Sylvain VAN DER WALDE wrote:
"Rob Morley" wrote in message
t...
In article
Chris Bacon wrote:
Sylvain VAN DER WALDE wrote:
"Rob Morley" wrotet...
Chris Bacon wrote:
Sylvain VAN DER WALDE wrote:
[ engine tuning/ compression ratio ]
Comments: The length of the stroke is controlled by the combined
design of the cranckshaft and connecting rod.
Why the *combined* design of the crackshaft and the contorting rod?
Surely just the throw of the crank?

The crank can be offset from the bore, in which case the length of the
con rod makes a difference.
I mentioned that in my answer to Chris, but then decided that it might
not
be relevent, and deleted that entry. I believe that the reason for this
offset is to reduce the pressure on the thrust "face" of the piston,
and
thereby reduce wear.

That's certainly an interesting idea - do you happen to know
which engines this is used in?


I'm an "old boy", now. I worked in the motor trade between 1956 and 1988,
approx. I don't think that the "interesting idea" in question is a new one.
It _may_ well be standard in many engines. I heard of it many years ago; it
may well have been in the 50's or 60's. I can't really add more.


I think advances in materials technology have made it largely irrelevant.

The theory is that it reduces piston sidethrust on the power stroke..

But better materials make piston/cylinder wear (and friction)
acceptable up to sensible lifetime limits..gone are the days when the
bearings were replaced every 30,000 miles, and pistons at 60-100,000,
with the accompanying rebore..

Sylvain.

P.S. Don't let a person's age put you off. We remain "young at heart", most
of the time.

Just a thought. Is the Wankel rotary engine still being used by anyone? I
believe that Mazda used one in some of their cars not so long ago.

I think so.
But is a rare bird.

Most interesting design I saw was a twin crank horizontally opposed
geared H layout.

Very compact and light..and low CG..



Sylvain.

Here's one:

http://www.cleangreencar.co.nz/page/prius-petrol-engine