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Date: Fri, 21 Dec 2007 17:23:54 -0600
From: David Staten <Dastaten@earthlink.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Supercharging
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Ernest Christley wrote:
> wrjjrs@aol.com wrote:
>> Greg,
>> Superchargers are sometimes simpler to implement, but there are other 
>> reasons they aren't as popular on aircraft. First they are a power 
>> robbing device. There is a net gain in power of course, but the 
>> charger can require 10-15 HP to drive it at WOT and it makes the 
>> engine less efficient. The other problem is you must be sure the unit 
>> is up to continous use in the boost RPM range. Lastly the mount must 
>> be solid enough to hold up to continous use as well.
>> Bill Jepson 
> Doesn't the same apply to all intake charging devices?
>
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A turbocharger uses waste heat to power the compressor, rather than 
siphoning the power off the power train. So.. No.. not all intake 
charging devices have the same penalties. The penalty of a turbo is the 
heat involved on the hot side components. The penalty on the 
supercharger is the loss of a component of the HP gain to drive the 
device by belt or gear. More so than with a turbo.

On WWII era radials, there were even "power recovery turbines" which 
took exhaust gas and flowed it over a turbine wheel to add power to the 
drive shaft.