The Moriya Story #4 - Stoppage Vent for the Major

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Well-Known Member
HMEM Supporting Member
Mar 1, 2021
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Spring Valley WI
I usually run Moriya Major around 500 rpm. At that speed she yields a nice steady quiet movement of air from one end of my 20' long workbench to the other. Every hour or so, a drop of oil is applied to the piston and on the displacer rod. For this, the engine should be brought to a standstill obviously so that nothing will disastrously get caught in moving machinery.

Removing the alcohol lamp of course will stop the action ... eventually. It takes long minutes for the engine to cool down to a stop. And then more minutes of heating to build back up to speed.

The Waheed fans made in Pakistan had a "button" protruding from atop the engine enclosure for stopping the engine. It was a just a plunger which when pushed down made frictional contact with the crankdisc. Pressing down rather hard forced the engine to reluctantly grind to a stop. Effective, but a rather brutal method to stop an engine otherwise more than willing to keep on going.

In the case of Moriya Major, I decided on providing a vent to the atmosphere to accomplish engine stoppage. Anyone who has made a model Stirling engine knows well that a tiny leak anywhere can easily be fatal to its operation.

The engine of the Major had to be taken apart in order to drill a passage through the base into the workspace. The exit was tapped 1/4-28 to take a bleed screw with a flat filed on the threaded section. A clearance hole had to be made through the Leg Plate on that side to let the bleed plug seal against the engine base. Unscrewing the vent plug just a few turns creates a leak sufficient to quickly stop the machine. The SS wire handle on the vent screw stays cool enough to handle.

The smaller fan, Moriya II, is also similarly equipped; in that case, the vent passage is already included in the drawing for the engine Base. The bleed screw is the same for both fans. The vent is also convenient for checking that the engine machinery turns freely after assembly or making any alterations.


  • Moriya Major.png
    Moriya Major.png
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  • MM Vent.png
    MM Vent.png
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  • MM Preesure Release.png
    MM Preesure Release.png
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  • MM Vent Plug.png
    MM Vent Plug.png
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  • Moriya II.png
    Moriya II.png
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