h a l f b a k e r yCeci n'est pas une idée.
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An engine has several limitations when it comes to RPM. One is the potential for valves to "hang" open longer than they should and become food for a hungry engine. This idea takes shape from a solid metal bar with a notch cut for each valve. The bar has a gear at one end, with an alignment mark.
The bar is connected to the workings of the engine, much as the cam is today, but with an exposed gear to allow the connection on the side of the block, and the ability to remove the bar as needed for maintenance and or engine performance shaping with a bar of different configuration.
These notches are cut from the bar, and angled to allow for the intake and exhaust gasses to pass as needed. This basic system would remove the need for a cam (as we know it), lifters, valves and springs, all of which are moving in a plane (save the cam) that is non rotational, and thus a weaker link. This shaft is inserted into the engine and rides on a small amount of oil within the length of the tube.
Different engine designes might be better suited for this than others. The "valve shaft" or "rotary valve" would allow for extremely high rpm's without the risk to the pistons that are created when a spring looses it's performance traits. All this will not solve the problem of the pistons still having to move in that non-rotational plane, but should help the reliability, and perhaps the efficiency.
An additional aspect to this is the ability to change the "valves" of an engine with the removing of a cover plate on the side, removing the old valve shaft, and replacing with a new one (checking the index for timing). The thought is that an engine could be built with relatively large openings for these valve notches (thus allowing larger amounts of fuel into the engine, increasing hp.), and with a few minutes of modification (replacing the valve shaft), taking the car from "wild" to "mild" for city driving and better gas mileage. Sure, there would need to be some other adjustments (fuel, etc...), but I believe it would allow options we don't have currently without pulling the heads off and working the engine from the ground up. Thoughts?
Very very baked and sucessfull
http://www.coatesengine.com
Amazing torque and horsepower, lower manurfacturing costs, needing no lubricant, no sealing problems, higher compression, lower emissions.... very baked and in production! [venomx, Oct 04 2004]
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Annotation:
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That "hanging" is often called "float." |
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There is a system that uses, in essence, a small crankshaft to drive valve motion; each valve stem attached to a journal. The offset of the journal defines the lift. The system is called "Desmodromic" and the only contemporary engine I have heard of that uses it is the Ducati "Desmo" motorcycle engine. It does prevent float, requires no springs (however Ducati uses springs) and no camshaft. I am not sure if duration can be controlled, though. |
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I am trying to picture the system you have described and it isn't clear to me whether the rotary bar is, in itself, the valve or if the valves are traditional and ride in the notches. If it is the former, I wonder about a couple of things: how effectively could such a thing be sealed against the cylinder pressures and how large durations could be achieved while leaving enough material on the shaft to close the "valve." |
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Thanks. I knew there was a technical term for it, but knew "just hanging there..." wasn't it. Not sure if I explained it well enough, but if not, give me some questions I might be able to answer. |
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Just letting my mind wander around on this one... |
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Yeah, sealing might be an issue, but I wouldn't think it would be more difficult than the piston & rings, would it? <later edit: yes, it would.> However, just a notch in a rod wouldn't cut it: for example, the exhaust can't just go out of the cylinder and into the rod. It needs to pass through and go somewhere. And the notch can't be wide enough to simultaneously cover the cylinder port and an outlet port, as that would produce a long dwell at the cylinder port, but only a very short effective exhaust time where they were both open. However, if the notch leads to a section of rod which is basically a tube, and the exhaust outlet is through a separate port which can have a non-critical dwell, that objection goes away... |
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Heat transfer probably would make it inadvisable to attempt exhaust and intake on the same bar, but double overhead shafts aren't any novelty, so I can't raise that as a complaint... |
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You'd want to go from "fully closed" to "fully open" as rapidly as possible, and likewise at closing, so circumfrential measure of the notches would be limited as much as practicable, while being extended along the length of the bar sufficiently to provide the necessary opening area. |
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I don't see any show-stoppers yet, although I keep having this feeling that someone has to have tried this before... |
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It must be a good idea, because it's already been done! See 'Cross Rotary Valve'. |
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Thanks for the great feedback. I added the admin notes...made sense...tks jutta. I see the link for Aspin, but didn't get the same sense of delivery (I understand the valves are a bit different), it just wasn't where I was going in the original thought. Now, Cross Rotary Valve is a great concept it looks like. |
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I see this as probably having dual overhead rotary valves, as lurch suggested. The idea came as a solid rod with an obvious design for the gas to go somewhere in exhaust, and intake strokes but a hollow rod would be even better, and easier to plumb the heads. |
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I am a bit concerned about exhaust gas burning the opening face of the exhaust valve...and potentially changing the dwell, etc... Seems like the valve would run very cool due to the large surface area of the rod, but that one exposed end of the notch might get scorched. Would the heat be dissipated enough to keep that from becoming a weak link? I don't know. Thanks for the notes. |
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See my link to the Coates Engine, but..... |
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I had an very closely related idea about how to do this in a DIY fashion, that could be done by a small moderatley equipped engineering workshop. It's this idea, but mixed a bit with Coates' solutions. |
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What you do is you go for a roller barrel design, and like the coates engine you use. With no complex spherical shape just a cylinder with a cut port, you could machine such a barrel shaft on a lathe. |
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Roller barrel / rotary valves have three distinct advantages. 1. Your eliminating the poppet valve from obstructing gas flow, and from creating 'hot spots' like with exhaust valves. Which has a all round improvement on the engines power and torque, emissions, economy and increase the thermal limits of a cylinder for high-output applications. |
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2. Much less overlap between valve openings is necessary for high speed operation. Such that the actual overlap would be so little a engine that might idle sweetly at 600rpm yet wouldn't not reach peak airflow untill 9000rpm for example. Poppet valves in a high lift engine can take 30-40 degrees of crankshaft duration to become significantly open. A large port roller barrel would reach the same opening in about 5-10 degrees. In addition the overall flow of the ports would be about double a poppet valve system. |
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3. There is also no limit to port size or shape, 70-80% of a the cylinder head area could be port compared to 50% for the best 5-valve engines! |
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Formula 1 engines need CRAZY valve systems to reach 18,000rpm, I wouldn't imagine limits on a rotary valve F1 engines up to 25,000 rpm. |
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StandardBet: gas wouldn't burn the face of the valve as if it's rotating a new surface would be constantly exposed. |
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We are working on the RV engine with University of Maryland Mechanical Engineering Department. Go to WWW.USPTO.GOV and check patent # 6,293,242.
Or several related patents under Iskender V. Kutlucinar
Regards,
ARR, Inc.
4273 Howard Avenue
Kensington, MD
20895
USA |
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Hello Fellers!
My idea incorporates a notched pipe indexed in time with the firing order of the engine riding inside of another fixed notched pipe fed by a standard intake manifold, injection or carb doesn't matter by incorporating a twin over head rotary valve system one reduces mass and gains the ability of an additional 4-6000 usable rpm
I am about to begin such a project for my 65 nova sedan
it has a 230 ci 3.8 litre I-6
engine by replacing the head with a rotary design of my own
I will run into a few differant problems like the spark distributor I've solved this by modifying it to run it off of the timing belt and using a MSD 6-AL Spark Computer to ensure spark throwing capabilties into the 15000 rpm range reliably the other problem is cooling but I think I have solved that mystery by incorporating a 2 piece head and cutting water passages in to the bottom and top billets, sealing is no problem as the rear end of the inner pipe is capped off and the fixed pipe is press fitted
into the head itself. |
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this is why they invented the turbine. also, formula cars need to give up on pistons and just go to turbine powerplants |
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hey there
another idea to take the car from wild to mild which would take considerably less time is to have the rotation slow down for wild mode therefore letting more fuel/air in
this could be controlled by electronics as an on demand system that would kick in when the engine needs more power and when in the city and stop start traffic the bar would speed up so less fuel enters
the trouble would be keeping the rotation of the bar and crankshaft relative
the speed could also be used as a throttle mechanism!
thanks
Nick |
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