The Steamboating Forum

Can some one name this style of valve train. I think I understand how it works . The reversing lever rotates the eccentric shaft and eccentrics but the gears stay engaged with the drive gear on the crank. This is a model engine with 9mm bore x 12mm stroke. Just wonder ing what its called and if it was ever used on full size engines. a setup like this would make an interesting triple or quad.





Frank

From a practical standpoint, using spur gears to drive the eccentrics might get pretty noisy at speed. Slide valves can have pretty significant forces; piston valves of course don't. Note that this sort of gear is not useful for adjusting the cut-off, only for providing forward and reverse; it's akin to a sliding helical groove that permits adjustment of the phase angle, but not the amplitude of the valve motion.

- Bart

I see the shifting lever in the lower picture that allows you to change the relation between the the crank and the valves. Interesting! what does the crank in the upper picture on do?

wsmcycle wrote:I see the shifting lever in the lower picture that allows you to change the relation between the the crank and the valves. Interesting! what does the crank in the upper picture on do?

I'm thinking it might be the throttle .

Frank

barts wrote:From a practical standpoint, using spur gears to drive the eccentrics might get pretty noisy at speed. Slide valves can have pretty significant forces; piston valves of course don't. Note that this sort of gear is not useful for adjusting the cut-off, only for providing forward and reverse; it's akin to a sliding helical groove that permits adjustment of the phase angle, but not the amplitude of the valve motion.

- Bart

Do engines with a slip eccentric have a way to adjust cutoff? or are they just forward and reverse?
If you were to build an engine with a separate eccentric shaft like this could it be driven from the end by means of a cogged belt and if it could, could you make up one of the drive cogs to shaft connection as a "slip" joint to reverse all your cylinders?
And as I see it an engine built for one way rotation, for say generator use or for use on a boat like Barts is designing with a kitchen? rudder a cogged belt would work rather nicely.

Not trying to reinvent the wheel (or in this case the steam engine)when I see a design that is unusual my mind starts wondering.

Frank

racerfrank wrote: Do engines with a slip eccentric have a way to adjust cutoff? or are they just forward and reverse?
If you were to build an engine with a separate eccentric shaft like this could it be driven from the end by means of a cogged belt and if it could, could you make up one of the drive cogs to shaft connection as a "slip" joint to reverse all your cylinders?
And as I see it an engine built for one way rotation, for say generator use or for use on a boat like Barts is designing with a kitchen? rudder a cogged belt would work rather nicely.

Not trying to reinvent the wheel (or in this case the steam engine)when I see a design that is unusual my mind starts wondering.

Frank

I built Otter's original engine from a refrigeration compressor; it had a slip eccentric and would operator only in forward or (sometimes) reverse.

A timing belt drive is pretty nice for a engine, although a bit 'modern' looking. They're quiet, long-lived if not overloaded, and don't make a mess in the boat slinging oil about. I've been strongly considering using one to drive the right angle gearbox for Sea Lion's camshaft.

Here's a short clip of something in a bit larger form:

That is called Maudslay's valve gear. There isn't much about it in any of my books.

http://www.homemodelenginemachinist.com ... php?t=7063

JohnG