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ok, i know that there have been sleeve valve engines in the past (the Silent Knite company made them). it was hard to find much good information on them, but im pretty sure this idea is not the same (though it may seem that way) i could be worng.
anyway, the idea is that your cylinder liners would
have slits cut on the sides of them running vertically down the cylinder. they would be as tall as the stroke of the piston, so there would still be solid material at the top and bottom of the sleeve. the slits would be cut on opposite sides of the cylinder liner (180 degres apart), one for intake, the other exhaust.
there would be another sleeve outside of the first one, its inner surface mated concentrically with the inner sleeves outer surface. the outer sleeve would also have special slits cut into it.
the inner sleeve would remain stationary with respect to the engine block. the outer sleeve would only rotate concentrically about the inner sleeve.
lets assume that i have worked out the timeing for a 4 stroke piston, which i actually have using 3d simulation. i had to add a third control sleeve to facilitate the timing. i got the openings to time correctly with the phase of stroke. it is possible to have valve overlap of exhaust intake openings to a certain degree. i have about 10 degrees of overlap in my design, so i think forced induction would be preferable.
this system would be good because: 1) more control over the geometry of the combustion area since there are no poppet valves in the way. furthermore, you wouldent need a head since the intake and exhaust ports would come out of the block, which would obviously elimintate the need for a head ghasket. 2) no linear innertia effects that casue poppet valves to float off the cam, so the engine could theoretically rev much higher. 3) less moving parts then a normal cam driven valve train. (even after the gear train that rotates the sleeves [ not 100% sure on this one]).
my main concerns are that: 1) this would create more friction than a cam/poppet engine since there would be more contact area between the sleeves. this brings me to concern #2) lubrication...i have some ideas to shoot oil through the sleeve mate surface, it involves scrapers on parts of the sleeve to keep oil from mixing with the air charge and exhaust gas. 3) blow by...im not sure how well these sleeves would contain an explosive charge...though if compresion piston rings can do it, i would assume the goemetry of the sleeves would do it.
The Aspin rotary valve engine
http://www.isdm.co.uk/aspin/
It uses a rotating conical valve, rather than a sleeve. [angel, Aug 05 2006]
the revetec homepage
http://www.revetec.com/
[auricom_mech, Aug 07 2006]
[link]
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Poor capitalizing, spelling and punctuating put me off, but I read this anyhow. This idea is has probably been tried. It sounds familiar, and quite like any other sleeve valve. |
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Engines are old, important and highly researched. If you want to propose something truly new, you have to make a very good case for it. And do your research. Read the books on engine development by Bill Gunston. I learned a lot from them, including sleeve valves. |
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I don't see that head gaskets are going to be eliminated in this design. Standard engine cylinders could probably be built in one piece, but a head is handy and a gasket isn't much trouble. [-] |
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you seemed to have missed my idea %100. we'll just assume it was from my terrible spelling. i will try and post a link to an animation of this model i am working on. if a picture tells 1000 words, an animated 3d simulation must tell at least [(1000^2)*(number of frames in animation)] maybe then you will get it. |
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i 3d model better than i spell, don't worry ;) |
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maybe you will Bun me when you see it. |
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I have a neat very old book(1930s) on cars that has a description and pictures of a sleeve(piston) valved engine, in that case the openings were horizontal(more like a 2 stroke) and the sleeve moved up and down on a secondary crankshaft. Also the Piston rode inside the Sleeve and the sleeve moved up and down in the bore. This approach is somewhat more elegant than what you have proposed and does not require the fixed sleeves. |
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You have another issue in that youre verticle slots will not be able to be properly sealed throughout the entire piston stroke unless the pistons are inordinately long in the skirt.(many 2 stroke engines utilize the crankcase as an intake chamber to get around this) As to complexity a conventional OHC configuration is very simple, can handle RPMS well past 10000(which is a LOT) and is easy to maintain. Combustion Chamber geometry is not especially limited by the valves, many higher performance engines utilize multiple valves percylinder to gain more control over the distribution of the Fuel air mix rather than Geometry. |
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thats a good point, the solution is that the slits in the outer sleeve move up the material in a helix. so by the time the bottom of the skirt would normally be letting air into the crank case, that section of the helical slit has already moved out of the way (i didnt want to get into that in the initial description becasue i have been getting a lot of bones cuz people have been "getting bored half way through"). |
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also, IMO this is a more elegant design, since you dont have to push material up and down. that takes a lot more energy than to just keep it spinning in the same direction. (ideally this would be on an engine with a CVT so the engine would stay at about the same RPM, so once the sleeve valves got spinning they would require VERY little energy to keep them spinning) is this logic correct or am i forgetting somehting? |
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the problem is not the outer sleeve its the inner one. The piston would have to be taller than its stroke length to ensure that gases can not escape through the lower end of that slot. |
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Also this design would preclude the use of Piston rings to ensure a good seal and so a fitted piston would be required, which I think may lead to greater drag on the engine, it would also impact its long term durablity. |
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1. Thermal expansion of sleeves. (Particularly with the extra control sleeve.)
2. Drive complexity. (Let's see - rotation at right angles to your drive shaft, in a different axis per cylinder, and on a different plane - yowza. I'm pretty sure this is going to be one complex bugger.)
3. Sealing. (If you don't have a head/gasket, then all the parts are going to have do be assembled through the crankcase side of the block. That means more risk of blow-by into the crankcase.) |
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yeah, you guys are right about that stuff. in particuaar what jhom said about the inner sleeve being the problem with massive blow by into the crank case. |
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have you guys heard of the revetec engine?
[link]
it uses a pair of tri-lobe cams to transfer power from the pistons to the drive shaft (there are no crank or conrods). apparently they are going to be putting these engines into vehicles in India, and maybe china. |
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i sort of designed this valve system for thoes engines...since i think they are a really good idea. there is no lateral movement of the piston since all the force gets directed downward (there is a torsional force from the "dual" nature of the tri-cams.) |
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anyway, if my sleeve valve idea were used with this type of engine, do you think special compression rings could be made so that a section of the ring would stick out into the inner sleeves ports? or like jhom said use a "fitted piston"? would a fitted piston create much additional drag in this revetec design? |
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if all the sleeves were made of the same material, would the thermal expansion be controllable? or maybe the outer sleeve could have charecteristics to make it expand a little more readily than the inner one? |
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i do agree though that the excessive heat would probably be the biggest inherant problem with this design...i'm trying to sort that out. |
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would it work if we just had individual hemisphere (or whatever shape would be best) caps that screw on the the tops of the cylinder liners? maybe a gasket and single head would still be a better idea....though the head would obviously be a lot smaller and less complex than normal, since all the complexities and bulk has now been moved into the block! |
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Take a look at the Burt-McCollum single-sleeve system. Apparently it works quite well, and has been used extensively in aircraft engines. |
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