The Steamboating Forum

Yes, but you are talking relatively small engines, low horsepower etc. Neither the engine under discussion or the engine I mentioned fit those criteria, although they are small by ship sizes. Kapanui (30ihp Simpson Strickland Compound 4.5 + 9 * 5.5) has no flywheel, but a large 29 by 31 prop (four large blades), and yet her engine is incredibly smooth, even flat out (400rpm). As a testament to its smoothness, there was a mark on the brass cylinder block cover that showed where the oil can sat all its working life, obviously for many years. I could put the oil can in the same spot and leave it there for weeks if only running in sheltered waters, and it won't come off. Only a big rolling sea or wake with throw it off the engine.

In a smaller engine, a flywheel would be necessary, as shaft and prop are smaller, over 25IHP i doubt they are necessary provided the engine is well balance in the first place.

Daniel

DetroiTug wrote:
I used to believe this as well. After running without a flywheel and with the flywheel, I have concluded that a balanced multi-cylinder engine definitely runs smoother with a flywheel even though one is not needed for rotational inertia. The propshafts we typically run are long and smaller than ship-sized diameter in scale which can twist under torque loading.....

-Ron

Not to split hairs here but I didn't claim an engine could not have an acceptable level of smoothness without a flywheel, but rather it would run smoother with one. All materials deflect under load. Some research on transducers, string gauges will show the levels of deflection with load and it is surprising. An engine/ boat may run smooth without one, but it's guaranteed there are oscillations from torque pulsing being absorbed by the propshaft rather than the absent flywheel. Whether noticed or not.

-Ron

Nice video, good to see radial (Marshall's) valve gear on a tripple.

John

Nice video Ron.

The flywheel on the Doty has a counterweight as well....

Many modern I.C. engines have two flywheels, one at each end of the c/shaft to even out the oscillations. The front one, whilst much smaller, is usually attached with an interleaved resilient rubber ring, to further assist the process.

That is besides the "Dual Mass" type flywheels which are designed to absorb harshness from the drive-train.

Making new crosshead guides...

Old:





New:

Plates and bars were initially blanchard ground to final outermost dimensions, then machined to spec.

Now the question is, to oil groove or not to oil groove? I have seen with a single horizontal line and other with elaborate grooves like on the old guides above, or concentric rings. What are your collective thoughts and experiences?

Also a shot of the pump arrangement better showing the setup:



There will be two round columns front and back of the condensate pump ram with a connecting bar across the top. They will act as crosshead guides, with the associated crossheads bolted to the horizontal bar.

Hi Wes,

Great looking work!

On the question of the oil groove, I would. They provide several benefits. They distribute the lubricant evenly between the two plates, they provide an area where debris can exit from between the two mating surface and they lower the friction between the two mating surfaces. When two planes that mate one another perfectly and have oil in between, vacuum and pressure can form between the two, the oil grooves act as a vent. If you have some "Jo-blocks", take two and stack them together - they'll fall apart, and then "screw them together" with a twisting action, they will adhere to one another like they are glued. That is the oil being displaced and a vacuum forming between the two. In machine tools this is some times referred to as "sticktion"

They can be simply two interweaving zig-zag lines with a ballnose endmill.

-Ron

Hi,
I agree with Ron yes for oil grooves made with a ball nose cutter.
Regards
Jack

Ball Nose?
What depth related to the Ball Radius?