Engines > Restoration of Model Engines

Two Uniflow Engines

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Jasonb:
I am wondering if anyone has either of these two Uniflow engines, as they are on their way to me as non runners and it would be a simpler job if a known runner existed so that valve timing could be compared or a drawing found.

The first is the "G1 Uniflow" High Speed Dynamo engine of 1923 and the second a Bassett Lowke "Uniflow"

Jasonb:
The Drawings for the Bassett Lowke have showed up in "Newnes Practical Mechanic " of 1950 and the engine was introduced in 1949. Said to reach 4,100rpm on 120psi steam. Now I have to resist the temptation of making one :ShakeHead:

The Jackson-Rigby G1 engine was possibly in Model Engineer in 1923 vol 48 No 1136, if anyone ha sthat I would be grateful of a scan.

Jasonb:
The two engines arrived and I had them both running withing 15mins, 5 of which was sorting out suitable adaptors for the air supply.  :pinkelephant: :pinkelephant:

However I may have spoken too soon🤐🤐🤐🤐  After getting the G1 to run and thinking my work was done it started to misbehave. It would run OK for a while then the speed would go up and down before it stopped rotating and just oscillated back and forth.

The cam position was adjusted a few times from below but it still happened as if stopped from oscillating I could hear air still flowing out the exhaust at BDC even if the cam was nowhere near the open position.

Off with the head to have a look at the valve. It did not look like it was really closing and a could feel it was in contact with the base circ;le of the cam if not actually lifting so 5thou was taken off the end of the valve stem and put it back together for another try.

Same again so another strip down and I thought the valve was sticking a bit, though hard to tell as the spring is held down by the head. Out with the Mic and the bottom of the stem is 0.127″ compared with 0.124″ just under the head so into the lathe and Emery it down parallel and put the engine back together.

Same again. Off with the head once more and the valve did not seem to be sitting down so my thoughts turned to the tappet that I could not see. So off with the flywheel, Big end cap off so the piston could be pulled, loosen cam and slide out the crankshaft. The tappet dropped out.

On closer inspection the top of the tappet is threaded for a push rod and there is a lock nut. This nut was loose!! Which was allowing the valve lift to alter while the engine was running and when the lift became too high air was passing all the time.

I reset the pushrod length and locked up the nut before putting the engine back together.



All seems to be running as it should now.

Will take a better video over the weekend as the base plate still has to go back onto the bottom of the crankcase.

Jasonb:
Should have said that thanks to a member on ME forum I have a copy of the old ME that the G1 was mentioned in as well as the build article for the "Don" engine mentioned in the old advert

PaulR:

--- Quote from: Jasonb on May 01, 2026, 08:41:14 pm ---On closer inspection the top of the tappet is threaded for a push rod and there is a lock nut. This nut was loose!! Which was allowing the valve lift to alter while the engine was running and when the lift became too high air was passing all the time.

I reset the pushrod length and locked up the nut before putting the engine back together.

--- End quote ---
Nice, a simple fix once you were able to track it down. Looking forward to seeing it running.

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