Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Steam => Topic started by: xrad on September 13, 2013, 08:51:13 pm
-
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 (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...
-
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 (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...
-
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 (http://www.youtube.com/watch?v=1K-2Ob2kqvQ)
see the build with tips:
http://www.homemodelenginemachinist.com/f31/xrads-stuart-triple-21925/ (http://www.homemodelenginemachinist.com/f31/xrads-stuart-triple-21925/)
-
Nice looking engine 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
-
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 (http://www.youtube.com/watch?v=ny_MEHWgLDg)
I will post some pics of the mock up soon.....
-
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.
-
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
-
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
-
mmmm not sure if have missed something here Xrad.... %) ....a beautiful prototypical looking condenser....but won't the condensate [liquid] be oily? .....Derek
-
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.
-
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=9TlwleHfXdE)
http://www.youtube.com/watch?v=AUlyQP11JYI (http://www.youtube.com/watch?v=AUlyQP11JYI)
-
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. >:-o
Thanks, Ken/Landlocked.
-
Maybe you could use a hull bottom heat exhchanger for the return flow like some real steamers.....
-
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.
-
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....
-
Very interesting drip oiler. Could you share some close-up pictures?
-
Here are the original build pics:
http://www.stationroadsteam.co.uk/stock%20pages/5590/index.htm (http://www.stationroadsteam.co.uk/stock%20pages/5590/index.htm)
I will add some more pics soon
-
Thank you! Why have you removed the central drip oiler after adding the copper covers?
-
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.
-
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....
-
An interesting concept xrad....... %)....but forget the calculations :D ....[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
-
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...
-
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 (http://www.youtube.com/watch?v=8vS_iotWU24&feature=youtu.be)
-
OK now I see what you were doing. Very interesting.
-
repaired a water pump. Bought from a nice guy named Vern who lives in northern plains area. Pump needed some repairs including removing all the expanded gasket goo, and repairing of a valve rod. Ball valve surfaces needed some cleaning.....
It is a steam hog and may be better on my 3/4 Northern rather than the trawler....
http://www.youtube.com/watch?v=HfBsafxi12k&feature=youtu.be (http://www.youtube.com/watch?v=HfBsafxi12k&feature=youtu.be)
The basic function of a 'shuttle' pump:
There are 2 valves. The position of the 1st vale to encounter 'steam in' is determined by the position of the piston rod. There is a rod inside the piston rod. it is loose and has less travel than the piston rod. It controls the position of the first valve. The first valve position controls steam to the second valve (the shuttle valve). This controls steam to the piston. Top side is prettty direct. The steam also travels inside a hole bored into the cylinder wall to get to the far side of the piston.
Wtaer side of pump pretty straightforward with four ball valves and double acting piston. I estimate the piston to be about 20-25 % less diameter than the steam piston.
The original valve rod was in two pieces. I made the mistake of thinking that I had all the pieces, so the first one I made was too short. I added about 6mm more to the second rod and this was perfect. New one out of brass, old one steel.
Timing is easy, just make sure that 'steam in' valve travel is appropriate to uncover the ports and that the valve rod is long enough so that the piston rod can act unimpinged. The shuttle valve needs no timing, but shuld be (Very) free to move. Pump worked best when I could shake it and hear the 'shuttle' valve sliding back and forth.
-
Well.......the Sweden burner was a flop. I got it to burn well but it jumped from the end to the jet and would then cycle with a popping sound. And then I added the smoke stack and it ran like crap....so....time to build my own burner.
It is 1.5 in wide and about 4 inches long. Solid brass base and thick brass tube. Screen mesh just inside of the stainless perforated end. This keeps the flame from jumping to the base port. The base port flares 20 degrees for mixing gas and air in the brass tube before burning. Lights easily hot or cold. uses number 8 jet(and uses no more gas than my smaller 3/4 in burner). 4-40 set screw.
Might have to build a surrounding guard so as not to draw too much cool air into boiler when firing. about 1/4 inch gap around the burner.
see vid:
http://www.youtube.com/watch?v=Z09Bvdtlmu0&feature=youtu.be (http://www.youtube.com/watch?v=Z09Bvdtlmu0&feature=youtu.be)
-
Did a steam test after a few more minor adjustments to burner. Added an air regulator. Smoke stack in place. 10 minutes even to 70PSI blowoff. Able to maintain 55-60 PSI with part open steam valve (maybe 1/15 open). Boiler was about 5/6ths full with cold water (not ice cold). My best boiler build is ~8 minutes to steam so I am VERY happy with the results. A fill water preheater would do well here and may be built into the condenser. Just need to build the burner surround collar so the fit to the boiler is better. The above mentioned 1/4 gap between burner and boiler burner tube was mostly plugged with a bit of aluminum foil.
Basic layout comming together.
BFord Low water detection unit.
6v 100 psi open/close valve (normally closed)
6vbat
hand pump
Electric pump (allegedly can hit over 100 PSI, yet to test..alternate is twin double action steam pump)
Boiler and engine
Side water tanks
gas tank
Not pictured is adjustable voltage regulator w/readout and several 6v relays to run the waterpump, lights, valve, etc...might need a bigger battery
long way to go........
-
Did some lagging today. Used 3/4 character hickory left over from flooring, ripped down to a 1/4 plank and then ripped to smaller pieces. Honed a curve on the backside but was too lazy to bevel all the edges. Went with a thicker cut for strength and looks. Brass straps.
The wood has a very tight grain and is strong and cheap. A few drops of CA glue to hold position while the bands were applied. Blue mark applied to inside of curve so that I stained the correct side.
stained and oiled...no poly or anything on top...just let a natural aging occur..
I was just looking at micromark's nickle plating kit. I should have plated the cylinder head and valve chests to avoid the rust back when it was all apart. I will have to make an air compressor valve attachment to blow out the engine after running. Anyone else do this?
-
Really enjoyed taking a fresh look at this thread during some down time thanks. :-)) :-))
-
THANKS! Appreciate the comments.
BOILER BURNER UPDATE:
Well, looks like burner number 3 was a bust because after it is placed into the boiler burner tube for over 20 minutes, the stainless screen becomes too hot and 'back burning' occurs. It sounds like an afterburner with a real loud roar. I tried to place the screen/screens in all different positions and burner tube lengths, but it did not prevent the back burning. Why?...because the whole burner heats up too much and the thin screen can not dissipate the heat well enough to prevent ignition of the gas before the tiny pores of the screen. This only happens when the burner is inside the burner tube where the air circulation is directional and minimized.
So..how to fix?.... Addressing the back burning first: The 4th design incorporates a .3 in thick brass slug with 150 #54 holes drilled through. The .3 in length is arbitrary but seems more than thick enough to prevent gas burning through the pores even when hot. This slug was then pressed into the end of the short tube and tested. This burned well but not really hot. Took a while to get the boiler going. So back to the long tube with an axial gas flow design. Beveled base port mixes air/gas well with the longer tube. The collar is for air adjustment with several different air hole sizes tried as well.
Then, when things started looking good, the 'long' burner was placed into the boiler and WOW boiler tube harmonics and a standing wave with the burner jet created the worst loud whistle(like a flute). When the burner was far enough out to stop the whistle, it was too far out of the boiler. The standing wave actually compressed the flame decreasing heat when in too far...so..back to the drawing board.
I decided to press the brass slug back into the long burner tube about 1/2 inch. This significantly decreased the standing wave nearly to nill, but the burner was now running poorly due to lack of oxygen at tip.
Next, I drilled 8 holes ~3/8 around the burner tip to allow air into the flame. WOW!! this was it. Now the 1/4 inch gap around the burner (when inside the boiler tube) really supplies air into the burner tip and the burner roars out the end with a really hot flame. Almost all of the orange glow is gone and the flame base is blue/white in color and dancing well on the brass slug!! The boiler really heats up well now, and with the wood lagging. The flame is hot enough to melt brazing sivler rod if placed in the flame three inches or closer to the slug end. However, it does not seem hot enough to melt the cross tube brazing due to the water drawing heat away. Burner can be turned down to less heat if needed by bottle valve.
Pics show the attempts, and vid the final iteration.
see vid.
http://www.youtube.com/watch?v=JTg72W_h630 (http://www.youtube.com/watch?v=JTg72W_h630)
All 2-56 screws stainless. 3 set the slug and three set the tube. tube and base brass. Air collar bronze
-
Seems to me your problem is no external air holes on the burner body ,check out the firetube burner from clevedon steam as I use this one with no problems
Cheers
John
-
THANKS for tips! I have three of Jerry's burners. The outside visible holes are actually outside the inner burner tube in a burner shield of sorts.The only holes in the main tube are for air at the jet support. Mute point as my burner design works great now. I get my number 7 and 8 jets and jet mounts from him. Nice stuff!
My next issue is boiler filling. I have an ebay Microcosm electric boiler pump. Very nice unit. I tested this unit from 6-14.5 volts and even when pumping at its best, it only manages about 100ml in 90 seconds. Much too little a volume for me and it really did not like to pump against 65psi, although rated for it by seller.
next I tried my duplex pump. Works great once I removed a beetle from the water side. don;t know how it got in there....The issue is valve control. I have several servo controllers as in the pic, but nothing really worked well. I was going to try a servo type solenoid with 10mm retraction, but then I still have to rig up another valve into the system.
I also tried a Clippard high pressure pneumatic valve(as recommended and sold by Bill Ford). This did not work at all and as soon as temp and pressure was at working levels, the valve blew through the top. Not enough flow through the valve anyway. So on to something else.
On ebay, I found what I think will solve the problem. A high pressure high temp steam/hot water valve 1/2 NPT. Pricy but should work. Runs off 12v so I can wire a relay through the WLDS to operate the valve. Once this all works, and my stainless 'flask' water tanks arrive, I can do the hull layout better and get to building the engine/boiler support frame.
As a side note: I get my stuffing 'tubes' ,propellers, electronics, and other bits from Nick at Harbor Models. VERY fast email replies and shipping. Always excellent service from him. One of my favorite bit is a servo relay used for lights on another trawler I built.
http://www.harbormodels.com/ (http://www.harbormodels.com/)
-
This is proper engineering. I just wish I had the facilities to be doing some myself.............. But I build on the dining table so I think "er indoors" would get all ansty if I plonked a lathe and pillar drill on there {-)
I am very very impressed ............
-
Are you fitting the inner tube of the burner into the boiler ? as mine fits snug into the furnace tube on the outside dia of the burner which allows air to mix with the gas.
Cheers
John
-
Xrad.......I also have a Microcosm electric boiler pump
The pump appears to be of good quality.....however the as supplied 12v DC geared motor sounded like a VW engine in a tin can..... >>:-(
Have substituted a locally purchased 12v geared motor & added a 4.0 mm shaft size plumber block for support
Yet to be installed or commissioned, however the boiler relief valve is 3 Bar [45 PSI] so will be lighter duty..................Derek
-
Hi fellas, Thanks for the replies!
Decoy: My Microcosm pump must have been made on a Wednesday because it was fairly quiet and pumped well once oiled with a few drops of steam oil. There is an inner O ring on the piston which I have a feeling won't last too long.
SouthSteyne2: No , it is not snug due to required air flow for 1) to keep the flame oxygenated and hot, and 2) to keep the burner cooler. I tried adding a foil damper between the burner and the burner tube but it did not make a significant difference in boiler heating as the flame was less hot. The increased heat from decreased airflow was minimized by decrease in burner flame temp, and also the gas was not burned as efficiently. The cooling effect of the 'air collar' is minimized by the much greater increase in burner flame temp. I don;t have a temp gauge that can measure this, I only used time to blowoff valve pop for several different designs. 10 min is the best I can get with this burner set-up and room temp H2O. It is a really hot flame but also not very noisy. Kind of a nice balance.
Peter61: As far as 'er indoors' I am the man of the house which means nothing really; as long as I want to make a big mess in my little corner of the basement, all is cool.
-
I could have gone to the hobby store and bought a small thrust bearing, but I decided to build a thrust bearing. Bronze case, brass disc on a stainless 3/16 shaft. Half filled with oil. About 2x2 inches. I may decrease the diameter of the internal disc if the friction is too much. It is about 1 inch right now.
The case was made as a mirror image machining process. 3/16 bore first, followed by internal case boring to required diameter and depth of the brass disc. Then the outside of case machined down for bolt spaces. All this as one process on the lathe w/4 jaw chuck. Then split the case with slitting saw on the mill. reversed the halves and screwed together with thin gasket.
The mounts yet to be designed.
This bronze bar was harder in some spots than others, which I did not like as machining was at times not so easy.
-
MAde a new thrust bearing. See pic below. 3/16 stainless rod and some real flanged bearings. very smooth. Not thrust bearing per se, but will work with the forces required.
Tested the steam valve with boiler water level detection unit. starts about 45 sec into video. see the flashing LED which tells that relay activated and steam flows starting the duplex pump. Valve rated for 265 degrees(stainless/viton 23$ on ebay). I ran it for about 45 minutes with no issues.
My method of aging props, I use copper plating for all my models...my signature on my builds.. Salt water, 7 volts, copper wire.
video at :
https://www.youtube.com/watch?v=37BZJHCT9wM&feature=youtu.be (https://www.youtube.com/watch?v=37BZJHCT9wM&feature=youtu.be)
-
tried another new piston and O ring on my shuttle pump. Still no pressure to speak of. Piston is .0015 less than bore diameter and O ring is proud by at about 1/4 tp 1/3 its diameter. Snug fit water side and the engine side of the pump works great. Just does not make pressure. I put in 4 new stainless balls and checked all the seats. everything looked clean and had a good fit. I might use the engine side to power a hand pump. suction is pretty good but I can put my finger over the outlet and stop the flow with mild pressure. My other pump, I can;t stop the flow with my finger...
Made two universal joints the old fashion way with two steel pins. allows for some deflection in the shaft alignment. More than I will need.
pump vid:
https://www.youtube.com/watch?v=K2wb7Fm4qYs&feature=youtu.be (https://www.youtube.com/watch?v=K2wb7Fm4qYs&feature=youtu.be)
-
I am absolutely so impressed with the precision work you are doing here ......... Really enjoying this thread. :-))
-
Been side tracked with an Alfetta turbo project and my Tich. Not a boat, but thought you would enjoy:
https://www.youtube.com/watch?v=WW0-xH-wxw8 (https://www.youtube.com/watch?v=WW0-xH-wxw8)
PS: I am using the boat boiler!
-
Did some work on my stuart triple: Copper cladding w/patina, condenser straps, condenser mount, straightened drain cocks after punching out some aluminum washers. DEI exhaust wrap insulation under cladding.
-
Xrad,
Showed my wife your work to compare it with my hack work. She exclaimed that it must be one of those crazy Brit's whose work that I'm always amazed by. Thanks for keeping up our side of the pond's reputation. Becoming a machinist is on my retirement goal list.
Landlocked/Ken
-
Hi Ken, thanks for the compliments. But, my skills are not anything to be proud of yet. I forget more than I can remember with the mill and lathe setups.....
Riveting is fun...I made a few tools to accomplish this and will build a control box for my yard boat and post pics soon.
Cheers, X
-
Hello!
Very pleasant to follow up. :-))
Something new for me.
Thanks.
Regards.
-
Thanks KBIO
Starting work on a Scott type boiler (not Scotch). It is basically a 3x9 in tube with 12 or so pigtail coils on the bottom(outside the boier). The flame shoots through the pigtails. It is a combination of a flash boiler and a watertube boiler. I have one on another boat and once I rebuilt it, it steamed up very fast and can maintain steam well.
I di a few tests with the copper pigtails and I will post results.
Think of it like a Stuart small boiler on steroids....will post pics soon
-
Thanks KBIO
Starting work on a Scott type boiler (not Scotch). It is basically a 3x9 in tube with 12 or so pigtail coils on the bottom(outside the boier). The flame shoots through the pigtails. It is a combination of a flash boiler and a watertube boiler. I have one on another boat and once I rebuilt it, it steamed up very fast and can maintain steam well.
I di a few tests with the copper pigtails and I will post results.
Think of it like a Stuart small boiler on steroids....will post pics soon
xrad,
The Scott boiler you describe is by a design of A.Rayman a well known straight runner in the past and the Co, author of EXPERIMENTAL FLASH STEAM and still alive today.
Some time ago I posted some pics of this design which was powered by a pressurised paraffin blow lamp.
The engine had an open crank case and at a boiler pressure of 150 p.s.i did 15,000 r.p.m. free running.
It's a super fast steamer but not a Flashsteam boiler, mine would get up to 150 p.s.i. in less than 2 mins with the burner working at 60 p.s.i. and could delivery very high Super heated steam.
Here is the link to the thread.
http://www.modelboatmayhem.co.uk/forum/index.php/topic,24875.0.html (http://www.modelboatmayhem.co.uk/forum/index.php/topic,24875.0.html)
George.
-
Thanks George. Nice work!
Here is my basic plan, nothing too difficult to make. Also pic of near final build bits on the triple....
The Scott boiler(or my variation) I am thinking of is described on page 190 of Model Power Boats by Hobbs, 1929. This is likely in reference to David Scott's design from about 25 yrs earlier for model boat use.
-
Thanks George. Nice work!
Here is my basic plan, nothing too difficult to make. Also pic of near final build bits on the triple....
The Scott boiler(or my variation) I am thinking of is described on page 190 of Model Power Boats by Hobbs, 1929. This is likely in reference to David Scott's design from about 25 yrs earlier for model boat use.
xrad,
Thanks for the pics of your proposed mods to the Scott boiler.
I am always interested in peoples experiments in boiler design so I would be obliged if you could post a larger pic as I can't make out some of your sketch and I don't have the publication that you refer to.
If that's not possible I can P.M. you my mail address and you could send it by e-mail.
What size and type of burner do you propose to use ?
What type of fuel are you going to use?
George.
-
Hi George, I will be using the burner I designed shown above in post 30. Here is a larger pic of the plan. The three front views on bottom are different methods for inserting the pigtails. You want some flow so that the hot steam drives the cooler water at bottom of tank down into the pigtails. This is obtained with one end of the tail reaching higher into the tank. Final pigtail design not chosen yet. Alternating 'high' next to 'low' tail length may be better for mixing?? Or all 'high' on one side...don't know yet.
Some surface are calculations, so don't pay attention to that mess. All I can tell you is that when the burner hits a 6in coil, the water steams nearly instantly, and then some general calculations on how many pigtails, and how much volume in tank and the the time to steam the tank----just guessing really, but somewhere around 10-12min or less. How long to pressure of 60lbs...don't know???
Endcaps .0625...I may go thicker
Copper tank is .090 thick (L) x 8 in long. Seemless, very nice, bought 18in off ebay for 45$ delivered a few months back.
Waiting on some 3/16 22 g copper tube for the pigtails.
Electronic water level sensor in middle below steam dome. One stay down the middle, probably brass or stainless...
-
Hi George, I will be using the burner I designed shown above in post 30. Here is a larger pic of the plan. The three front views on bottom are different methods for inserting the pigtails. You want some flow so that the hot steam drives the cooler water at bottom of tank down into the pigtails. This is obtained with one end of the tail reaching higher into the tank. Final pigtail design not chosen yet. Alternating 'high' next to 'low' tail length may be better for mixing?? Or all 'high' on one side...don't know yet.
Some surface are calculations, so don't pay attention to that mess. All I can tell you is that when the burner hits a 6in coil, the water steams nearly instantly, and then some general calculations on how many pigtails, and how much volume in tank and the the time to steam the tank----just guessing really, but somewhere around 10-12min or less. How long to pressure of 60lbs...don't know???
Endcaps .0625...I may go thicker
Copper tank is .090 thick (L) x 8 in long. Seemless, very nice, bought 18in off ebay for 45$ delivered a few months back.
Waiting on some 3/16 22 g copper tube for the pigtails.
Electronic water level sensor in middle below steam dome. One stay down the middle, probably brass or stainless...
Hi xrad,
Thanks for the pics
Your boiler idea is more or less the same as the one that I made,my boiler had a 2" dia shell with 9 x 1/4" dia coils coming from the underside as shown in pic No 1.
The burner had a 1.25" dia flame tube with a vaporizer coil around the tube , jet in burner was .025" and burned paraffin ( kerozene ) from a copper tank pressurised to 60 p.s.i. as shown in pic No 2.
I fitted a sight glass as shown in pic No3 and to get a decent column of water made banjo fittings top and bottom of the tube.
This proved useless as the turbulence inside the boiler under steam was so violent that a water level reading was impossible.
Pic No 4 shows 3ft of 1/4" dia copper super heater tube coiled down the inside of the casing in direct line of the burner,
150 p.s.i. was raised in about 30 secs and it was necessary to have a constant water feed.
I never had this rig in a boat as I went on to develop a flashsteam plant with a Uniflow Poppet valve engine which I installed in a deep "V" hull boat.
I look forward t seeing your further development of the boiler.
George.
-
Hello!
It will be intesting to open a post jut for this type of boiler/burner.
I do not want to spoil the Xrad's one, but i have a question! :o
I made a Scott boiler same type of yours.
Mine is 15cm long and fitted with 8 coils of 6x1x 25cm long, underneath.
I have a 20mm diam burner with 0.35 (from the corner shop)
I feed with gaz @ +/- 2 bar , tank pressure.
I usually get +/-6 bar pressure in 4 min.
My question is: what do I have to improve to increase my steam production.
I need to feed a fast 4cc engine à 7 bar steady and +/- 1500rPM with a 60mm propeller high pitch.
I wonder if the parafin burner shown by George is not the solution.
Sorry to interfere , thanks fot your answer. Eventually in MP.
Regards. :-)
-
Nice George. The blow lamps are nice for heat and good for 1/4 in coils.
KBIO: Check to see if your coils are touching. You may try to space the coils by 1/2 the coil diameter, AND then add a cap at end of coils so that the heat must escape out between the coils. Of course, you also have to build deflector inside boiler housing close to the outside of coils. Look closely at my design (bottom right of picture is a 'Y' shape deflector that runs the length of the coils to the flue exit).
I would need to see pics of your boiler.
Otherwise, bigger boiler and more heat....
-
Hello! :-)
Thanks for those informations. Yes, my coils are touching and isolation is around/touching the coils.
I'll do pic tomorrow with more details. maybe I open another topic to avoid to spoil yours, as we have pleasure to follow it. What you think???
Cheers.
-
Spread the coils apart a little bit and open the insulation so heat can circulate . The rear of the insulation/shield should be open to the rear flue and the last pigtail should be blocked on the backside forcing the heat through the gaps in the pigatils. I made this change on my last boiler and it made all the difference. The direct heating surface will increase to almost 50-60% on the coils.
-
Hello!
I have to resize my pics, i am not too clever with this! :embarrassed:
Cheers!
-
Hello!
It will be intesting to open a post jut for this type of boiler/burner.
I do not want to spoil the Xrad's one, but i have a question! :o
I made a Scott boiler same type of yours.
Mine is 15cm long and fitted with 8 coils of 6x1x 25cm long, underneath.
I have a 20mm diam burner with 0.35 (from the corner shop)
I feed with gaz @ +/- 2 bar , tank pressure.
I usually get +/-6 bar pressure in 4 min.
My question is: what do I have to improve to increase my steam production.
I need to feed a fast 4cc engine à 7 bar steady and +/- 1500rPM with a 60mm propeller high pitch.
I wonder if the parafin burner shown by George is not the solution.
Sorry to interfere , thanks fot your answer. Eventually in MP.
Regards. :-)
Yves.
I think that your problem is that you want a boiler to feed your engine that is going to produce a fast boat.
I am of the opinion that it cannot be done using L.P.G. and your small 20 mm dia burner.
During my early experiments with this boiler and a burner I wanted to fire it with L.P.G. the burner would start off very good but with the large .025" jet it started to perform like all other L.p.G. burners by the large volume of gas being used it dropped the temperature in the tank which dropped the pressure until there was virtually no power in the burner.
I then changed to paraffin burner with a vaporizing coil and the fuel tank pressurized to 60p.s.i. which solved the burner problem
As the burner was fired from the 60p.s.i. tankit had to be pumped up when the pressure in the boiler started to drop.
When I developed my flashsteam plant I again used paraffin as a fuel with 3- burners each with a .025" jet and the fuel pump and the water pump were engine driven, this meant that if the engine stopped on the water the burners were extinguished immediately.
One of the problems with a pressurized fuel tank is that if the boat stops the burners keep going which can cause problems.
XRAD is spot on regarding having spaces between the coils but if as you say your boiler is to the same design as mine you need to have a clear passage to allow the gases free passage to exhaust, it has been known with this design to put the exhaust pipe just below the casing opening to act like a blast pipe as the loco boys do.
Also the super heater coil going down into the casing acts as a breaker to hold the heat and spread it around the coils.
If you want to go fast and produce steady high pressure steam as high as 7bar you will need to go to paraffin as a fuel and a large burner to burn it.
What engine are you proposing to use ?
Here is a pic of the boiler that I built, hope that the pic is large enough to see the coil spacing.
Also the link to my flashsteam thread, have a look on page 2 where there are some pics of the engine with the engine driven water and fuel pumps, just click on the image for larger pics. ( page No 2 post No 26)
http://www.modelboatmayhem.co.uk/forum/index.php/topic,24568.25.html (http://www.modelboatmayhem.co.uk/forum/index.php/topic,24568.25.html)
George
-
Hello.
Thanks for the drawing George.
This is exactly the one I did: A.Rayman. O0
I open a new post in R&D steam , to leave the Xrad's clean and easy to follow up.
I'll have plenty questions, anyway.
thanks and see you there.
Regards
-
Thanks KBIO.
Here are a few pics of the pig tails brazed into place. There are 13 3/16 pigtails on 0.5 in centers, with opposite side offset by 0.25 in. which leaves just the right amount for air space between coils......
Pigtail diameter determined by the burner, which was built first and runs well.
-
Hello Xrad.
Thanks for this clear explanation. I guess that I have to rebuild the boiler, as per Rayman's drawing, and listen to what you say with Ooyah.
I'll follow your interesting post and I opened one in R&D to avoid spoiling yours with my comments.
Cheers.
-
Boiler end plates: First, determine the diameter which is the inside shell diameter minus x2 the thickness of the endplates, plus a hair more. I made a former out of hard oak floor remnant formed on lathe.
Cut out the endplates. I used .065 copper. Too thick for shears, and would not fit into my small plate shear. so had to use the lathe. This required a center bolt hole which will be used for the brass stay threaded lug. Cut copper out a bit bigger than the boiler diameter because you have to form the edge. If you do a nice job cutting it out, you will not have to trim anything after forming. Copper is a PITA to machine so go medium slow rpms with sharp cutting tool. I found that a few drops of tap magic worked fairly well.
Once the copper is cut out, heat it until light cherry red. I focused the heat on the edges that will be formed. Easy to form over hard oak a bit at a time. Took four heat cycles to get the piece perfect. Many little hammer dings which will fill with silver solder. SAnd and egt rid of any rough or sharp edges.
Then I gently pressed into boiler end after fluxing the boiler and the end plate. Silver soldered up well. Need to get near red hot for solder to flow. don't overdo the flux so less runs into boiler.
My torch is a small tip for fine work , but I have it hooked to a bottle of MAPP and a big O2 tank so it just works for the endplates.
-
Here is a brazed end plate. I wanted a nice solder bead so I recessed the endplate. I have to do some work on the steam dome and a few fittings before I braze in the other endplate.
The end hole went a little wonky during drilling. The other holes are drilled just undersized and then reamed to correct diameter.
I need a pickle solution...
-
Note: above post states "light cherry red." By this I mean just lightly turning red....
-
Had to get some more silver solder....finished most of the brazing except for sight glass mounts. Tested citric acid(purchased at local health food store). About 2 tablespoons into 1 liter H2O and soaked for 10 hours leaves nice finish. easy to polish if i wanted to.
My H2O pressure set-up tested to 200+ psi multiple cycles without issue. I guess that with any pressure vessel, One test to test pressure (ie one cycle) is not enough. I performed about 15 cycles to 200+ psi and held pressure there after each cycle. My operating pressure is about 60-70 psi. So looking good so far. After final bungs brazed, another pressure test will be performed.
cost so far:
~100$ silver solder
~60$ for copper
sight glass set-up 6mm ~ 50$
time in machining bungs, steam dome, and building tank = ~10 hours
Still have to make steel housing and smoke stack.....
-
First steam up: My calculations were close. It took 10 minutes to reach 25 psi and 13 minutes to reach 50 psi. This is with several small fitting leaks and a leaky safety valve. Also found a pin hole leak #4 coil solder joint(hence the orange flame). Last coil has copper baffle soldered to it.
Also, no side baffles or casing which will improve heat conservation.
Otherwise...lookin good...
Vid:
https://www.youtube.com/watch?v=tP6ES3Kt7bY&feature=youtu.be (https://www.youtube.com/watch?v=tP6ES3Kt7bY&feature=youtu.be)
-
Hello!
It looks nice and performing good.
I have a better idea of the copper end plate which will definitly force the heat around the coils toward the bafle.
It will be interesting to see the performances and the behavior with in the final assy.
Cheers.
-
Thanks KBIO
On one of my other Scott type boilers, I tried a brass tube with a solid brass cone on the end. It was about 1/3 to 1/2 the internal diameter of the coils. This ran up the middle of the coils to try to disperse heat to the coils. Concept looked good on paper, but did not work well in real life. In one experiment, the brass tube melted (no cooling water), so then I tried a solid brass rod with cone tip pointed at flame. I varried the length of the cone in the coils in 3 positions(towards the front at the tip of the heat cone, in the middle of the coils, and 1/3 from rear; but it made no real difference in time to steam pop off.
The 3 biggest improvements to design were
1) flame heat
2) rear most coil baffle.
3) spreading the coils
4) helpful but not necessary: wood lagging on top half of boiler.
The detriments were
1) narrow chimney bad..need the largest chimney reasonable in the model design (and depends on height as well) There is a time required for heat to be absorbed into the water, and to get this correct is a balance between the maintaining at a 'set' value heat entering the system and then heat absorbtion, and then the heat leaving the system.
2) heat flow from out of the coils needs no significant restriction as it enters the smoke box towards the chimney (so about 1/2 inch gap to internal baffle all the way around the coils)
3) Flame heat must be kept up. I used a partly heated fuel cannister kept at near room temp. If the gas cools, less heat and worse boiler perfomance.
4) impingement of airflow to burner is as much an issue as backpressure from poor exhaust, so need to watch this as well
The boiler steam test in my above post was with cold water out of a basement tap. Probably in the 40 degree range. Room temp water would have shortened the boil time. Also the boiler was nearly full (I suspect 80% full) so that is about 720cc, which is a good amount to heat off a number 8 jet.
-
Boiler box almost complete...
-
9 minutes to 50psi with the above setup.....
-
Boiler nearly done. If you add ten tablespoons of citric acid to hot water, your boiler will be clean enough in one hour. Rinse inside and out very well.
Components of the boiler base: Outside shell, inside cone baffle, bottom shelf(stainless). The internal cone baffle opens slightly towards the smokebox. This is to allow the heat to expand and flow out towards the smokebox because of the last coil blocking baffle. So there is about 1/4 in air gap at the front progressing to about 1/2 in at rear(smokebox) end. If you hold your hand over the smoke stack, the heat does not come shooting out. it has a more gentle but relatively hot flow pattern. Much heat is contained and therefore transferred to the water by my baffle design.
using harbor freight blow torch. I bought the 29$ version because it had a piezo start. Yep, crap. that lasted until just after the first heatup. Buy the 19$ one. Hooks right up to propane tank. It makes a VERY hot flame. I had it set on med low via handle valve. Too huch heat and all your fittings will fall off. It has a ~2.5 inch dia torch head so not good for small jobs...
Hardwood lagging almost done...
Painted with VHT 900 degree brake caliper paint. It will not take direct flame, which is why the baffle is not painted.
Remade the water side of my pump, now it works great(only one side used now). 3/4 steam piston, 1/2 water piston. There was something wrong with the original internal channels. Even with new balls and seats, it never had any pressure.....If you look really closely, you can just see the edge of a bright spot in the front top of the water pump cylinder. this is a small drill hole for air relief from topside of piston.
-
For any beginner boilermaker like myself, this has been a great project, and not too complicated. I think this boiler is much more efficient than the Stuart and runs better with gas (stuart would be better with the blow torch on parrafin/kerosene).
I think this is now a great match for the Stuart marine twin going into the Tramp Steamer. I have a good duplex waterpump, hand pump, electronics for water level control.
Now to design the water tanks and general layout.....
-
finished the lagging. Overall looks OK. Not the best , but surely functional. Will be hidden by boat structure anyway...
I don;t like philips head screws, but that is all my local hardware store had. Need to find some tiny lag bolts....
I cut the stainless straps on a harbor freight 8 in shear/brake. I tried to cut the boiler box plate with it (.05/18 gauge steel) and I damaged part of the shear. Still works fine for thinner sheet...
There is a 25 cent coin in the last pic for size reference..
Last pic is the harbor freight sander. Ok for hobby use but nothing more. On sale for 60$. Belt top acts like a drum sander which is perfect for the lagging inner curve, and the disc for the bevels. Also sanded the trimmed floor board to the required thickness before ripping each plank off on my micromark hobby saw. Using 120 grit. This floor wood was VERY dense and very hard. Even the dremel had some problems sanding out the holes for the steam fittings. Free wood sample from local flooring store....don't know the species....
No, I don't work for harbor freight, they just happen to carry the tools I need....
-
Well, you learn something new every day. I've got one of those sanding stations. I didn't know it tilts up though!?
Jerry.
-
loosen the big two nuts a turn or two , just behind the sanding disc. They form a clamp on the belt positioning base.
By the way Jerry, nice models on your blog.
Total cost: about 225$ parts, silver solder costs more than anything. About 20 hours total build time. Nice cost for the overall effort considering that a boiler of this type does not exist, and the closest unit is Maccsteam's(The boiler company I would buy from if I had to choose one) 4.5 in boiler at ~900$. And they don't offer the mounting box.
-
Two engine boiler combinations. The horizontal boiler and Mildura are for the trawler hull. The coal fired vertical boiler and Stuart marine twin are for another all wood launch design loosely based on the 'African Queen' style.
-
had to repair one stripped bung on the top of the boiler. And the bung was damaged as well and I did not feel comfortable threading up a size. This required the big propane torch to keep the boiler body hot and the little oxy-map torch to do the fine work. New sight glass and a few fittings. Came out well and holds 190 psi with no leaks that I could detect. 200 psi gauge, hard to see in the flash. No rupture either! When you buy stuff off ebay, there is always the chance that it is a not a good unit, but this one worked out well. The original work was done very nicely. Two internal water tubes and water jacket down to the bottom mud ring. Just have to lag it and build a base. Holds about 850 ml.
-
Hi Xrad, when you have a moment could you please post a photo of the hull and contact details for Microglass. It is not often you come across a decent size hull for a steam plant. Thanks, Ian.l
-
Orion Mouldings (Fifie hull and Pilot schooner hull) :
http://www.orionmouldings.com/modelboats.htm
Microglass:
http://www.microglass.net/index2.html
60in Royal Navy steam tug hull from microglass shown on page 2 of this thread
-
fire door done. brass and steel, wood handle. I was going to acid wash the patina, but then this is going to be a work boat..maybe I will leave alone.
-
coal and wood. too much heat loss, cold outside...blow off at 50 psi. Coal firing is an art form I don't yet possess.
-
messing around with the vertical boiler. Using a Chinese camping burner . 15$ ebay. bought 2 and came in about 1 week. removed the legs and sparker and trimmed to fit the inner tube of boiler, took 5 min to get to fit perfectly. Tried it like it was and slow to boil due to the burner flame mostly going right up the chimney. so....mad a copper inverted cone to disperse flame against the boiler walls (glowing red thing in video..attached to burner top with the center screw in pic)and lowered the burner to where the coal would be (raised the boiler). wow..runs great and does not use much gas. Raised the blow off a bit. Now keeps pressure at about 70psi with the safety valve open full time when all other valves closed. This will make a great boiler for the stuart marine twin.
https://www.youtube.com/watch?v=TF1MzWBAODI&feature=youtu.be