sweet william cylinder head clearances

[JohnR]

I am finishing up my build of a Sweet William locomotive . I have a problem with starting especially if the cylinders are cold.
There is a tendency to hammer which I assume is due to insufficient clearance between the piston and cylinder head. I can not
get the condensate out fast enough. Is there a recommended clearance between the piston and the cylinder head at top dead center?
Thank you.

[Builder01]

Do your cylinders have drain valves?

David

[JohnR]

Yes. Automatic

[K. Browers]

Hello John.
I have looked at my Sweet William drawings and if it is built according to the words and music (it is a British design after all) you should have a total clearance on each end of the stroke of .09375" or 3/32". You could also check that your holes for the cylinder cocks are not covered by the pistons in their travel. The drawings do show the piston to be thick enough that you could take a skin cut from either end to give you more clearance.
Cheers
Karel

[Fred_V]

Get rid of the automatic cocks.

[Benjamin Maggi]

I am building a Sweet William too (It is in the build log section) but I am not that far ahead. I would love to see or hear more about your engine!

[Bill Shields]

dump the automagic cocks and groove the holes for the drains toward the cylinder heads so that they are not covered by either the pistons or the rings if you don't have enough meat to take off of the pistons themselves.

after that is done 3/32" is more than enough clearance (i have locos with a lot less clearance...)