F1, trickle-down, etc.

[Wild Thing]

I would argue that a 5cc model airplane engine doesn't run anything close to the piston speed of a 100cc kart engine. rpm and piston speed are different things. The kart engine with 5cm stroke revving 24000rpm would be about equal to a 2cm(?) stroke of the 5cc engine running at 60000rpm. I would think that they rev substantially less than that though.

Talking about piston speeds is pretty irrelevant though, what is more important is the centrifugal force generated at the base of the con rod. Rpm increases this force exponentially while stroke increases it linearly.


> On Sat, 29 Sep 2001, Wild Thing wrote:
> >The F1 engines are not running "insane" piston speeds. Look no further
> >than a 100cc kart engine. They have a 5cm stroke and rev to 24000rpm,
> >while F1 engines have around 4cm stroke and rev only 18000rpm. And kart
> >engines have mandatory steel con-rod, none of those $$$ materials that
> >the F1 engines use. What impresses me is the valve acceleration that the
> >F1 engines run. The valves move so fast that valvesprings are simply to
> >slow to close them (a spring takes time to decompress even without load).
> 
> Yes, and 5cc model airplane engines run piston speeds that are
> higher still.  When you reduce the size of something, you lose mass
> far faster than you lose strength.  An F1 cylinder is 300cc, not 100cc.
> The stroke may be the same, but the piston weighs quite a bit more than
> the kart piston, so the forces involved are considerably higher, even
> for a slower engine speed, and the specific strength of the kart pieces
> will be higher.  By any measure against production engines, or even most
> car racing engines, these piston speeds are very high indeed.  The fact
> that there are even higher speeds out there doesn't alter that fact.
> 
> The valve acceleration wouldn't be possible without the pneumatic valve
> systems currently employed.  Renault is rumored to be using a camless
> valve system in their current F1 engine.  If this is true, and becomes
> commonplace, there's yet another place where F1 engines are leading the
> technology stakes.
> 
> james montebello
> 
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