Vehicle: Car: Engine: Cylinder
Poppet Cylinder   (-2)  [vote for, against]
Why not use the same idea for valves as a cylinder?

How come we don't just use the same idea for a poppet valve for the cylinder, you wouldn't have the same issues of seating it as you would a valve, since the sealing is already done. It's more complicated and stupid, but why didn't anyone who posts dumb things say this one by now?
-- MarcStinebaugh, Mar 09 2007

I don't know.
-- zeno, Mar 09 2007

Maybe it's just too stupid?
-- BJS, Mar 09 2007

maybe they just did. Or maybe you just stole MY idea.
-- the dog's breakfast, Mar 09 2007

Uhm Im not sure I follow your logic. Poppet valves open and close they have no linkage and so cannot really be used in a power application. They also do not seal throughout their range of motion and so only seal when in the closed position. Perhaps I am misunderstanding but I do not believe it would be possible for this to work.
-- jhomrighaus, Mar 09 2007

A poppet valve is a nice, lightweight bit of metal, easy to fling back and forth. Using a piston to seal the opening requires:

-More mass in the form of an extended cylinder skirt that keeps the piston aligned at full extension

-Piston rings, if you want a good seal. But how do you compress them when the piston slides back in? Maybe just machine it out of solid graphite. Good luck with that, by the way.

-Lubrication of the piston. Tricky. Ooh, emissions bad, and lossy too. On the upside, the oil changes itself, you just add a quart every 500 miles.

This idea has a few merits:

-The extended cylinder skirt and opening need not be symmetrical, thus shooting the charge into the firing cylinder in whatever direction you choose.

-The cylinder valve can be driven with a crank instead of a cam - how far the piston has to travel to open the valve duplicates the function of the cam's extended low spot.

-Crank drive means no valve float even at F1 speeds. A thrown conrod maybe, but no float.

-More exciting backandforthy stuff to look at.
-- elhigh, Mar 13 2007

random, halfbakery