Model Engine Maker
The Showcase => Engines => Topic started by: K.B.C on November 20, 2013, 12:06:47 PM
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Having recently signed up and asked by Jo to show some pics of my flash steam plant efforts and as it's not a machining build I hope this is the correct place to post.
In 2001 I read in one of the M.E. mags of a video showing the exploits of a Mr R. Kirtley and his flash steam hydro I bought the Video and was hooked.
I wanted to put this in a boat but not to race it around the pole, it had to be R/Controlled here is my efforts on the engine and coil.
The first pic is a Cross Section of R.Kirtley's engine PICESS 11 and from this I made my own drawings in order to build the engine.
2nd pic is the finished engine but never dreamed that it would be so successful, so if I may now continue with some pics as I progressed.
3rd pic is of the cylinder which is 1.125" bore x 3/4" stroke and is made from Mehanite grade cast iron with the exhaust slots shown at the bottom of the piston stroke,these were all drilled and filed by hand as at the time I didn't have a Mill.
4Th pic is the cast iron piston made from Mehanite grade cast iron and It is machined to take a cast iron Dyked ring, which if you look at the cross section it has an " L " shaped cross section so that the steam pressure acts on the inside of the ring pushing it against the cylinder wall.
Pic 5 Is of the Con rod which had to be High grade Dural but as I couldn't buy any of this material in small pieces I used a piece from the crank shaft of my light weight cycle ( not the one in use I may add ) it Has a 3/8" bore needle roller bearing pushed into the big end and a Cast Gunmetal bush in the small end.
Pic 6 Is of the piston and the con rod assembly with the hollow bored gudgeon pin ready to be pushed in and held with a pin from the underside skirt of the piston.
I hope that this is of interest and I shall continue with the engine before going on to the Coil.
George.
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Cool! I'm going to get into this one a bit tonight!
Dave
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Eagerly waiting for the next post :ThumbsUp:
Is this the one that set fire to you're lasses flowers
I will take cover
cheers
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Nice read George!....I'm going to be adding more economizer to my boat....I am very interested in your sizing calculations for heating surface.
:ThumbsUp:
Dave
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Hi George
Please continue with more details! It is a rare occasion to read something about flash steam engines and also flash steam boilers which makes it even more interesting!! :cheers:
Florian
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Eagerly waiting for the next post :ThumbsUp:
Is this the one that set fire to you're lasses flowers
I will take cover
cheers
Guys ,
This is a bit of a private joke but I will explain it later when I get to the fire up stage, after I have beaten Mr Heslops head in with a large cudgel, after all what are friends for, it's as well that he is about 200 mls from me .
George.
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I'm much further that 200 miles, and I don't care if it works or not, but I love the look of that engine. What colour cudgel do you prefer?
Cheers, Hugh.
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after all what are friends for, it's as well that he is about 200 mls from me .
George.
George.
I'm going to enjoy this. :ThumbsUp:
All I know about flash steam, came from Frazer. He's around 125mls from me. Just far enough, at times....... ;)
David D
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Thanks gentlemen its nice to know I'm so popular and I thought they were friends
On a serious note thanks for posting George as you know the interest is rekindling and I have burning desire to build a plant.
I will go quietly
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Continuing with the Flash steam engine pictures.
No 1
The crank case was made from a piece of 2" square Ali, a simple 4- jaw procedure.
The cast iron cylinder is bolted on a machined ring and the Ali ring shown is the exhaust ring before the exhaust stub was welded in.
No2
The main shaft which has 3/8" bore ball race at the front end and a 5/16" bore ball race at the rear, the main shaft is machined from a 1/2" dia high tensile bolt and the "V' pully flywheel has a pull cord to start the engine.
Fitted on to the main shaft is a cam with 1/32" lift to operate the poppet valve and is driven by a dog clutch on the boss behind the balanced flywheel at the front.
Unfortunately at the time I never had any pics of the main shaft and the fittings but no doubt you get the drift.
When inserted in the Ali housing the whole lot is pulled together by the large hex nut on the main shaft which also has a drive dog for the prop shaft.
No3-4
Is of the drive assemble inserted into the Ali crank case and at this point the cylinder head and steam chest are bolted on,the cylinder head is made from a billet of mild steel, by this time I had purchased a mill/drill which was far too light but I managed to get the cylinder head made using only about 30 fuses, this mill drill is now replaced with a very much heavier one.
The steam chest has 4- bolts holding it on to the cylinder and inside this is a cast iron valve guide to take the poppet valve which sits in a seat of the same metal.
The pic shows a 5/32" dia rod placed in on top of the cam guide just to show the position.
The cylinder head has the steam inlet and the other at 90deg is for the lubricator ( more later )
No 5
Is the poppet valve which fits inside the cast iron guide in the cylinder head, I tried various type of metal for this, High tensile steel for the valve and the seat but the heat wa such that it burned the edges of the valve,
next I tried silver steel hardened but the heat just softened the valve and the seat to eventually after talking to R Kirtley I machine the valve and the seat from the exhaust valve of a Cummins diesel engine which cured the problem and it's still in after 2- years.
The poppet valve is held in place with collets at the base just like the old petrol engines and held in tension with a strong spring which I wind myself , at the top of the spring there has to be a heat sink other wise the spring would be annealed every time the engine ran and the tension would be gone requiring a new spring, the heat sink material is SANDNYO a very hard ceramic material which can be machined.
No 6,
Bit out of position but this shows main shaft assembly bolted to the crank case with the exhaust ring fitted before stub is welded in.
NO7.
Poppet valve fitted and held in place with spring, heat sink shown at top of spring.
Wrong size of pic and don't know how to delete a pic once posted .
New pic posted.
Next post I can get on to the fuel and water pumps.
George.
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Continuing to put the engine together I needed to make a drive for the water and fuel pump.
this consisted of an extension of the main shaft and then a 90 deg cross shaft .
No 1
I started with a block of Ali and machined the shape on my new mill which allowed much heavier cuts, once the bracket shape was done the black marked piece had to come out.
No 2
Shows the mounting plate for the bracket , it had to be lined up to be straight thro' from the main shaft and sat on the machined register for alignment.
No 3.
The final shape of the pump drive bracket with the 3/16" ball races fitted and shaft lined up
No 4
The pump bracket and the adapter plate to line the bracket up with the main shaft and the drive disc to take up on the crank pin of the main shaft.
This disc is mounted on a shaft with 2- ball races fitted and the worm and wheel to drive the pump shaft.
This is a 4- start worm to give a 6/1 reduction from the main shaft.
On final bench test the engine was doing 15,000 rpm so the pumps are driving at quite a speed.
No5.
The drive disc to with holes to pic up from the engine crank pin, only one is used the other hole is for balancing the shaft.
No6
The final assembly with the cross shaft and the main shaft mounted on ball races and lined up with the main engine shaft.
No 7,
The exhaust jacket with the exhaust stub welded in, it's now beginning to look like an engine, I shall start soon on the water and fuel pumps.
George.
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WATER AND FUEL PUMPS.
No 1 The fuel and water pump were made from the same block of Ali, water pump is 1/4" dia ram and fuel pump is 3/16" dia.
The fuel pump is made side by side of the water pump to keep the fuel cool and stops vaporization.
Fuel mix is 4/1 ( 4 Paraffin to 1 petrol ) the little bit of petrol aids start up.
No 2.
The bracket bolted to the side of the crank case, this at a later date had to be made a little bit longer as it kept slackening off.
No 3
Water and fuel pump.
The 3/16" dia fuel pump has a latch on it which connects to the water pump to allow me to get the burners working before the engine takes over on start up , just before starting the latch is connected back to the fuel pump.
Pumps are driven from a disc on the cross shaft and the stroke is adjustable by tapped holes in the disc to shorten or lengthen the stroke, by experiment 3/8" stroke is about right.
Connecting rod is made from the same bicycle Dural crank and has a needle race fitted.
No 4
Ball valves are fitted to both pumps and are set at .015" lift
No5.
The hand pump like the fuel pump is required to pump water into the coil after the burners have heated the coil, so after firing up the burners water is pumped into the coil until pressure is felt and with the fuel pump latch in place the engine can be fired by the pull cord on the "V" notch in the fly wheel.
The water pump bore is in direct line with the engine driven water pump and the latch on the water pump hold it in place while the engine pump takes over.
No 6.
The completed engine.
Burners and coil next.
George.
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This is very interesting, George.
--Tim
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Very Interesting!
Keep it coming George!
Dave
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FLASHSTEAM COIL.
As it's freezing fog outside today I decided to continue with the Flash steam pics in the warmth of the house.
The coil is 32 ft long and is made from 316 stainless 1/4" dia O.D. tube, as the tube only comes in 6 m lengths i has to have a welded sleeve joint to get the 32 ft.
No 1
This is what I had to achieve so a tapered former had to be made to wind the tube on to.
No2
The former was made from a piece of red hard wood found at the local timber yard and of no use to the yard.
The finished taper was 3" at one end down to 1.5" at the other, nothing very technical, all done by eye.
No 3
The tube was wound on to the front 3" dia part by using a spanner on the 3- jaw, barring it round and trying to keep the tension on the tube at the same time , so you can imagine the carry on with 6 m of tube wafting behind you
No 4
The rear part of the coil is wound on the smaller dia by the same method.
No5
When both parts were wound I made a stainless sleeve and a friend Tig welded the joint, this is the only way to with stand the intense heat on the joint, at this point I could arrange the coil to have 1/4" gap between each coil and turn the last few at 90 deg to the main coil.
No 6.
The short pipe at the 3" dia end is the steam pipe to the engine and the long pipe to the smaller end is the water feed to the coil
Now having the coil made the next thing was the casing and the burners.
George.
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COIL -CASING and BURNERS.
Now that the coil was made I had to figure out what type of material to make the casing from, on the weekly shop at TESCO i spied a 30 litre St/St pedal bin that had a large dent in it which was listed as £36 so after negotiating with the floor manager I paid £10 for it.
This material turned out to be .015" thk, which suited the purpose fine.
No 1
Is the casing and the coil , the casing is all Pop Riveted and made square as it was easier to mount in the boat,
No 2
Shows the coil inside the square casing with a round inside liner, a previous inside liner was made square but the intense heat stretched the metal but when it cooled down it staid in the stretched condition and eventually closed down on the coil restricting the gas flow around the coil, so the new one is square.
The white material is Ceramic wool to keep in the heat and prevent the timber boat going on fire.
No3.
This new plant had 3- burners so I made the flame tubes from the same .015" St/St, the jets are supported in the steel spider shown on the tubes.
No 4.
The spider is cut from the one piece of mild steel, the screwed fitting in the center takes the fuel line from the vaporizer which is 3 ft long 3/16" dia 316 St/St tube bent like a paper clip down inside the coil in direct line of the burners. .
The spider is bored down each arm meeting at the middle and the ends are plugged, the ends have screw fittings ( 1 BA ) to take the steel jets that are made from St/St and each have a .025" hole in them.
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No 5.
Flame tubes spot welded to the front plate which has brackets to hold the spider and the front plate is screwed to the casing.
No 6 .
Trial fitting of the coil and casing in the boat and the engine in position with steam pipe not yet fitted.
No 7.
Completed casing and burners.
Just the pics of the complete steam plant fitted in the boat to come.
George.
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George, I'm loving this thread. I have lots of old ME's from the forties and fifties, ETW was always reporting on the 'international' events post war, featuring the best of England against the incredibly popular Gems Suzor from France. Keep it coming. Ending with a vid in action.
Cheers, Hugh.
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George, I'm loving this thread. I have lots of old ME's from the forties and fifties, ETW was always reporting on the 'international' events post war, featuring the best of England against the incredibly popular Gems Suzor from France. Keep it coming. Ending with a vid in action.
Cheers, Hugh.
Hi Hugh,
If you are interested in Flash steam there are 2- good books available.
Flash Steam x ET Westbury and Experimental Flash Stem x Benson and Rayman, the Benson and Rayman is a more modern update from the Westbury era.
I am just about to conclude my Flash Steam thread but I am afraid that I don't have any videos of my boat in action. if you go on to you-tube try ( British A/S Class hydro ) and this is a video of the 120 mph engine that I copied with help from R.Kirtley the builder who is shown on the video.
George.
High,
Here is the you tube link to a Flash Steam record breaker. ( https://www.youtube.com/watch?v=hVN8iHfQl3s )
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FINAL PART OF A FLASH STEAM ENGINE AND BOAT.
No 1.
Is the boat that the engine is installed in, it's 42" long and weighs in at 25 lbs with fuel on board.
The fuel which is 4/1 Paraffin to petrol, 1-part petrol to help it to start.
No 2
Show s the layout of the steam plant with the water tank on the Starboard side and fuel on the Port side.
water is filled into the tank to enable the boat to get started and when in the water there is a pickup just in front of the prop which can be seen in pic No1.that pumps water into the tank when the boat is in action.
No 3.
Closer view of the engine and pipe work with the fuel and water tanks, both made from .015" sheet brass, the fuel tank holds approx 1- pint of fuel and uses about 1/2 Pint on a 5 min run, note at this stage the cylinder head is still bright from machining.
No 4.
The cylinder head is burned after only 2- runs, it's now burned black after a season on the water.
No 5.
Hydrostatic lubricator that feeds Steam grade engine oil to the engine under pressure when the engine is running
No 6, -7-8.
Are pics of the boat at speed, it can do 40 mph with a submerged prop and I believe that it would go faster if I changed to a Surface drive prop.
However the boat is controlled by 2 - channels on R/C, stop and steering using 15k pull steel geared servos but it's becoming very dangerous as there are many swans on our pond and if I hit one of them I and the club would be in serious trouble as I think it would kill one if hit without any trouble. The boat has been laid up for the past year until I can think what to do with it.
It's very much uncontrollable and it could only take a radio glich to cause some serious damage.
The name OOYAH comes from the shout that one gives on touching a highly superheated steam pipe, as I have done to my cost many times but that's the attraction to steam.
I have no idea of the steam temperatures or the steam pressure but some of the Flash Steam boys down South of who's engine and coil I have copied talk about 1000 C and 2000 p.s.i.I don't think that I am up there but not far off.
To those who asked me to post details of the engine I do hope that it has been instructive, any questions and I will be only to glad to try and answer them.
George.
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I bet that rudder quadrant has tough duty!.....I take it the servo's are forward?
Thanks for posting this....very interesting!
Dave
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I bet that rudder quadrant has tough duty!.....I take it the servo's are forward?
Thanks for posting this....very interesting!
Dave
Yes Dave,
The rudder and post has a hard time of it, the post is 3/16" dia stainless and the rudder which is 16 swg ( 1/16" thk ) is S/Soldered to the post with a sold brass arm inside the boat,
This is operated by the servo in the front of the boat via a heavy duty bicycle brake cable.
The other servo operates the blow, down or stop valve. which can be seen on my last post on pic No 3. between the brass water tank on the starboard side and adjacent to the pump, it's also operated with a H.D bicycle cable.
It comes off the cross piece on the water line from the pump and breaks the pressurized circuit and stops the boat.
The flash steam system works on a closed pressurized circuit and when I operate the blow down the boat stops in about 6 ft.
Pic No 1 shows the servos in the front compartment with the fire wall between them and the engine.
No 2.
Is of the rudder and the prop with the water pic up to the tank .
Please excuse the condition of the paintwork on the boat as it's had a few bashes and dings at the pond wall and after all the boat is just a test bed for the steam plant.
George.
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That's very impressive George! Any idea of the RPM of your engine?
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That's very impressive George! Any idea of the RPM of your engine?
Hi John,
The engine does 15,000 rpm running free on the bench and probably about 25% less in the water under load and with prop slip, the pumps are geared down 6/1 from the main shaft.
As it's a submerged drive if I changed to a Surface drive the revs in the water would be greater therefore the boat would be faster but as I have already intimated it's too fast as it is.
George.
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I have a lot of experience with high speed, radio controlled, model boats but no experience with flash steam. This series of posts was very interesting and reflects the state of the art in flash steam. For radio control you need more than just on and off, though. I read the treads on microprocessor controlled flash steam on Model Boat Mayhem. Has anyone considered a simpler, mostly mechanical system?
It would seem to me that a servo controlled variable link between the two pumps and their crank something like that in the picture below would work. Modern radio systems allow variable mixing between the two channels that control the water and fuel pumps. That, along with the design of the linkages, would allow a variable ratio between the two pumps as well as control over the total flows. It all depends on how the engine responds to these changes. I notice that most flash steam engines have a means of varying the pumps' delivery. How does the engine respond to changes in the fuel and water flow?
Lohring Miller
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I have a lot of experience with high speed, radio controlled, model boats but no experience with flash steam. This series of posts was very interesting and reflects the state of the art in flash steam. For radio control you need more than just on and off, though. I read the treads on microprocessor controlled flash steam on Model Boat Mayhem. Has anyone considered a simpler, mostly mechanical system?
It would seem to me that a servo controlled variable link between the two pumps and their crank something like that in the picture below would work. Modern radio systems allow variable mixing between the two channels that control the water and fuel pumps. That, along with the design of the linkages, would allow a variable ratio between the two pumps as well as control over the total flows. It all depends on how the engine responds to these changes. I notice that most flash steam engines have a means of varying the pumps' delivery. How does the engine respond to changes in the fuel and water flow?
Lohring Miller
What you have to consider with this Flash steam plant is that it's designed on an engine in a Tethered Hydro for max speed, which at the moment is above 120 mph and that is R.Kirtley's Pisces 2.
Pisces 2 is designed to run out of fuel after about 6 laps with no other method of stopping it.
My aim was to get the boat running as fast as I was able to design it without tethering it to a pole with all the associated wading gear and helpers, so R/C was to be the method.
All that was required was steering and stop.
This plant works on a closed pressurised system so to stop all that is required is to break the pressurised system by installing a screw down valve just after the pump and the boat at 40 mph stops in about 6 ft by R/C., also the engine will not run on anything less than 150 p.s.i. and very lumpy at that.
There is about 6 years of development in my plant, this being the second and larger engine installed, in all my researches over the years I have never come across anybody who controlled a flash steam high pressure set up and this goes back to the 1930's from researching Model Engineer mags in the Mitchell library in Glasgow which has one ,if not the , best reference library in Europe.
Now I am not saying that it can't be done but it will need somebody to give it a try and there isn't much room for fitting some sort of controllable pump system in the boat, to me it would be defeating the purpose of a racing flash steam plant to have a controllable system fitted.
Your reference to the flash steam plant in Model Boat Mayhem was built by flashtwo and it was not flash steam, the designer Ian conceded to me in posting that this was so, but it did produce super heated steam in a D10 slide valve engine.
If the heat that is produced by my coil and burners had to be put into a D10 it would melt the valves and severely damage the engine, it may even melt the brass pistons and seize the engine.
Also Ian's engine was only producing well below 700 rpm at 20 psi where as mine is doing 15,000 on the bench and probably about 10,000 in the water with temps possibly 1000 c and unknown pressures.
Ian's main aim in his boat was to develop all the electronic gear that he could design to control his boat.
I would not like to try and control the speed of this flash steamer as it's quite a handful tearing around a pond with swans and ducks in attendance without having to think about controlling the speed at these dangerous speeds and that is why it's been laid up this past year until I decide what to do with it.
Back to your original statement that for R/C you need more that "on and off " that may be the case for the R/C boats that you use which I presume is I.C. but the most important function on a Flash Steamer is " steering & stop "
George.
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I didn't mean to be critical. A very few people including yourself have done a lot to advance the state of the art in flash steam. I couldn't find any serious attempts to throttle a flash steam plant either, so I thought about how it might be done. It seems that in experimenting to get the water and fuel flow adjusted correctly someone might have noticed how off optimum settings varied the speed.
It seems to me that the steam rate would be proportional to water inflow and that the heat needed to evaporate the water would be proportional to the fuel flow. As long as the tubing didn't melt with too little water and too much fuel, it should be a safe experiment. It's also possible to flood the tubing with too much water and too little fuel. That would hydraulically lock the engine, a damaging occurrence. I'm afraid the only to find out would be to build a flash steam power plant and try it.
The boats I race that are similar in size to yours use a 26 to 31 cc internal combustion engine and run in the mid 60 mph area around a 1/6 mile oval. We race at full throttle but need to throttle the boat at the race start and while retrieving. We set the radio controlled 26 cc gas straight a way speed record of 109+ mph in 2004 with an outrigger hydroplane similar to the tether hydroplanes.
Lohring Miller
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After some searching I found this variable stroke mechanism. It would vary the stroke of both pumps the same amount, but maybe that's all that's needed. It should be easy to control with a servo but would still need the blow off valve for a firm stop.
Lohring Miller
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Lohring,
You have to realise that these engines are not like your I.C. engines that can be bought off the shelf, installed in a boat with R/C and you have full control over the speed range.
If you read my post No 11 at pic No 3 you will see that the stroke of the pumps are adjustable via the drive disc on the cross shaft from the engine, these holes are pitched on the disc to give 1/4" stroke, 3/8" 7/16",and 1/2" stroke and after much experimenting 3/8" seams to be the optimum stroke.
Move it to the next hole up and it runs too wet, move it to the next one down and it runs out of water therefore steam.
There are quite a few parameters that would preclude me from considering going any further with the set up.
Firstly it's going fast enough.
Secondly there is no space to try and fit some sort of system in.
Thirdly the minute adjustments required to get a control system to work is too great
Fourthly the intense heat generated by the burners would melt any servo system that would have to be mounted outside of the compartment that the 2- existing ones are in as there is no space in the compartment.
Lastly as I will possibly not be running the boat very often I just don't think it's worth the effort, over the years of research and what is happening down South in England these steam plants are out and out racing and record breaking boats and they are very delicately balanced with no thought of speed control, I don't think speed control would work.
However you seam extremely interested so why not build a steam plant with speed control but please do it soon , as at 75 years of age I may not have the time left to see your efforts.
George.
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I'm only a little behind you at 70 and am still working on projects I started thinking about in high school. Internal combustion two strokes have been by main focus, but flash steam is very interesting. I have built IC engines and hop up parts so I understand the even greater effort to build a flash steam power plant. I was hoping for a little input like that in your reply on the effects of varying water and fuel flows. It's easy to dream up solutions, but there's no substitute for actually doing the experiment.
I may actually take you up on your challenge. You can never go fast enough. LOL
Lohring Miller
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Lohring,
I do wish that I could give further input to your question on speed control so to give you a little bit of background on my experiments.
About 2002 I saw an advert for a video on flash steam which I bought and was hooked on the subject, it was about R.Kirtley's experiences in attaining 120 mph round the pole with his Hydro.
I can safely say that even up till now I was the only one in Scotland experimenting in high speed flash steam so I had nobody to bounce ideas at with the subject being so specialized, R.K lives in the N/E England 200 mls from me but he was very helpful with me on my building and to eventually get going but there is a certain amount of time that one can phone for advice so it was a lonely road that I was on , mainly by trial and error with no thought on controlling the speed of the beast.
There were many break downs and rebuilds but eventually I managed to get the thing running with a diary kept of the adjustments made and only one at a time.
The first engine was 3/4" bore x 3/4" stroke with 22 ft of Stainless 316 tube and 2- burners, which was eventually wrecked and rebuilt.
The current engine is 1.125" bore x 3/4" stroke with 32 ft of 316 Stainless tube and 3- burners, the main problems arose with the intense heat generated and trying to get a poppet valve to with stand the heat that was generated.
I tried H.T steel with the same material as a seat but had to constantly adjust the .015" gap on the cam follower.
Silver steel oil hardened eventually annealed and again the tappet clearance failed.
The eventual solution was to make the poppet valve and seat from a Cummins diesel engine exhaust valve which cured the problem.
The cast iron piston ring is called a Dyked ring, which has an "L" shaped cross section and when the steam hits the piston top it pushes the ring against the cylinder wall and is very effective.
As you can appreciate all of this was taken 1- step at a time and I had a very full diary of notes on all the changes that had been initiated.
Sometimes the engine would run great and then the next outing it would splutter round the lake so it was an investigation as to what the problem was, with many a sleepless night trying to figure out what was wrong.
So I hope this short history will let you see that I didn't have any thoughts on speed control at the time but mainly trying to get the correct metals to with stand the heat and the pressures.
If there was 1- thing that I would change it would be to have a surface piercing prop set up rather than the current submerged one to allow the engine to rev more freely but I am afraid that this is only a dream and a small dream at that.
My main concerns are the danger that it causes and if it went A.W.O.L due to a radio glitch as it has done in the past with a piece of cord wrapping around the rudder and off setting it causing the boat to go crazy before stopping it .
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It's easy to dream up solutions, but there's no substitute for actually doing the experiment.
You have no idea as to how true your statement is, I have had many ridiculous suggestions which I had to take with a pinch of salt and still try to remain civil at the suggestions.
Please don't think that I am being facetious or nasty in suggesting that you have a go at a Flash Steam plant, I am not and if you do I will be only to willing to pass on things that I have learned.
George.
P.S.
Lohring
Here is some interesting reading ( http://www.onthewire.co.uk/bamf2.htm )
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George,
I must commend you Thank you for yet another glorious, cogent and extremely informative post!
:praise2:
Thank you!
Dave
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I've really enjoyed this thread. What diameter tube did you use for the boiler?
Cheers, Hugh.
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Thanks again for your reply. When we were working on the first gas powered RC boat to go over 100 mph we spent days trying different ideas. If one in 10 worked, I was happy. I think the first step after reading everything I can find (I've studied On the Wire backwards and forwards) would be to build the pump system. I have a selection of high power electric motors from model racing boats to drive the pumps. After that the boiler system would be next followed by a motor.
Funny you should mention surface piercing props. My current project is a milling fixture to make propellers. Several of my friends have been bending and breaking propellers at speed trials. I think I can at least mill wax patterns that can be cast in high strength metals. i might be able to mill steel props. We'll see.
As you know well there are very few people working with flash steam. Thanks to the internet, they can communicate a little better. Maybe we can advance the state of the art.
Lohring Miller
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George,
I must commend you Thank you for yet another glorious, cogent and extremely informative post!
:praise2:
Thank you!
Dave
Hi Dave ,
Thanks for the kind words it's appreciated.
George
Hugh,
The Stainless tube is 316 grade 1/4" o/d x .032 Thk wall and has a bursting pressure of 8,000 p.s.i..
The beauty of a flash steam coil is when it burst and this has happened with another coil ,there is only a hissing noise with no danger to health,
This coil blew when I had it under water pressure and fired up, so I should have either fired the engine or dumped the pressure with the bypass valve.
At the time when I purchased the tube is was £32 for a 6m length so to get the 32 feet for the new coil I had to have the joint sleeved and TIG welded.
George.
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Thanks again for your reply. When we were working on the first gas powered RC boat to go over 100 mph we spent days trying different ideas. If one in 10 worked, I was happy. I think the first step after reading everything I can find (I've studied On the Wire backwards and forwards) would be to build the pump system. I have a selection of high power electric motors from model racing boats to drive the pumps. After that the boiler system would be next followed by a motor.
Funny you should mention surface piercing props. My current project is a milling fixture to make propellers. Several of my friends have been bending and breaking propellers at speed trials. I think I can at least mill wax patterns that can be cast in high strength metals. i might be able to mill steel props. We'll see.
As you know well there are very few people working with flash steam. Thanks to the internet, they can communicate a little better. Maybe we can advance the state of the art.
Lohring Miller
Hi Lohring.
I am really pleased to see that you are about to take up building a flash steam plant and speed control it, I am sure that you will be the first to do so, as previously stated I have never come across anybody who has tamed a high speed flash plant.
If I may ask, what type of engine are you planning to build?
Fuel to be used ?
Type of tubing for the coil?
With your experience with high speed I.C. and Gas boats I would recommend that you have a surface piercing prop and a shallow "V" hull and you have the advantage of friends to bounce ideas at, so I look forward to your progress
George.
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Thanks George, I've always wondered.
Hugh.
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Currently I'm waiting for a copy of Experimental Flash Steam. The engine will be the last part of the build since the pump design will be key. I spent a little time yesterday while snowed in to check the internet for materials. Seamless 316 stainless steel tubing http://www.ebay.com/itm/Coil-Tubing-Welded-ID-194-OD-1-4-50-Ft-L-Wall-028-316-Stainless-Steel/221262739145?_trksid=p2045573.m2042&_trkparms=aid%3D111000%26algo%3DREC.CURRENT%26ao%3D1%26asc%3D27%26meid%3D3369944555047739346%26pid%3D100033%26prg%3D1011%26rk%3D4%26rkt%3D4%26sd%3D230982947265%26 (http://www.ebay.com/itm/Coil-Tubing-Welded-ID-194-OD-1-4-50-Ft-L-Wall-028-316-Stainless-Steel/221262739145?_trksid=p2045573.m2042&_trkparms=aid%3D111000%26algo%3DREC.CURRENT%26ao%3D1%26asc%3D27%26meid%3D3369944555047739346%26pid%3D100033%26prg%3D1011%26rk%3D4%26rkt%3D4%26sd%3D230982947265%26) (is welded OK?) seems to be readily available in up to 50 fool lengths as does high temperature material like Nitronic 50 http://www.onlinemetals.com/merchant.cfm?pid=10706&step=4&showunits=inches&id=886&top_cat=0 (http://www.onlinemetals.com/merchant.cfm?pid=10706&step=4&showunits=inches&id=886&top_cat=0) for things like valves.
The problem is all the fittings and supporting parts. The best flared connections seem to be the 37 degree style with a sleeve. The flaring tool for these costs at least $100, though. Did you use standard 45 degree flare fittings? Were they available in stainless steel? Did you buy the pump check valves? Where? Are any of the other parts like lubricators available? If not are there some standard designs? I notice that earlier flash steam engines used pump lubrication. Are there any issues with cast iron pistons and cylinders at high temperatures? Has anyone tried different materials? I don't want to reinvent very much if I can help it.
The design will be very close to yours since that seems to be the state of the art. I have several fiberglass hulls available as well as all the hardware and boxes of propellers so that won't be a problem either. The only US radio controlled steam 1/16 mile straight a way record was set in 1994 at 9 mph. I would be seriously disappointed if that can't be improved by a factor of 10 using an outrigger hydroplane design.
Lohring Miller
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Have a look on the MY Hobby store sight as they sell the drawings for Pices II drawing number M72.
I think an article about the plant was serialised in the Model Engineer but cannot remember when.
cheers and good luck
frazer
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Currently I'm waiting for a copy of Experimental Flash Steam. The engine will be the last part of the build since the pump design will be key. I spent a little time yesterday while snowed in to check the internet for materials. Seamless 316 stainless steel tubing http://www.ebay.com/itm/Coil-Tubing-Welded-ID-194-OD-1-4-50-Ft-L-Wall-028-316-Stainless-Steel/221262739145?_trksid=p2045573.m2042&_trkparms=aid%3D111000%26algo%3DREC.CURRENT%26ao%3D1%26asc%3D27%26meid%3D3369944555047739346%26pid%3D100033%26prg%3D1011%26rk%3D4%26rkt%3D4%26sd%3D230982947265%26 (http://www.ebay.com/itm/Coil-Tubing-Welded-ID-194-OD-1-4-50-Ft-L-Wall-028-316-Stainless-Steel/221262739145?_trksid=p2045573.m2042&_trkparms=aid%3D111000%26algo%3DREC.CURRENT%26ao%3D1%26asc%3D27%26meid%3D3369944555047739346%26pid%3D100033%26prg%3D1011%26rk%3D4%26rkt%3D4%26sd%3D230982947265%26) (is welded OK?) seems to be readily available in up to 50 fool lengths as does high temperature material like Nitronic 50 http://www.onlinemetals.com/merchant.cfm?pid=10706&step=4&showunits=inches&id=886&top_cat=0 (http://www.onlinemetals.com/merchant.cfm?pid=10706&step=4&showunits=inches&id=886&top_cat=0) for things like valves.
The problem is all the fittings and supporting parts. The best flared connections seem to be the 37 degree style with a sleeve. The flaring tool for these costs at least $100, though. Did you use standard 45 degree flare fittings? Were they available in stainless steel? Did you buy the pump check valves? Where? Are any of the other parts like lubricators available? If not are there some standard designs? I notice that earlier flash steam engines used pump lubrication. Are there any issues with cast iron pistons and cylinders at high temperatures? Has anyone tried different materials? I don't want to reinvent very much if I can help it.
The design will be very close to yours since that seems to be the state of the art. I have several fiberglass hulls available as well as all the hardware and boxes of propellers so that won't be a problem either. The only US radio controlled steam 1/16 mile straight a way record was set in 1994 at 9 mph. I would be seriously disappointed if that can't be improved by a factor of 10 using an outrigger hydroplane design.
Lohring Miller
Lohring,
The tube at a glance looks O.K. but I am concerned at the 1500 p.s.i max and that it's welded whereas mine is solid drawn and by memory had a 8,000 p.s.i max, it's a very good price but it depends on the level of power you are trying to achieve with your boat and if you go for the 3- burner set up I don't think that 1500 p.s.i is enough.
The stainless steel I can't comment on as mine is an Alloy steel made from the exhaust valve of a Cummins diesel engine.
I use a flaring tool which has a 45 deg angle with steel nuts and can be made and disconnected without damaging the joint.
As Frazer says the drawing is still available, the article written by R.K. for M.E. mag is not but I have it on file and if you P.M. me your mail address I can mail it to you, this will answer a lot of your questions on pumps and the engine build have a read at this and then if I can be of help I shall be only too pleased to do so.
The article is a very good read and I think it's the only write up on a record breaking Flash Steamer..
George.
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Lohring..........this example of 316 stainless steel as welded tube [AWT] is actually produced by an automated fusion process which sounds fine
It may have the chemical properties according to ASTM276-316, however by the nature of manufacture has two continual longitudinal soft spot/lines in the heat effected zone on either side of the fusion weld & hence does not have the mechanical properties of the same standard ...viz the markedly reduced maximum WP
Grade 316 stainless steel is also non-hardenable by heat treatment .......
The flaring process when using AWT tubing would also result in non concentric or tearing of the softer material [longitudinal soft spots] during that process
I do think that George is alluding to the use of cold drawn seamless [CDS] tubing........which is certainly superior considering the disadvantages of AWT........Derek
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I was afraid that that welded SS tube was too good to be true. The seamless tube that I could find doesn't come in as long lengths or as low a cost. The problem areas as far as I can tell are valves as well as cam and lifter wear. I'll spend more time thinking about that while I'm building the pumps. I'm glad standard 45 degree flare fittings can be used. It sounds like all the check valves and fittings are custom made. I can do that, but it all takes time. I appreciate everyone's help and suggestions.
Lohring Miller
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WATER AND FUEL PUMPS.
Hi George,
Thanks very much for all this info, most of it is clear to me but the pump, not so much.
Apart from that I have lot more questions about speed control; suitable materials; temperatures; pressure and lubrication.
Do you have a drawing from the pump, something that shows the (one way) ball valves; plungers and all?
Do I understand it correctly that the pump stroke length is fixed during running the engine?
Is there a type of "waste gate" for excess water and /or fuel pumped or is it controlled is any way?
How is the engine speed controlled?
The steam inlet has a connection for lubrication, how is the oil pump powered and is this pump lubricating other parts too? Any details of this oil pump?
About the fuel, is the fuel pre heated so that is there is pressurized gas at the jet holder inlet?
What are the best material for pumping water - plungers and cylinders; what is best for the piston and
the working cylinder?
So enough question for today I think, reason for all this is although I never heard of flash steam engines, I thought of it myself and like to build one. After I started searching the internet I found that there already exists engines like this. Which is good now I can make use knowledge from others.
I wonder if there are people here who have idea's about making it fuel efficient.
Regards
Edmund
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WATER AND FUEL PUMPS.
Hi George,
Thanks very much for all this info, most of it is clear to me but the pump, not so much.
Apart from that I have lot more questions about speed control; suitable materials; temperatures; pressure and lubrication.
Do you have a drawing from the pump, something that shows the (one way) ball valves; plungers and all?
Do I understand it correctly that the pump stroke length is fixed during running the engine?
Is there a type of "waste gate" for excess water and /or fuel pumped or is it controlled is any way?
How is the engine speed controlled?
The steam inlet has a connection for lubrication, how is the oil pump powered and is this pump lubricating other parts too? Any details of this oil pump?
About the fuel, is the fuel pre heated so that is there is pressurized gas at the jet holder inlet?
What are the best material for pumping water - plungers and cylinders; what is best for the piston and
the working cylinder?
So enough question for today I think, reason for all this is although I never heard of flash steam engines, I thought of it myself and like to build one. After I started searching the internet I found that there already exists engines like this. Which is good now I can make use knowledge from others.
I wonder if there are people here who have idea's about making it fuel efficient.
Regards
Edmund
Hi Edmond.
The pumps are very typical of the ball type that are common in model steam engine and boiler feed pumps in that they have a ball on the suction side and one on the delivery side with the pump having a ram type plunger.
I don't have any drawings of these pumps other than the sketches in my note books and regarding the types of materials used in the engine I can only offer to mail you a copy of the original builders article which was published in Model Engineer Mag which can answer your questions on materials used, please contact by P.M. don't put your e-mail address on the forum.
I must question your ambition to control this plant as it is designed as a racing plant which in the original Hydro achieved 120 mph and possibly higher now.
This plant is uncontrollable and is a bit of a beast when let go, as it is a closed loop pressurised system any opening of bleed valves immediately loses pressure and the engine stops.
The pumps have a fixed stroke and driven from a disc on the 90 deg cross shaft and is adjustable via holes on the disc and by experimentation the correct stroke is found.
The fuel system is preheated in a vaporizer of 3ft long x 3/16" dia Stainless 316 tube stuffed down the coil and is heated by a plumbers blow lamp to get the burners going before starting, just like a Primus stove.
Regarding fuel efficiency on this plant it's not a consideration as it tries to burn as much fuel as possible to give the highest temperature and pressure available, I hastily add that I have no idea of the pressures or temperatures when the plant is on full song.
The lubricator is worked from the cold water pressure and bleeds high grade steam oil into the engine every time the valve lifts on the engines rev cycle.
All that it is is a cylinder with a free fall piston inside , it's pushed down and filled with oil when the engine isn't running and once running the pressure builds and injects the oil thro' a .025" hole into the steam line every time the valve lifts..
Now back to controlling the engine, this plant is designed purely for high speed racing, record breaking, with no thought of controlling the speed, as far as I know nobody has ever tried to speed control it but you are welcome to have a go.
I can recommend the book EXPERIMENTAL FLASH STEAM by J.Benson and A Rayman which catalogues various steam plants from the past with dimensions of pumps and many other suggestions.
I do hope that this information helps.
George.
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My current thoughts on control involve both controlling the water and fuel pumps' stroke coupled with variable valve lift and cutoff timing to throttle the engine. You would still need a blow off valve for a full stop. The problem with pump stroke control is delay in effect coupled with matching requirements to power output. I need to play with a spread sheet to calculate the steady state requirements. Delays make the dynamic requirements a lot harder to estimate. The direct pump coupling matches output to engine speed. See the above patent for a variable pump stroke mechanism.
A more direct throttling is needed, and variable valve lift and timing is the simplest efficient answer. It has been used on steam engines forever, but high speed versions are much more recent. The simplest one I've found is a Honda mechanism pictured below. It needs to be light, simple, and durable to match the current fixed valve mechanism. I think the above is possible, especially with modern radios.
Each control can be on a separate channel and they can either be mixed together or manually controlled. Telemetry can send temperature information (and probably pressure information) back. You could manually make on the fly pump stroke adjustments to match the engine requirements. It would take experience, but on the fly adjustments are currently done with the fuel supply on model IC glow ignition engines during a race.
Materials are the big area for experiment. I see some flash steam engines use 4340 steel for the cylinder. Stainless steels were not successful. Cast iron pistons seem heavy for high speed engines. Maybe a two part piston with a steel crown and aluminum skirt would work. It all takes a lot of experimenting.
Lohring Miller
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I can understand roughly how you intend doing it.
I had thought about using an electrical driven pumps controlled via a feed back loops looking at engine rpm and say outlet temp but this doesn't take into consideration that the burner would have to be modulating and I dont know if this possible with a petrol/paraffin mix.Gas wont be able to give enough therms and suffers from freezing.
Will the compression of the engine simply make it stop. I dont know just asking as these plants have been designed to run flat out.
Will watch with great interest.
best wishes
frazer
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Unlike conventional boilers, flash steam boilers contain very little water under normal conditions. This means that they can't store energy in the form of hot water to be turned into steam when acceleration is needed. That's what makes them safe, though. I notice that it takes some time for the tether hydros to get up to speed. I'm not completely sure why this should be. It may be that with a fixed pump stroke the fuel and water supply depends on rpm and it takes a while to accelerate with the high pitched prop. Increasing boiler draft with speed may also be a factor. Would a blower help at low speeds?
The other problem is that it should be easy to flood the boiler if the water supply increases faster than the increased fuel can heat it. That will destroy the engine by bending or breaking the rod and or crankshaft if water gets into it. I've had that happen with 26 cc IC engines. Manual pump stroke control could be risky because of this. Throttling alone might result in too high of a pressure rise and or during deceleration. Balancing the two inputs will be tricky. I'm open to ideas on how to do this. I'm sure full size power plants have a series of sensors and computers that regulate the pumps. I'm hoping that the mechanical connection to the engine is mostly self regulating.
Lohring Miller
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Hi, P.I.D control maybe the way forward a little like cruise control in a car using feed back loops.Its a long time since I played with electronics so no doubt things will have moved on considerably.I had though of using a PIC chip as per Flash Two.
Would prop slip not be a factor for the acceleration time.
I dont know just mulling over a few ideas I once had
Cheers and good luck.
frazer
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People have tried a lot of different control systems. The issue seems to be the lag between the inputs and the steam output. Doble used a mechanical temperature sensor that controlled the steam generation. See a great quick coverage of the car at Jay Leno's Garage (http://www.jaylenosgarage.com/collections/steam-cars-1/#videos) It's still probably the state of the art in automobile steam power.
I have a lot of rpm versus speed data on model and full size boats. After the propeller "hooks up" there is a very direct correlation between rpm and speed. Below is a graph of data from an electric outboard hydro. Model hydros act very similarly.
Lohring Miller
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Hi Edmond.
The pumps are very typical of the ball type that are common in model steam engine and boiler feed pumps in that they have a ball on the suction side and one on the delivery side with the pump having a ram type plunger.
I don't have any drawings of these pumps other than the sketches in my note books and regarding the types of materials used in the engine I can only offer to mail you a copy of the original builders article which was published in Model Engineer Mag which can answer your questions on materials used, please contact by P.M. don't put your e-mail address on the forum.
I must question your ambition to control this plant as it is designed as a racing plant which in the original Hydro achieved 120 mph and possibly higher now.
This plant is uncontrollable and is a bit of a beast when let go, as it is a closed loop pressurised system any opening of bleed valves immediately loses pressure and the engine stops.
The pumps have a fixed stroke and driven from a disc on the 90 deg cross shaft and is adjustable via holes on the disc and by experimentation the correct stroke is found.
The fuel system is preheated in a vaporizer of 3ft long x 3/16" dia Stainless 316 tube stuffed down the coil and is heated by a plumbers blow lamp to get the burners going before starting, just like a Primus stove.
Regarding fuel efficiency on this plant it's not a consideration as it tries to burn as much fuel as possible to give the highest temperature and pressure available, I hastily add that I have no idea of the pressures or temperatures when the plant is on full song.
The lubricator is worked from the cold water pressure and bleeds high grade steam oil into the engine every time the valve lifts on the engines rev cycle.
All that it is is a cylinder with a free fall piston inside , it's pushed down and filled with oil when the engine isn't running and once running the pressure builds and injects the oil thro' a .025" hole into the steam line every time the valve lifts..
Now back to controlling the engine, this plant is designed purely for high speed racing, record breaking, with no thought of controlling the speed, as far as I know nobody has ever tried to speed control it but you are welcome to have a go.
I can recommend the book EXPERIMENTAL FLASH STEAM by J.Benson and A Rayman which catalogues various steam plants from the past with dimensions of pumps and many other suggestions.
I do hope that this information helps.
George.
Hallo George,
Happy New Year for you and everybody else here!
About the pumps, for the moment I have enough information and want to concentrate on more important/unknown things.
Controlling speed is essential for what I have in mind so that must be done one way or another.
I was thinking of a slightly different “flash” engine then showed here, I want to flash water into steam IN the cylinder and not before.
If you or anybody have some good reason why not, please enlighten me.
Thinking that will solve at lot of problems in exchange for a lot of other problems :-)
Injecting a speed/load dependent amount of water is doable and we can think of several ways
of doing just that, we can think of a high pressure plunger like in a diesel line pump which is perfectly controllable. Or we van use a computer controlled solenoid injector, again like in current diesel engines. Either way, the pressure before such injector must kept above the vaporizing pressure at all time. In addition to that we do not want a pump wasting a lot of energy by pumping hight pressure water around. These are a few problems that can be solved without too much difficulty in my opinion.
There are “constant pressure valves” and one can think of a pump regulating system.
The variable stroke suggested here in the forum is far to complicated for my liking, it must be simpler and with less parts.
Making steam/superheated water, not hindered by any knowledge I wonder if a monotube is the most efficient way to make steam or heated water. A furnace out of a solid well heat conducting ( nano ) metal might be a lot better, although I could be wrong here.
Such furnace can and must be kept at the max allowed temperature by modulated burners, nothing new here.
So injecting a zero amount of superheated water means a full stop, injecting the maximal amount of superheated water means a near instant maximum amount of power.
So the engine is perfectly controllable this way.
The fuel system is -for this moment- clear enough for me.
Efficiency however is very much of my interest, throwing away steam or condensed heated water isn't something I would do. I would extract as much as energy from the steam and condense it,
separate the oil from it and use it again.
Another thing that got my attention is the air needed for the burner,
is it clean cold air! I wonder what the temperature from your exhaust is. Why not pre-heat the
fresh air for the burner with the (wasted) heat from the exhaust?
Lubricator : although I have some idea how it works a drawing would help.
I am always looking solutions a simple as possible but not simpler :-)
Edmund
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This developer has spent a lot of time trying to do what you propose.
http://www.flashsteam.com/
Lohring Miller
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This developer has spent a lot of time trying to do what you propose.
http://www.flashsteam.com/
Lohring Miller
Hi Lohring,
I have seen this website, please tell me what you think about it.
Personally ( not hindered by any knowledge ) I don't see much in adding steam trough a valve compress it and so on. It is wasting a lot of energy more then anything as far as I can see.
The whole idea of modifying and imitating an IC engine is not what I am after. I did not see anything
as a regulating system for the pressure pump and the injector does not look very spectacular to me either. I do understand that flashing superheated water does not immediately result is 100 % steam but the first thing to do is looking for the highest possible temperature/pressure and heating/isolating the "cylinder" as much as the lubrication will allow it.
To make it even more SiFi, I am not thinking of an conventional cylinder/piston engine at all.
I am thinking of a "jonova" kind of engine, that is a part that I already have CAD drawn.
It doesn't really matter for all principles used in other flash steam engines, these will be the same but the jonova engine offers some significant advantages compared to conventional piston engines.
Edmund
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Hi Guys,
I think that we are moving away from the original objective and that is to control the High speed flash steam engine that I posted which is a copy of R.Kirtley's PISCES 11 120 mph+ Hydroplane.
The technology being discussed is beyond me and the desire to further my engine experiments is no longer there, so I shall bow out but if there are any questions that I feel I could answer and is relative to my steam plant I will come back in.
May I remind you that the objective is to control the 120 mph+ engine powered by flash steam and include that the finished plant and boat must not be below the 14 lbs all up dry weight of the boat that the Steam Hydro record chasers are confined to.
I look forward in anticipation to your experiments.
George.
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Has anyone looked at the numbers for fuel and water output from the pump. I may be wrong, but I get around 16 cubic inches per minute of fuel and 30 cubic inches per minute of water at 1600 pump rpm. For the fuel that gives around 175 horse power of heat at 17,900 BTU per pound of fuel. That's reasonable since the power plant can't be more than 5 to 10% efficient at converting the fuel to shaft power. At 5% that would be 8 3/4 hp.
However, I get 1 pound per minute or 60 pounds per hour for the water. Even really efficient engines use 10 pounds of water per hour per horsepower. It's more common to use 20 to 30 pounds per horsepower per hour. Did I screw up my calculations or is there a reason for this discrepancy? From my experience with a 110 mph RC hydro that ran a dyno tested IC engine, I would expect that it takes around 5 or 6 hp to go 120 mph.
Lohring Miller
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Has anyone looked at the numbers for fuel and water output from the pump. I may be wrong, but I get around 16 cubic inches per minute of fuel and 30 cubic inches per minute of water at 1600 pump rpm. For the fuel that gives around 175 horse power of heat at 17,900 BTU per pound of fuel. That's reasonable since the power plant can't be more than 5 to 10% efficient at converting the fuel to shaft power. At 5% that would be 8 3/4 hp.
However, I get 1 pound per minute or 60 pounds per hour for the water. Even really efficient engines use 10 pounds of water per hour per horsepower. It's more common to use 20 to 30 pounds per horsepower per hour. Did I screw up my calculations or is there a reason for this discrepancy? From my experience with a 110 mph RC hydro that ran a dyno tested IC engine, I would expect that it takes around 5 or 6 hp to go 120 mph.
Lohring Miller
Hi Lohring,
Like the Hydro record chasers I have never been concerned with fuel consumption other than trying to burn as much fuel as I can and getting as much heat from the fuel as possible.
I don't disagree with your figures although they don't correspond exactly as per K.N. Harris's in his book on Stationary and marine Steam engines but near enough, these figures are for Saturated steam not high pressure flash steam.
I have done a little Calc using H.P. figures as P.L.A.N divided by 33000 which is how I have always calculated H.P. but as I don't know what pressure my Steam plant works at I have used theoretical figure on Steam pressure based on what the record chasers can achieve which can be as high as 3000P.S.I.
I have used 1000 P.S.I. and from the Calcs it comes out at 14.06 H.P.
500P.S.I. would be 7 H.P. and 2000P.S.I would be 28.12 H.P.
My pumps work at 6/1 from the main shaft so at 15000 rpm it will be 2,500 strokes per min.
The water pump at 1/4" dia x 3/8" stroke delivers 45 cub " /min
The fuel pump at 3/16" dia x 3/8" stroke delivers 25.46 cub"/ min.
These figures are theoretical as in the water the revs will be lower, I think the only way to get accurate figures on pressure and steam temperature is to have gauges to monitor them on bench testing.
I can tell you that I ruined a 300 P.S.I. gauge on the steam line in one of my efforts to find out the pressure, due to the modulating pressure as the valve opened and shut it blew the gauge apart , so I very quickly abandoned the idea of measuring the pressure but I am sure that there must be more reliable methods of measuring.
So, some food for thought.
George.
HAPPY NEW YEAR TO ALL, BEST WISHES FOR 2014
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Hi Guys,
I did not (yet) calculate anything because I don't even have a complete design finished.
Having said that I am more then interested in efficiency and how much fuel is burned and I do NOT agree with George here. You can burn a lot of fuel and wasting a lot of heat while you may get even more heat with less fuel if you can limit the amount of wasted heat!
By the way , it would be so nice if you guys started to use "decent" units instead of those weird lengths of body parts :-). Seriously, it really make sense to use Newtons Meters Watts Kelvin and so on.
I know it is not gonna happen, it is tried before and failed.
About pressure : If you measure the temperature, isn't hat enough to give you the pressure as well if you look at the steam table?
About the actual rpm : AFAIK the formula1 commentators are measuring the SOUND (frequency) of the F1 cars and that is -at least in principle- very easy to translate to the actual revs.
Edmund
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Frequency has been used a long time my modelers to measure rpm. Because of the doppler effect it's easiest when you are at the center of the circle. However, you can measure both the speed and rpm. See http://www.supercoolprops.com/articles/dopplerwind_correction.php and other articles on the same site. We have used sound analysis to estimate rpm from youtube videos, but most don't have a good enough sound track. If it's your vehicle, modern data loggers work a lot better.
Efficiency from the fuel isn't really a concern for these small power plants. If it is, you need to get a lot fancier with the burner design. See the patents at http://www.cyclonepower.com/patent.html for the most modern flash steam power plant design. A simplification of some of these ideas would work in models. You need to have clear goals. Mine have been to set various speed records. I have been on the team that has held the world gasoline powered RC boat record since 2004 and the full size electric boat world speed record since 2008. Those are relatively easy goals compared with producing an engine to compete with modern IC automobile engines.
At this point it would be interesting to set an RC model steam powered speed record. I wouldn't be happy if it wasn't over 100 mph (160 kph). That takes around a 1.8 cubic inch (30 cc) engine producing 5 or 6 hp (3700 to 4500 watts). I don't care how much fuel and water it takes except as how it relates to this power. That would only take a brake mean effective pressure of around 100 psi (7 Bar). What's really important for RC vehicles is good control. Modern radios are nearly bulletproof. However, no one has made a high power, controllable, model steam engine that I know of.
Lohring Miller
PS Steam design for automotive power plants died in the Great Depression. English speaking engineers of that era grew up with British Engineering Units as did I in the late 1950s and early 1960s. Those are the units their data is in. Many of my measuring tools as well as my lathe and milling machine are from the same era. Metric units are a lot easier and modern tools can work in either.
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Has anyone looked at the numbers for fuel and water output from the pump. I may be wrong, but I get around 16 cubic inches per minute of fuel and 30 cubic inches per minute of water at 1600 pump rpm. For the fuel that gives around 175 horse power of heat at 17,900 BTU per pound of fuel. That's reasonable since the power plant can't be more than 5 to 10% efficient at converting the fuel to shaft power. At 5% that would be 8 3/4 hp.
However, I get 1 pound per minute or 60 pounds per hour for the water. Even really efficient engines use 10 pounds of water per hour per horsepower. It's more common to use 20 to 30 pounds per horsepower per hour. Did I screw up my calculations or is there a reason for this discrepancy? From my experience with a 110 mph RC hydro that ran a dyno tested IC engine, I would expect that it takes around 5 or 6 hp to go 120 mph.
Lohring Miller
Hi Lohring,
Like the Hydro record chasers I have never been concerned with fuel consumption other than trying to burn as much fuel as I can and getting as much heat from the fuel as possible.
I don't disagree with your figures although they don't correspond exactly as per K.N. Harris's in his book on Stationary and marine Steam engines but near enough, these figures are for Saturated steam not high pressure flash steam.
I have done a little Calc using H.P. figures as P.L.A.N divided by 33000 which is how I have always calculated H.P. but as I don't know what pressure my Steam plant works at I have used theoretical figure on Steam pressure based on what the record chasers can achieve which can be as high as 3000P.S.I.
I have used 1000 P.S.I. and from the Calcs it comes out at 14.06 H.P.
500P.S.I. would be 7 H.P. and 2000P.S.I would be 28.12 H.P.
My pumps work at 6/1 from the main shaft so at 15000 rpm it will be 2,500 strokes per min.
The water pump at 1/4" dia x 3/8" stroke delivers 45 cub " /min
The fuel pump at 3/16" dia x 3/8" stroke delivers 25.46 cub"/ min.
These figures are theoretical as in the water the revs will be lower, I think the only way to get accurate figures on pressure and steam temperature is to have gauges to monitor them on bench testing.
I can tell you that I ruined a 300 P.S.I. gauge on the steam line in one of my efforts to find out the pressure, due to the modulating pressure as the valve opened and shut it blew the gauge apart , so I very quickly abandoned the idea of measuring the pressure but I am sure that there must be more reliable methods of measuring.
So, some food for thought.
George.
HAPPY NEW YEAR TO ALL, BEST WISHES FOR 2014
George,
There will be some decrease in actual initial pressure as steam enters the cylinder......very quickly. Unless the passages are really big, there will be a significant amount of wire drawing at the rpms you speak of...I suspect a very large valve is required to minimize that pressure drop across the valve.
Dave
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Edmond,
If I can refer you back to my post No 53 you will note that I say that I try to get as much heat from the fuel as possible
which also means that I am looking for max efficiency so you can disagree as much as you like but these burners are very efficient and to compare these engines and generators to F1 cars is quite ridiculous in the amount of money involved and is thrown into F1 engines to a guy working in a small workshop but can still get a Hydro to do 127 M.P.H.
Lohring.
Having had some words with the current record holder he like me doesn't know the pressure on the engine when it's at full bore other than to say that the steam pipe to the engine burns red, this I can confirm as mine also burns red from the generator to the engine, and as a guesstimate near 1000 p.s.i. is not far off
I shall refrain from printing his comments on your statement that 100p.s.i. will achieve 100 m.p.h.+ other than if 100 p.s.i is your goal, best of luck and we look forward to your efforts.
Dave.
The timing cycle of my engine and others is that the cam engages 4Deg before T.D.C and closes 50 deg after T.D.C.
and the valve head is 5/16" dia with a 1/32" lift.
There will be a very marginal pressure drop but don't forget that when the valve is closed for the remaining 306 deg the fuel and water pumps are still pumping and the engine awaits the next slug of flashsteam to hit the C/Head.
The burners are designed to take in air as the boat moves forward so the faster it goes it takes in more air and fuel creating a hotter burn, more pressure and more steam.
Now I have no wish to down cry anybody's thoughts but I feel that until you have built and tried a flashsteam plant you will realise the pressures and heat involved to get in excess of 120 m.p.h.
George.
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George
Please forgive me. I meant no disrespect of denouncement in the least!....I love reading and learning this build. It's fascinating!.... Please accept my apology if I came across in a negative manner, as it wasn't my intent at all. :praise2:
3000 PSI!......Yikes!...
Dave
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George
Please forgive me. I meant no disrespect of denouncement in the least!....I love reading and learning this build. It's fascinating!.... Please accept my apology if I came across in a negative manner, as it wasn't my intent at all. :praise2:
3000 PSI!......Yikes!...
Dave
Hi Dave ,
No need to apologise, no offense taken.
3000 psi is a figure that is very much on the high side and was recorded while experimenting with a steam turbine, not by me I hastily add, 1000p.s.i. is nearer the mark .
George.
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Hi Lohring,
I understand that data loggers will work perfectly for rpm measurement but if you don't have one..
An -on board- sound recorder might do the trick as well.
You clearly accomplished your goals by setting records, you already earned my respect for doing that.
My goal is or at least I am aiming to make a engine which is as fuel efficient as a a modern IC engine and is not too big or too expensive for mobile applications.
So I have a lot to think about. I might have seen something like that cyclone power thing in the past but I haven't seen any figures about efficiency. I did not yet read the whole part in detail because it is not my first priority.
My biggest problem now is how to make a speed/power control. Electronic control can help a lot but I have no knowledge to build that, pure mechanical isn't so easy either. At least I haven't found
a simple solution for that.
I am truly impressed by the amount of power your and other flash engines produce and although the poppet valve system works obviously very well for high power output and small dimensions, I am looking for another solution because I am afraid of problems if I want to scale up such an engine.
That is one reason why I want to “flash” into the cylinder and not before.
The dimensions wow that is something else, even one HP is not the same as “our” or general accepted -pk- which means hp too :-). ( I am not saying -pk- is a good dimension, it should be Watt)
It doesn't make life easier, and when I am looking at a English steam table, all I see is a bunch of numbers that doesn't mean anything to me. I have to recalculate to know what it actually means.
I am looking forward to your new records. ( and speed control )
Edmund
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Edmond,
If I can refer you back to my post No 53 you will note that I say that I try to get as much heat from the fuel as possible
which also means that I am looking for max efficiency so you can disagree as much as you like but these burners are very efficient and to compare these engines and generators to F1 cars is quite ridiculous in the amount of money involved and is thrown into F1 engines to a guy working in a small workshop but can still get a Hydro to do 127 M.P.H.
Lohring.
Having had some words with the current record holder he like me doesn't know the pressure on the engine when it's at full bore other than to say that the steam pipe to the engine burns red, this I can confirm as mine also burns red from the generator to the engine, and as a guesstimate near 1000 p.s.i. is not far off
I shall refrain from printing his comments on your statement that 100p.s.i. will achieve 100 m.p.h.+ other than if 100 p.s.i is your goal, best of luck and we look forward to your efforts.
Dave.
The timing cycle of my engine and others is that the cam engages 4Deg before T.D.C and closes 50 deg after T.D.C.
and the valve head is 5/16" dia with a 1/32" lift.
There will be a very marginal pressure drop but don't forget that when the valve is closed for the remaining 306 deg the fuel and water pumps are still pumping and the engine awaits the next slug of flashsteam to hit the C/Head.
The burners are designed to take in air as the boat moves forward so the faster it goes it takes in more air and fuel creating a hotter burn, more pressure and more steam.
Now I have no wish to down cry anybody's thoughts but I feel that until you have built and tried a flashsteam plant you will realise the pressures and heat involved to get in excess of 120 m.p.h.
George.
Hi George,
Sorry you are absolutely right, it was my own bias what made me read it wrong.
As I said before I did not yet calculate much in terms of efficiency but just by looking at the design
of the heater : cold air is used for oxygen, that alone made me wonder if you couldn't get more
heat in using waste heat to pre heat the “fresh” air/oxygen.
Variating the amount of air what I will do in my engine isn't necessarily because you only operate at full speed. However if too much is air sucked in then heat is wasted. If not enough oxygen is available the the highest possible temperature won't be reached either.
Again I don't know if it is worth the trouble but these kind of things come to my mind looking at those beautiful toys.
I am not comparing these engines with formula 1 cars, all I said that AFAIK commentators use the
sound of the engines to determine the rpm, something which can be done with these models too I think.
As I said to Lohring, I am very impressed by the performances of these engines, (and the people who makes them) don't get me wrong about that.
Edmund
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Yes It is amazing the amount of variables conspiring to prevent any of this to work....but it is evident that George has certainly figured it out! :praise2:
Thanks for sharing all this George!....it's a lot of work to post all this and answer questions...please proceed! :ThumbsUp:
Dave
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George, I think you misunderstood my 100 psi statement. That was for brake MEAN effective pressure and can be calculated for a two stroke from BHP = BMEP x Displ. x RPM / 396,000 where displacement is in cubic inches. For a 30 cc engine (1.8cubic inches) the power with a BMEP of 100 psi would be 100 x 1.8 x 10000/ 396000 = 4.5 hp, so the needed BMEP will be a little more, maybe 130 psi. See many on line references or derive it from the equation posted below.
The reason the mean pressure is so much lower is that the steam expands from its peak pressure of maybe 1000 psi down to atmospheric pressure at the exhaust. If you have a late cutoff the mean pressure will be closer to the peak pressure but the efficiency will be very poor. A very short admission gives high cycle efficiency. There are also pressure and temperature losses in the flow through the valve so the cylinder pressure won't equal the boiler pressure. The compression work in a uniflow engine deducts a lot of work from the expansion work as shown on the
PV graph. (http://www.flickr.com/photos/9511023@N03/6782131921/) That doesn't make it less efficient, it just lowers the work per cycle.
Model data loggers are very affordable, but using them takes practice. We used the Eagle Tree (http://www.eagletreesystems.com/} on both models and full size boats. It would take special instrumentation to read steam pressures, but speed, temperature (with the thermocouple attachment) , and rpm are straightforward.
Lohring Miller
Power
BHP = PLAN/33,000
P is brake mean effective pressure, in PSI
L is piston stroke, in feet
A is the area of one piston, in square inches
N is the number of power strokes per minute
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Hi Lohring,
Yes you are quite correct I misunderstand your 100 psi statement, I also for some reason in my calcs divided N x 2 why I don't know., but now that you have pointed out my mistake it makes it even more frightening as at 15000 rpm on the bench gives a theoretical 28 H.P. and a possible 11000 rpm in the water gives 20.6 H.P.
The 11000 rpm was recorded in a water tank so it's nearer the mark.
You have so very much more experience than I have with your I.C. and full size engines and friends with a common goal around you, where as I have ploughed a lonely road with nobody in Scotland working with flashsteam, which is why I have copied R.Kirtley and P.Windross steam plants but not wanting to go so fast and the deep "V" boat with submerged prop is quite a bit slower and as I was not concerned with weight it also helped, my boat all up without water or fuel is 25 lbs, the record breaker are restricted to 14 lbs dry weight.
I have never felt such exhilaration when after the years taken to build the plant when on the first pull of the starting cord it fired into life, you think that your I.C. engines are noisy, just wait until you fire a flashsteam Uniflow poppet valve engine ( AWESOME ) make sure that you have a silencer fitted.
Do you scratch build your own engines ?
George.
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George, don't apologize. As you said above there's no substitute for actually building a flash steam plant, and I'm still in the BS stage. I'm planning to copy as much as I can from everyone who has preceded me in flash steam. The more I read on the Cyclone site, the more I learn. I just need to pare down the complexity to come up with something I can build. You and the other model flash steam builders have been doing that for quite a while.
The last complete engine I built was in high school over 50 years ago. It was a 10 cc two stroke racing engine. From years of learning things the hard way I now never build something I can buy that does the job. There are very inexpensive 23 to 31 cc two stroke crankcases, crankshafts, connecting rods, and all the fasteners, bearings, and other parts are readily available. We have run these parts to 8 hp and 25,000 rpm. I plan to build the steam cylinder and piston along with the pump and valve systems. Of course the burners and boiler systems need to be custom built. I think just building those pieces will be plenty of a challenge.
Lohring Miller
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I came across two ideas that may improve the power of a flash steam power plant. The first is to wrap a couple of coils around the exhaust ports to help preheat the water on the way to the boiler. The other is to use a jet condenser to lower the exhaust pressure. This would work well in a boat with lots of water available. See the picture below.
Lohring Miller
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I came across two ideas that may improve the power of a flash steam power plant. The first is to wrap a couple of coils around the exhaust ports to help preheat the water on the way to the boiler. The other is to use a jet condenser to lower the exhaust pressure. This would work well in a boat with lots of water available. See the picture below.
Lohring Miller
Hi Lohring.
I see no problem in using I.C. engine parts but would have second thoughts on using Cylinder heads and pistons as I think that the fierce heat of the steam coil will effect them, that is if you make and use a similar coil and burners.
I see no need for water coils wrapped around the exhaust port to pre-heat the water before the coil, don't forget that the water pipe enters the furnace and travels about 24 ft getting hotter and hotter before flashing in the very hottest part of the coil which is about 4" from the front face.
I have absolutely no experience in a condenser in the exhaust and if there was an advantage to be had the guys that are chasing records would have tried it, plus there is very little room on board for all of the extras that you are considering.
Don't let me dampen your enthusiasm but I think that you are looking for ideas that are going to be very difficult to install and keep the weight down.
Best of luck.
George.
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I'm in the process of reorganizing my shop around a new to me lathe so the steam project is going to be all talk for a while. I agree simpler is always better. I'll see if I can put together some preliminary drawings. Pump control, if needed, could be as simple as a rod that holds the intake check ball off its seat. I think the Honda variable valve system for both opening and cutoff control would be as easy as an external throttle valve. I'm working on understanding John Wetz boiler control system (http://kimmelsteam.com/wetz.html). He ran really simple and crude monotube boilers with it. The goal is a power plant that's buildable with as good control as a racing IC engine.
Lohring Miller
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Hi Guy's,
I like to start building something and keep the costs limited as possible.
Does anyone know if it is possible to build a piston/cylinder for the pump section which can be lubricated with water cq doesn't need lubrication?
Any suggestion what materials can be used for that?
Thanks
Edmund
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As far as I can see, none of the pumps are lubricated. It's the engine cylinder that gets the steam lube. Teflon packing in the pumps shouldn't need lubrication.
Lohring Miller
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Hi Guy's,
I like to start building something and keep the costs limited as possible.
Does anyone know if it is possible to build a piston/cylinder for the pump section which can be lubricated with water cq doesn't need lubrication?
Any suggestion what materials can be used for that?
Thanks
Edmund
Edmund,
There is enough information in the Model Engineer Mag article by R.Kirtley on his PISCES 11 steam plant to make pumps that I e-mailed to you and Lohring.
R.K's pumps are made from Aluminium with stainless steel rams, the water pump has a Silicone "O" ring at the end and the fuel Pump that uses Kerosene ( Paraffin to the U.K. ) uses a black Nirile ring as the Kero melts Silicone.
My pumps are made from a solid block of Ali but the pump bores are sleeved with Brass, rams are Stainless steel and have "O" rings at the end as shown at the beginning of this thread which if you look at you will see a small C/Sunk hole above each ram which takes an occasional drop of oil.
George.
Edit,
I should have added that pumps need not be made in Aluminium but can be made from stock round brass.
The operating principle is the same with a St/St ball on the suction side and delivery side.
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looking forward to seeing some metal cut :popcorn: :popcorn: :popcorn:
cheers
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George,
Thanks again for all information you send me.
What I am looking for is something like an (old type) diesel fuel pump with a plunger without piston rings or (silicone) sealing. Preventing oil would help a lot since I want to make it a closed circuit, condensing the exhaust steam, heat and use it again for the next cycle.
If it must be lubricated I need an oil separator and a lot additional stuff that comes with that.
What I have in mind is an engine size from anything between 100 to 500cc per rotor (Cylinder) but I haven't found a better -know how- source for flash steam engines then this one.
Edmund
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Edmund,
I think that you are worrying too much about oil being carried over into the steam, you can make a pump without the "O" ring but you will eventually get water egress out of the pump barrel and I would suggest that you do put in an "O" ring but don't oil lubricate the ram.
I have made many pumps and don't recall any oil being carried over, in fact I forget to lubricate the ram with no adverse effect.
Here are a few pics of a Stuart Launch engine that I have recently built with an engine driven pump but you can easily make it an electrical drive if wished.
George.
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George - Stunning work is in evidence on this thread.
As a steam neophyte I have a very long way to go, but flash steam does interest me I admit. I have the Westbury book, and have the other, newer book on order.
It strikes me that your thread here is another such rare and valuable ressource on the subject, and it will be most helpful to me when I start tinkering with this aspect of things...
gary
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Hi Gary,
Like you when I started I knew nothing about Flashsteasm and as there was nobody else in Scotland interested in the subject I started from scratch.
As you may know the flash steam enthusiasts are all down south of Hadrian's wall and are all racing round the pole at ridiculous speeds, however I didn't want to be involved in long trips South or getting kitted up with waders and helpers, I wanted to be able to sale from the pond side and to control with rudder and a stop valve.
The 2- most informative books are Westbury's but the best is "Experimental Flashsteam by Benson and Rayman"
If you look up on the Net another source of info is "On the Wire `" so have a look there. I have a copy of an article by Bob Kirtley who held the world record of 120 m.p.h. at one time and he published the article and I can mail it to you for reference.
Now I don't know all the answers but when you get started if I can help I would be please to do so.
George.
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Many thanks George.
I live well South of Hadrian's Wall but am actually from just North of it (Dumfries). I lived in your city for seven years too, back in the 80's.
Flash steam seems like a very arcane world to me, with little bits of knowledge hidden away in secret corners of the world (and internet).
I tend to have far too many projects on the go, and some of them sit untouched for years while others get full attention, so it's very possible that I will start experimenting with flash steam in the foreseeable future and then go quiet on the subject as I focus on something else, like a mill engine or whatever. Too many ideas, not enough spare time.
However, I have just bought an antique brass paraffin/petrol blowlamp on ebay to see if I can press it into service as a burner (I could have bought a new gas one but an old shiny brass one complete with embossed lettering on the tank seems like more fun). I have the Westbury book and the Benson and Rayman one is in the post to me. So let's see...
Your offer of advice is much appreciated. I won't hound you but I do in fact have a couple of questions for you at this stage if you don't mind:
- Is the vintage liquid fuelled blowtorch likely to be any good as a burner (it was only 16 quid...)? Westbury says a single flame isn't optimal but that people do use it, and I'm wondering if it might be adapted or augmented in some way.
- What is your view on copper vs stainless steel tubing for the boiler?
- Is there any kind of pump that can be pressurised by hand that is powerful enough to push water through a clack valve into the boiler while it is running an engine? I'm wondering about a primus stove type of pump but have no idea if that would generate anything like enough pressure. Or maybe some kind of hydraulic water pump combined with a pressure vessel to avoid having to pump non-stop... I am not averse to things electrical but I prefer to avoid them in steam applications if I can. I'm also aware that the pump can be driven by the engine once it gets going but that's quite far down the line for me. Any plant I make will be stationary, not on a boat, so it wouldn't matter if I had to hand pump it. I have a feeling that Westbury goes into this to some extent but I haven't read that far yet.
Your thoughts on these matters would be appreciated. No rush, and feel free to just tell me to go and read the books or this thread more attentively if you like! :)
Best wishes,
gary
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*PS - I just looked ahead in the Wesbury book and on p 66 and p 67 he appears to answer my question about a hand-pumped pressurised feedwater system. I'd still be interested in your thoughts, of course, but no rush.
gary
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The hand pump is only for priming at the start, as soon as the engine is running the pump on the engine delivers water at a set rate to keep the engine running.
I used to run tethered flash steam hydros but the light weight class 8lbs dry weight the engine and boiler etc are a smaller version of Bob Kirtleys steam plant. I broke Frank Juttons B class record a lwhile ago and I have his B class boat TNT.
Forget the Westbury flash steam book it is dated you need a copy of Experimental Flash Steam Benson and Rayman.
You can use either copper or stainless steel for boilers for the fast flash steamers stainless has been used in all the modern hydroplanes.
Alan Raymsn also wrote a booklet "High speed marine steam engine" based on a Stuart Turner 10v cylinder casting it a good source of info on slower flash steam plants I have copper flash steam boiler in a straight runner that gets up and planes with Raymsns engine.
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Thanks for the advice, Old School.
Funnily enough I just watched a youtube video on Bob Kirtley's plant, and very educational it was too.
I ordered the Benson and Rayman book yesterday - looking forward to it.
Re the hand pump - I was wondering about a hand-pumped pressure vessel that would feed the boiler over a period of time, rather than a simple hand pump, in lieu of an engine-driven pump. Westbury seems to be saying that's an option, though I admit I need to look more closely...
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Hi Gary, Flash steam is indeed an interesting area for your experiments. I have had the Bensen and Rayman book on my shelves for so long I can no longer remember where I bought it, but it only mentions first published in 1973 in the flyleaf. I highly recommend it to you.
I can help with a few principals but I will leave it to those more experienced with the practicalities to talk about the practical issues of which I am sure there are many.
So a few principals. You can definitely make a hand pumped flash steam unit for your stationary engine, and you will find that blowlamp quite satisfactory. Remember Bensen and Rayman were into really high performance, but in their book, they also cover a more moderate plant for a non-racing model.
Think of a flash boiler as a boiler with a really large heat transfer area in the form of a single long water tube, and a very small water capacity. You pump in water at one end and it comes out as steam the other. The division between the water boiling section and the superheater section is not clear, and indeed varies with varying operating adjustments.
Now, that boiler configuration means that you need a more steady flow water input than a standard boiler; an initial fill then operate until fuel runs out, preferably before water runs out, is not practical. You have to maintain the water injection while the burner and engine run.
There was an excellent series of articles in ME many years ago on flash steam for a railway locomotive. Someone with a more organised collection than I might be able to find the reference for you. The author actually included a small pressure tank which he half filled with water to even out the flow, and a similar arrangement would allow you to hand pump the system, though you would still have to be pretty consistent with the pumping. The tank goes on the inlet side of the coiled tube.
The length of the tube means there is quite a pressure drop along the tube, so the water pressure required is much higher than what the engine sees. However, a lightly loaded engine does not need much pressure at the engine end, so it should not be too high at the inlet.
Remember, when water boils, it’s volume expands about 1000 times. You can get the exact figure from the steam tables if you make an estimate of the outlet pressure and temperature, but you don’t have to pump a big volume of water. And it takes much less work to pump water than it does to compress an equal mass of steam. It’s not like running your steam engine on air with a bike pump.
So your first question, about pumping against the pressure.
Let’s assume you need 50 psi at the inlet to the tube, like your present boiler. If your engine has a piston area of one square inch it will be 1.13 sq. in. diameter, and the force on the piston will be 50 lbf. Possible to pump with a similar diameter piston, but very hard work. But you don’t need to have a similar diameter piston on your water pump. If you have say 1/4 inch diameter water pump piston, the area is only 0.05 sq. in. and the force required is only 50 x 0.05 = 2.5 lbf. Easy! And you don’t have to keep up with the engine speed, you only need 1/1000 of the steam volume. So even allowing for the smaller volume per stroke, you should be able to keep up with a moderate engine speed. But you will soon work out why the normal is an engine driven pump. So building that is part of the challenge. I suspect that bought gears is the way to go for both you and I.
The Bensen and Rayman talk about the use of SS tubes and the length of tube required, so I will leave you to read the detail, but their early experiments were all with copper tube. Their investigation of SS tubes was because they were chasing extremely high temperatures and pressures in their quest for performance. Again a moderate plant should be OK with copper. I will be interested to hear what those who have run racing hydroplanes have experienced.
I suggest one of the practical issues to come to terms with is how to start the plant. Going from atmospheric pressure and temperature to running continuously involves a sudden pressure rise once the water starts boiling, and you don’t want to push too much water direct to the engine if boiling starts part way along your tube. Again, this is an area I am keen to hear about from those who have the practical experience.
Once the plant is running, the back pressure from the steam will compress the air above the water in that tank I mentioned. The water level will fall as the steam is consumed by the engine, and you need to get pumping to keep the level in range. Obviously a level glass is necessary. And it is a pressure vessel so needs to be designed as such, and equipped with a safety valve. If you pump intermittently, the pressure and hence engine speed, will vary, but I assume this will be acceptable for you, and a larger vessel than might be practical for a locomotive or boat will help with the hand pumping. After a few runs you will have a better idea of how much air to leave in the tank before you first tighten the plug. As the pressure rises, you have to pump more water to maintain the level, and do more pumping to replace that consumed.
Overall pressure and speed control is a heat balance. The burner produces heat which will partly go up the chimney, and partly evaporate the water. If the engine does not pass all that steam, the pressure will rise and the engine speed will increase. Be ready to pull the burner out! It needs to be easy to remove until you have some running experience. And it is a good idea to start with a smaller or gentler burner. Even start with your silver soldering burners for additional control until you feel comfortable with the system. Some of those Bensen and Rayman used must have been frightening to be near. As part of their optimisation they used figure 8 coils with separate burners in each of the loops, just to get in more heat. Anything in the quest for more speed. Needless to say their engines were pretty sophisticated as well.
I am sure you will have more questions, but that should give you some of the basic theory as a start. A great project to be thinking about. I am not sure where you will decide to go from here, if you decide to do some experimenting, you may like to start a new thread of your own rather than resurrecting this one. But really good to see some of those with practical experience in the area also coming in, and an interesting topic revived. I suspect you will have quite a few following if you decide to carry it further.
MJM460
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Wow... what an amazing response, MJM460!
A combination of theoretical treatise and practical manual in a single post. It pretty much answers all my questions at this stage, and gives me a great deal to take forward if I decide to pursue this past buying the blowlamp on ebay. :)
Assuming I do, I will surely start a new thread on the subject.
Only one part of your post had me a bit puzzled - it's where you say
'Once the plant is running, the back pressure from the steam will compress the air above the water in that tank I mentioned'
I had assumed that there would be a check valve between the water source and the reservoir. Am I to understand that this isn't needed (i.e. that the system will balance itself as long as the reservoir is a proper pressure vessel) and that a tap or globe valve of some kind will suffice?
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Hi Gary, thank you. I have tried to point to some of the practical issues, but I emphasise that I don’t have some of the important answers, particularly on the best way to start the system. This is where it is especially important to get the benefit of practical experience. Do you start heating the tube, then start pumping in water, or is it better to pump in some water, then light the burner? I am still hoping that Old School and KBC might share some there experience in this and other areas of the flash steam plant. They are the experts.
Sorry to have confused you with that sentence. I see the accumulator tank which is pressurised with the system in operation as separate from an atmospheric pressure reservoir which would be on the inlet side of the pump. So two vessels in the system as I remember it from the articles. It looked like a well thought out system. A piston pump includes a check valve as part of its basic function so pressure should not go back to the reservoir. Sometimes in this sort of situation, two check valves in series are recommended. I have not assumed a check valve or shut off valve after the accumulator tank, but it may be a good idea, or even necessary in practice. That would require a slightly different start up procedure.
When the system is at atmospheric temperature and pressure, the pressure is the same all the way through. I think that if you start pumping in some water, if the engine is in a position where the inlet valve is not open, or you hold the flywheel, you will start to compress the air trapped in the accumulator and in the long coiled tube. When you get to about 15 psig, the volume of the air will be reduced by approximately half. If you then light the burner, the pressure will increase throughout, forcing some of the water back from the tube into the vessel, so the pressure stays equal everywhere. The engine will probably run on this pressure, but it’s all about how you juggle the water input and heat input, to get it running smoothly without filling the engine with water or getting excessive pressure. So you see the problems. I am not sure whether the water starts boiling very slowly, or quickly flashes to steam over a length of the tube. The latter will result in severe pressure spikes, and is best avoided. Tapping into existing knowledge on how to deal with these problems is a better idea than trying it out without some knowledge of what might happen. Perhaps I am over thinking it, but of course I am used to working out these procedures for full size systems, where the dangers are real. It tends to make me cautious. Startup is always more tricky than steady running.
Once the system is running, there will be a pressure loss along the tube so the pressure at the pump and accumulator will be somewhat higher than the pressure at the engine inlet, and you will have to pump to maintain a level in the accumulator to replace the water that is turned to steam and passes through the engine.
I hope that makes it clearer.
MJM460
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I have no experience of using a reservoir my plant the water was pumped directly into the coil. On the hydroplanes the boiler was heated to dull read by the 3 blow lamps, the the water was pumped in steam was generated instantly the pumped would almost look up, the the engine was started with a pull cord.
Somewhere on the internet is a simple flash steam plant for an oscillating steam engine using a small coil a pencil type gas blow lamp and a plastic pop bottle with water in it pressurised with air. My brother has built one of these and it works. Imwill get the details when I get back home racing tether cars in Poland this weekend.
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I will get the details when I get back home racing tether cars in Poland this weekend.
Although I do find the original subject here interesting .... any chance of some pictures (perhaps in a separate thread) ?
Best wishes
Per
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Guys -
your input is greatly appreciated. Lots of knowledgeable people offering friendly advice is the truly great thing about this forum.
However, I do not wish to dilute George's impressive thread any further with my rookie questions, so what I propose is this: when the antique blowlamp arrives (hopefully early next week) I shall - as a couple of you have suggested - kick off a new thread with a photo of it (and maybe a couple of other pics too) along with a post in which I will try to respond to the good stuff you have posted above.
Hope that makes sense, and look forward to catching up with you in a few days.
Thank you!
:ThumbsUp: :ThumbsUp: :ThumbsUp:
gary
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Hi Gary, that sounds like a good plan. I look forward to your new thread appearing so the discussion can continue.
MJM460
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:ThumbsUp: :ThumbsUp: :ThumbsUp: :ThumbsUp:
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Well, I didn't wait for the blowlamp! New thread now underway...
http://www.modelenginemaker.com/index.php?topic=9294.new#new (http://www.modelenginemaker.com/index.php?topic=9294.new#new)
Hopefully see you over there.
Thank you for your comments up to this point.
George - thanks for allowing me to briefly piggyback on your topic.
gary