DetroiTug's Tug is going together

[DetroiTug]

Update to the tug progress.

Here is the economizer bypass network with the relief valve installed. The coil is 3/8" copper with a .050" wall thickness. The relief valve is 1/4" NPT and sold for 1-1/2" scale locomotives. It's adjustable and set for 100 psi.



Here is the front 6 1/2" bollard installed.



Here is the rear 6 1/2" double bit bollard installed. These were ordered from Elliot bay.



Getting the cabin windows trimmed out and the removable windows assembled:





The 19 X 25 prop is on and I still haven't had the opportunity to test it. Two rainy weekends in a row.

-Ron

[DetroiTug]

Finally took it out for a few hours to test the new changes.

First thing out, the main feedpump was inoperable. I bled it out, pecked on the check valves, pulled it's relief valve a few times, it began working - temporarily.

The new prop runs really smooth, but it changed everything and not for the better. It was rather difficult to come to any conclusion, as I was fighting the feedpump and not sure if to build the fire up or shut it down on the questionable supply of make up water. I closed down the firebox and dropped the throttle, and began hand pumping. The glass stayed half full.

The new Economizer, was making all sorts of noises when the feedpump was trying to work, it was concluded that this was feedwater flash boiling on start up. (Good call on the relief valve Fred). What appeared to be happening when the feed pump was off, the economizer was boiling all the water out of the feed line back to the feedpump. I would have to bleed out the pump every time to get it pumping. So I decided to isolate the economizer coil, the little relief valve kept popping off. And- when the economizer was full of water and the feedpump working, it was making a clanging noise. So it looks as though, it needs to be supported better. When it was working, the line coming out was much hotter than the one coming out and no loss of boiler pressure was observed. With some tweaks - it will work.

The prop is coming off. The engine was just fighting too hard against it. It appeared to change everything, when the feedpump was running, it had to run for longer intervals due to the slower RPM. The fire didn't seem to burn as well, lower stack velocity with lower RPM. The boat seemed sluggish with the engine running at lower RPM, obviously not getting in to an RPM range where appreciable horsepower is attained. 50 PSI and 6.4 mph on the GPS, but the whole boat was shuddering under the load above this pressure. With the other prop, everything seemed much smoother.

Any ideas on the idle economizer - boiling the feedwater out of the pump situation? The clanging I can fix.

-Ron

[artemis]

Finally took it out for a few hours to test the new changes.

First thing out, the main feedpump was inoperable. I bled it out, pecked on the check valves, pulled it's relief valve a few times, it began working - temporarily...

...The new Economizer, was making all sorts of noises when the feedpump was trying to work, it was concluded that this was feedwater flash boiling on start up. (Good call on the relief valve Fred). What appeared to be happening when the feed pump was off, the economizer was boiling all the water out of the feed line back to the feedpump. I would have to bleed out the pump every time to get it pumping. So I decided to isolate the economizer coil, the little relief valve kept popping off. And- when the economizer was full of water and the feedpump working, it was making a clanging noise. So it looks as though, it needs to be supported better. When it was working, the line coming out was much hotter than the one coming out and no loss of boiler pressure was observed. With some tweaks - it will work.

The prop is coming off. The engine was just fighting too hard against it. It appeared to change everything, when the feedpump was running, it had to run for longer intervals due to the slower RPM. The fire didn't seem to burn as well, lower stack velocity with lower RPM. The boat seemed sluggish with the engine running at lower RPM, obviously not getting in to an RPM range where appreciable horsepower is attained. 50 PSI and 6.4 mph on the GPS, but the whole boat was shuddering under the load above this pressure. With the other prop, everything seemed much smoother.

Any ideas on the idle economizer - boiling the feedwater out of the pump situation? The clanging I can fix.

-Ron

The "clanging noises" is primarily due to water hammer in the looooong economizer coil. The best fix is to run the feed pump at about 2/3 engine speed and use a "ram/displacement" type pump (piston pumps seem to cause water hammer more than any other type). As to the "boiling the feedwater out of the pump situation", since the exchange of water from the economizer backwards to the feed pump is probably creating the boiling then it would seem the installation of a check valve on the input side of the economizer, but just after the "bypass valves" configuration, would correct this.

As to the propeller, get a copy of Dave Gerr's Propeller Handbook. You've got all the data for your hull and plant so you should be able to figure the prop out:

1. Figure your probable hull speed using his updated formula for hull speed: The formula is: V = 1.24*L^1.433 / D^0.311 where v is kts, L is feet and D is displacement in pounds.
2. Determine the pitch of your propeller using his pitch formula.
3. Calculate your engine HP at about 90% of max. rpms (or wherever the engine is happiest).
4. Calculate your diameter using his formulas and your pitch, HP, and rpms from the above.
OR
Read the article "A Logical Approximation of HP" by Evers Burtner in the Nov/Dec 2010 issue of Steamboating Magazine - you'll get close to the same answer. If anyone wants to reprint it here, you have my permission as editor.

[SL Ethel]

I have a guess as to what is causing the shuddering, and it's not the prop per se. I have a similar sized steel launch with single cylinder 3x4 stepped up 1:1.3 driving an 18x22 prop. I definitely don't get high engine speeds (about 300 rpm max), but the engine is smooth even at max pressure at low RPM. Originally, I had a similar shuddering problem (made worse by the chain drive), that was cured entirely by a heavy flywheel from an antique gas engine. The large torque loads combined with the slow speed caused a pretty large amplitude vibration without the flywheel to smooth out the torque over the dead centers. Fitting a heavy flywheel wouldn't give you back the snappy performance of a lower pitched prop, but I suspect it would make the engine run smooth again.

On the other hand, it sounds like you are getting great performance with your new prop - over 6 mph on just 50 psi certainly seems to indicate the the engine has plenty of torque to handle the steeper prop. If your engine was running smoothly enough that you were comfortable using higher pressures, you might well still get very brisk performance, and would almost certainly have less trouble maintaining boiler pressure.

Cheers,
Scott

[DetroiTug]

Ron,

Thanks for the input on the economizer. What would be the best check valve for that application? What type? I need something that seals 100%. Apparently a the pump checks are leaking through, allowing steam pressure in the economizer to push all the water out of the pump system.

Re: The prop. I'll just go back to the other. It used only slightly more steam, I just hate hearing the engine strain like that. It can't be good for it. The boat just ran much better. When I get the economizer issues resolved I may give it another try later on, it's easy to swap.

Scott, Thanks for the input. This is a twin, and I'm not sure it would really have any dead spots, only spots in the rotation of lower torque. This winter I am going to go ahead and add the flywheel. My thinking has been the prop and shaft would smooth the torque.

Spent the day mounting the new steering wheel:





-Ron

[farmerden]

Ron OK I've studied and looked at the name and numbers on your boat.Are they decals ,painted, or did you flame cut the hull? Whatever ,it looks right!! Den

[stevey_frac]

She looks absolutely beautiful, and I'm entirely jealous.

She's a true and proper steam tug.

--Steve

[DetroiTug]

Den,

Those are decals from West Marine.

Steve,

Thanks for that. She's an absolute pleasure, roomy, smooth ride in rough water, fast and very maneuverable. If I built another, the only changes I'd make is stretch it out a few feet longer and use heavier steel.

-Ron

[stevey_frac]

It's probably somewhere in the depths of this thread, and i've simply forgotten...

But did you use a condenser?

--Steve

[DetroiTug]

Steve,

No condensing, just pulling straight from the lake.

-Ron