Excessive motion of the valve when in mid gear

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Excessive motion of the valve when in mid gear

Post  AndrewR on Mon 17 Aug 2015, 1:54 am

Hi there folks,

I hoping someone will have some ideas for me. I seem to have excessive motion in the valve when in mid gear (about 9.5mm). This motion is just enough to open the steam passages to the cylinder by about 0.5 to 1mm each side. Not a major issue but gets a bit hairy on the occasion a piece of crap got under the regulator and I couldn't close it off. The engine ran in reverse and there was nothing I could do to stop it save dropping the fire and waiting.
I have spoken to Steve and he advised the test model only had about 6mm movement when in mid gear. If I could drop the extra 3.5 off my engine then the steam passages to the cylinder wouldn't be exposed.
What are other builders experiences?

Any help/thoughts much appreciated.

Cheers Andrew

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Re: Excessive motion of the valve when in mid gear

Post  Grahambro on Tue 18 Aug 2015, 1:46 am

Hi Andrew,
Mine has about 5mm movement in mid gear and doesn't run in that position.
How did you determine your mid gear position?
I did mine by moving the reversing lever and rotating the engine by hand until the movement was minimal then marked this position - the die block should be close to centre of the expansion link. Then moved the lever to full forward and rotated again so I had clearance allowing for thermal expansion. The 2 notches between full and mid where then marked - the one closest to full to Steves dimension but the 2nd notch based on the lubricator actually incrementing. Reverse was done same as full forward.
Hope this helps

Graham

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Re: Excessive motion of the valve when in mid gear

Post  AndrewR on Tue 18 Aug 2015, 3:06 am

Hi Graham,
From memory (and admittedly thats bad!) I followed Steves instructions for the initial setup.
Several of the "old hands" down here have had a nosey and the general agreement is the mid gear is about as good as can be. Even moving it back and forward a bit doesn't make much of a difference in the valve movement.
It's interesting the amount of movement you are seeing ties in with what Steve saw on the control model (and a mate over here who has a 4" clayton shuttleworth with similar valve setup also sees about 6mm movement)
Steve sent me the diagrams for the eccentrics so I could verify they were correct as that was our first assumption as to where the fault was - but the eccentrics are correct.
Unfortunately, none of that explains the extra movement in my engine. Crying or Very sad


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Re: Excessive motion of the valve when in mid gear

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