Stuart Number 4 to match a 50 psi boiler?

[Sir Smithers]

Hi all.

New to the site, I was wondering if anyone can help me work out if a Stuart number four would be well suited to run from a boiler that's max rated to 50 psi. I have a 12 foot wooden dinghy that i am converting. I have searched the internet alot and cannot find any real and complete sets of drawings and plans for an engine of around 2-3 hp that will be nicely matched to my boiler for my father in law and my self to machine. If any one can point me in the right direction for any plans or ideas I would be very much thankful.

Regards,

Brent

[Mike Rometer]

Brent, you could try taking a look at Ray Hasbrouck's designs.


http://hasbrouck.8m.com/index.htm

[Sir Smithers]

Thanks Mike, I shall do. Thanks for the welcome message, tried to reply but the internet connection in the Congo isn't the best at times. I have another question regarding the hot water fee tank placement. I will be running the boat mainly on fresh water rivers and lakes. With regard to the feed water, I noticed when I steamed up the boiler, the water in the feed water tank (which is adjacent to the firebox) got so hot that the hand pump failed to pump into the boiler. So I had to drop the fire and maintain the pressure in the boiler till it cooled enough for me to blow off the boiler a little.

After reading alot on the forum, they talk of an economizer. My idea is this. I take water in from the below the water line, through a system of filters directly to the hand pump, from there it travels up the side of the boiler and enters the flue above the fire box. from there I take the pipe up the flue some distance and "U" bend it back down inside the flue for it to exit out, down the out side of the boiler and into the inlet valve of the boiler.

Currently the feed water comes from the hot well (on the side of the firebox) to the pump and then into the boiler. The pump fails to operate as the water in the hot well is too hot. I may be swinging a dead cat as I am only steaming up the boiler at this point and not using the steam for work. Maybe as we steam with the engine running down the river the rate at which the water is consumed will cause fresh feed water from the river that is being pumped into the hot well will reduce the temperature to a level where the pump will work thus eliminating the need for an economizer?.

Only problem I see with that is when we are moored and the fire is still on and heating the hot well with out cooling water being delivered from the river.

Sorry for the long winded question, maybe you have a schematic or a description of what would be best in this case?.

Any help would be great, as I am building this steam plant in my head at the moment.

Kind Regards Brent

[fredrosse]

What is making your hotwell "hot"? Is it close to the firebox/boiler, or is there a steam supply somehow heating the water in the hotwell? In general, with a condensing steam plant, the condensate returning to the hotwell can be of a high enough temperature to give trouble with the feed pump, and some cooling of the water to the feed pump suction will solve the problem. For starters, you may just cary a fresh water tank with boiler feedwater at ordinary ambient temperature, and replenish with dockside potable water, lake water, etc. The economizer is a good addition reguardless of the hotwell problem, and will increase the available steam output. From the looks of your boiler it would be difficult to get even one real horsepower out of the plant, although it may have more heating surface than is apparent in the photo. Could you describe, or better yet, determine the fireside heating surface area of the boiler?

One half to one horsepower is very adequate for a smaller launch. One fellow in our group does very well with a Stuart 5 engine in a 12 ft Wherry Hull, and has no trouble keeping up with all the other steamboats. That boat uses distilled feedwater brought by the owner to every outing, and uses just a few gallons of feedwater during the outing. He runs with atmospheric exhaust (non-condensing).

The sidewheeler I built runs with less than one horsepower, and displaces 1500 pounds. While it is not fast, I find it adequate for cruising. My boat has two 15 US Gallon water tanks, (110 kg total) and I can run at full load for nearly 5 hours without seeking any additional water. I plan a condenser in the future, but presently run just with exhaust to atmosphere, so there is no condensate recovery.

[DetroiTug]

"The pump fails to operate as the water in the hot well is too hot."

The feedpump should pump hot water. The coil mentioned going through the flue and then to the feedwater inlet is essentially an economizer. Sounds like what is going on is the water boiling in the economizer with pumps off is building pressure and feeding back to the feedtank. It's blowing all the water out of the pump system, that is a possibility why the tank is getting hot and the pump fails to work. Probably need to add an soft seat check or a shut off valve right before the economizer.

I've found that check valves in feed pumps do not seal positively and will leak through over time.

-Ron

[Sir Smithers]

great guys, thanks for the input. I drew up a schematic of what I think would work on our set up. if you wouldnt mind to comment that would be much appreciated. As soon as i have a working, and easy to operate system i shall post by all means.

Brent

[Sir Smithers]

Hi fred.

Yes the original fire box has the feed water tank mated to it, so as the fire burns inside so the water is then heated in the hot well. I have redesigned the firebox, to have a bigger foot print for the fire bed. I will also build a separate tank for the feed water and go with my design to use an economizer as I would like to warm the water a little before it goes into the boiler.

I will source a small engine for the boiler through the members of the steam loco club here in Johannesburg.

As for the boiler, its main water content area is cylindrical in shape, and the hot gasses pass through the center of the boiler up the flue, about half way up the flue there are two pipes traversing through the flue, I can only think that water is present in the two pipes, I will get some photos and up load them so you might be able to determine the type and power of the boiler.

Kind regards

B