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Hi David,
You are right on all counts, fortunately- it is not a timber beam. Its actually a engineered box beam very similar to wooden spars built for aircraft. But, without quite as much attention to weight savings {:>). I used Liquid Nails Subfloor adhesive after discussing my project/needs with their technical staff (learned a bit about wood glues/adhesives) and deck screws to build the beam. It weighs around 180 lbs.
Its basically a warren truss enclosed in plywood. It just took less work (more lumber, but less work), to have the building material store cut me 16" wide strips of plywood (4 to a sheet) and then use those as the webs rather than cutting out the gussets necessary for each brace/flange interface to build an wooden open warren or Pratt truss. It would be interesting to see how light the beam could be made, but I've been working on building hangars and doors since around March and wanted to see the light at the end of the tunnel {:>). Besides, I can't fly until the door is finished as my aircraft is trapped inside!!!
Appreciate your comments
Ed
----- Original Message ----- From: "david mccandless" <daval@iprimus.com.au>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, August 13, 2006 6:23 PM
Subject: [FlyRotary] Re: Emailing: DoorOpenLside.jpg
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.
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