joe@zinfandel.UUCP (01/11/85)
Hello.
I have an idea that fits the discussion about the further
improvement of valve actuation. Let us assume a functional rpm
range of 500 to 7000. Create 5 different cams. Each shall be
optimal for a different subspan of the original RPM range.
The first one for 500 to 1500, the second for 1500 to 2500,
the third for 2500 to 5000 and the last for 5000 up. Align
them in order to form a single long shaft and smooth the
transitions to make a single long cam that varies smoothly
along the axis of rotation. In the limit, the best is to have
the cam profile ideal for 500 RPM at one end, ideal for 7000
RPM at the other, and varying for the ideal linearly in between.
Using this cam with an RPM driven positioner which slides
the cam along the axis of rotation so as to position the cam at
the ideal profile for the given RPM should be easy, with very
little power requirement. The only high cost will be in machining
the cam itself.
" Cogito ergo Spud. " ( I Think, therefore A Yam. )
Joseph Weinstein Zehntel Inc. (ihnp4!zehntel!zinfandel!joe)
P.O. Box 8016
(415)932-6900 Walnut Creek California 94596burden@cheers.DEC (Let there be light........) (01/17/85)
Either Fiat or Lancia tried a similar thing. They had a cam with lobes that were larger in diameter at one end. As the engine speed changed the cam was moved back and forth a little bit. At low rpm the valves would only open a little but as the engine speed increased the valves would open wider. They might have also designed the cam for longer duration at higher speeds too, I'm not sure. As I remember they had to use fairly small cam followers to make the system work properly. Dave Burden decvax!decwrl!dec-rhea!dec-cheers!burden DEC, Spitbrook Road, Nashua, NH (603) 881-2559 42 42" 48.8'N -- 71 27" 23.7'W "I mean, if I went round saying I was an Emperor because some moistened bint had lobbed a scimitar at *me*, people would put me away." -- Dennis
meyer@waltz.UUCP (01/18/85)
Hmmm. Wouldn't your cam stick out of the current block dimensions by a foot
or two? Actually, this would require that the cam surface for each valve
to be about 3 or 4 inches wide -- which means each valve has to be spaced that
far apart. This would probably require a 4 cylinder engine to be the size
of an 8 cylinder.
Still an interesting idea though!
==============================================================================
Dane Meyer
ARPA: ==> Meyer%waltz%TI-CSL@CSNET-Relay
CSNET: ==> Meyer@TI-CSL
USENET: ==> {convex!smu, ut-sally, texsun, rice}!waltz!meyer notes@isucs1.UUCP (01/27/85)
Somehow, I don't think that you have ever seen a cam.
It is simply not the kind of thing that you can slide
back and forth while it is rotating (or at any other
time). Things like lifters and cam bearing journals
would tend to really get in the way.
Mike Drew