Timing the Trevithick dredger engine-3. How embarrassing….

As planned I removed the engine from the boiler, to discover why it would not work with compressed air yesterday.

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After yesterday’s failed attempt with compressed air, I removed the cylinder and piston and valve assembly from the boiler to check the steam passages, throttle and rotary valve. 

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These components were removed so I could see what was going on.

I wish that I had checked this before going into print yesterday.

I discovered that the bronze cylindrical insert with the steam ports had never been fixed/Loctited into position.  Clearly it had rotated with the first engine movements yesterday, causing all steam passages to be blocked.  No wonder I couldn’t get the engine to do anything!

And worst was that I had mentally made a note to secure the insert, when I inserted it, a month or so ago.

So today I drilled and tapped a hole for a stainless steel grub screw to hold the insert into position.  I decided not to Loctite it at this time, but will do so when I am sure that the timing is correct.  I might need to alter the shape of the ports, and the insert would need to be removed to do that.

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Tapping the thread for the grub screw using the shop built tapping head which I made to Mogen Kilde’s design a couple of years ago.  I have never broken a tap while using this tool.

After reassembling the components I ran another test with compressed air.

Somewhat to my surprise, at 20psi the engine ran for a few revolutions, before  settling down into a back and forth motion.  It still needs to be timed, but hey, it moves.  But by this time it was becoming hot in the workshop, so I left the timing for another day.  Maybe tomorrow pm.   Not Thursday because it will be HOT.  42ºc  (107.6ºf)