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Old Jul 02, 2014, 09:32 PM
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Are You a Gambling Man?

Ernst:
It will take a while to settle on a steam engine for your model. In my case with the W.T. Preston, I originally considered a gear motor electric drive and started construction on the boat itself. This way I didn't waste build time on engine selection. Several months into the build, I decided two things: First, a steam engine was to be the final power plant I wanted, Second, I planned to go forward with the electric drive as an interim engine and made sure that all the electric drive components could easily be removed from the hull when the steam engine was ready to install. This turned out to be a good choice. With the boat essentially done, with electric drive installed, I was able to do tests in my test tank to check for heel, trim and draft. ( I estimated the weight of the steam engine and added appropriate ballast to bring total weight to 37 pounds for correct displacement) The electric drive also gave me some idea of how efficiently the paddle wheel coupled with the water. I also verified how much slippage was occurring between the paddle wheel and water. Research on paddlewheel slippage yielded a figure of 20%. This was verified in my test tank. As some have suggested, installing twin cylinder high speed steam engine, with reduction drive seems like the way to go, UNLESS you just have to have a scale drive system and have the money and time to do it.

We are all rooting for you and stand by to help any way we can.

Mike in Edmonds
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Old Jul 03, 2014, 07:33 AM
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Thank you all very much for that input!

So much to consider while I try to start building the ship itself...

Ernst
The good news like Mike says is that regardless of what propulsion you choose, you know you will have two wheels and a connecting shaft. What you choose to make that shaft go around is wide open and fairly easy to change out if you plan ahead. Based on that wreck photo, the original was definitely an inclined engine. You could easily make yourself a dummy steam engine with a functioning piston and crank that are turned by a belt or gear drive electric motor hidden from view.

Frankly I would not recommend steam unless you are a steam junkie with a lot of disposable income! I am wrestling with this on the Miami because it is way simpler (and cheaper) to build high fidelity dummy steam engine that looks like it is driving the shaft, when in fact the shaft is driving the engine. Depending on how nicely the hull turns out, I may go Mike's route and have a scale engine made by someone off the Mendota engine drawings I have. My machining skills are pretty basic - i.e., suck.

You will also find that a model steam engine will not sound or smoke like a real one, so you are stuck with adding an electrical system for sound and smoke anyhow. Might as well add a motor and ESC while you're at it and save thousands of dollars and lots of headaches.

Leave yourself open for all the various options like Mike did.

Here is a link to my small Keokuk in 1/32 scale. The 1/16 scale version has a scale engine room. This little one is a pretty basic twin engine twin boiler arrangement, and even at that I have over $4K just in the materials for the propulsion system. This model is about 1/2 the size you're talking about, so do the math before you take the plunge!

http://www.shipmodels.info/mws_forum...1bf394ee54615a
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Old Jul 12, 2014, 12:44 AM
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Took a Week off to go Camping

Back to work on Preston. Dave has been busy making the cylinder drain system for the engine while I was gone. Getting closer.

I spent a week on an alpine lake in the Cascade Mountains, and though how nice it would be to run the Preston on Lake Kachess. But it is just a little too far away to make that worthwhile.

Mike in Edmonds
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Old Jul 12, 2014, 01:30 AM
Submarine or Target?
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Looks like a great place for an early morning swim, too. Glad you had a good break.
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Old Jul 20, 2014, 04:27 PM
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Mr Coffee boiler RIP

Will after I don't know how many test running of the engine Mr Coffee has given up the ghost. The heating element goes open at temp so no steam.

Will have to see what Goodwill has in stock for a replacement.

Dave
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Old Jul 24, 2014, 11:04 PM
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Steam Engine Reversing Gear

Dave has worked out the details of the reversing gear. See the jpg image. We are using a linear servo that can extend over an inch with a force of 40 newtons (8.99 pounds of push) The single servo will rotate a jackshaft with bell cranks on either end. Lift links attach to the hourglass cages. A tiny bit of slop must be provided for in the lift links, so each lift link will have tiny centering springs to allow for this play. I'll program the servo on the DX10t to precisely move the correct distance to protect the eccentric rods from being bent by the linear servo over-driving the lifting mechanism. In the drawing you are looking at one side of the engine. The 3/16" jackshaft will extend athwartships connecting the other cylinder/reversing gear mechanism. Servo travel speed will be set to smoothly reverse the steam engine.

Mike in Edmonds
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Old Jul 24, 2014, 11:38 PM
I fly, therefore, I crash!!!
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Looking forward to seeing this in action Mike!!

SteveT.
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Old Jul 25, 2014, 12:43 PM
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Ariel WA
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For those folks that would like to see the reversing gear in action, here is the full PDF file. If you click between page 1 and page 2 you will see the reversing gear shift from Fwd at the lower position to Reverse in the upper position.

Dave
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Old Jul 25, 2014, 04:48 PM
I fly, therefore, I crash!!!
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Very good Dave...

SteveT.
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