From: peon@pacific.net.au
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Date: Thu, 9 Oct 2003 10:25:55 +1000
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Subject: True Displacement of the 13B rotary Egnine Take 3
Reply-to: leon@aerota.com
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In-reply-to: <list-2629177@logan.com>

Hi Ed,

Thanks for the kind words.

It just dawned on me that the main problem here in this 
equivalency thingy is that we are trying to compare different types 
of I.C. combustion cycles.  To wit:  Otto Cycle as opposed to 
Wankel Cycle etc.

See,  if we do it on a PER REV basis,  then in the case of the 4 
stroke 4 cylinder,  it only ever gets to suck on two jugs!  The other 
2 jugs are either exhausting or powering.  Same idea (sort of) as 
what happens in the Wankel.

Another way to look at it is considering the POWER STROKES 
per rev that outputs on the crankshaft.  Over the years,  I have 
almost exclusively explained performance equivalency  on this 
basis.  With a 13B,  we get one 654 cc power pulse per rev per 
combustion chamber.  A 2 rotor has 2 pulses per rev,  just like a 
normal 2600 cc 4 banger.

The only difference of course is that the DURATION of the Wankel 
Cycle power pulses is somewhat longer and overlap compared to a 
piston engine,  which is why the 2 rotor Wankel is smoother (no 
torque reversals),  and also sounds different.

Anyway,  I think we have now beaten this one to death.  As you 
rightly say,  it really doesn't matter because the only thing that is 
important is the "bang for the buck",  the inherrent reliability,  and 
the power to weight ratio.  

I mean,  where else can you get a BRAND NEW 300 + BHP 
powerplant that bare long weighs around 130 Kgs for around $15K 
AUD or $10,500 USD? (a 3 rotor 20B with 9.7:1 rotors)   What 
does a bare long (no manifolds or accessories) IO 540 weigh,  and 
how much do they cost?

Same goes for the 2 rotor 13B. $10K AUD for a BRAND NEW 
200+ BHP engine that weighs bare long around 95 Kgs.  But I'm 
preaching to the converted here,  so I'll get out of your way now ... 

Cheers,

Leon