Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

I think we can get value from both.

  Example 1,  An engine goes into lockout at 820 rpm, slows to 440 rpm, seemingly coasting forever, and achieves 45 hits per minute.

Example 2, an engine goes into lockout at 800, rpms, coasts seemingly forever, slows to 400 rpms, but fires 59 times a minute.

Which engine is running slower?

Spring selection and tension only tell part of the story.
Hits per minute only tell part of the story, especially if an engine double taps or triple taps to get to lockout. Might be the engine that hangs longest in lockout is actually going slowest before firing, but takes two or three pops to get to lockout. Might be a Governor is a bit sticky on the top or the bottom or both? Might be the engine is running too rich or lean, or at a less than optimal timing to get a strong pop when it comes out of lockout.  Bearing condition can make or break coasting.  (I remember watching a video about prep for a motorcycle jump. The crew chief tried half a dozen front wheel bearing sets before choosing the smoothest and most free running). I think of our Chinese main beatings as middling at best.

Just as with throttle controlled engines, we’ve all seen hit dnd miss engines happily and reliable ticking over slowly with a regular heartbeat like single strong pop, and we’ve also seen engines stuttering on the edge of stalling, firing erratically as they barely hang on. 

A recent first run video of a quarter scale hit snd miss restoration was perhaps the sweetest sorta little engine I’ve ever heard. (About nine inch flywheels I reckon). A long, lingering coast down punctuated by the tapping of the mechanism, and a single, throaty “whump” as it fired with authority before locking out. The SMOOTH of the old bronze bushes was palpable.