Questions part 3: Another variety pack.

[AspiringHowardHughes]

While duplicate spark plugs were common, I hope to get by with a single one in this instance. Hopefully the ideal plug placement along with good turbulent mixing in the cylinder would allow for this. If needs be, the desired number of spark plugs could be situated in a non-rotating "island" of appropriate size within the ceiling of the cylinder, but of course this would increase the perimeter of the sleeve from which oil may escape and combustion gas intrude.

I think it is inaccurate to call this cross-flow scavenging, given that the entirety of the height of the cylinder is consumed by the port. Uniflow would be a better description, and uniflow is about as good as scavenging gets unless I have some pretty serious misconceptions. In any case, this design could also be constructed to use loop or cross-flow scavenging, needing only appropriate placement and angle of the manifolds.

I am aware of valve timing diagrams, I just think this sort of system deserves a little more careful design because there is only one "valve" and thus many intake and exhaust characteristics are inextricably linked. Imagine trying to implement a useful form of variable valve timing with this design!

 

[special ed]

If I may throw in a suggestion from a non engineer/non degreed person with many years of model airplane glow fuel engines. I suggest a prototype proof of concept engine, two cycle, glow plug ignition, using standard glow fuel, 70% methanol, 29% Castor oil lube, with 5% Nitromethane ignition helper. Standard old time glow fuel formula. The glow plug is used for starting and the combustion keeps the plug element hot. It is classed as an Otto Cycle, a semi diesel.

 

[Bretoal2]

If I may throw in a suggestion from a non engineer/non degreed person with many years of model airplane glow fuel engines. I suggest a prototype proof of concept engine, two cycle, glow plug ignition, using standard glow fuel, 70% methanol, 29% Castor oil lube, with 5% Nitromethane ignition helper. Standard old time glow fuel formula. The glow plug is used for starting and the combustion keeps the plug element hot. It is classed as an Otto Cycle, a semi diesel.

70 + 29 +5 = 104 %. Well well well....

Nevertheless, I bet OS had already made some models as descripted....

 

[Engineman]

70 + 29 +5 = 104 %. Well well well....

Nevertheless, I bet OS had already made some models as descripted....

Fuel mixture composition is sometimes quoted in "parts" that don't add up to 100 or "100%", so that they can be easily mixed without computation.

Eng

 

[AspiringHowardHughes]

What does "OS" indicate? I hope to sometime make an actual model of this engine but have not done so thus far. Maybe it will happen as a component of my school pathway?

 

[don4331]

While duplicate spark plugs were common, I hope to get by with a single one in this instance. Hopefully the ideal plug placement along with good turbulent mixing in the cylinder would allow for this. If needs be, the desired number of spark plugs could be situated in a non-rotating "island" of appropriate size within the ceiling of the cylinder, but of course this would increase the perimeter of the sleeve from which oil may escape and combustion gas intrude.

Duplicate spark plugs were required because single plugs/wires/magnetos weren't reliable / You need more than one in a >5" bore to efficiently / quickly ignite the mixture

What does "OS" indicate? I hope to sometime make an actual model of this engine but have not done so thus far. Maybe it will happen as a component of my school pathway?

O.S. ENGINES OFFICIAL

O.S. ENGINES（小川精機）、O.S.PROFESSIONAL、UAV、ドローン用動力源。UAVエンジン製品情報。

www.os-engines.co.jp

 

[special ed]

The model airplane engines of the 1950s were loop scavenged and ran reliably whether Enya .29 & .35, O.S. .29 or .35 from Japan, or Fox .35 from the USA. O.S. began making model airplane engines in 1936. I suspect your design would run well on glow fuel with glow plugs for ignition. Examples of unusual types such as O.S. Wankel rotary and the Aero engine with the piston/cylinder parallel with the crankshaft have run on glow fuel and plugs. Perhaps a piston baffle per the 1950 engines would keep mixture in the combustion chamber long enough for good ignition, although ruining some of the flow through principal. Keep working on the project and remember to apply for patents.

 

[Bretoal2]

Yes, O.S. is a model engine manufacturer. In the '80 they made some four-strokes models, with rotary valves in the head, but hey were discontinued (curious, isn't it ?).

 

[AspiringHowardHughes]

The scale model engine market was not something I had considered previously. It makes sense that miniatures could serve as a helpful proving ground for a new design.
I will go searching for some diagrams of that latter unique engine you mention, Ed.
Another thing I ought to do is research the policies of my school (UOttawa) when it comes to intellectual property.
Thanks for the advice.

 

[Bretoal2]

The scale model engine market was not something I had considered previously. It makes sense that miniatures could serve as a helpful proving ground for a new design.
I will go searching for some diagrams of that latter unique engine you mention, Ed.
Another thing I ought to do is research the policies of my school (UOttawa) when it comes to intellectual property.
Thanks for the advice.

You are still focusing on the issue of intellectual property. However, I remain convinced that the real question regarding earlier patents lies elsewhere; it boils down to this: why did a particular process—patented in the 1930s, 40s, or 50s—never reached industrial production stage? Is it not because, from a practical standpoint, it simply didn't work? By "didn't work," I refer to the various pitfalls an industrial product can face across any sector: excessive development and manufacturing costs, poor efficiency, lack of reliability, prohibitive maintenance requirements, stiff competition from other designs, and so on.

Clearly, apart from the Bristol Burt-McCollum system, no other "sleeve-valve" design achieved commercial success. The Hercules and Centaurus engines were paragons of efficiency and reliability (with a Time Between Overhauls—TBO—exceeding 3,000 hours!), but the technology was inherently suited to high-output engines, a category that went into steep decline after 1945 with the advent of jet propulsion. After leaving Bristol, Roy Fedden attempted to build a "small" sleeve-valve engine for light aircraft and even automobiles—but it was not successful.

And even the OS model engine with rotary valves in the head was discontinued...

 

[AspiringHowardHughes]

I am focusing on the issue of intellectual property because I feel I may very well be the first to think of this design. If there are patents that at all resemble what I am describing, I would love to read up on their development and difficulties. Those who have read my dedicated post on the subject will recall that I did a great deal of investigation into any remotely similar designs, finding none that resemble mine to any serious degree.

That other valving methods (which were mechanically substantially different) did not succeed is not much of an argument against this one.

Prior to the inception of the sleeve valve itself, it could be said that "no valve design other than poppets achieved commercial success". Obviously this situation did not remain once new designs emerged. Could Freevalve, for example, be criticized prior to even hitting the market simply because there already exists a status quo?

The one solid piece of evidence against my design being successful (besides actually building or thoroughly virtually simulating it) would be reading of someone else having previously tried it and failed. I am of course eager to hear any such story, but in the absence of this I think a little more optimism is in order.

-A.H.H

 

[z42]

Speaking generally, when one is new to a field one usually has all kinds of new and radical ideas for how to do things better. Later one learns that things are done the way they are for reasons, and people back in the day weren't idiots and had come up with similar ideas but discarded them, again usually for good reasons.

As for patents, people patent things they believe have commercial potential. Lack of a patent describing ones invention might mean one has discovered something genuinely new and innovative nobody has thought of before, but more likely the idea has been discarded long ago as unworkable before getting to the patenting stage. Especially if one is inexperienced in the field.

 

[Simon Thomas]

Patents are a pain to search.
For US ones, I use this site. Patent Public Search Basic | USPTO I suggest you use the basic search, search by name in both boxes, put 'Roland' on the first box and 'Chilton' in the second box. (I can't work out how direct link it.)
There are 188 hits for his patents.
A typo in 2146428 would not have helped. Should be 2146528.

 

[Bretoal2]

Patents are a pain to search.
For US ones, I use this site. Patent Public Search Basic | USPTO I suggest you use the basic search, search by name in both boxes, put 'Roland' on the first box and 'Chilton' in the second box. (I can't work out how direct link it.)
There are 188 hits for his patents.
A typo in 2146428 would not have helped. Should be 2146528.

These are the three patents I mentioned somewhere recently. However, since our friend has started multiple threads on essentially identical topics, it is quite hard to keep track of everything.

Getting back to Chilton : I was actually planning to put together an illustrated post showing the three phases of his work on sleeve-valves —inception, refinement, and decline. This perfectly illustrates a point we have been making for a long time in this thread and its offshoots : a "good idea" does not necessarily result in a reliable, durable industrial product.

Unfortunately, I have to step away from my computer for three or four days, but I'll be back!

 

[YavorD]

...

1: What factors influence the designer's choice of compression distribution between the pre-compression system (supercharger/turbocharger) and the engine cylinder itself? Do the different general balances selected by each nation (and where in that range each engine lies) represent different priorities with respect to the desired performance of the engine, or is there a truly ideal theoretical setup that each real-life effort tries to approach?

2: How does the above question apply to diesel engines? Similarly, are advancements in pre-compression systems (variable-speed drives, additional stages, turbocharger installations, inter/intracoolers....) more or less critical for diesel applications? Unfortunately, I do not have much data on the few diesel aero engines that saw service.

...

My contribution concerning items 1 and 2.
The most important factor must be operating conditions for which the engine is designed. Introduction of a new engine in commercial and military environment is a very long process. Conceptual design is aiming at a certain class of aircraft in a specific operating conditions. Five to then years later the world looks not exactly as it was described in the original design document, used to convince investors to fund the design of a new engine.
Concerning the choice between gasoline and diesel - my feeling is the aviation gasoline is a niche product while diesel engines can operate on jet fuel. Concerning design of the supercharger - multi-point high pressure fuel injection is the norm; light, reliable, highly-effective variable speed drive is still questionable today. If a supercharger is necessary, it may be feasible to use a turbocharger, not a mechanical drive. If a high compression ratio is necessary, then one may need to look on intercooler(s) and two-stage turbocharging. Well, it was not the same situation before 1950 but it was clear at the time the market share of the piston engine is shrinking, particularly concerning the high-power applications.

 

[Shortround6]

A major problem for the high output sleeve valve engines turned out to be cooling.
You need a direct path to get rid of the heat as efficiently as possible. Thin oil interfaces between the sleeve and walls/head are an obstacle to heat transmission.
Post war, high output Hercules engines resorted to copper alloy heads when they could not get aluminum alloy heads to stay cool enough despite numerous redesigns.
The post war commercial engines were redesigned several times and finally made 2300hp(?) using 115/145 fuel and water injection for take-off. They also managed to get the 2360 cu in Hercules engine to weigh as much (within 20lbs?) as a late model P&W R-2800 commercial engine. Both with single stage, two speed superchargers.

You can get sleeve valve engines to work. For very brief periods of time they may have worked better than poppet valve engines, but the poppet engine guys were not staying still and they came up with better springs, better valve alloys/designs, better valves seats, better acceleration curves on the cam lobes and more.
I am old enough to remember when 6000rpm car engines were considered pretty hot stuff and required double over head cams. By the end of the 60's the Americans were making a number of large V-8 engines that could make 6000rpm or more using push rods. They could also survive over 7000 rpm in racing applications (road racing for 3-5 hours per race).
Motorcycles were a different story. I had a 1970 Ducati Desmo 350 that was red lined at 8500rpm. Legend had it that it was possible to run the engine without valve springs (although starting would be nearly impossible). There were extra cam lobes and rocker arms than were forked at the end to go around collars on the valve stems to yank them shut so it was impossible to float the valves. Better materials made even higher rpm available without resorting to trick valve gear.

You can get a cylinder design to work; the question is if works better than existing designs and at what cost/s in materials and manufacturing.

 

[Simon Thomas]

You need a direct path to get rid of the heat as efficiently as possible. Thin oil interfaces between the sleeve and walls/head are an obstacle to heat transmission.

Have you got figures for the temperature drop/heat flow across the oil interface?

 

[z42]

Have you got figures for the temperature drop/heat flow across the oil interface?

We had some discussion on heat flow across the sleeve in page 3&4 of this thread a few years ago: Advantages of sleeve valves for H-24 engines? (which you might remember, as you were a prolific poster in that thread)

 

[Simon Thomas]

That was the point of the question, there are insignificant temp drops across the oil interfaces. I'd love to see data that shows these big obstacles from the oil film.

The major problem mentioned was only a major problem for getting long TBO's from the cylinder heads. The changes made to the spark plug cooling area were not required for normal cylinder head life, but for getting 3000+ hours they needed to improve the thermal behaviour around the spark plugs. The changes were not correcting a failure, but rather improving cylinder life. If the TBO's were the same as the poppet valves, no changes would have been required.

Modern Continental IO-520/550 cylinders get to a max life of about 3/4000 hours before fatigue cracks typically render them non-repairable, and they have far less power/cylinder than the big radials.

 

[Shortround6]

Have you got figures for the temperature drop/heat flow across the oil interface?

That was the point of the question, there are insignificant temp drops across the oil interfaces. I'd love to see data that shows these big obstacles from the oil film.

I do not have any numbers and I may very well be mistaken.
The Sleeve valve vs Poppet valve arguments can be very partisan and without real numbers to back them up. Then we wind up with theory.
It may be true (quite likely?) that the oil to cylinder interface is 'transparent' to heat transfer.
What is not so transparent is the sleeve moving up and down about 2 1/2 inches at 1/2 rpm. For most of the length of sleeve this doesn't really matter. It does matter ( I think?) up in the head area and in the area where the ports are.
What is the heat transfer across the 'gaps' which are moving? What is filling these 'gaps'? Oil or oil/air mix or ??? Granted a 2 1/2in movement means that the sleeve is spending a lot of time in the middle of that movement but that is at/near the hottest part. What is the heat transfer in the top 1 1/4 in of the horizontal fins around the head? What is the heat transfer in the area of the cylinder where the 5 ports are?

I have read a number of articles that exhibit at least some bias (or perhaps I am revealing my own).

https://www.newcomen.com/wp-content/uploads/2019/11/The-Piston-Engine-Revolution-Chapter-6-Hassell.pdf

Page 11 (?) talks about the US having to use two valve heads instead of 4 valve heads on two row radials. Trouble with this is that the US very rarely used more than 2 valves in any radial engine. US was moving to the sodium filled exhaust valve in the larger engines by 1930. By 1940 they were using them in 200-300hp radials built by Continental, Jacobs and Lycoming let alone P&W and Wright's bigger engines. It was basic design practice in the US for cylinders of certain size/power regardless of number of cylinders or rows. By 1930 P&W and Wright were moving to totally enclosed valve trains which Bristol never did on their poppet valve engines. I will note that totally enclosed valve train does not mean either pressure lubricated or even supplied by engine oil. That took a while longer. The Sleeve valve certainly solved the Bristol radial valve lubrication by grease gun problem, but that problem didn't exist for many other engine makers.

Both sides are guilty of mixing time lines. And both sides rarely mention the difference (and problems) that better fuel made.
Financial considerations are rarely mentioned like the amount of money invested in tooling in both camps (Sleeve valve and poppet) and other financial considerations like tariffs for the British and indeed the British commonwealth after WW II and for part of the 1950s.
The post war Sleeve engines (Bristol) were great engines if you don't count cost. Maybe they were great even if you do count cost but getting costs are hard. Both for initial purchase and maintenance/overhaul. This is complicated by the US engines dominating the market and having easier access to spare parts and repair facilities around the world so again, direct comparisons are hard.