Stuart Turner Comound steam engine, poor casting of cylinder block.

Hi folks! I has worked with the cylinder block to final size. But i has a problem: The distance of inlet steam ports is not correct. It will be 5/64" inlet port + 5/64"+5/32" exhaust port + 5/64 + 5/64" inlet port for both high pressure/low pressure cylinders. I measured between outer inlet port and inner inlet port and got results: The outer distance between the two inlet port is 15/32" (correct distance) in both HP/LP and inner inlet port distance is difference both in HP and LP. HP has 37/128" and LP has 9/32", it must be 5/16" in inner distance between the two inlet ports.

Is it common the distance is not allways correct due wrong in casting?

Is it possible to make a carefull change to correct distance with a microscopic increased inlet port distance and change the distance in the "D" valve to keep correct overlap/keep the inlet ports closed in same time with the "D" valve in the center position?

I has not still created the exhaust port in the cylinder block.

Some idea and suggestions?

Hi Jen,

I find it hard to visualise what you mean. It should be possible to compensate by adjusting the width of the exhaust port and/or the dimensions of the valve, but a sketch of what you have and what it is meant to be would help.

Neil

Hi..

Since i has not received message here, then i took time to study how it affected the timing in case the width of ports is changed. I learned out the lap must not be changed for inlet port and there is not lap in exhaust port, close both two inlet port in mid of position only. Then i adjusted the ports with milling end pin carefully. The valve blocks need adjusting to close both two of the inlet port in mid of position, the "lap" on inlet port is ok (enough material to right size with milling pin.).

Jens Eirik