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From: david mccandless <daval@iprimus.com.au>
Subject: Re: [FlyRotary] Re: Emailing: DoorOpenLside.jpg
Date: Mon, 14 Aug 2006 06:23:54 +0800
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>

Hi Ed,
I do not need a door nor a hangar, but as the discussion progresses I 
am becoming more interested.
I would have thought that a Warren type truss, fabricated from, say, 3 
inch channel for chords and 2 inch angle for webs, would have been a 
better and lighter solution than a timber beam.
Is that big center beam a laminated truss or a plywood fabricated beam?
I am an old structural engineer from 40 years ago, I have a lifelong 
love of bridges, and have never loss my interest in beams etc, so this 
is not meant to be criticism but rather to satisfy my own curiosity.
BR, Dave McC

On 14, Aug , at 5:51 AM, Ed Anderson wrote:

> I am convinced (but have not done a comparative analysis) that this 
> arrangement does produce less outward force on the top of the door 
> frame/hanger than a bi-fold.  The hydraulic ram ends up at a 47 deg 
> angle to the ground and so supports  approx  70.7 % of the door 
> weight.  If the door weighed 600 lbs finished then I estimate the door 
> frame would support approx 200 lbs and the ram 400 lbs.  Since the 
> "balance" point of the door is along the axis of the beam this should 
> mean very small outward forces once the beam is raised.