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Valve ideas?
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Posted by: fatherturtle---------------------
I am not a 4-stroke lover or anything but I was thinking. I know most people are saying that crazy kx 250 guy asking all his stupid questions. Well i guess now I have some stupid ideas to ponder or for somebody to try.
Ok doesn't the 4-stroke design seem pretty inefficiant. I mean why the heck would you want some piece of metal getting pushed toward your piston just to(you hope) get pulled away from it by some hefty valve springs? Doesn't seem smart to me. Why not change the valve train to a gilotene type valve. It would require less moving parts and you wouldn't have to worry about anything possibly colliding with the piston or the valves. I believe my idea would require less power also.You probably could even have a larger opening than the standard valve type. Now you probably are thinking what? A system that uses Different valves I don't get it or it's already been done.
Maybe it has I don't know just some cr_p I thought up. I know my writing sucks so bad Webster couldn't help me out on Gilotene. Sounds good to me, I guess it will stay. 
Posted by: SpeedyManiac---------------------
Interesting idea. I really have no idea why it wouldn't work, but setting up the timing might be more difficult.
Posted by: fatherturtle---------------------
I don't think it would be any more difficult than the standard valve. I think you probably could use a cam and timing chain. I think the difficult issue would be to get a good seal of the valve. Have you ever heard of any valve idea like this?
Posted by: marcusgunby---------------------
Its like a rotary reed valve on a 2 stroke.
Posted by: fatherturtle---------------------
Not quite what I was thinking, more like two sperate valves that would work independently in the head. When the fuel air mixture is needed this rectangle valve slides open to let the intake charge in then closes. When the exhaust valves must expel the spent fuel charge it opens then closes. Seem plausible
Posted by: gixer---------------------
Just one quick question.
You state a rectangle valve that slides up and down. The combustion chamber is a sphere. So how is this rectangle going to work with that?
Posted by: fatherturtle---------------------
It dosn't have to be that shape I thought it might be easier to imagine it that way.
Posted by: Taliesin---------------------
I remmember in college researching various valve systems for 4strokes.I went thro a load of books endless designs have been tried in the past.Mostly some type of rotary valve etc.
But in the end they were all failers for one thing or other like poor pressure sealing, rapid wear, high oil consumption etc.It seems that strangely enough that the simple poppet valve is hard to beat.I like the ideal of Desmodromic actuation where the valve is opened & closed by cam action. Less force is needed & hence less energy also you can control the opening & closing better allowing more radical valve profiles.
Posted by: fiejasgr---------------------
Interesting idea, I agree with the replies above on problems with sealing compression in and oil out of the cylinder. You also would have greater wear issues due to more metal to metal contact, there wouldn't be a simple vavle guide here. and my last thought would be the additional wieght you would gain with either larger cam lobes or high ratio rocker arm assemblies( a gilotine vavle would have to travel alot farther to produce the same size opening as a poppet valve wich in turn would lead to problems of its own). For the most part poppet vavles work very well until something fails, just like a connecting rod.
A two stroke motor is definately less complecated leaving less to fail, but it also has a narrower range of good usable power
A four stroke developes a broader range of good usable power, but in turn has more things to go wrong (and ussually when one thing goes it takes alot of others with it) just stating the obvious there.
They both have thier own strengths and weaknesses
Jake
Posted by: fatherturtle---------------------
I agree with all your guys ideas. I just think that the standard valve is a primitive idea. I think sealing and wear would be an issue but with the new materails it could be possible. If you used titanium with roller bearings maybe it would be possible. I think you would have more control over your valves and could possibly have larger ports. Also I would think that your reliability would go up if we could just figure out the sealing issue. Just my .02 cents one of many ideas I have.
Posted by: gixer---------------------
Looks like you are just going to add more moving parts to the system.
Posted by: Kapt. Krunch---------------------
Coates Engine is the design you're looking for. The valve is a rotating dowel with a slot through it. Very easy to swap "cams" just change the "dowel" for a different one with ports that are shaped or sized differently. There's also no valve float! Rev to the moon, as you are only limited to the strength of your engine internals and your capability to supply fuel/air.
Posted by: Kapt. Krunch---------------------
A German road racing team in the 90's used a DR800 with a custom rotary valve head to run in sound of singles competition. The rider was Katja "something-or-other"...
Posted by: Jaybird---------------------
IF Detroit would have had a Coates-ish train of thought (pun intended) way back when...they would look at the modern valve assembly and consider it a Rube Goldberg approach from some quacks, and quickly shoot holes in the design and theory.
The DOHC would be seen as a better attempt, but still no cigar, and would be poo-poo'ed by the Motor City big-wigs right away.
I don't look for domestic automaker genius' to grow more brains any time soon.
Heck, they are in the ICU now, from hemmoraging.
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