[WWI] rotaries--2 stroke or 4?

[Douglas Anderson]

This debate is about to be solved. And for those with a slightly engineering twist, petrol heads and those with an interest, your fantasies and desires are about to be fulfilled. Yes, I am back in Cape Town, which means that the RFC manual I will collect and scan and send to the group. Which reminds me, how do I go about posting a pdf that all may access and download

Ray Boorman <fokkereiv at gmail.com> wrote:   One of the early Gnome Rotary methods uses the vacuum in the cylinder
to open a poppet valve in the piston, this then draws fuel both oil
and gas from the crankcase into the head, then at the right point the
valve closes because of the upstroke of the piston an hey presto you
have a 2 stroke method used in a four stroke engine.

The Monosoupape used transfer ports instead of the valve in the
piston, this made for easier service. Later the LeRhone used a single
pushrod to operate two valves in the head one the intake the other the
exhaust. Although even in this engine the main intake comes through
the crankcase which is why you see the intake tubes go from the
crankcase to the cylinder head.

All of these used methods that were the same as two strokes used, but
were in fact four strokes. However there is no reason why a two cycle
would not work.

Crankcase compression used by modern two strokes didn't really get
going in a scientific fashion until the racing DKW two strokes of the
late 20's and 30's. In fact many methods were used to get better
compression some even included using a compression cylinder that
supplied gas to the working cylinders. Up until that time the
crankcase was used more for the transfer of gas not compression,
which is how most of the rotaries worked, albeit they were 4 strokes.

Hope that helps.

Ray

On 3/11/07, Nigel Cheffers-Heard wrote:
> Generally speaking, two strokes use crankcase pressure for transfer.
> since the rotary has a common crankcase, and some of the pistons are
> up, down, or in between, the volume remains relatively constant,
> therefore no "suck and blow"| to make the process work.
> The two stroke diesels you speak of, and indeed huge modern ship
> engines, use superchargers or turbochargers to effect scavenging and
> transfer without using crankcase pressure.
> N
>
> Nigel Cheffers-Heard
> su3264 at eclipse.co.uk
> 0771 261 4514
> Bridge Inn
> Topsham
> Exeter
> EX3 0QQ
>
>
> On 10 Mar 2007, at 0:46, iban wrote:
>
>
> >
> > seems to me (iirc) that at least dornier was working on 2-stroke
> > diesel aero-engines (solved the total loss lube prob) from very
> > early on. wonder if they tweaked an oberursel in their experiments
> > perhaps?
> >
> > iban.
> >
>
>


 
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