A Smaller Steam Engine For A Smaller Boat

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Thanks guys ! I just about have it wrapped up, just a small item but it has been bugging me since I built the control valve for the engine. It needed a better looking nut on the center post that holds tension on the valve

I am waiting on the engravings for the name plates that the local trophy shop is making for me. After those are in place it will get a bunch of pictures and then off to the pond to see if it all works in the real world.

This is the old nut, just an 8-32 that was in my hardware box.
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Here is the upgrade. The dome shape was just made by getting the shape close with the lathe and then finishing with a file and sandpaper.
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I love my new collet holders. Cutting a hex shape is so much faster this way than with my rotary table.
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The Acorn nut was well executed, but frankly I think it looks a little pretentious used in this location. IMHO. Can't wait to see the boat in operation. Great work!
Pete, If you make the whole brass piece and the acorn nut into one piece it would look a lot better,

I am going to eventually change something but not sure what at the moment. The valve works fine as it is until the pressure gets around 30psi. At that point it gets enough push from the steam to lift off the seat. The easy solution would seem to be just hog down on the nut or make a stronger spring, but the tiny little hs-55 servo that is hooked up to it can't deal with the increased friction. Pond trials may show me that less than 30psi is plenty to run with. It will all work out but I am ready to float it and quit working on it.
30PSI should be more than ample Pete, any more is just a waste of energy and steam.

Don't fall into the trap of trying to get speedboat speeds out of your great boat, it should glide along quite serenely.and majestic, gently puffing away..

That's a good point this is a slow paced type of boat isn't it. If it will move at 10-20psi in the pond then that's all the better. Bench runs showed me that it runs smoother at low pressure and it's because of the water pump. When it has to overcome the higher boiler pressure it makes the engine speed up and slow down a bit as it hits the work side of the stroke. Low psi means a little less fuel too.
I have a few days off coming up and I hope to run it in the water then.
The maiden voyage is over ! I took it out to the little city pond last night and set her loose. The boat worked and did putt around a little bit but it was a very short outing. The water level was in the pond was very low and that made it so I had to cross 6 feet of mud to get to the water's edge. that made it really hard to fiddle with the boat. Just getting it in and out of the water was tough and I nearly fell into the mud a couple of times, once while holding the boat. That fact alone made this outing not much fun. The city also put a fountain in the center of the pond which is loud and churns up the water. I am going to have to scout out a new place to run my boats I guess. That combined with a couple of problems that revealed themselves and you have a quick short run. Here is what I found with the boat. The biggest problem is the directional control valve. It lifts off its seat too easily. Even at 20psi it starts wasting steam. I did take it apart and found a bit of FOD in it so that didn't help but it needs work. I don't think my blade pitch is good. It ran ok forward but won't pull at all in reverse. I will have to mess with the prop blades and try to fix that. Another problem is my feed water tank setup. Under a load in the pond the engine uses a lot more water than running on the bench. I increased the pump stroke to keep up with the usage. Well with that increase the pump only pulled water from one tank. My tanks are connected to each other with a 1/4" tube and the pump is tapped into that tube close to one tank and that is the tank that ran dry while the other stayed full. I need to change that design too. The last problem may fix itself when I get better efficiency out of the system. I had to turn up the burner to get the boat moving better. The burner got so hot that it started burning the gas on the backside of the ceramic. That got the base for the boiler really really hot. It's good I put an air gap and a metal drip pan between the boiler and the hull, otherwise I might have had a cooked boat !
It's all fixable, just a bit disappointing for the maiden run.
I like it even though you said there's work to do.

Just watching the video looks like a peaceful day at the pond. Sorry about the mud.

Thank You for posting,

With the slow engine speeds of a steam engine you can get away with flat blades on your prop.
That is all we had before manufacturers started to get into the act and made nice pretty curved ones.

That might be why you don't get much shove in reverse or it just might be the rudder being too close and stopping water getting to the prop and causing it to be too inefficient.

Other than that, your boat looks great on the water.

She looks gorgeous on the water! :thumbup: What is a maiden voyage without a few wrinkles to iron out? ;) I'm sure you'll have those taken care of quickly. Good job!
Very majestic craft. I'm sure you will sort out the minor problems
Thanks everyone! It did look good out there. It wasn't too peaceful in my head but it did accomplish what the original goal was , to carry it with one arm and just plop it in the pond. I guess the biggest letdown was thinking I had it all perfect and sure enough I was wrong. Oh well I still like working on stuff so it's back into the garage I go.

The first attempt at fixing the water delivery problem is to make the connecting pipe between the two tanks much bigger. A quick test by siphoning from the pump feed line is promising. Here is a shot of the old and new pipe.

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The control valve is gong to get a thrust bearing instead of the spring. I have a little bearing from a r/c buggy I had long ago. I made a shroud for it and it is going to be held down by the acorn nut. I added a set screw to the nut because I found it moves when the throttle lever moves. It did it with the spring and the new setup. I also filed a little vee notch in the spool part of the valve at each slot in an attempt to get a better transition from stop and full throttle. If this doesn't fix the problems I had then the next attempt will be a total redesign. I'm not thrilled with the design of the whole valve.
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The prop was easy I just flattened out the curve of the blades a bit and twisted them all to match. This may not be the last pitch adjustment, at least it's easy.

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So I worked on all the problems that showed up on the first run and then took it back out for another test. I found a better pond for this run and had a very good outing. All I had to do was fill the boiler feed water tanks up when they got low. The rest of the time was spent running the boat all over the pond. I am thrilled with how it ran this time. I guess this should conclude the thread. I may update it with a video when the weather gets cold. This run was on an 85F day so the steam doesn't show up all that well.

Thanks to everyone that followed along and especially to those that helped me by taking the time to post ideas and suggestions to help me get this built !!




The engine video didn't show this view down the stack, its hard to get a good image with all the heat and steam fogging the camera. It's kind of neat looking so here is a still shot
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What a lovely job. Sometimes it's nice to appreciate a good run in the light of earlier problems successfully overcome.

I'd be worried, if it were mine, about what I'd do if it sank (but that says much more about my state of mind than about your boat). Do you have buoyancy tucked away anywhere? Or maybe a log string and a small buoy so at least you could wade in and find it?

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