Custom Made Mechanism
 


Hydraulically Operated Trapdoor Mechanism


The design of this mechanism had to fulfil several criteria:
 

That of being able to cope with the inertia of a heavy steel framed trapdoor (80kg) and the friction due to the snug fit of the door in its frame.
 


The mechanism was made to lift the hinge side of the door first, to allow enough clearance to open (because the main hinge centre is well below floor level), this also providing the extra gearing required to overcome initial friction.
 

It had to be fail safe; in that it should not be able to trap anyone in a powered state.
 


The door is only powered open - closing under gravity, initially with spring assistance.
 

Ideally it should be able to cope with power supply failures.
 


The hydraulic power-pack is 12volt driven, with the battery under constant float charge.
 
image of side elevation from CAD drawing
This animation helps to visualise
how the mechanism works.
 
Both the design of the mechanism and the generation of the animation were produced from WORKING MODEL™, a parametric kinematic design program, which enables the design and simulation of real world conditions.
Animation of trapdoor mechanism






Copyright © 1987-2016 John A.R.Markham