I got a question about stuff

[Cyruscosmo]

Hey all!

So since I joined this site I have spent the better part of my free time during work at lunch or the last hours of the night "when I should have been sleeping" reading these forums. I have found more useful information than I currently know what to do with and over all it has answered enough of my questions that I have nailed down the hull I want to build. I ran across a few links on the forums to a few websites that offer plans and have found my future project. http://www.selway-fisher.com/Steam2030.htm#26 Mike Bells version Annabelle only with an 8' beam.

I have 32' of floor space in my new shop that is 20' wide so I will be using the stretched version of the Edwardian plans at 30' LOA and 8' beam. I got an e-mail back from Paul at selway-fisher confirming that my choice is already in the plans as a possible alternative method of construction.

So... Since I am new to the steam engine business I have a little trouble equating HP to Steam. The boat in question requires 15-20 IHP... Ok what the heck does that look like in pistons crank valves and prop? If ya told me to build an I.C.E. mud bogger I would know which engine, trans, running gear and tire size to start with but here it sounds more like Greek to me.

I guess a better way to put the question is... May I ask the advise of those who have many years of experience? What boiler, steam engine and prop combination would you start with? Since I am building the engine, boiler and all I would like to at least bark up the right tree in the first place. Even if I can't climb it yet.

I will listen: Fore I would like to make new mistakes, not those that have already been learned!

Scott

[mtnman]

This site has some info on engine size HP and speed.
http://www.reliablesteam.com/RSE/RSEengines.html

[Lopez Mike]

Once upon a time I was planning a sailing passage from one port to another across a possibly hurricane ridden ocean. I did a lot of reading and research. But what worked best for me was to ask all the other boaters when they were going to leave. I plotted the results and left at around the median date.

Instead of calling it SatNav, I called it StatNav. Using crude statistics to make my decision.

I recommend many evenings reading through Rainer's collection.
http://www.steamboating.de/steamboat/st ... -radow.php

Look especially at hulls similar to yours.

However interesting calculations might be, there is a good deal to be said for experience. Most of these boaters are more to share why their power plant choices are or are not working for them. Any designs that diverge greatly from the norm are likely a mistake.

Statistical design?

[fredrosse]

If you look in the FAQ section of this website, you will find some technical stuff, relatively simple, that will get you into the ballpark for sizing up a steam plant for a boat. Hulls-Power Requirement, Engine-Power Output, Engine-Steam Consumption, and Boilers, Steam Output & Efficiency. While far less accurate than a properly educated boat design specialist/Steam Plant Design specialist, the information given is going to hold true for the majority of steam launch configurations, within 10% more or less.

Internal Combustion power for many boats is very much overstated, as if more horsepower is more impressive to the customer. When I am driving my car at 70 MPH on the turnpike, it is producing something like 20 real wheel horsepower, yet the manufacturer has stated 140 horsepower maximum. The higher power may be used on occasion, but for the great majority of cruising the real power needed is lower than one might think. Displacement boats don't need much power, one or two horsepower per ton of displacement is adequate, doubling that amount for extreme conditions of wind and sea is typically far more than adequate.

[Cyruscosmo]

Hey Mike

Actually I had spent a few weeks reading through Rainer’s entire website. I have sent him a couple e-mails as well looking for information about the boiler he built, but then I realized he might not be able to read what I wrote. So I started looking around for another place and landed here.

I have pretty much nailed down what equipment is used how and where to put it. What fuels serve best in what boilers under various conditions and how to lay the controls out so the skipper is not dancing all over the place. So yes I have used the statistics of what I learned to have a good place to start in that respect.

The puzzling part is the engine itself and Fred’s comment makes sense, I have read that reference in a few other places about HP per ton.

The specs on the boat plans I got say 15-20 IHP the problem for me is I don’t know what HP looks like in steam pertaining to piston diameter stroke and steam pressure. So I can read the specs on the various steam engines I find but if they don’t list IHP then the numbers are just numbers for me.

The reliable steam site Mtnman listed gives both but I have found the same specs on other engines claiming more and even less HP so there again…

So what I am thinking of is a double compound in the 3" + 5" x 4" range as I have read that I can use a bit smaller boiler.

I like the setup of Rainer’s boiler and since I am a certified welder it would be a snap to build if only I knew where he got the plans. Or if he designed it himself would he share the specs so I can build one too.

Anyway I am narrowing down my starting point bit by bit…

Cheers!
Scott

[Lopez Mike]

You may know all of this but Indicated Horse Power is the integral of pressure v.s. piston travel during the power stroke. All very fine, BUT! I have yet to see an indicator card on any of our small engines and I would be hesitant to hook my indicator up to such a small engine as the volume of the connecting pipe and the movement of the piston in my indicator would screw everything up.

I should be possible to build a low volume indicator for small engines using modern solid state pressure transducers and small bore, short connections. I'm thinking about it. It may have been done already.

In my humble opinion (the sound you hear is Barbara having a laughing fit), specifying I.H.P. for a small boat is just a snooty way of saying, "I know more than you do and don't ask embarrassing questions and the emperor does have new clothes!"

Fred? Bart? Is there some decent rule of thumb that he can multiply the I.H.P. and get a rough number for B.H.P. on our little engines? Two thirds? Half? I dunno.

Of course Brake Horse Power is an illusive and much abused parameter in small steam engines. If the engine ports and boiler were big enough, the maximum B.H.P. would occur just as the engine flew to bits from to high a speed.

I stand by my earlier recommendations. The odds are that your boiler will gasp before you will be able to sustain any high speeds. Few of us have powerful enough boilers. And Rainer won't have any problem reading your emails. He is just a very, very busy guy.

Probably the big underlying boat design decision is whether to worry about weight. I mean, the whole boat. I'm a devotee of keeping the boat as light as possible to cut down fuel consumption. We can gabble all day about waterline length and length to beam ratios but fuel consumption pretty much follows displacement at moderate speeds.

Thanks for asking these questions. It wakes most of us up and gets us to thinking and arguing.

Mike

[Cyruscosmo]

LOL Mike!

When I get carried away explaining something or asking questions my brother gets this flat look and tells me "You are giving me a headache". That is my Q to zip it, around him anyway so feel free to tell me to zip it if I get carried away. I was the kid who asked those questions and I would have asked the emperor, "What cloths?"

Ok Thanks for the heads up on Rainer I was a bit worried he may think I was some goofy American. Maybe I am, I just now noticed he posts messages here. Maybe just one lil PM.

Ok about the bridge from automobiles to steam launches I found some common ground I can wrap my mind around and work with. The Stanley Steamer was made with a 20 hp 4" + 4" x 5" steam engine that ran at 600 psi. It produced 7 tons of force on the crankshaft; at least that is what the article says. I know the launch is not the same as a car on the road but I am getting the relationship now and feel better about my engine starting point.

Now... how come I see all these steam locomotives with only one eccentric and a reversing... Umm quarter circle thingy, and the steam launches have two eccentrics per cylinder? Locomotives go backwards too so what gives? And yes I think I know the answer but am gonna ask anyway.

As far as weight goes I am not really building for speed. I will be happy if I can push her to 15 knots if needed and hold around 10 ish. I am not sure what her hull speed is, I guess I better ask the architect.

On a side note Mike what do you think a trip up the inside straight to Alaska would be like on a 30' Steam Launch? Smallest craft I been on the sound with was a 37' cutter, just curious.

Cheers
Scott

[Oilking]

Mike,

The Portland has electronic pressure transmitters attached the indicator ports of both cylinders, plus a servo transmitter calibrated so one rotation equals one foot with a string attached to the cross head to track the piston motion. These are periodicaly connected to a laptop computer for monitoring. This is on two 24" cylinders with a 10' stroke so small volumes are not an issue. The pressure transmitters are about 2.5" long and 1.5" OD with a 1/4" or 3/8" connection. The motion servo is about the same size except for the spool (~3.81"dia.) with a 12" circumfrence, and mounting bracket. The Crosby Indicators are still on board, but appear to be relegated to the status of antique curiosities.

Dave

[Lopez Mike]

If you build a wood burner, I will be able to trace your progress up the inside passage by the clear cuts. No matter what fuel you decide on, there is no getting around the limitations of size when you are dealing with range. The bigger the boat, the greater the range. With a 24' boat and 5 h.p., I find a ten mile trip doable. That is ten miles out and ten miles back. Anything beyond that gets funny to see. Wood piled everywhere!

I've forgotten the length of your chosen design but I would cut those speed estimates in half. My overall length is 24'. My waterline length ranges from perhaps twenty feet at the dock and lightly loaded, to 24' at 6.3 kts. my maximum speed.

So first of all, what is my waterline length, 20' or 24'? Second of all, at 6.3 kts. my stern wave is about at deck level and a bit alarming to look at. There isn't a chance that I would ever see ten kts. Any engine and boiler combination that would push the hull to ten kts. would sink her at the dock.

With judicious cramming of the firebox with nice dry hardwood I can maintain 5 kts. The sweet spot is more like 4 to 4.5 kts. 'Your results may vary'.

There are two types of locomotive valve gear, Stevenson and Walschaerts. Yes, there are others but statistically, those are the only ones every built in any quantity. Stevenson uses an eccentric and Walschaerts uses and eccentric crank. There are two eccentrics per cylinder on Stevenson, usually buried between the frames, and one eccentric arm per cylinder on Walshaerts gear.

Stevenson was used from the beginning until well past the turn of the century (1899-1900 for you kids). It is robust and easy to keep in running order with limited skills. As locomotives got more powerful, the room for valve gear in between the frames was taken over by bracing to absorb the larger and larger cylinder forces. Also, between the frames was always a horrid place to work on things and a filthy environment for machinery.

Locomotives can be confusing for boat people as most of the more modern designs had piston valves with inside admission so the valve gear lagged the motion of the crosshead. Looks screwy. My engine is that way. The combination of inside admission and a piston valve has advantages though. Much lower valve gear loads because of the piston valve and only cylinder pressure on the valve rod packing due to the inside admission. Makes for wimpy looking valve gear.

I dunno where these article writer get their numbers. A seldom used orifice for mathematics I suspect. Let's see. Only one cylinder pushing at a time when stalled. 4" piston has 12.57 square inches of area times 600 psi is 7,540 lbs. Under four tons. Now the crank arm is 2.5" so that produces 1571 ft. lbs of torque. Serious numbers but not seven tons whatever that number meant.

Now that is at stall. The moment the engine starts to turn (remember, no turning equals no power), the losses in the ports start to nibble away at the cylinder pressure. Steam cars are famous for tremendous bursts of acceleration. But, as several of us have been harping on here, the boiler produces the power. Steam cars are a hoot and will snap your neck back leaving a stop light and can climb a short hill like you wouldn't believe. But they are fuel and water hogs.

A very few modern steam locomotives were designed with big enough ports and large enough grates to sustain serious power and speed. The LIMA super power designs regularly produced 4000 to 7500 h.p. in sustained operation at freeway speeds. This in a package that was seriously limited in volume by tunnel sizes and the need to negotiate turns. Incredible power density. Enough draft to lift the bed of coal off of the grates. I have seen it myself. But they weren't designed to cross oceans. They had to be practically rebuilt every year and needed serious maintenance work weekly. Laughable by marine standards. The modern internal combustion locomotives drove them to the scrappers

There is probably a limit to the size of a post here. I'll stop now. heavy rains produce spare time to type and type. Sorry.

Mike

[fredrosse]

“Now... how come I see all these steam locomotives with only one eccentric and a reversing... Umm quarter circle thingy, and the steam launches have two eccentrics per cylinder? Locomotives go backwards too so what gives? And yes I think I know the answer but am gonna ask anyway.”

ANS: There are many many steam engine valve mechanisms, and many locomotives used the Stephenson Links, with two eccentrics, typically these eccentrics were mounted inboard of the driving wheels. But for maintenance reasons it was generally found that alternate valve mechanisms were more suitable for mounting outboard of the drivers, allowing easier maintenance and adjustment. The outboard valve gear arrangement dominates actual later steam locomotive practice.

“As far as weight goes I am not really building for speed. I will be happy if I can push her to 15 knots if needed and hold around 10 ish. I am not sure what her hull speed is, I guess I better ask the architect.”

ANS: Assuming 30 feet LOA, LWL of around 27 feet (with Plumb stem) and 1.75 tons displacement, about 7 knots will be the maximum practical speed, with a 7 HP driving engine giving reasonable margin for weather, wind, and waves. To push the boat up to 10 knots, 20 to 30 horsepower will be required, a heavy price to pay for those 3 extra knots, and a steam plant considerably larger than almost all steam launches. 15 knots, horsepower goes up to more than 100, not a realistic target for a steamer that is what we usually consider reasonable.