2 Stroke Reverse Uni-Flow Cam Engine 2

[voltech444]

Here is some info on this Fairchild-Caminez cam engine that I think has some potential for a modern make-over.
The Fairchild-Caminez 447 engine was a four-cylinder air-cooled radial intended for aircraft useage. It was designed by Harold Caminez, who had previously worked in the Engine Design Section of the US Army Air Service. The pistons acted on a leminiscate-shape cam, which made only one revolution for every two piston cycles, so for the same number of power impulses the engine ran at half speed. The pistons were connected by steel links to keep them pressed against the cam; the cylinder were steel with aluminium heads.
The Fairchild-Caminez 447 was first flown in an Avro 504 from Farmdale, Long Island, New York, in 1926. It was successfully endurance-tested in 1927, and was the first ever axial engine to receive a US Dept of commerce type certificate.

An IC engine expert speaks:
"Flight tests revealed what should have been predicted: a very large fourth-order torque variation due to the unusually heavy piston assemblies with their large ball-bearing rollers. Since the cam had two lobes, the second-order interia torque of the conventional 4-cylnder engine becomes fourth order in the arrangement in question. The engine was abandoned on this account."

(Quote from The Internal-Combustion Engine in Theory and Practice by Charles Fayette Taylor, 2nd edition, pub MIT press 1985, p579. This is a standard work on IC engines)

It was indeed abandoned due to vibration problems in 1929.

Stroke:

115 mm

Bore:

143 mm

Capacity:

7.3 litres

Compression ratio:

5.2

Power:

150HP at 2400 rpm

Flying weight:

164 kg (1.1kg/HP)

Output/volume:

20.5 HP/litre

I have written on physics forum for the last few years about a reverse uni-flow compression ignition 2 stroke engine. Here is some info i copied from LIM Technologies website:

"Once the LIM type engine has started, all four events occur in an only slightly modified sequence. As the power stroke ends, EXHAUST begins, then almost immediately, new air is forced into the cylinder; at the same time that exhaust continues. This new air displaces the remnants of the previous POWER stroke and COMPRESSION then takes place, completing the cycle.

The mechanical resemblance to a two-stroke is only that the piston acts as the exhaust valve. The major mechanical improvement, compared to a four-stroke, is the use of most of the head area for intake valves, since the exhaust leaves through the ports disposed around the girth of the cylinder.

The crank case, as in a conventional four-stroke, is home only to the bearings and crankshaft, the connecting rods and the main lubrication system. Another LIM advantage is that the main lubrication system has nothing to do with the valve train, although it may be involved with lubricating the compressor.

The compressor is external to the cylinder, but is vital to making a LIM type engine what it is. The compressor enables the LIM type engine to resemble a conventional four-stroke because it forces the fresh charge of air into the cylinder, and the coincidental displacement of the remains of the previous cycle.

The LIM Cycle is just three events: Ventilation, Compression, and Power. Two-stroke engines and four-stroke engines are explained in greater detail on other pages in this site."

So my idea is to take both of these designs and combine them, to make a 2 stroke reverse uniflow diesel cam engine. This Caminez cam design could work very well with some modifications. If you study the LIM engine, there is always downward force on the pistons, so the roller would always be forced down against the cam; it may be possible to remove those control arm things. The only time the pistons would not have down force is during start-up and engine braking. If the supercharger had a clutch and an electric motor it would be possible to spin the SC and create boost which would push the pistons down into place. With four cylinders, a motor like this would create 4 power strokes per revolution, not have a camshaft or pushrods, it would have a very high power density and actually be pretty simple mechanically. Could make use of new, lighter, ceramic ball bearings. SI or CI. For highest efficiency and power, a turbocharger and supercharger could be used along with water injection.

Here is another cam engine design that could also be used: The Daniel cam engine patent: US 817,905 of 17th April 1906.
This French engine by Paul Daniel of Levallois-Perret, near Paris, is the first to appear in the Cam-Engine Gallery because it was the subject of quite a comprehensive description in Model Engineer & Electrician for 28th April 1904. It is described as having been exhibited in "the last few days of the Paris salon", which possibly refers to the Exposition Universelle of 1900 in Paris, though that it would seem to indicate a pretty serious delay in reporting the fact. Perhaps some other exhibition is meant.
The report did not say if the engine was running.

There is a big roller d built into the bottom of the piston a which pushes on the top of the big elliptical cam e, and a little roller x' which bears on the inside of the cam. There is an automatic inlet valve p', and an exhaust valve k operated by rocking lever h, which is driven by an eccentric on the main output shaft; since this went round once per cycle, there was no need for a separate cam-shaft running at half engine speed.

The Daniel engine was a water-cooled four-stroke, the cam system allowing it to complete one cycle for each revolution of the output shaft. The patent shows a four-cylinder engine with two groups of cylinders and cams, and air-spring cylinders to take up the backlash in the cam system.

here is my sketch of a conventional crankshaft driven RUDIST (reverse uniflow direct-injection super-turbocharged) engine:

Link

There's more info I got I just wanted to get this up here first and i'll keep adding to it. I would appreciate your thoughts on this engine design. Thank you!

 

[Hoxton]

Upon which criteria are we to judge this engine?

 

[MikeHalloran]

You should also be aware of the Marchetti engine, a four stroke 8-cylinder radial using two quartered cams, each similar to those of the Caminez engine, with roller rockers controlling the pistons.




Mike Halloran
Pembroke Pines, FL, USA

 

[voltech444]

I'm mainly trying to determine the feasibility of the concept and design challenges to make this engine work. This is a rough frame, but the main goal is to make a 2 stroke cam engine with minimal parts. If something like this worked it would have lots of applications where high power/efficiency is required.

 

[BrianPetersen]

The usual thing that kills all of this type of engine mechanism that use cams to convert piston motion to shaft motion is the contact stress at the cam interface.

What's wrong with a normal crankshaft and rods? What does this accomplish that a normal crankshaft and con-rod arrangement doesn't?

 

[MikeHalloran]

You might want to work out the kinks in a Forward Uniflow ... etc., by hacking an old GMC two-stroke Diesel.



Mike Halloran
Pembroke Pines, FL, USA

 

[voltech444]

Well there are a few advantages a camshaft can have over a crankshaft. Cam engines don't have the long dwell time at tdc and bdc like crank engines do, which means a more efficient transfer of energy, and it's better for emissions too. If you consider that 4 pistons (or more) can turn one camshaft, there's considerably less rotating weight.

The reverse uniflow is superior to uniflow for 2 major reasons. First, there is no camshaft required to operate the intake valves, so no valvetrain. Second, since the intake valve can stay open during the compression stroke (once the exhaust port has closed) which enables running boost from the turbo/super and up the power density.

Putting together both of these designs yields a much more powerful and efficient engine that could actually cost less than a conventional ICE. Since there's no valvetrain there's less weight and space, and less issues with timing belt/chain issues. The pistons are in perfect counter balance to eachother, and no counter weights are needed. There are some other vibration challenges but I think with modern materials those vibrations could be drastically reduced or eliminated. Possibly connecting 2 or 3 quad modules together could reduce vibration and improve idling.

I've been going over this design on paper and in my head for years. At this point I'd rather see it get built, even if it's not by me. If we could build a motor like this it would be a game changer. I would be really excited to see it used as a range extender for an EV, in a hybrid, aviation, racing, marine; really anywhere where high power density and efficiency is required. I think the reverse uniflow and cam engine are each huge possible improvements by themselves and together could make something incredible.

 

[BrianPetersen]

Hmmm, where to start.

All of your claimed advantages about dwell time near TDC are out the window if you can't make the contact stresses at the camshaft (the one connected with the pistons, not with the valves) work out to be acceptable.

The Fairbanks engine kinda dealt with this because of the linkage between the opposed pistons. The camshaft only needs to deal with the net difference between them. It's still going to be a tough situation.

Take note of the compression ratio on that Fairbanks engine: 5.2:1. Efficiency ... Lousy. It can't have been a diesel engine, therefore it must have been spark-ignition, and would have had all of the disadvantages of a normal carbureted two-stroke. Efficiency: Lousy. Emissions: Lousy (misfiring). Smoothness: Awful (misfiring).

If you're proposing to allow the intake valves to simply operate as check valves, enjoy your very low redline before the valves are not able to close quickly enough. Yes, there are plenty of high-revving two-stroke engines that use reed valves for admitting air to the crankcase ... but reed valves don't have to withstand combustion chamber pressure!

Do some calculations ... please.

 

[voltech444]

LIM Technology did a study and proved valve bounce to be negligible. Here is a short summary of the reports findings:

"VALVE BOUNCE

Questions raised by knowledgeable people regarding valve bounce were answered in 2006, with the publication of the report by Douglas M. Baker, Ph.D. Dr. Baker describes how valve movement was measured at high speed. Valve bounce occurred on opening, and we know how to eliminate it. Time to open the valve to full lift was faster; dwell was longer, and closing was faster than conventional cam profiles can allow. Valve bounce at closing, due to the small mass of the valve and the deceleration shown in the diagram below, seems to be a non-issue.

The chart above tells the story of valve bounce in our camless engine. Blow down begins at 126 deg. after BDC. It appears that the valve begins to open at 145 deg. In the engine tested, maximum valve lift would be about 0.450 inches. In about 30 deg. of crank rotation, the valve reaches about 90% of its potential lift. After a bounce of just over 1/10 “, ending at about BDC, lift resumes, continuing for another 70 deg. As the valve retracts, its rate of closure slows to a nearly soft landing after the exhaust ports are sealed by the piston. Experts had thought that valve bounce would be a factor in closing the valve, when in fact bounce at closing is negligible. Unlike in any conventional valve train, there is some bounce in the opening, but we think it is benign."

So according to their findings valve bounce is not an issue.

From what i've read about silicon nitride ball bearings, they should be able to handle the contact stresses, the cam could be made of a similar material. I understand the fairbanks engine was an in-efficient 2 stroke, but the reverse uniflow solves all of those problems. Scavenging is done with fresh air, regardless of if it is SI or CI, so emissions should be about the same as a 4 stroke DI. I've read papers that have determined reverse uniflow to be the most efficient 2 stroke design; they didn't even investigate the potential of operating the intake valves without a camshaft.

Here are a few of those research papers you can read for yourself if interested:
CONCEPT OF MODERN CONTROL SYSTEMS ON TWO
STROKE REVERSE UNIFLOW COMBUSTION ENGINE: Link

NUMERICAL ANALYSIS OF A DOWNSIZED 2-STROKE
UNIFLOW ENGINE: Link

A Fully Variable Valve in an Optimized 2-Stroke Diesel Engine: http://contest.techbriefs.com/2014/entries/automotive-transportation/4733

Performance Tests of Reverse Uniflow-Type Two-Stroke Gasoline DI Engine: Link

Developing a 10cc Single-Valve, Reverse Uniflow, 2S Engine: Link

So maybe my head is little up in the clouds trying to combine both engine designs. How about a reverse uniflow with a conventional crankshaft? I've talked to the owner of LIM technologies, he's built 3 running prototypes, 2 were converted detroit diesel 2 strokes and the other was a DD 4s. He's put over a million dollars of his own money into building this engine; and now he's simply out of money and pretty much gave up on the project a few years ago. He did have a patent on his intake valve design but i think that expired because of non-payment of annual fee's. The cam engines are interesting and could have some potential; there are definitely a lot of issues to work out though. How about we just compare the 2 designs on their own? A reverse uniflow diesel with a conventional crank, and a cam engine as a 4s SI or CI?

Thanks for your participation!

 

[voltech444]

Also, keep in mind; the fairchild engine was originally designed and built in 1927, thats 90 year's ago! Things have changed enormously since then in regards to new higher strength materials and the more we know about engine design and efficiency now. Just the fact that they were able to make this design work with the materials they had then should be proof enough that given a modern makeover this engine could work. At least in my opinion...

 

[voltech444]

A Fully Variable Valve in an Optimized 2-Stroke Diesel Engine:

Link

 

[BrianPetersen]

What RPM was the engine running at under the conditions in which that first chart was made?

What was the compression ratio of that engine? What was the peak cylinder pressure? (Higher means needing heavier valves which means slower operation)

So you want to use gasoline direct-injection ... fair enough. Gasoline direct-injection two-strokes are in production by Bombardier for snowmobiles and outboard motors without any intake or exhaust valves at all. (They use piston porting as with normal two-strokes) They do indeed have much better fuel consumption than conventional two-strokes. But these engines are not called upon to meet automotive emission standards. Nor are they expected to last 300,000 km without an overhaul - and that's an issue with any form of piston-porting.

It seems that most inventors are blind to the downsides of their invention. Sorry for busting bubbles but you're not getting me to invest ...

You may be interested to research the design, and the eventual fate, of the Commer TS3 diesel engine. Look it up. Ask yourself what your design does that that design didn't. And that one was good enough to be in actual production for quite a few years.

 

[tbuelna]

The biggest issue facing the Caminez engine was durability of the cam mechanism. The roller/cam contact had serious skidding/sliding problems due to the dynamic loading from the 4-stroke engine cycle.

 

[LionelHutz]

Every ask yourself how wise it is to attempt a new engine design by combining "the best of" from a number of failures, especially when one has been around over 100 years yet hasn't managed to gain any traction?

 

[voltech444]

I think the caminez engine would have less problems with dynamic loading if it ran on the RU 2 stroke cycle. Just because a motor failed almost one hundred years ago doesn't mean it can't work with a modern makeover. There were so many new motors being built back then, they just chose the one that was the easiest to work with, not necessarily the best one. And the RU engine was not a failure, LIM built 3 working prototypes, they have all the information about those engines and the tests that they did; so you guys should look at some of that information for your self. I've shown lots of evidence that the RU engine works and is efficient for the basic prototypes that were built. MatLab simulations showed RU engines having very good scavenging ability. Everybody wants to tell me a RU engine could never work, even though I have proof of it working with 3 engines from LIM Technology. Those were just basic prototypes, if we put a fraction of what we put into refining our current 4s engines into perfecting a RU engine, I believe it would be more powerful and efficient. I mean the 4s crankshaft engine has been perfected over a period of 100 years, so to say just because a first generation prototype can't put out better numbers than a 4s that's had billions of dollars of research and design from numerous different companies, is kind of unfair and not an accurate comparison.

Can somebody show me a failed RU engine? There has never been one put into production, so I think it would be unwise to say something can't work just because the company that produced it was not able to bring it to production. I mean it's not too unbelievable to think that maybe the engine manufacturers would not like to sell an engine that could possibly last much longer and give better mpgs. They make plenty of money selling their same old 4s engines, as long as that's the only option available to consumers, they have no competition or reason to design a new type of engine.

 

[BrianPetersen]

Explain to the rest of us why this engine should be more efficient than a Commer TS3. I can point to at least one advantage that engine would have over yours ... less surface area for heat transfer per unit volume.

Explain to the rest of us why this engine should be more efficient than a Detroit Diesel. The scavenging goes in the opposite direction on those. So what? It doesn't take all THAT much power to operate a camshaft and valves. And in any case, the energy to open and close your valves is still there ... just not coming from the same source. (It's coming from pressure drop across the scavenging path, which means it's coming from the power that it takes to operate the forced-induction scavenging blower.)

Spark ignition with gasoline direct injection? Explain to the rest of us why this engine should be more efficient than a Bombardier E-Tec snowmobile or outboard engine.

All of those engines have either been in production in the past and given up on, or are in production today. Skip how the motion of the pistons is controlled. The combustion system doesn't care. Thermodynamically and scavenging-wise, your system has analogies to all of the above.

Dwell near TDC is a bug, not a feature, if you have a good fast-burn combustion chamber. More time near TDC means more time for heat loss and more time for detonation if you are using a combustion system that uses premixed air and fuel (e.g. spark ignition).

 

[PackardV8]

Did the X-Files ever have an episode explaining how the petro/industro complex buys up and kills off or gets committed all those demonstrably better engine designs? The conspiracy theorists among us ignore that capital has always been available for potential breakthroughs in most every technology. That there aren't funds pretty much means it's been looked at and judged very unlikely.

If one follows the long history of IC engine design and production, there have always been investors and engineers and corporations willing to bet millions trying any wild-hair idea which promised to obsolete the conventional IC; radials, 2-stroke, sleeve valve, opposed piston, rotary valve, turbine, Wankel, Miller-cycle, in addition to your cam-X-link-opp-slider-swash-plate whatevers which provided Popular Mechanics articles for the past hundred years.

Getting way OT, but my son is a venture capital mergers and acquisitions manager. He travels the world constantly searching for any likely idea to be funded, any emerging company to be bought. The world today is awash with liquid capital looking for a breakthrough idea. If it isn't getting funded, it can't get anyone beyond the inventor to believe in it. The entire venture capital establishment will sometimes miss a big idea on the first go, but more often they're willing to fund ten remotely possible R&D/startups, just on the chance one will hit it big.

I asked him about the likelihood of any new IC design and production funding. He said the general consensus is the existing IC are going to see us to the end of the line. Most R&D is going into electric. However, every new design is constantly evaluated, because consumer research indicates most drivers today have range anxiety about electrics and will want a fall-back IC. So compact, efficient, standby, quiet, vibrationless, bring it on.

jack vines

 

[MikeHalloran]

Consider this bit of advice from my few decades of product development:

If your new product relies on ONE rediscovered/ breakthrough/ revolutionary/ magical/ underappreciated/ misunderstood technology, your schedule becomes even more of a fantasy than is otherwise likely, and you will surely blow your budget, but you may be able to pull it off.

If your new product relies on MORE THAN ONE such technology, teething problems with each of the rediscovered, etc. technologies will interfere with development of the other(s), and add YEARS or DECADES to the project.

I.e., you will almost surely run out of money and investors before you get your engine in any sort of production, as it has been described.

OTOH, the odds against you are not insurmountable if you limit yourself to a RU engine with a normal slider-crank, or to a normal two or four stroke top end with cams in the crankcase.



Mike Halloran
Pembroke Pines, FL, USA

 

[3DDave]

Mike - I agree. I worked for some people who started thinking all sorts of things could be done but they always failed to recognize what seems to me was a fairly simple notion.

The notion is, after analyzing the existing products and market, how did you come to believe the current competitors missed the advantage you offer?

For certain there are some cases where the incumbent has too much money tied up to change or has a malformed notion of their position, but it is pretty rare that a big gap will remain open for long. I am pretty sure the last gap like that in propulsion was filled with the turbojet engine and its variants and that gap waited for materials that could withstand the conditions.

 

[LionelHutz]

I mean it's not too unbelievable to think that maybe the engine manufacturers would not like to sell an engine that could possibly last much longer and give better mpgs. They make plenty of money selling their same old 4s engines, as long as that's the only option available to consumers, they have no competition or reason to design a new type of engine.

Now you're just using conspiracy theory arguments to justify your posts. 100 odd years of R&D effort by countless different COMPETING companies have landed us where we are today.