms of piston sealing, piston ring wear, etc. The crosshatch keeps just enough oil in the surface to lubricate the compression rings. Can this be achieved by a method other than honing? Perhaps, but honing is the way that I know how to do it. Some engines nowadays use a plated hard coating on top of an aluminum cylinder block, but even those are honed to get the proper surface finish for good ring sealing.

I know the original poster is dismissive of the effects of lubricant oil past the cylinder wall ports. I strongly encourage the original poster to study the experience of Detroit Diesel. In those engines, only the inlet ports were piston-ported (the exhaust used cam operated poppet valves in the head) and this means that theoretically (almost) all of the oil allowed to escape would go through the cylinder's combustion process ... but even this was not good enough for today's emission standards, and Detroit Diesel had to abandon their heritage of two-strokes and go to a four-stroke poppet-valve design. Some outboard boat motors and snowmobile engines and small scooters still use two-strokes but only in applications subject to less stringent emission regulation, and even those are going by the wayside. Even if you manage to get piston ring sealing to be as good as with a "cylindrical" piston engine, I still think this issue will come back to bite you. In your situation the exhaust is unavoidably piston ported, and you are going to get unburned oil out the exhaust EVEN IF you solve all of the other issues.

Regarding the wear issues, the upper "wear ridge" is seldom seen any more in a normal piston engine if proper maintenance has been done. It's not unusual to see a standard piston engine with 300,000 km or more and the original crosshatching (honing) on the cylinder wall is still there. Why solve an imaginary problem? Sure, a standard piston has side loading on it. They're designed to handle it. So what?

RE: Toroidal Opposed Piston Engine

frankydevaere - I wish you luck because to me it seems you are trying to make your design as difficult a project as possible.

You posted this is the second generation engine design. Do you have a constructed and working first generation engine design?

I don't see the present piston designs as having any real friction or wear issues. Engine refinement has sure given cylinder bores in new engines nice long lives.

Concerning the Wankel and racing. Race sanctioning bodies love to either limit or handicap racers using numbers such as engine displacement. It's easier to ban the Wankel than to police displacement parity between a piston engine and a Wankel engine. The Wankel tends to trade durability and longevity and emmissions for power and weight, which just happens to fit well into the racing world. A race engine only has to last one race and emmissions don't matter It's too bad the Wankel can't race when it appears to be well suited towards racing.

 

RE: Toroidal Opposed Piston Engine

@Brian - when has such feedback ever been well-received?

RE: Toroidal Opposed Piston Engine

(OP)
Very well said Brian about the inventor-focus-merits. For your information, this design is open source, not licensed.

EDM is the word. Electric discharge machining. We call it in dutch vonkerosie '( could be litterly translated as sparkerosion ). Do quite a lot machining for the plastic moulding industry. That's where the idea popped up for being able to make toroidal shapes with narrow tolerances, as long as they are not to long/deep. And indeed it's an expensive process just because it's so slow. However it doesn't matter how hard the material is. Made once holes in rather big bearingballs for a special application. Have no idea about the need for the scratches for having a oilfilm in conventional engines or in this one.

Concerning the so what. This vertical friction force may be not longer a wear-ridge for the present state-of-the art engines but it"s still a powerloss for the engine that can not be ignored. I think the idea op placing that reactionforce elsewhere where lubrification is not so difficult should'nt be that bad at all.

Lubrificationleaking across the upper inletport is indeed an issue. Scavinging with pure air , instead of a mix fuel/air is a must. Didn't know that detroit switch over (had to switch over) to 4 stroke.

RE: Toroidal Opposed Piston Engine

(OP)
further

Where does the oil in a detroit diesel come from. Oil mist from the scavengingblower or from the upperinletvalve. or oilfume from under the piston ?


 

RE: Toroidal Opposed Piston Engine

Detroit Diesels have a normal crankcase and oil sump just like a 4-stroke engine. They have a scraper ring at the bottom of the piston to scrape the bulk of the oil off the cylinder wall so that an *excessive* amount doesn't go past the ports, and they have something to limit the amount of oil that goes out past the ends of the wristpin. The exact details of it, I don't know - I haven't had one of those apart.

The power loss by side loading of the pistons, if it is an issue significant enough to warrant dealing with it, can be controlled by methods far less complex than toroidal pistons. Longer con-rods and offsetting the cylinder bore slightly towards the power-stroke side (and this method is becoming more common) go a long way towards doing that.

RE: Toroidal Opposed Piston Engine

Spark erosion is the term generally used foe electron discharge machine. It is a common toolmaking practice

The rate of erosion depends on the current density applied. High current density is fast but leaves a very pronounced orange peel effect compared to normal bore or optimal bore finish. It also erodes the electrode or copper ball at the faster rate. The electrode is sacrificial and to get a progressively smaller bore as you progress down. This is all corrected by a final finishing pass at low current to get fine orange peel and more accurate size. I see two finishing passes required here. It sounds VERY expensive to me.

Oil control will be an issue without fancy profiles on the ring face as the top edge will seal on the outside and the bottom edge on the inside. The outside will therefore seal combustion gas well but not oil and the inside will do the opposite. Maybe not enough to be all that significant, but an issue none the less.

If the piston is located by a moving beam fixed at the piston end so it cannot rock, you need no more skirt than is required to support the rings and attach the piston to the arm or beam. The piston and beam could in fact be one piece of metal.

You still have what appears to be two crank shafts driving gears that drive the output shaft.

Unless I am reading it wrong, these pistons do not keep going around, they go to and fro in a curved bore, thus reciprocating and requiring all the energy necessary to do that.

Also piston rings are responsible for by far the greatest portion of metal on metal friction in an engine. The piston skirt is almost negligible in comparison and you still have the rings required and possibly even an extra ring to offset poor ring fit to the surface.

Regards
Pat
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for site rules
 

RE: Toroidal Opposed Piston Engine

(OP)
I looked at some drawings and article of the Detroit diesels.
In Europe this engine is unknown, in fact there are no 2-stroke diesels that i am aware of except for the UK-dair-opposed piston-airplaine engine, .

It's seems strange that this Detroit diesel is coping with even a more difficult valve-train than in a four-stroke, just to be a two-stroke. I mean the valve train in a fourstroke is rotating half the speed of the crankshaft. The detroit valve train is rotating at the same speed. That is racing, giving the time that the outletvalves opens and closes during scavenging.

It seems in many articles that detroit engines coped with oil consumption. Some writers blaming the lower compression and oil ring scraping up oil into the inlet ports, others blame the seals of the blower...

It's all about thermal efficiency and mechanical efficiency.

Thermal efficiency op opposed pistons is not really being discussed here.

Mechanical efficiency :

Free piston or side friction is one issue.The side force on a piston is a consequence of the connecting rod having to move sideways as it goes up and down, and hence cannot easily be avoided on a conventional piston engine.

Making the connecting rod longer will help but this will result in an engine that is tall and heavy.

The side thrust is responsible for 8 to 15 per cent loss of mechanical efficiency . An explosionforce for lets say 10000N on a piston in the first 6 degrees angle gives a side force of 10000N x tg 6degree = 1000 N.
Who wants to pull 1000N (200 pounds) resting on 10cm2 face.

Piston offset (1mm) is more a solution for the piston flipping over in TDC. ( i presume piston"slap" is the word )
 

RE: Toroidal Opposed Piston Engine

(OP)
@patprimer.

Nice info. For your information it's even possible to EDM ceramics if the product has a electrical resistance less than 100 Omh.cm ( miw with TiB2,TiN,Tic particles).

EDMachining ceramics should go even faster than steel-products but witch a greater roughness.

Would love more info on that.

RE: Toroidal Opposed Piston Engine

You're going to have the same issue with lubricant being scraped past the ports. You're going to have a worse issue because of the oil being scraped past the exhaust ports as well instead of just the intake ports. The Detroit diesels topped out around 2500 rpm, which is in a common range for engines of that size; sure, the valvetrain is going twice as fast as a four-stroke at the same RPM but doing that at 2500 rpm is not a major problem.

Wrist-pin offset of 1mm can be for piston slap but that's not what I'm talking about. On quite a number of newer engines the crankshaft is not on the centerline of the cylinder and the offset is frequently in the 4 - 10 mm range. Examples that I know of:

2011 Yamaha YZ450F http://www.yamaha-motor.com/sport/products/modelfeatures/209/0/features.aspx

2011 Kawasaki ZX10R (they have a big recall on these engines, but not for this reason!)

2011 Honda CBR250R

The last couple generations of Toyota Yaris and Prius

It's plausible that the total amount of piston friction is in the 8 - 15% range of engine power output but to think this would be completely eliminated by not having side loads is excessively optimistic. Offsetting the piston is claimed to reduce total engine friction by a few percent, which is only a small improvement - but if you're designing new engine castings anyway, designing in an offset between the crank and bore centerlines is free and presents absolutely no manufacturing difficulties whatsoever, so one might as well do it.

RE: Toroidal Opposed Piston Engine

if "total amount of piston friction" is meant to include the rings as part of the piston assembly, then that's the right neigbhorhood.  Otherwise, divide by 3 to get the right neigborhood for the skirt alone.

 

RE: Toroidal Opposed Piston Engine

Hi-

      This engine design is similar to some previous designs.

  Examples: The Tschudi engine was a spark ignition engine with four curved pistons running in a torodial track.  But this was a four stroke engine, not two stroke.   Also, the James two stroke opposed piston engine had pistons moving in a torrodial track.  I think that the Canadian government provided some funding for research on this engine some decades ago.

Also,  there is yet another torroidal engine at  this thread on the eng-tips.com website:      thread71-240200: another super engine


Some references that describe the above engines and other related ones are listed below.

Note that such designs have been around for a long time but have virtually never made it to production.   


Norbye, Jan P.  "Rivals to the Wankel:  A Roundup of Rotary Engines" , Popular Science, January, 1967.  

Setright, L.J.K.  Some Unusual Engines,  Mechanical Engineering Publications. 1975. ISBN 0-85298-208-9.  

Chinitz, Wallace.   "Rotary Engines", Scientific American Magazine, February, 1969, Volume 220,  Number 2.  See pages 90-99.


j2bprometheus

RE: Toroidal Opposed Piston Engine

(OP)
In this film : http://www.youtube.com/watch?v=f3mzTIY_zPc

you can see the mechanics. Everything is reduced to a single motorshaft, de pivoting and rotating joints are replaced by some sleeve-mechanisms. Have now idea, how , in this case , is arranged that outlet ports opens en closes before the inlet ports.

RE: Toroidal Opposed Piston Engine

(OP)
http://www.pattakon.com/pattakonOPRE.htm

This guy is enthusiastic telling that in his NO-friction-free opposed piston engine the need for lubrication at the expolsionsides of his pistons is practical nihil. On this expolionside , there is only need for compressionrings. The transfer of the wrist pin - i.e. of the thrust loads - away from the hot combustion chamber and away from the ports,to the cool compressionside, solves another problem of the opposed piston engines: it allows "four stroke" like lubrication and oil consumption.

"The lubrication (and the oil consumption) is as in four stroke engines. The oil rings never pass over the ports and flooding with oil is needed only at the compressor side of the piston (the cool side) where the thrust loads are taken."

Also Stirling engines use Rohmbicdrive to get frictionfree pistonmovements (http://en.wikipedia.org/wiki/Rhombic_drive ) beause they cannot effort having lubrication-oil burning up in there enclosed working-medium.

Does friction-free pistons require less ( or none ) lubrication-oil and therefor limit ( exclude )the problems that conventional 2-stroke diesels ( Detroit ) have (had )?

Are friction-free pistons the sollution to put two-stroke diesels back in the emission-picture ?

RE: Toroidal Opposed Piston Engine

I see inefficiency written all over that design. Saying nothing about costs to build it. And why even bother? The old tried and true is a much better design.  

RE: Toroidal Opposed Piston Engine

(OP)
cilinderoffset : yes that's the way to reduce side-friction during expansion and alows a bigger ( but more accepatble ) side-friction during compression.

Talking about motorbikes ( driving a Yamaha Fazer myself ), this dutch dieselbike is also free-piston.

Love it ? http://thekneeslider.com/archives/2006/06/19/neander-turbo-diesel-motorcycle/

100hp and 144 foot pounds of torque at 2600rpm.

 

RE: Toroidal Opposed Piston Engine

Piston rings rely on an oil film to avoid metal-to-metal contact. If there is no oil, the piston ring will locally melt and seize to the cylinder wall. That's what happens when a normal engine is run without oil.

Also, piston rings rely on an oil film to complete the seal. The tiny oil film blocks the path for gases to escape past the piston ring.

And ... Piston rings rely on gas pressure from above to work its way in behind the piston ring and force it against the cylinder wall. The more gas pressure there is, the more pressure the piston ring pushes against the wall. The initial tension is only to roughly hold it in the right position to get this process started.

The friction due to side loading of the pistons is much lower than the friction due to the pressure needed to maintain proper piston ring seal. Many racing engines use only a single compression ring instead of two, to cut down on piston ring friction. BUT, low oil consumption and maintaining compression for good cold starting and maintaining low piston ring leak-down for lower emissions are not priorities in those applications.

AND ... Piston rings need a little bit of oil to help transfer heat. If you don't do that, something melts, and the engine goes boom.

Piston ring without oil = seized engine. If clearances are made exceptionally large and the speed is kept low in order to avoid seizure, metal-to-metal contact without lubrication = very quickly worn out.

Wankel rotary engine apex seals have a tough situation because they also have compression/combustion space on both sides of them. Look how long it took to develop Wankel engines that seal properly ... AND ... they are designed to deliberately use a small amount of oil, because the apex seals will not last long without it!

RE: Toroidal Opposed Piston Engine

Quote:

Does friction-free pistons require less ( or none ) lubrication-oil and therefor limit ( exclude )the problems that conventional 2-stroke diesels ( Detroit ) have (had )?

No.

The rings and cylinder bore have been refined over the years to cut down on drag and wear and oil usage. Still, there is a need for oil to lubricate if you want a long operating life.

You're posting about details that you should already know if you are building this thing. Doesn't matter though since you haven't answered a very simple question. How will you ensure the piston/swingbeam and engine block don't expand at different rates causing the piston to contact the bore damaging or seizing the engine?
 

RE: Toroidal Opposed Piston Engine

(OP)
absolutely right about de Wankel apex seals. The space to mount a seal between the compressionchambre and expansionchambre is awful limited. Blow by, however, is not so critical, you simply loose power . Blowby in a conventional is worse, it's towards the crankshaft.

The biggest problem in a Wankel is that the rotor of a wankel is completely closed in and is continouisly building up heat that must get out through these axep seals. Ordinary pistons don't have this major problem.The intake piston is extra cooled by the incoming air, the outletpiston can be forced cooled by oil. The opposed piston Junkers and GM were done that way.

I believe oil is injected into the wankel in small quantities by an airpump . Don't know if the engine meets emissions-regulations, we don't see them a lot in Europe.

RE: Toroidal Opposed Piston Engine

(OP)

Wankelrotor can be considered as a free piston, there is no side thrust. But this rotor is continuously heating up.
Machining a trochoidehouse within tolerances is not really conventional. What about honing, lapping.  ?
The Wankelhouse has an unequal thermal expansion. Its continously heated on the expansion side and cooled on the compressionsite.

RE: Toroidal Opposed Piston Engine

(OP)
I know Greglock , suppose he putted his drawing in 1920 on the internet, ...

For your information, I have a small other prototype running in my motorhome working as a generator .

RE: Toroidal Opposed Piston Engine

"Blow by, however, is not so critical, you simply loose power."

If it happens under load, it can result in detonation in the next chamber due to the unexpectedly high VE.  Detonation under load is generally disastrous, breaking the tip seals or the dowels that hold the rotor housings in place.  Pragmatically, compression loss only happens under load if there were other major problems anyway.

Cooling is not that difficult, oil is used for the rotor and the water jacketing is designed so that the combustion space sees the coolant first.  They've been mass-producing them continuously for 44 years, I'd say they have a handle on the major issues.  The most recent spate of problems seems to be a double-shot of excessive reduction of the injected oil, and improper driving habits.

 

RE: Toroidal Opposed Piston Engine

In all the designs including the one posted; am I the only one, but I see lots of parasitic loss and just lots of rotating mass and parts, not much less than what is already in our in-efficient SICE's (or non S) now. Whats your estimated efficiency rating of this? is it multi fuel? What's it's O2 or Nox output? has any of that been tested?

RE: Toroidal Opposed Piston Engine

(OP)
yes you right izzmus, blow by in the exhaust chamber is not so crital, blow by in the compression is.

Cooling is not difficult but very, very omportant.

Further : It seems that Ford also is playing around with a free opposed piston engine. They also lubricate their pistonrings with a injected oilmist according to their dec,2005 patent : http://www.freepatentsonline.com/6971341.pdf


Why is there suddenly so much interest again in the old opposed piston engine ? We have Bill putting millions of dollars in it and also carcompanies studying the item ?

I also noticed the name Peter Hoffbauer again ( from ecomotors and formal master of the first VW-Golf diesel)  on this patent.

RE: Toroidal Opposed Piston Engine

(OP)
@ Greglocock : LOL, i never met your sister in law.

RE: Toroidal Opposed Piston Engine

I personally like the design of toroidal piston engines. However, I find it pretty complicated compared to the standard engines, which means that it might be more expensive to make.
The problem is that all the current knowledge(acquired during many years) is based on manufacturing parts for standard piston engines, which, even if it may not be the best solution, will make it cheaper to make, and make it harder for other technologies to be as competitive regarding the manufacturing costs.

Concerning the Russian car with the toroidal piston engine, I don't find the performances and fuel saving very interesting. 130km/h and 3.5l/100km in a small car is something that has already been done in the past with no technology at all (check out the Citroen AX with the 1.4l diesel engine).

RE: Toroidal Opposed Piston Engine

Another pretty animation. Do you have any links to examples of running toroidal engines? "Running" animations and running physical engines are two very different things.
 

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