Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[xrad]

Hello fellow model boaters:
Starting a new project...a few years in the making. I have been researching this for a while. It needed to fit a big old Stuart boiler. I found a great likely not used 1035 from around 1979. It is not the 491 or 492 model but a big 14 x 3.5. Steams up fast w/16 cross tubes.
Engine build in progress. It is a kit bash of tiny power twin with my own designs.
I wanted something big this time so going with a Microglass 60 inch tug hull, which by its early 20th cent design is perfect for my early century trawler. The hull will be modified to my design...which will be a cross between the 'Venture' and the old fishing trawlers. A workboat project, dirty and used.
Crankshaft run-in:
http://www.youtube.com/watch?v=ZvqSO70DYwA&feature=c4-overview&list=UUYQskpmHyALB5hsentYB_6g

Should be done in a year or two.........I like to start them...not so great at finishing them...

[xrad]

Some fun calculations for this little engine(english):
 
bore: .75
stroke: .85
rpms: 250
pressure: 40
 
about .08hp for the twin
 
If I raise the pressure to 60psi..then about .134hp........
 
it is not very much but more than enough to turn a 4-5 inch prop..no I did not calculate torque...but this little undersquare engine should be just fine...if I can time the valves correctly....
 
About the engine:  Bronze 1.6in  block machined down.  Brass pistons from 3/4 rod. stainless 1/4 crankshaft, silver soldered counterweights, cast fe flywheel from England (ebay) ~3 in?) stainless hardware from http://www.americanmodeleng.com/id41.html  VERY nicely cut threads, but you better buy bulk or you pay much more..... They also have draincocks for 15$ each..that saves MUCh time in the build...

[xrad]

Nearly finished rebuilding my Stuart Triple expansion....nearly...
might go into the trawler if she runs well enough..
 
see the video of first live steam run:
http://www.youtube.com/watch?v=1K-2Ob2kqvQ
see the build with tips:
http://www.homemodelenginemachinist.com/f31/xrads-stuart-triple-21925/

[SteamboatPhil]

Nice looking engine xrad 

[xrad]

Hi steamboatphil!
thanks for reply.  I am planning to convert the triple to a double single or a triple single to get a smooth running RC engine.  will update as work progresses. Planning to pick up the 6 ft hull on monday. will pot pics..
cheers, x

[xrad]

Met Carl of Microglass half way and picked up my 60 inch hull. VERY nice work. A little trim and some glass and she will go from tug to tramp steamer.  Carl was very nice. Wish I had more time to talk with him. We could share many boat build stories.
 
Looks like the Stuart triple will not work for this build. A hair too big and requires too much attention to let loose on the lake.  I started to build a surface condenser for it, and I fixed the condenser pump so it actually pumps water well now...and makes some neg pressure.
 
Anyway, the cool thing is that i found a VERY well machined Stuart double marine engine. The seller Station Road Steam (Jayne and Mike) were VERY nice and shipped that bad boy to me in less than 5 days!! WOW.
 
It runs at very low pressure like 5 psi in one direction...a little rough in the other and that requires about 10-20 psi. Reverses well. Super smooth. eccentric straps a little loose but no big deal....
 
See the vid:
http://www.youtube.com/watch?v=ny_MEHWgLDg

I will post some pics of the mock up soon.....

[xrad]

Working on my Stuart triple (ST) . Needed much work and finally runs great at about 10-15psi in one direction and not so hot in the other. I would have to split the eccentrics to time her better (as ST casts each as a pair and not independently adjustable) Too much effort.....so......decided to build a surface condenser to get her running even better. Works GREAT!
 
I had to redesign the vac/water pump by ST because it did not suck well.  The cooling water comes out hot and the condensed steam comes out cool! engine runs real well with it all hooked up.
 
There is a deflector(not shown) inside the condenser which spreads out the exhaust steam as it enters the condenser.  There are 21 3/16 tubes about 3 or so inches long giving surface area of about 40 sq inches.

[Landlocked]

Love all the engineering.  A true steam plant in miniature with hardly any RC compromises.  How are you moving your cooling water through the condenser?  Ram/scoop flow or do you have a shaft driven pump?


A Stuart double marine engine with "complete" engineering is on my bucket list (well my modeling bucket list -- I want a full size steam launch but I need to start buying lottery tickets....).


Ken/Landlocked

[Landlocked]

Just noticed your "cooling water hot" and "condensate cool" note:  Sounds like too much cooling water flow -- too much "condensate depression."  Hot cooling water is ok but no need to overcool the condensate.  Sounds like your condenser is a "counter flow" design if the condensate is getting cooler than the cooling outlet.


Ken

[derekwarner]

mmmm not sure if have missed something here Xrad.... ....a beautiful prototypical looking condenser....but won't the condensate [liquid] be oily? .....Derek

[xrad]

Hi Guys, Good points!
 
Yes, the cooling water is warm -hot depending on the rate of steam through the engine. This water is 'clean, and could be used for preheated boiler fill, or re-routed back tot he main cooling tank.
Yes, the condensed water is 'oily.' which will always be an issue if you add oil to the engine steam 'in' (displacement or other lubricator).  Some models have an oil seperator and then reroute the 'cleaned' water back to the boiler or holding tank. I will just have a waste water tank for this oily water. I think it would not be good to add oily water to the boiler, although I have seen this done many times in closed systems

One nice thing about the design is that it is easy to add a metering valve to the 'cooling water' side of the condenser, and therefore regulate the flow as needed.  I estimate the present 'unrestricted' cooling water flow to be about 1.5 liters in 20 minutes. easy to calculate exactly, just have not done it.
 
 The important thing is that the incoming steam is 'condensed' and thereby creating a slight vacuum making the third cylinder more efficient. The engine does run much better with the condenser operating at 'full cool'...but maybe there is a middle of the road or more efficient level of cooling to be obtained.
 
Right now, the cooling system is gravity feed for test setup. pic below. There is a provision for a water pump to be operated by the ST #2 cylinder....or I could add one off the crankshaft.....
 
I could also add a small radiator and fan driven by the crank to cool the 'cooling' water as is heads back to the holding tank.
I have read several books on condenser design, especially Audels Engineering and Mechanics Guide books 1-7.  Some condenser design is based on boiler size, some books say it was the engineers perogative, and some have clear surface area minimum requirements (condenser must be at least such and such size for IHP etc.)
It seems better to have more than required surface area, without too much waste in materials and construct time so that you don;t fall short of creating the vacuum, and instead create the dreaded backpressure.
My steam exhaust inlet to the condenser  is .25 ID and my condensed water outlet to the pump ID is .10.  It is really cool to watch the increase in condensate as you increase the engine rpms and steam throughput, almost and instant change.
 
Audels also describes that the exhaust 'pipe' should have gentle bends and downslope, which I tried to follow.

 

[xrad]

I have a copy of the 1970's ST triple plans and they make no mention of the condenser(size shape etc).  Maybe there was a build book for reference, but I don;t have it.  Here are two vid of the condenser in action.
 
http://www.youtube.com/watch?v=9TlwleHfXdE
http://www.youtube.com/watch?v=AUlyQP11JYI
 
 

[Landlocked]

Xrad,


Interesting.  Your cooling water flow isn't much more (if any) than my preheat flow is through my oil water separator for my TVR1A.  I still get a lot of steam exhaust which shows the difference in efficiency that comes from compounding.


It makes me wonder if, instead of insulating the tank, a better approach to dealing with my excessive condensate build up in the separator would have been to relocate my bypass throttle valve to before the preheater instead of just before the boiler. Most of my preheat flow gets dumped back to the feedtank -- which makes the incoming feed warmer -- something you wouldn't want since it would make your cooling flow warmer as well.


The engineering answer to my problem is a now obvious DUH! but not sure if I have room to do it that way.  I'll have to go look at things.  Damn, thought I had finished with the engineering work and I could work on superstructure.  Please keep sharing so we all learn.


Thanks, Ken/Landlocked.

[xrad]

Maybe you could use a hull bottom heat exhchanger for the return flow like some real steamers.....

[xrad]

Built a simpling valve for the triple. Basically a branch off the HP line after the lubricator. Runs straight into the LP chest.  Can control pressure/flow with the needle valve. Works GREAT to start the engine. As soon as she warms up, it becomes counterproductive and will actually slow the engine. It seems that valve timing is pretty good for triple expansion and not so good for triple double action. May be timing, may be that the pressure is now against the lower pressure IP cylinder. 
 
The real benefit is that I hardly have to turn over the flywheel by hand to get her going. As soon as the water squirts out of the cylinder, tighten up the cocks and the simpling valve and away she goes. I was reading a marine steam book last night about condensers and triple expansion engines. Although this triple runs well at 10-15 psi, it runs really well at 50 psi with the main throttle valve just cracked.  Seems that ~50psi is nearer to what a triple expansion needs in terms of steam expansion...rather than 10-20.  Makes sense.

[xrad]

Bought an ST twin from Station road steam.  Very nice model. Needed a few bits. This will go into the steam trawler.  Made some copper covers and insulated with exhaust wrap inside(can;t see due to covers) Added drain cocks ,doubled the link rods, made gaskets, repacked the rod holes, smoothed the valve surfaces, insulated the hotside pipes and painted. Will move oil supply when new piping arrives..maybe a ~ 1 inch mechanical pump feeding the manifold.....
Also, I did spend some time with a thin piece of spring steel running the edge in and out of the cast ports. There was much in the way of Fe granules knocked off , thereby opening up the passages a little bit better.
 
Also have a burner from old Swedish torch. Runs great on isopro. Size is better for my 2 inch fire tube in the Stuart boiler (black one pictured above)
 
I love machining and drill/tapping of the old Stuart cast iron. Very smooth and easy to work. BUT!!! cylinder/valve chest rust and sticky rings is an issue(even with appropriate steam/oil lubrication on the hot side). I added the drain cocks for three reasons:
1) easy starting/ water drain
2) keep open when done running to dry out cylinders
3) I can inject a few drops of thin oil directly into cylinders after running (usually the next day) and give a few cranks by hand
 
Some neat tidbits about this engine. The oiler in the original pic was fully functional drip oiler. It worked well when hot and fed seven lines to the engine. three to the mains and two two the straps and two to the main rod pins at the cross slide. The oil drips into a reservoir on the cross slide and the lubricates by a small hole(which when checked were not drilled completely through..but are now!) the cross slide rod pin. This rod pin is circumfrentially grooved and the oil will then work its way around the pin and then down the center of the drilled rod. It then lubricates the the rod big end journal. Really neat little engine.....
Each main has its own 1/16 lubrication tube and the spinning of the crank draws the oil down into each main. You can watch over a few minutes at higher rpms the oil running down in the reservoir 'cups.'  I plan to add a larger reservoir.  Obviously, this whole system works much better when it is hot....

[KNO3]

Very interesting drip oiler. Could you share some close-up pictures?

[xrad]

Here are the original build pics:
http://www.stationroadsteam.co.uk/stock%20pages/5590/index.htm
 
I will add some more pics soon

[KNO3]

Thank you! Why have you removed the central drip oiler after adding the copper covers?

[xrad]

KNO3(aka flash powder?): The original builder used the drain cock casting stubs as a mount (7ba) for his drip oiler.  You can see the four bolts in the pics.  The other side of the cylinder casting was too thin for the drain cock 5/32 40 depth.  I drilled and tapped the four stubs for correct drain position.  Remounting the drip oiler reservoir in the same location now precluded by the drain cocks.
Easy to make a new mount for drip reservoir or locate a 1.5 inch mechanical lubricator more remotely.

[xrad]

New manifold almost done.  1/4-40 drip oil reservoirs x2. 3/16-40 outlets x8 with 1/16 piping(not comlete).
Note the extra copper pipe through the manifold. This is to be connected with the exhaust outlets adding heat to the manifold allowing the thick steam oil to flow better.
 
The drip oil reservoirs were originally made with two side port breathers. these are not needed and were soldered over with some brass pipe. Breather is in the top cover.  There are a few deep traps in the manifold to catch dirt, etc....

[derekwarner]

An interesting concept xrad....... ....but forget the calculations ....[referencing lube oil viscosity, pressure drop due to tube length + bends + resistance due to surface finish + surface tension of the fluid???]

Have you trailed filling a 2" length of 1/16" OD tubing x 0.014" wall thickness with light oil & checked the result? ...would be most interested in understanding the results

I went through a similar exercise some time ago in trying to understand if I could get oil to my engine crank journals from a common lubricator box.......

The end result was that the words equal + adequate   did not apply ...static tests were a non result .....capillary action was still found necessary .....Derek

[xrad]

Good points.   After seeing how well the original setup worked, I figured I would give mine a shot.  I was tired of filling the 7 small reservoirs evey 10 min or so...And they drained unevenly with the mains drawing the most oil....The strap lines just barely touched the straps when rotating and drew the least oil.  All bearing surfaces also get a shot of oil before starting...

[xrad]

The oiler works well. However, most of the oil goes to the mains, which is fine by me. Not so much out at the crossheads or straps. This is fine as these normally all get a shot of oil before running.
 
I ran her for twenty minutes. You can see the oil drop in the pics. Look for the very faint black mark on the front glass.  Oil volume dropped by almost 1/3. I had to open up the metering needle fully on both for best action.  Also, look at the last pic for the way I ran the exhaust pipe through the manifold. It gets very hot, and once hot , the oil flows better.  It is a 3/16 threaded brass pipe, which can be unscrewed to remove the manifold.  Both pipes will be plumbed into a larger manifold once location in ship is determined.
 
Also, the 'Sweden' burner works great. Lights in one shot. Uses less fuel than my smaller burner. I  run it on med-low to low and it keeps up steam just fine. I bought an old model boat steam book from 1929. It has a pic of a stuart boiler which looks nearly identical to mine. There is a section on proper burners and the pic of the pariffin burner looks just like the Sweden burner. These two go together very well!!
 
Vid:
http://www.youtube.com/watch?v=8vS_iotWU24&feature=youtu.be

[KNO3]

OK now I see what you were doing. Very interesting.