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Sourcing or Designing a Heavy-Duty Parallel Lift Door (Parallelogram Linkage) for Under-Porch Storage

gregorysherm

New member
Joined
Sep 3, 2019
Messages
2
Location
Oakland, CA
Hi everyone,

I am planning an exterior under-porch storage area and need help sourcing hardware or designing the mechanical geometry for a specific type of door.

I want to replicate the exact movement of an interior cabinet parallel lift-up system (like a Blum Aventos HL or Sugatsune SLUN), but scaled up to a much larger residential/commercial size.

The Setup & Motion Profile:

  • Opening Dimensions: 5 feet wide by 4 feet tall.
  • The Motion: The door must be a single, solid panel. When opened, it needs to pop slightly outward to clear the exterior trim, and then travel upward in a perfect geometric arc without rotating. Its final resting place will be directly above the opening header, remaining entirely vertical (perpendicular to the ground), completely outside the storage cavity.
  • The Goal: I want a completely trackless interior to maximize every inch of the storage cavity, and I have plenty of vertical clearance directly above the opening.
The Door Construction: I intend to keep the door panel as lightweight as possible to minimize the structural load on the mechanism. I’m planning on a rigid aluminum frame, possibly with minimal steel reinforcement at the main stress/pivot points, skinned with a lightweight composite or thin wood cladding. Estimated target weight will likely be between 35 and 55 lbs.

Where I Need Help: Since standard high-end cabinet hardware maxes out around 20 lbs and a 36" width, I need to step up to heavy-duty mechanical solutions.

  1. Hardware/Manufacturers: Are there any commercial or industrial manufacturers (similar to Weber Knapp or Southco) that make off-the-shelf 4-bar parallelogram linkage arms and counterbalance systems capable of handling a 5-foot-wide, ~50 lb door?
  2. DIY Fabrication Geometry: If I have to custom-fabricate the linkage arms from steel square tubing, what is the best way to calculate the pivot point placement and gas strut sizing? I know I will need a solid torsion sync bar running across the top to connect the left and right arms to prevent the 5-foot-wide panel from twisting/racking when opened from one side.
  3. Gas Strut Specifying: If you’ve built a similar parallelogram mechanism, how did you calculate the initial compressed leverage requirements for the gas springs so the door doesn't require massive force to break from a dead stop, but also doesn't violently slam upward at the top of its arc?
Any sketches, calculator tools, link-age simulator recommendations, or hardware leads would be massively appreciated. Thanks!
 

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firebirdparts

Well-known member
Joined
Jun 8, 2016
Messages
10,684
Location
Kingsport, TN
It’s notable that Aventos uses a synchronizer. I might not have thought of that.

the movement geometry is really simple. Getting a spring to hold the weight but allow it to close is very tricky.
 
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