The Steamboating Forum

I'm continuing to work on the design of the engine for our large boat; I'm getting the hang of QCAD at last.
Here's a PDF of the cylinder assembly sans support ring.

http://smaalders.net/barts/cylinder%20assembly.pdf

Still lots to figure out, but some highlights here include steam jacketed cylinder using a liner from a Detroit D*l.,
5.75 x 5.75 bore & stroke, single acting poppet valves, etc.

On my next pass I'm going to clean up the parts so it's more clear where the passages are; I need to spend some time figuring out cross-hatching as well since that will help.

- Bart

Bart,

Are you going to be using automotive valves?


Id sure like to see more of the engine !!

TahoeSteam wrote:Bart,

Are you going to be using automotive valves?


Id sure like to see more of the engine !!

Yes, I'll be using automotive poppet values. A handy link for valves is this:

http://www.melling.com/Portals/0/Size%2 ... 0Chart.pdf

This has poppet valves listed by head diameter & stem size; most are orderable via summit racing quite reasonably.

Started making the crankshaft today by cutting out the crank cheeks from a chuck of prehard I found scrap.

http://smaalders.net/barts/crank%20cheeks.pdf

I've got most of the engine figured out... still need to draw up the variable dwell cam for the poppet valves, but that will let me control cut-off from 5% to 12%, which is plenty for a cylinder this big.

- Bart

Is this going to be a single cylinder engine/
I'm not real familiar with this style engine. Which side of the valve is the inlet pressure on? Face side or stem side?

FRank

racerfrank wrote:Is this going to be a single cylinder engine/
I'm not real familiar with this style engine. Which side of the valve is the inlet pressure on? Face side or stem side?

FRank

This is a single cylinder double acting poppet valve uniflow. The steam is admitted at each end of the cylinder from the steam chests; the steam pressure in the steam chest acts to keep the valve closed. Since uniflow engines have fairly high compression, the valve actually opens against only a small pressure differential. If vacuum is lost or water accumulates, the poppet valve is forced open against the steam pressure, much as a slide valve lifts under the same conditions.

The head and cylinder are both jacketed w/ steam, there will be be condensate drains leading to a common dynamic steam trap and then into the condenser.

Since the boat will be equipped w a Kitchen rudder, there is no need to stop or reverse the engine; it remains running in the same direction all the time. This should help make the boat much easier to maneuver, and removes the need for the engine to be self-starting in order to single hand the boat.

Much of what I'm doing is described in Prof. Stumpf's book:

https://books.google.com/books?id=_mtMA ... pf&f=false

- Bart

The phrase "Sea Lion Engine" makes me immediately think of the Napier Sea Lion - which is off-topic, but interesting all the same I think. Napiers started building aircraft engines in World War 1, to other peoples designs, which (like most at the time) were not good. They therefore designed their own: the Napier Lion, which had 12 cylinders arranged as three banks of four as a broad Vee with another bank vertically in the middle, and by 1917 it was in service, albeit with curable bugs. https://en.wikipedia.org/wiki/Napier_Lion It actually dominated the higher power engine market worldwide between the wars, producing 500 to 600 HP in standard form, and about 1300 HP when tuned. It was only really superceded by engines like the Rolls Royce Merlin and Bristol Hercules in the UK, and various engines of slightly later vintage in the US.
However, to come back to marine versions, it was adapted for marine use as the Sea Lion just before 1920, and proved to be a most reliable and useful engine. It was remarkably widely used in military and racing craft. New RAF RTTL launches were still being built in 1956 using three 600 hp Napier Lions, http://www.asrmcs-club.com/boatswebsite/rttl1a.html and were still in full use in 1970, not being disposed of until 1977. Three Sea Lions were first superceded by two Sea Griffon petrol engines of 1700 HP each, but the quantity of fuel needed for a 500 mile range with these or Sea Lions made the launches floating bombs waiting to be detonated, so Napier Deltic diesels at about 2,000 HP each, took over fairly quickly. So that's 1917 to 1977 with essentially the same engine in ordinary (not preserved) use. That's remarkable by any standards.

That's an interesting story - thanks for the Wiki link.

My brother is (among other things) a yacht designer, and he's working on the design of our big boat, while I'm designing and building the engine. His
website is here; http://www.smaalders.net/yacht_design/

As our small 19' steamer is named Otter, the big boat seemed destined for a name of a larger sea mammal.

At some point when we're further along with the boat design, I'll start a thread on the boat, along w/ links to the lines and interior drawings.
We'll be constructing a model this winter at 1/12 scale both to evaluate hull design and interior layout.

The power plant design criteria are this:

* capable of being wood fired
* needs only intermittent attention so that the boat can be readily single handed if need be.
* efficient operation at lower power levels consistent with speed length ratios near 1.1.
* minimal odor from lubricants since engine shares habitable interior space.
* robust construction consistent with year round operation (aside from storms) in the relatively
open waters in the US Pacific Northwest.

The boat will have a pilot house overlooking a raised forward deck; the engine and boiler will
not be directly adjacent to helmsman position.

This has led pretty directly to the following engine design decisions:

* Use a uniflow cylinder design + poppet valves to maximize efficiency and thus range with wood
firing. Uniflow engines with proper valve gear are quite efficient at very short cut-offs while
having ample power at longer cut-offs.
* Use a Kitchen rudder to provide reversing w/o need to reverse engine, This also provides much
better maneuverability than a traditional rudder, particularly in reverse. Since there's no need to
reverse the engine, coolant pumps can be roller type. This also allows us to start the engine running
and getting the plant to steady state w/o moving the boat - very handing when leaving a mooring or
anchoring out.
* All bearings will be rolling contact with grease lubrication to reduce odor, maintenance. Cross head will
use V-grove cam follower bearings; top of connecting rod is forked and uses needle bearings; big end
is a "sealed" spherical roller bearing. Poppet valves are driven by rocker arms on needle bearings,
with roller cam followers running on disk cams.
* Where appropriate, I'm using commercial components rather that custom designed and built parts.
A plate style heat exchanger w/ a glycol cooling loop as codenser, a Hypro piston pump for boiler feed, roller pump
for glycol circulation, roller bearing pillow blocks for main bearings are all examples of this approach.
The static sealing in the engine is done with O-rings or formed in place automotive RTV.

- Bart

Bart,

Sounds like an exciting project, looking forward to your build thread. Engine looks good.

-Ron

Bart,
I am full of admiration for your project - no ifs or buts.

In 1969 I did my RN Officers' boat handling training, in 30' i.c. engined launches using Kitchen rudders. Frankly, they were complete bastards to manouvre compared with civilian craft I was already well used to, with ordinary rudders and reversing gearboxes.

Reversing gearboxes are both cheap and efficient these days, and while Kitchen rudders undoubtedly work, and are a nice idea, in the light of experience I wouldn't install one myself.

Hi Barts

I have designed an engine a lot like this, but also quite different.

I would highly recommend you look into using balanced poppet valves. They are not difficult to make and they will take a lot of stress out of the valve gear. Just think if you have 2 Square Inches of valve surface, and you are running at 150psi, you already have 300 pounds of force required to open the valve. If it were balanced it would be 5 pounds of force or so regardless of the pressure.

I like the whole Uniflow idea a lot, and I see you have put thought into keeping the steam passages as large as you can. Most engine designs have multiple bottlenecks, really you only want 1 bottleneck, and that should be the control point. This will keep efficiency high.

I especially like the exhaust idea on a Uniflow, as the steam expands so much they have a much larger space to remove the steam, again reducing the resistance of the steam flow.