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From: "Jack Ford" <jackoford@theofficenet.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-869505@logan.com>
Subject: Re: [FlyRotary] Re: Fw: Rx-8 Rotors useable in 91 13B?
Date: Thu, 14 Apr 2005 19:02:20 -0700
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Section modulus for a rectangular cross-section (strength in bending) 
bh^2/6; Moment of inertia (stiffness) bh^3/12, (Taken around the neutral 
axis) so strength in bending is proportional to the depth squared, stiffness 
to the depth cubed.
The two values are related and one can be easily calculated from the other. 
s=I/c.

Jack Ford

----- Original Message ----- 
From: "Ernest Christley" <echristley@nc.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, April 14, 2005 6:36 PM
Subject: [FlyRotary] Re: Fw: Rx-8 Rotors useable in 91 13B?


> Ed Anderson wrote:
>
>> Thanks, George
>>  Appreciate the information on the seal grove.  Perhaps we'll just skinny 
>> down one  of Tracy's seals as on their web site they are reported 800% 
>> stronger than stock, then just stick them in the RX-8 rotor slot.  I mean 
>> even if milling the seals to fit reduces there strength to 200% of stock 
>> that should still be fine.  Must discuss with Tracy when he returns from 
>> Sun & Fun
>>  Ed
>
>
> I'm going completely off the top of my head here, and stand a good chance 
> of being wrong, thereby, BUT...
>
> The seals (as they cross the exhaust opening) become a cantilevered beam, 
> with a fulcrum or support point at the edge of the exhaust opening. 
> Doesn't a beams bending strength increase as the 4th power of the distance 
> between the sides?  I do know that if you split a beam in half, you'll 
> have much less than half the strength.
>
> The other issue would be that stronger doesn't necessarily equate to 
> stiffer.
>
> -- 
> This is by far the hardest lesson about freedom. It goes against
> instinct, and morality, to just sit back and watch people make
> mistakes. We want to help them, which means control them and their
> decisions, but in doing so we actually hurt them (and ourselves)."
>
>
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>