Typical timing for air-driven engine?

[Peter.]

Some simple questions for the members:

Firstly, how is a typical air driven-engine timed with regards opening and closing the cylinder valves? Is it a simple matter of opening at TDC and closing at BDC?

Are single-acting cylinders timed differently to double-acting ones? Also, are they timed differently to steam-driven cylinders?

Pete.

 

[Tin Falcon]

Peter: IIRC entire books have been written and entire careers spent on the study of steam engine valve timing. this is not nearly as critical in models. although a subject to study. IIRC the KN Harris book model stationary and steam engines explains valving pretty well.

Also typical is a broad statement there are oscillators, d valve slide or spindle valve cross slide valve and corliss plus likely a few more.
Many steam engines have one valve that works to open the intake as it closed s the exhaust then opens the exhaust as it closes the intake. so at or beyond TDC the intake opens and stays open a bit then at BDC it closes as the exhaust port opens.

In a double acting engine the one end is in power mode and the other end in exhaust. at the end of the stoke it changes as the piston is pushed back. Double action simply means the piston is pushed in both directions as apposed to one direction in a single action .

http://www.animatedengines.com/index.shtml]This site may help you visualize how they work
http://www.animatedengines.com/index.shtml[/url]
Tin

 

[Cedge]

Basic rule of thumb.... steam engines area timed at 90°. For instance with the piston at full extension (3:00), the eccentric is set at 90° or 12:00 / 6:00 depending on the direction you want it to turn. Same with a twin cylinder but mirrored so that a power stroke will always be available. This allows a twin to be self starting.

Steve

 

[Peter.]

Thanks for the replies folks!