Front Viewport


This is the final idea for the removable front dome.  The finite element analysis is complete and I have ordered the two rings.  The Analysis was done using my original dimensions, but I have since changed them slightly in order to reduce weight and allow easier machining for Emile who is making them.

Final Dimensions


It’s a bit awkward to see in these pictures but these are the final dimensions for the weld in ring and dome seat.  I changed it slightly for easier machining and less weight. 

The weld in ring will be steel, dome seating ring aluminium.

Emile will machine 4 hold down retaining lugs into the aluminium ring which I can then use to build the releasable catches.  There will also be a machined hinge bracket at the top.  The “O” ring groove has been moved to the dome ring for anti corrosion reasons.

Weld in ring OD = 608mm, ID = 510mm

Aluminium ring is the same but with a lip OD = 578mm

Analysis on the Original Design.


Its very difficult to model the pressure acting on the dome itself and how that transfers onto the seating face of the ring.  So, the surface area of a flat disk was used and the pressure that would be on that applied to the seating face. 

Its only an indication and not a fully accurate analysis.

Area of disc OD 580 dia = 264207 sq mm or 409.5 sq in

Pressure = 220psi = 90090 lbs force or 400740N

Seating face area = 70987 sq mm or 0.070987sq m

Pressure acting on seating face = 400740/0.07987 = 5.645MPa = 818psi


The analysis shows a safety factor of 2.8 with 0.2mm deformation at 56 bar or 818psi (550 meters depth).


Deformation of the elliptical endcap would occur before failure of the ring itself.


The Dome itself is rated to 150—200 meters and would fail at approx 100—150 bar or 1450—2175psi (1000+ meters depth).

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