Very cool and very interesting. Congrats, Mike..!!!
I built a 55 with 4 screw cylinders and I believe they are bigger than what are on your newer engine.
I also think this one has smaller screws than what Jensen uses on their 4 screw cylinders.
When you receive it, please measure the outside diameter and compare to your pre-war #25 cylinders and let us know.
Whatever the origin, the modification work looks excellent!
Thanks, Gil!
I can’t wait to examine it when it arrives on Monday. 😁
One thing I find interesting is the early style block-off plates used on the valve chests. If someone modified the normal cylinders that would be found on an engine like this, I would think the valve chests would have the rivets plugging the holes like you’d usually find.
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The extra large exhaust pipes and the early style port covers (on the steam chests) are features found on mine due to the early cylinders I used. I have only seen the large exhaust ports on the smaller military air pumps Tom Sr. made for the DOD.
Gil,
These cylinders measure 1” OD just like all my pre-war cylinders. The engine base casting does have the corners ground off where the cylinders mount. There is also a washer behind each crank to accommodate the wider spacing of the cylinder centers due to their size. The plywood base is actually beveled like most are and it’s larger than a normal 55 base. The original box is marked for a model 20 engine. I believe this engine was built this way by Tom Jensen Sr as an experiment or just to use old cylinders that were laying around. He may have made a bunch of these cylinders that the DOD never needed and just wanted to use them up. Your guess is as good as mine, but I really can’t see some hobbyist just having these cylinders and doing this modification in their home shop on their own.
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