What speed for the paddle-wheel?

[geoff_p]

As mentioned on another thread, I'm building a double-diagonal steam-engine, loosely based on ET Westbury's design.  So far, one-half runs on air, from about 200/300 rpm (depends on its mood) to about 800 rpm (after which, the bolts all come loose!)

I think the Strongbow design will suit my engine and meagre modelling skills. 

The Strongbow's paddles appear to be 4" (inch) diameter (someone, please correct me - that's just scaling off the drawings) so I wonder what sort of rpm would move the model realistically?  The engines will direct-couple to the paddle-shafts on extensions to the crankshafts, and the two engines will be coupled together as appropriate.

Please note, the attached photo is the 'prototype' Mk#14.  Castings for the 'real' pair are underway between rain-storms.

Geoff

[andy]

The similar engine of mx DIESSEN is coupled direct to the wheels with about 12cm diameter and is running fine. Regulation of speed by valve, I suppose it runs about 300rpm maximum in water. Original ran 40-80 revs only.

These engines are strong enough for the wheels, I hate gears and belts.

Andy

[bill stafford]

i operate a aussie side wheeler paddler model , i work to 300/350 rpm at the paddle shaft, any slower and the model wont handle any wind at all, if it is a calm day , i just slow the electric motors down , you have too generate forward motion for the rudder to work.
 i would recomend a reduction from the steam engine of 3:1 too, as this will allow condensation in the cylinders too clear .most aussie paddlers w short throw , high speed cylinders , in full size , use some form of gearing , typically 3:1, for just the same reasons
good luck bill s

[geoff_p]

Interesting, two quite opposing views - geared or direct drive - but both aiming for similar revolutions.

I hope that the relatively long stroke (30mm) of my engine will permit quite low-speed operation though I have to admit, I hadn't considered condensation in the cylinders.  Bother!

Geoff

[andy]

The stroke of my diagonal engine is 36mm, the pistons are 34mm and 20mm. This engine is a little bit too powerful, twice 20mm was enough as well. Only for comparing with the measurings of your engine. Power output only is 1/200 hp, but torque is on such a high level, that I always put my fingers off from the engine room.

Andreas

[geoff_p]

Thanks for that, Andreas.

How many fingers can you count now?

Geoff