# Uniflow design theory



## Anatol (Aug 8, 2020)

Hello Everyone
I have been thinking a lot about uniflow engines and I have some questions. In the literature, it is argued that uniflow engines derive efficiency from the fact that the exhaust exits at BCD and so does not cool the cylinder head/inlet ports. 
But - whatever 'exhaust' is not exhausted close to BDC is recompressed, and by the time the piston is at TDC, the pressure is/can be greater than supply steam pressure, which means that when the inlet valve opens, compressed exhaust steam is pushed back down the inlet passage, until piston has dropped far enough to draw the exhaust back in to the cylinder and then be followed by fresh steam.  this is clearly inefficient in two ways - recompressing exhaust takes energy, and the delay in getting fresh stream also seems undesirable. 
Is my understanding correct? 
I know some Uniflow engines have/had relief valves in the cylinder head - this would allow the remaining compressed exhaust gas to be exhausted (but only after it had been compressed and at the cost of cooling the head (?). 
What kind of valves were these - passive spring loaded or cam actuated...?
I've seen some double acting single cylinder designs - are these preferable to single acting types?
thanks for any input!


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## deverett (Aug 8, 2020)

Have a look at Uniflow steam engine - Wikipedia for an explanation.  Might not answer all your questions, but may at least answer some.

Dave
The Emerald Isle


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## Anatol (Aug 8, 2020)

Thanks Dave - I've been to the wikipedia page, and other sources. 

"The steam remaining within the cylinder after the exhaust ports are closed is trapped, and this trapped steam is compressed by the returning piston. This is thermodynamically desirable as it preheats the hot end of the cylinder before the admission of steam. However, the risk of excessive compression often results in small auxiliary exhaust ports being included at the cylinder heads."

 "This is thermodynamically desirable" I'm dubious about this, the devil, as always, in in the details, and I'm not a thermodynamics grad.  In any case,  "the risk of excessive compression" is not just an explosion risk, its also - it seems also highly ineffficient, but the addition of " small auxiliary exhaust ports"  seems to admit defeat. 

"To gain the maximum potential work from the engine a high reciprocation rate is required, typically 80% faster than a double-acting counterflow type engine. This causes the opening times of the inlet valves to be very short, putting great strain on a delicate mechanical part" This is also a concern. Though IC poppet valves are now highly developed.


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## Asm109 (Aug 8, 2020)

Your first concern about recompressed pressure being higher than incoming steam is baseless. It would be a violation of the second law of thermo for it to happen.
Hot High pressure steam is admitted to cylinder.  Steam is expanded, doing work and cools down. Now cool steam is vented at bottom. Now a small portion of the cool steam is trapped and compressed, heating up and requiring some work ( inefficiency) on it.  You started with a small volume of hot high pressure steam. Through some away and recompressed, you cannot get back up to where you started.


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## Charles Lamont (Aug 8, 2020)

I have just had a look at that Wikipedia article. It needs work. The parts you are quoting contain no references. Some of it is just wrong.

The inlet valve gear of a uniflow engine is no different from any other trip gear, except that it is often working a double-beat poppet valve, which will likely be lighter and subject to less friction than a comparable Corliss valve. It is true that while any engine is likely to be thermodynamically more efficient at a high piston speed, trip gear is not suitable for very high speeds.

Compared with a simple slide-valve engine running at the same speed, a uniflow engine needs a bigger cylinder swept volume to produce the same power output, but it will do so using less steam. It will be more efficient. 

The relief valves may be primarily for clearing condensate during warm-up - to avoid a hydraulic lock.

Asm109 - Nice try but no cigar. It is possible to have excessive compression. Typically a uniflow's inlet valve will close at say 5% of piston stroke, but the clearance volume the exhaust steam is compressed into at dead centre is far less. This can be accommodated by designing a sufficiently large clearance volume. However, providing auxilliary exhaust valves allows a smaller quantity of exhuast steam to be compressed into a smaller clearance volume, with less negative work done on it. This improves thermodynamic efficiency at the expense of greater mechanical complexity.


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## Anatol (Aug 9, 2020)

Hi Asm
with respect, I am not persuaded. Forget the steam for a minute. Imagine cylinder at BDC, full of air at 1 atmosphere pressure. Now compress that volume, from, say 10 cu in to 1 cu in, then to 1/10th cu in, at some point you'll get a pressure higher than supply steam pressure, regardless of temperature. 
That recompression is doing work, taking energy from the engine output. Of course, compressing poppet valve return springs is also doing work and taking energy. I don't know the relative scale of the losses.


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## Anatol (Aug 9, 2020)

Charles Lamont - I'd drafted the revised reply but did not realise I'd omitted to send it   
Thanks for your reply. 
"double-beat poppet valve" - Can you elaborate? I looked at the wikipedia page but it was not that helpful. 
"Compared with a simple slide-valve engine running at the same speed, a uniflow engine needs a bigger cylinder swept volume to produce the same power output, but it will do so using less steam. It will be more efficient."

thankyou, very informative, (cylinder swept volume = (roughly) stroke?)

"The relief valves may be primarily for clearing condensate during warm-up - to avoid a hydraulic lock."
so are you saying that the energy lost to recomperession is negligible? 

"Typically a uniflow's inlet valve will close at say 5% of piston stroke"
wpiudl it open before TDC? If so, would the recompressed exhaust effectively prevent inflow of supply steam till piston moved down?

"This can be accommodated by designing a sufficiently large clearance volume"
this being space in cylinder head where piston does not go? Hoe large would a "sufficiently large clearance volume" be, as percentage of total cylinder volume? 5%? 10%?

thanks!


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## Charles Lamont (Aug 9, 2020)

Anatol

You are right that the compression part of the cycle requires work, but that work brings the exhaust steam up to a state closer to that in the steam chest, so that when the inlet valve there is no sudden inrush of steam., which would be wasteful.

'Convincing' you qualitatively may be difficult. You are unlikely to grasp this stuff properly without some study of thermodynamics.

Cylinder swept volume is the area of the piston times the stroke.

No, I am saying I think the relief valves you say you have seen probably don't serve the purpose you think they do.

Yes the inlet valve starts to open before dead center, to ensure that it is sufficiently widely open to admit the necessary amount of steam freely without loss through "wire drawing" when the piston starts to gather speed.

Size of clearance volume, I don't know off the top of my head, and I need to get some breakfast, but nearer 5%..

Haven't we already been through all this at: Designing steam engines ?


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## Richard Hed (Aug 9, 2020)

Anatol said:


> Hello Everyone
> I have been thinking a lot about uniflow engines and I have some questions. In the literature, it is argued that uniflow engines derive efficiency from the fact that the exhaust exits at BCD and so does not cool the cylinder head/inlet ports.
> But - whatever 'exhaust' is not exhausted close to BDC is recompressed, and by the time the piston is at TDC, the pressure is/can be greater than supply steam pressure, which means that when the inlet valve opens, compressed exhaust steam is pushed back down the inlet passage, until piston has dropped far enough to draw the exhaust back in to the cylinder and then be followed by fresh steam.  this is clearly inefficient in two ways - recompressing exhaust takes energy, and the delay in getting fresh stream also seems undesirable.
> Is my understanding correct?
> ...


that is not possible.  To have a return pressure greater than the steam pressure would be going against the law of conservation of energy.  (caveats with that of course.)  If you couldn't exhaust at least 90% of the used steam, my guess, is that any machine would not work at all or at least very poorly.  However, examine the exhaust pports of other types of engines, particularly the slide valve, on so many of the little engines:  the steam enters the slide and the valve moves in such a way that it goes into the cylinder body thru a tiny orifice almost at the center of the part!  (This is really a poor design.) then the steam follows a pathway to the end of that body to the inside top (or bottom) of the actual cylinder where the piston resides.  The steam pushes the piston.  When the piston reaches near or at BDC, all that steam, that is, the same amount that went in weight wise, has to return thru the same pathway that allowed it in.  Now that pathway has not enlarged but the volume of steam is now about 10 or more times as large under lower pressure--how does it escape quickly enough to not cause a similar problem to what you are talking about?  Well, inside the valve, the escape port is a bit bigger, which helps, and the time for the valve to be open is a bit longer.

The steam manages to get out thru the same passageway it came in!  This causes serious problems many to do with the size and shape of the tunnel system in these little engines:  turbulence is the bane of moving any fluid quickly and with out loss of velocity thru friction.  The least amount of friction caused by any sort of conveyance is a round, polished surface.  The reason?  a circle has the least "surface" for any given "volume" and I don't have to explain why to polish.   So imagine a square thru hole for a moment, a square is the shape that has four sides  and has the least amount of "surface" for it's volume, approximating a circle (that is better than a rectangular form).  Now when that form is a tube, the corners get terrible turbulence, sukking up a lot of energy and slowing down the fluid.(This is particularly important in foundry work in the green sand.)  It is, however, easier to make a round hole thru metal than a square one.  (I had some square drill bits but they all broke, dang!) but there is more to it than that.  There are size constraints and possibly the need to have a minimum "volume" which means one has to squish that round hole down to an oval.  Well, ovals are harder to drill than square holes are.  (I was hoping some clever manufacturer would come up with oval drills.)  So what happens is a series of round holes are drilled in beside each other till you get an approximation of the size you needs.  YOu can chip out the remaining peices or mill them.  So after a "square hole" the next best thing is a pentagon hole which is really next to impossible to do, and then a hexagon.  The hexagon may not be as difficult, ultimately as the square.  But this should be noticed:  That even-sided holes are far easier to do than odd number of sides.  (I mean look, guys, can you even build a hole with ONE side?  how would you do a triangle?)  The point is that as you get more and more sides, you approach a circle which is really an infinite sided, closed geometric design.  

The next feature that causes turbulence is:  Corners.  Every corner is going to slow your fluid down.  Engineers typically have tools to round the corners of piping and whatnot for large projects, the larger the radius, the less turbulence.  But worse than turbulence (or maybe the grand caliph of turbulence) is the "bounce".  This is when a fluid is let directly into  a flat, perpendicular to the flow, surface.  it strikes that surface ded on and bounces back blocking the fluid from coming in.  This sets up a vibrational type of turbulence.  (Imagine a theatre pakt full of popkorn popping people when the theatre catches fire--the people jam the exits.  If even ONE person stands picking his pickel nosed protuberance just outside the doors of the theatre, somebody dies!  the same at soccer games in Brazil when the fans get in fights and then rush the gates.)  Anyway, perpendicular hole/interfaces are the worst of all.  MUCH better is to have a 45deg. angled ramp which would reflect the incoming fluid at 90 deg. to the march of the flow.  You can approach the circular method again over a ramp, but in this case, the best shape is not EXACTLY circular, it is a hyperbola or maybe parabola.  Well, try to make THAT with what we amateurs have!  A ball ended mill end would be just fine and the amount of difference is like the tiny difference between Einsteins theory of gravitation and Newtons theory for a ball dropt 10 feet from the surface of the earth. 

With all that said, the little steam engines that use this little valving system are VERY poorly designed.  So, along comes the Corliss which overcame some of these problems and created others.  (I just made that up.)  Later in the 1880's or later (does anybody know the date of inception for the uni-flo?) the uniflo idea was hit upon.  This is where there IS NO VALVE!  They are not spring loader or cams--they are HOLES in the cylinder wall that allow the steam to exhaust when the piston passes the holes.  Clearly, there is going to be VERY LITTLE turbulence in exhausting!  There are no square or round tubes or corners  to let the steam out, it is simply holes!

My understanding of the problem about why these uniflos never really took off is that the port exhaust causes some kind of trouble with the piston and rings as they pass.

******************************************************************************************
(Well now, with that grand tome, I expect some literary criticism:  Did the plot work out?  Was the hero killed properly?  Was it logically connected from opening to end?  Were the sentences perked up with lively witicisms?  How were the subtle, wry jokes percieved?  Will I get the Nobel Prize for literature like Bob Dylan?  Please feel free to write a positive review.)


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## Richard Hed (Aug 9, 2020)

Charles Lamont said:


> Anatol
> 
> You are right that the compression part of the cycle requires work, but that work brings the exhaust steam up to a state closer to that in the steam chest, so that when the inlet valve there is no sudden inrush of steam., which would be wasteful.
> 
> ...


Well thanx for showing me that "designing steam engines" forum.  My big problem with this particular discussion is that nowhere do I see exactly how much of the steam is exhausted?  This is important.  If 99% of steam is exhaussted, the tiny 1% left is virtually meaningless.  If 95% is exhausted, then the work of re-compression would be small but still significant.  If 90% then it is VERY significant.  What are the statistics?  Where is the cutoff to significance?


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## Anatol (Aug 9, 2020)

Charles
thankyou for your note



Charles Lamont said:


> You are right that the compression part of the cycle requires work, but that work brings the exhaust steam up to a state closer to that in the steam chest, so that when the inlet valve there is no sudden inrush of steam., which would be wasteful. 'Convincing' you qualitatively may be difficult. You are unlikely to grasp this stuff properly without some study of thermodynamics.



I am no applied physicist, but I do grasp some of the basics of thermodynamics. And I am ready to accept recommendations from those who know more! This all very interesting.

To paraphrase - the recompression of exhaust gas takes energy but that's ok because - even though the recompression uses energy that can only be partially scavenged on the next power stroke - the advantage is that it prevents "sudden inrush of steam".
I'm prepared to accept this if you explain why a sudden inrush of steam is bad.
So the standard counterflow is inefficient  because of the "sudden inrush of steam" phenomenon? Is this essentially the same argument as "the inlet end of the cylinder remains hot because exhaust happens at the other end"?

"I am saying I think the relief valves you say you have seen probably don't serve the purpose you think they do."

have you seen the experimental uniflow engine of Dan Gelbart? (easy to find on youtube). His relief valve certainly functions to exhaust all exhaust.

"Yes the inlet valve starts to open before dead center, to ensure that it is sufficiently widely open to admit the necessary amount of steam freely without loss through "wire drawing" when the piston starts to gather speed."

I was surprised to se you say previously that the inlet closes at about 5% of power stroke, because, even if the opening was symmetrical (5% before TDC) that would only be 10% of power stroke, thats less than I would have expected.

"Haven't we already been through all this at: Designing steam engines ?"

I went back to that thread, you're right there's lots of good info there, ! ( I had to stop partaking in the forum about that time for personal reasons - and haven't been back till now. I guess I'd forgotten some of the details we'd discussed, but that discussion didn't mention uniflow, mostly wobblers.)  
thanks
A.


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## Steamchick (Aug 10, 2020)

Hi, re "sudden inrush of steam". Our erstwhile  and esteemed Victorian predecessors did not have precise "Einstein's theories", but their livelyhoods depended upon steam so they managed it empirically, and pretty effectively. So to my point. When steam expands very rapidly, it is effectively adiabatic. Hence the energy within the steam powers the expansion. If suitably superheated, then only some or all the superheat energy powers the expansion (gas laws for adiabatic expansion hold true), but with insufficient superheat, the steam will then power the expansion by condensing some steam to water. Hence you need to refer to steam tables or otherwise combine gas laws and condensation calculations to mathematically predict what is happening. The Victorian engineers also understood the effect of shock waves and constant pressure change causing zones of higher and lower pressure, as they experienced the effect of the condensation causing "wet" steam when and where they didn't  expect it to occur. In James Watts' era, this wasn't  understood, but Corliss and his generation were designing for improved flow and pressure efficiency, based on a lot of real data from designs with problems, and some better designs, clever ideas and experiment to see what actually bore useful results. Finding the Design Textbooks of those eras is a bit difficult, as they have mostly become the latest theoretical driven text books that we have for use today. And so we fail to appreciate why they made certain design decisions. (Our judgemental position is not the same as theirs).
E.g. "wire-drawing" is a readily understood expression, but is really comparing something incompressible like water, steel, copper, nylon, with what they are really needing too understand: a 2-state (steam and water) compressible gas, that changes state from gas to steam or vice-versa in a non-linear fashion. But the phrase helped their less-educated brethren to understand flow and what they termed "back-pressure" to describe frictional losses of flow in passages. They could also easily compare work done in wire drawing with the change of cross-sectional area, and imagine a similar effect on steam in valve passages. Vis-a-vis speed of wire before and after drawing.

Hence they found it advantageous to have some back-pressure at the end of stroke to avoid a "rapid inrush" which caused condensate to form - which then wetted the metal surfaces and applied the steam oil carried in the steam to cylinder ends, not the bores, where they wanted it. Also condensate collecting at cylinder ends needed spring pressure relief valves to bleed out the condensate to avoid hydraulic lock at the end of stroke. So they learned from experience,  not theory, that this mis-named wire-drawing was better avoided by larger passages and some back pressure in the cylinder, maybe at some thermodynamic expense. But their studies made engines more reliable, which saved maintenance costs and lost earnings in return. So we should try and find some original texts to understand these "antiquated" designs, not necessarily simply apply modern theory.
I can write more drivel and rubbish ideas if you wish.
I am enjoying this fascinating thread.
More comment please.
K


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## Cogsy (Aug 10, 2020)

Well, you wanted some critique so I can provide a start.



Richard Hed said:


> that is not possible.  To have a return pressure greater than the steam pressure would be going against the law of conservation of energy.  (caveats with that of course.)



Not true - even if the cylinder dropped to atmospheric at BDC the pressure developed by compression could be very high, depending on the compression ratio of the cylinder. I know we don't normally consider a compression ratio for a steam engine but if you have a piston moving up a sealed bore you are going to get compression. Now the energy required to compress this volume of gas (one cylinders' worth) to 21 PSI might need, say, one cylinders' worth of steam at 5 PSI, but if you're bringing in 5 cylinders' worth of steam at 20 PSI then you have plenty of energy to get the work done with no thermodynamic laws broken at all.


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## Richard Hed (Aug 10, 2020)

Steamchick said:


> Hi, re "sudden inrush of steam". Our erstwhile  and esteemed Victorian predecessors did not have precise "Einstein's theories", but their livelyhoods depended upon steam so they managed it empirically, and pretty effectively. So to my point. When steam expands very rapidly, it is effectively adiabatic. Hence the energy within the steam powers the expansion. If suitably superheated, then only some or all the superheat energy powers the expansion (gas laws for adiabatic expansion hold true), but with insufficient superheat, the steam will then power the expansion by condensing some steam to water. Hence you need to refer to steam tables or otherwise combine gas laws and condensation calculations to mathematically predict what is happening. The Victorian engineers also understood the effect of shock waves and constant pressure change causing zones of higher and lower pressure, as they experienced the effect of the condensation causing "wet" steam when and where they didn't  expect it to occur. In James Watts' era, this wasn't  understood, but Corliss and his generation were designing for improved flow and pressure efficiency, based on a lot of real data from designs with problems, and some better designs, clever ideas and experiment to see what actually bore useful results. Finding the Design Textbooks of those eras is a bit difficult, as they have mostly become the latest theoretical driven text books that we have for use today. And so we fail to appreciate why they made certain design decisions. (Our judgemental position is not the same as theirs).
> E.g. "wire-drawing" is a readily understood expression, but is really comparing something incompressible like water, steel, copper, nylon, with what they are really needing too understand: a 2-state (steam and water) compressible gas, that changes state from gas to steam or vice-versa in a non-linear fashion. But the phrase helped their less-educated brethren to understand flow and what they termed "back-pressure" to describe frictional losses of flow in passages. They could also easily compare work done in wire drawing with the change of cross-sectional area, and imagine a similar effect on steam in valve passages. Vis-a-vis speed of wire before and after drawing.
> 
> Hence they found it advantageous to have some back-pressure at the end of stroke to avoid a "rapid inrush" which caused condensate to form - which then wetted the metal surfaces and applied the steam oil carried in the steam to cylinder ends, not the bores, where they wanted it. Also condensate collecting at cylinder ends needed spring pressure relief valves to bleed out the condensate to avoid hydraulic lock at the end of stroke. So they learned from experience,  not theory, that this mis-named wire-drawing was better avoided by larger passages and some back pressure in the cylinder, maybe at some thermodynamic expense. But their studies made engines more reliable, which saved maintenance costs and lost earnings in return. So we should try and find some original texts to understand these "antiquated" designs, not necessarily simply apply modern theory.
> ...


More rubbish, please.


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## Richard Hed (Aug 10, 2020)

Cogsy said:


> Well, you wanted some critique so I can provide a start.
> 
> 
> 
> Not true - even if the cylinder dropped to atmospheric at BDC the pressure developed by compression could be very high, depending on the compression ratio of the cylinder. I know we don't normally consider a compression ratio for a steam engine but if you have a piston moving up a sealed bore you are going to get compression. Now the energy required to compress this volume of gas (one cylinders' worth) to 21 PSI might need, say, one cylinders' worth of steam at 5 PSI, but if you're bringing in 5 cylinders' worth of steam at 20 PSI then you have plenty of energy to get the work done with no thermodynamic laws broken at all.


Thankyew, however, I did  point out (caveats with that plate of ice cream and strawberries.)  Well, did you like the plot?


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## Charles Lamont (Aug 10, 2020)

This discussion about losses is a matter of the second law of thermodynamics.
I suggest an interlude for a brief explanation (bear with the intruduction):


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## Richard Hed (Aug 10, 2020)

Charles Lamont said:


> This discussion about losses is a matter of the second law of thermodynamics.
> I suggest an interlude for a brief explanation (bear with the intruduction):



That indeed, was a nice refrain.  Where did you find it?


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## Richard Hed (Aug 10, 2020)

I am still wondering, however, in all this discussion, just how much exhausted steam DOES get exhausted thru the exhaust port.  It certainly is relevant to designing an engine well (something the uniflo should do exceptionally well>).  I too am trying to design a uniflo with up to 5 HP that powers something like a generator or aacts exactly like the old 5hps one would find on a farm--made to grind corn, power a saw blade, maybe grind grains, and leap tall buildings, and of course generate electricity and pump water.  (I hide the secret fact that I am a --god forbid -  a  , a  ... a prepper! waiting for the world to fall apart so I, I, Cornelicus Heddicus will become DICTATOR of the world, or OZ, which ever comes first, all because I, Cornelicus Heddicus, am the only one in the world to have the forsight to build this 5 HP engine.  Unfortunately it is a hollow crown sinc there will be no-one left to lord it over.)
Hope you don't tell anyone that.  

Seriously, on various engines, how is it determined how much used steam is exhausted.  Are there tables somewhere?  Formulas?  Empiric tests?


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## Charles Lamont (Aug 10, 2020)

Going back to Anatol's OP, the efficiency of a uniflow engine exhausting to atmosphere will likely benefit from auxilliary exhaust valves (controlled by valve gear).
A condensing uniflow engine exhausting into a good vacuum doesn't need them.

Without auxilliary exhaust valves, a non-condensing engine needs a large clearance volume to avoid over-compression.

Relief valves (which are different from exhaust valves) are needed particularly in the condensing case because they can have a smaller clearance volume of 1.5 to 2 percent of the swept volume without over-compression, but should the vacuum be lost the compression pressure could get dangerously high without relief valves.

I could not make out anything Dan Gelbart said over the racket the engine was making, especially as he appeared to have his back to the microphone.

Any sudden process is bad in thermodynamics as it is 'irreversible'. This is what the Second Law is all about. As Michael Flanders sings, "That's entropy, man."

Richard's long ramble about flow resistance in tortuous passages is generally on the right track, but I would suggest that in the case of a normal slide valve cylinder the thermal losses due to passing the hot steam and cool exhaust alternately through the same duct are considerably greater than the flow resistance, but that is no more than a well-educated guess. The Reynolds Number of the steam flow in model engine passages is much lower than in full size, mitigating the effect of the multiple holes and sharp corners.

As to the suggested problems with piston rings passing over ports, I am not convinced. Most main-line steam locomotives built after about 1925 had piston valves in which rings pass over ports, and in far more trying conditions than found in stationary engines, particularly as a result of pumping air through the cylinders when coasting.

Steamchick, in the 1909 edition of his famous 'Heat Engines' W Ripper* says, "The laws which govern the condensation of steam in the cylinder are not at present fully understood."

* William Ripper - Wikipedia


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## Charles Lamont (Aug 10, 2020)

Richard Hed said:


> I am still wondering, however, in all this discussion, just how much exhausted steam DOES get exhausted thru the exhaust port.  It certainly is relevant to designing an engine well (something the uniflo should do exceptionally well>).  I too am trying to design a uniflo with up to 5 HP that powers something like a generator or aacts exactly like the old 5hps one would find on a farm--made to grind corn, power a saw blade, maybe grind grains, and leap tall buildings, and of course generate electricity and pump water.  (I hide the secret fact that I am a --god forbid -  a  , a  ... a prepper! waiting for the world to fall apart so I, I, Cornelicus Heddicus will become DICTATOR of the world, or OZ, which ever comes first, all because I, Cornelicus Heddicus, am the only one in the world to have the forsight to build this 5 HP engine.  Unfortunately it is a hollow crown sinc there will be no-one left to lord it over.)
> Hope you don't tell anyone that.
> 
> Seriously, on various engines, how is it determined how much used steam is exhausted.  Are there tables somewhere?  Formulas?  Empiric tests?


It depends on the back pressure. An atmospheric engine will exhaust down to a bit above an atmosphere. In a steam locomotive, where the exhaust blast is used to draw the fire, the back-pressure is a bit higher. A condensing engine cylinder is more thoroughly evacuated by the condenser vacuum. So, as the exhaust valve closes, you will have trapped in the cylinder whatever volume that represents of more-or-less dry saturated steam at whatever the back pressure is. Steam Tables will allow you to calculate the mass. Equally, if you know the inlet pressure, and cut-off, and the amount any superheat, you can calculate the mass of steam you are starting with (neglecting condensation). The difference is the amount exhausted. I suggest you look into cylinder P-V or 'indicator' diagrams as a starting point.

For another way of thinking about the quantity of steam exhausted, I am tempted to quote Tom Lehrer: "Life is like a sewer ... you get out of it what you put in".


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## Richard Hed (Aug 10, 2020)

Charles Lamont said:


> Going back to Anatol's OP, the efficiency of a uniflow engine exhausting to atmosphere will likely benefit from auxilliary exhaust valves (controlled by valve gear).
> A condensing uniflow engine exhausting into a good vacuum doesn't need them.
> 
> Without auxilliary exhaust valves, a non-condensing engine needs a large clearance volume to avoid over-compression.
> ...


Yes, yes and yes.  However, that frictional loss IS energy loss (heat loss).  I suspect the back and forth thru the same passage, as you say, has some kind of loss like you are explaining--there is probably at some point a bit of "shock" in the sysstem somewhere which leads to inefficiency.  also, the length of the passage doesn't help at all.  In these typical slide valves a shorter tunnel/tube/passage way (I forget what it's called, sorry) could and should be supplied with very little design trouble and certainly easier to manufacture.

Thanx for mentioning my "ramble".  You could have at least said "entertaining ramble".  Did you like the main character?


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## Richard Hed (Aug 10, 2020)

Charles Lamont said:


> It depends on the back pressure. An atmospheric engine will exhaust down to a bit above an atmosphere. In a steam locomotive, where the exhaust blast is used to draw the fire, the back-pressure is a bit higher. A condensing engine cylinder is more thouroughly evacuated by the condenser vacuum. So, as the exhaust valve closes, you will have trapped in the cylinder whatever volume that represents of more-or-less dry saturated steam at whatever the back pressure is. Steam Tables will allow you to calculate the mass. Equally, if you know the inlet pressure, and cut-off, and the amount any superheat, you can calculate the mass of steam you are starting with (neglecting condensation). The difference is the amount exhausted. I suggest you look into cylinder P-V or 'indicator' diagrams as a starting point.
> 
> For another way of thinking about the quantity of steam exhausted, I am tempted to quote Tom Lehrer: "Life is like a sewer ... you get out of it what you put in".


That's great, that's too funny.  Yesterday I watched Jay Leno's vid on his steam car collection.  I didn't thimk I would enjoy it, but Leno is brilliant and he showed his two Dobles plus a cut-away of a Doble.  the Main Doble used the steam right down to the last drop before being sukt into the condenser.  It used th e steam about four times.  I really recommend that vid.  That Doble was a wonder and complex enough to take a look at the vid.  Just look up Jay Leno on utub.

Well for these little toy engines, are the steam tables and what not, are they not overkill?  Even tho' the principles are totally sound.  But for designing a system that is meant to DO something, it is sound advice.  I'm looking at between 2 and 5 HP.  That one I mentioned to leap over tall buildings.


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## Anatol (Aug 11, 2020)

Cogsy said:


> Well, you wanted some critique so I can provide a start.
> 
> Not true - even if the cylinder dropped to atmospheric at BDC the pressure developed by compression could be very high, depending on the compression ratio of the cylinder.



yeah, that's what I said too


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## Anatol (Aug 11, 2020)

Steamchick,
thankyou for that fascinating and knowledgeable historical view ! 
"So we should try and find some original texts to understand these "antiquated" designs"
wise words indeed. I have some of the old texts, notably - 

Hawkin's New Catechism of the Steam Engine 1897/1904. 
James+Doyle's Mechanism of Steam Engines 1914, 
Holmes, The Steam Engine, 1895
 and Harris' Stationary and Marine 1958 (recommended by fcheslop as
I recall. )
Do you recommend others in particular? (Re uniflow, I don't have Stumpf.


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## Anatol (Aug 11, 2020)

Charles Lamont said:


> This discussion about losses is a matter of the second law of thermodynamics.
> I suggest an interlude for a brief explanation (bear with the intruduction):




and other favorites, like "I'm a Gnu"

My favorite succinct paraphrase of the 1st and second laws of thermodynamics
1. you can't win
2. you can't break even.


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## Anatol (Aug 11, 2020)

Charles Lamont said:


> Going back to Anatol's OP, the efficiency of a uniflow engine exhausting to atmosphere will likely benefit from auxilliary exhaust valves (controlled by valve gear).
> A condensing uniflow engine exhausting into a good vacuum doesn't need them.
> 
> Without auxilliary exhaust valves, a non-condensing engine needs a large clearance volume to avoid over-compression.
> ...



Hello Charles
3 related remarks/questions concerning valves - 

"a uniflow engine exhausting to atmosphere will likely benefit from auxilliary exhaust valves (controlled by valve gear)."

why 'controlled by valve gear' ? What would be wrong with a passive poppet valve with a weak spring that opened at low pressure (ie after exhaust to ports) and stayed open till inrush of supply steam, which would push it closed. I guess you'd lose that recompression effect, inducing 'wire-drawing' ?

you said something about double beat valves - I searched but found nothing useful - they seem pretty obscure. 

"A condensing uniflow engine exhausting into a good vacuum doesn't need them."
yes, I'd thought of that. 

You mentioned a 5% cutoff for uniflow engines, and opening before TDC. A bash valve seems like a viable solution (?)

A


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## dazz (Aug 11, 2020)

Dan Gelbart's Uniflow Steam Engine


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## Charles Lamont (Aug 11, 2020)

Anatol said:


> why 'controlled by valve gear' ? What would be wrong with a passive poppet valve with a weak spring that opened at low pressure (ie after exhaust to ports) and stayed open till inrush of supply steam, which would push it closed. I guess you'd lose that recompression effect, inducing 'wire-drawing' ?


Yes, and they would probably let quite a bit of steam go to waste before closing. Try it!



> you said something about double beat valves - I searched but found nothing useful - they seem pretty obscure.


Not really. Mushroom poppet valves were the norm in smaller steam applications such as cars and lorries, but anything bigger tended to have double beat valves.
Do a search on Caprotti valve gear.
(And for an absolutely outstanding example of model engineering see this:  )



> "A condensing uniflow engine exhausting into a good vacuum doesn't need them."
> yes, I'd thought of that.
> 
> You mentioned a 5% cutoff for uniflow engines, and opening before TDC. A bash valve seems like a viable solution (?)


Indeed. Benson & Rayman's book 'Experimental Flash Steam' has a picture of Jim Bamford's bash-valve, uniflow, v-twin, racing model hydroplane engine on the front of the dust jacket.


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## Anatol (Aug 12, 2020)

Charles Lamont said:


> Indeed. Benson & Rayman's book 'Experimental Flash Steam' has a picture of Jim Bamford's bash-valve, uniflow, v-twin, racing model hydroplane engine on the front of the dust jacket.



I believe I have a copy of that , I'll go look . thanks.
"Do a search on Caprotti valve gear."
ok
thx A


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## Steamchick (Aug 12, 2020)

Thanks Charles. When I find that elusive Round Tuition I'll consider tracking down a copy for a bed-time read. Just have to get through the dozen or so similar books I inherited from father and 2 grandfathers, including the 1890s print of Maxwell's electromagnetic theory. So much to learn and experience, so little time....
K


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## Steamchick (Aug 12, 2020)

Arrrgghh! Spell check has changed Tuit into Tuition. - I need that as well, but don't  appreciate a machine telling me so!


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## Richard Hed (Aug 12, 2020)

Steamchick said:


> Thanks Charles. When I find that elusive Round Tuition I'll consider tracking down a copy for a bed-time read. Just have to get through the dozen or so similar books I inherited from father and 2 grandfathers, including the 1890s print of Maxwell's electromagnetic theory. So much to learn and experience, so little time....
> K


Just be careful when you read in Maxwell's theory that when "the four equations" are explained--those are NOT Maxwell's equations.  Maxwell had 20 equations.  It was Oliver Heavyside who took those 20 equations when he found them and condensed them down to the well know four equations which Maxwell gets the credit for.  If you can find it, Heavyside's explanation of that is out there in his published stuff somewhere.  I get upset by Maxwell getting the false credit. Heavyside was very important but gets extremely little credit for the great stuff he didded.


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## Steamchick (Aug 13, 2020)

Hi Richard,
I worked on Air "motors" - well single stroke actuators for Circuit breakers - back in the 1980s.
Very simple 2 piston assemblies, providing Huge forces for a short stroke - driven from an air receiver - with much lower forces for the return stroke. I am vague on how we did the calculations, but as we were dealing with non-condensing gases we would simply have used the gas laws... for adiabatic expansion. 
But for the Uni-flow engines, the calculations or the steam driven stroke should be like any engine, and allowing for adequate passages and hot engine, with adequate super-heat, the "filling"  should obey the gas laws for Steam expansion, with adjustment if it cools to condensing condition. (Insufficient superheat). Now as the steam in the cylinder is dry, you can use the gas laws to expand through the exhaust to a huge volume (the world) - which will be a constant pressure, to 3 decimal places! If however the steam has expanded to wet condition before the exhaust opens, then you will need to determine the steam pressure upon opening from steam tables, which (I think?) will account for the condensation... 
I haven't sat down to write the maths, but it should not be difficult - if you have the brain to understand Maxwell, Heavyside and co! From what I remember of 50 odd years ago, Boyle & co were relatively simple by comparison... It was Plank and Schroedinger that blew me away...


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## Cogsy (Aug 13, 2020)

Richard Hed said:


> If you can find it, Heavyside's explanation of that is out there in his published stuff somewhere.  I get upset by Maxwell getting the false credit.


Heavyside himself considered that it should be called Maxwell's theory and said as much in the first volume of his _Electromagnetic Theory_ books. And Oliver Heavyside is reasonably well known in mathematics with at least a few theorems and functions named after him. For a self-taught guy he did some remarkable work (actually even for a fully-trained guy he did some remarkable work!).


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## Richard Hed (Aug 13, 2020)

Cogsy said:


> Heavyside himself considered that it should be called Maxwell's theory and said as much in the first volume of his _Electromagnetic Theory_ books. And Oliver Heavyside is reasonably well known in mathematics with at least a few theorems and functions named after him. For a self-taught guy he did some remarkable work (actually even for a fully-trained guy he did some remarkable work!).


I didn't know Heavyside considered that as you say.  Even so, I thimk that today, it should be called the Maxwell-Heavyside equations.  The Theory is Maxwell's but the equations are not.  Yes.  It certainly surprises me that so many peeps on this forum are familiar with Heavyside.  It is a pleasure.


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## Richard Hed (Aug 13, 2020)

Steamchick said:


> Hi Richard,
> I worked on Air "motors" - well single stroke actuators for Circuit breakers - back in the 1980s.
> Very simple 2 piston assemblies, providing Huge forces for a short stroke - driven from an air receiver - with much lower forces for the return stroke. I am vague on how we did the calculations, but as we were dealing with non-condensing gases we would simply have used the gas laws... for adiabatic expansion.
> But for the Uni-flow engines, the calculations or the steam driven stroke should be like any engine, and allowing for adequate passages and hot engine, with adequate super-heat, the "filling"  should obey the gas laws for Steam expansion, with adjustment if it cools to condensing condition. (Insufficient superheat). Now as the steam in the cylinder is dry, you can use the gas laws to expand through the exhaust to a huge volume (the world) - which will be a constant pressure, to 3 decimal places! If however the steam has expanded to wet condition before the exhaust opens, then you will need to determine the steam pressure upon opening from steam tables, which (I think?) will account for the condensation...
> I haven't sat down to write the maths, but it should not be difficult - if you have the brain to understand Maxwell, Heavyside and co! From what I remember of 50 odd years ago, Boyle & co were relatively simple by comparison... It was Plank and Schroedinger that blew me away...


Well, to tell the truth, I never thot of that and I am very lazy but that doesn't look like a difficult thing to do.  Also, for models, I doubt that superheat (that is, REAL superheat up into many hundred degrees) will ever be used.  We aren't dealing with rocket science really, but if we wanted to, we could indeed go so far as to make rocket science calculations just because we can.


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## Steamchick (Aug 13, 2020)

Last Uni flow I saw was in a fast boat (I think it was the UK record holder for whizzing around in a circle). Steam supplied at high superheat as the flash  boiler was red-hot! Engine running at 50,000 rpm or whatever.... I think about 5cc? Sounded like an aero - engine 2-stroke I engine without silencer! No idea of pressure or temperature...
K


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## Anatol (Aug 15, 2020)

Steamchick said:


> Last Uni flow I saw was in a fast boat (I think it was the UK record holder for whizzing around in a circle). Steam supplied at high superheat as the flash  boiler was red-hot! Engine running at 50,000 rpm or whatever.... I think about 5cc? Sounded like an aero - engine 2-stroke I engine without silencer! No idea of pressure or temperature...
> K


50,000 rpm !?!


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## Anatol (Aug 15, 2020)

So... while we're talking recompression and relief valves (or not), there's been passing reference to condensers. It make good sense to reduce exhaust port pressure to < atmosphere. I see in principle how this might work, but has anyone made one recently? Firstly, I'd like to know clever solutions to avoid lots of plumbing. As Stumpf says, it defeats the purpose to have any obstacles in the path of steam flow from port to condenser. (I feuded a free source for Stumpf 1922, link is in the designing steam engines thread. 
I'm seeing a vessel with radiator fins or similar, with perhaps boiler feed water passing through to additionally cool the exhaust and so condensate can be recycled. Can anyone add details/design solutions? I've seen some images of 'jet' condensers but there doesn't seem to be much info, unless I'm missing the key search term. 
thx!


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## Steamchick (Aug 15, 2020)

50,00pm or maybe a factor of or 5 less... it was screaming! I çant remember, but the web will...
On condensers: for a small tug I used concentric copper tubes, steam and condensate outside, pond water drifting through the inside per outlet close to front of screw.very successful, as the pond had an adequate supply of cold.... (In Sunderland there is always an adequate supply of cold everywhere!).
But if you are pumping out a lot of kW of steam from your boiler, getting 1 or 2 kW from a high speed boat engine, then the rest (lots!) Of the kW need a Huge condenser... Look at steam tables for the heat in steam at 1 bar abs at 100C, versus water at 30C, based on the volume of water you boiler will use, and develop the heat flow required at the condenser.... Then look at the radiator on your car - which can take 10 or 15% of the power your engine can develop.... So if you have a 75 kW engine, the radiator can manage maybe 10 to 15 kW? It may give you a clue as to the size of radiator you could need, if you pro-rata size (areas) for your needs.
Does that help?
K


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## Steamchick (Aug 15, 2020)

Another clue to size of radiator... A flue tube boiler full of fire, after passing the steam through an engine, needs a condenser of similar size (heat exchanging surface area) to the boiler to get a suitable heat flow through the copper. But that allows for a boiler with hot gas average temp of 200 to 300 degrees C, versus cooling air of 20 to 30C. A flash boiler is much more compact, so don't compare size for size with a condenser! 
K


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## Peter Twissell (Aug 15, 2020)

Worth having a look at percolating condensors, in which exhaust steam is fed into the bottom of a heat exchanger, so it comes into direct contact with water (condensate). The condensate is cooled by the heat exchanger. Liquid to copper heat transfer is far more efficient than gas to copper, so a relatively small condensor can handle a lot of exhaust steam.
The condensor on a Stanley steam car is a percolator and is about the same size as internal combustion car radiators of the same period.


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## Steamchick (Aug 15, 2020)

Thanks Peter, A new one for me! But interesting!
K


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## Charles Lamont (Aug 15, 2020)

I found some footage of Paul Windross's record holding hydroplane:


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## Charles Lamont (Aug 15, 2020)

Water cooled surface condensers are quite compact, in marine practice often mounted on the 'back' of the engine.


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## Richard Hed (Aug 15, 2020)

Anatol said:


> So... while we're talking recompression and relief valves (or not), there's been passing reference to condensers. It make good sense to reduce exhaust port pressure to < atmosphere. I see in principle how this might work, but has anyone made one recently? Firstly, I'd like to know clever solutions to avoid lots of plumbing. As Stumpf says, it defeats the purpose to have any obstacles in the path of steam flow from port to condenser. (I feuded a free source for Stumpf 1922, link is in the designing steam engines thread.
> I'm seeing a vessel with radiator fins or similar, with perhaps boiler feed water passing through to additionally cool the exhaust and so condensate can be recycled. Can anyone add details/design solutions? I've seen some images of 'jet' condensers but there doesn't seem to be much info, unless I'm missing the key search term.
> thx!


Take a look at Jay Leno's Doble Steam engine vid on utub.  It's not what you're asking for but it does have a condenser and the Doble put all the steam to use two or three times before condensing it.  That car was BRILLIANT


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## Anatol (Aug 16, 2020)

Steamchick said:


> 50,00pm or maybe a factor of or 5 less... it was screaming! I çant remember, but the web will...
> On condensers: for a small tug I used concentric copper tubes, steam and condensate outside, pond water drifting through the inside per outlet close to front of screw.very successful, as the pond had an adequate supply of cold.... (In Sunderland there is always an adequate supply of cold everywhere!).
> But if you are pumping out a lot of kW of steam from your boiler, getting 1 or 2 kW from a high speed boat engine, then the rest (lots!) Of the kW need a Huge condenser... Look at steam tables for the heat in steam at 1 bar abs at 100C, versus water at 30C, based on the volume of water you boiler will use, and develop the heat flow required at the condenser.... Then look at the radiator on your car - which can take 10 or 15% of the power your engine can develop.... So if you have a 75 kW engine, the radiator can manage maybe 10 to 15 kW? It may give you a clue as to the size of radiator you could need, if you pro-rata size (areas) for your needs.
> Does that help?
> K



re 50,000 rpm
- what kind of valve works at that speed?

re (In Sunderland there is always an adequate supply of cold everywhere!).
- in LA not so much, we've got high 30s not 40s night and day at present

re It may give you a clue as to the size of radiator you could need,
Yikes. so getting vacuum on the exhaust ports that way seems difficult.
I'd already thought of running a vacuum pump, but that sounds like 'robbing Peter to pay Paul' as an old codger I knew used to say.  So with the uniflow, not only do you have to contend with too much recompression, but you have to accept wasting a lot of perfectly useful steam in exhaust - it difficult to see how they made their mark as 'efficient' with these factors working against them. But then I saw a graph that showed the Newwcomen engine as 1`% efficient, so there  was a lot of room for improvement , even 2% was doubling efficiency.

So what about that wasted steam?  There were some compound uniflow, but its difficult to reconcile the exhaust needs .... unless of course the second cylinder sucked the exhaust out... would that work - with a long stroke to allow further expansion?

re Does that help?
- yes, thankyou


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## Anatol (Aug 16, 2020)

Peter Twissell said:


> Worth having a look at percolating condensors, in which exhaust steam is fed into the bottom of a heat exchanger, so it comes into direct contact with water (condensate). The condensate is cooled by the heat exchanger. Liquid to copper heat transfer is far more efficient than gas to copper, so a relatively small condensor can handle a lot of exhaust steam.
> The condensor on a Stanley steam car is a percolator and is about the same size as internal combustion car radiators of the same period.



fascinating. I'd thought of passing exhaust through feed water, but was still thinking that through. thanks!


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## Anatol (Aug 16, 2020)

Charles Lamont said:


> I found some footage of Paul Windross's record holding hydroplane:




not a lot happens for the first 3 minutes...a couple of old geezers wading around up to their armpits in cold water in the drizzle. Not what I'd call a good time! But then that damn thing is scary fast. So - apropos of what? - bash uniflow? or 50,000rpm?


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## Steamchick (Aug 16, 2020)

Has anyone worked out how fast Paul Windross's engine goes when not in the water?I saw a demo at the Harrogate show about 5 years ago.... just running on the bench for a minute. Absolutely LOUD! The silencer on the side probably chops 20dBA or so, but compared to the voices, this must have been way over 90dBA on the water - note the changing tone due to Doppler shifting? (Reminded me of the 120+ dBA of Yamaha racing bikes in the mid-1970s!). Must have been doing 5000rpm Plus? 
A quote from another site... 
https://steamautomobile.com:8443/ForuM/read.php?1,22422 
"These engines probably have steam at about 1000 psi and run around 10,000 rpm. The boiler tubes may get to 1500 degrees F. They are non condensing uniflow engines with 54 degrees of steam admission and 102 degrees exhaust duration. Plan to throttle the engine with a variable valve lift and timing to reduce the cut-off. The boiler is around 30 feet of 1/4 OD .028 wall 316 stainless steel tubing." 
I reckon Paul's burners (3 off paraffin) must be well over 10kW each...(??)  and the flash boiler  - both fed by a pump on the end of the crankshaft. I think Paul's boiler has a lot of nickel alloy tubes - as he explained copper would fail at the pressures and temperatures achieved! - No idea what the superheat temp is, and pressure at the engine....
A great world record!
Well done Paul! (What next?).
K


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## Steamchick (Aug 16, 2020)

On one of my boats - using a tiny amount of steam compared to you - I use the exhaust back-pressure - from a Stuart and Turner Star engine - to push the condensate from the condenser to a reservoir - where the hot water mixes with the reserve and is then recycled back to the boiler. This isn't the "regular" use of a condenser to develop vacuum to improve efficiency, but the recirculated water enables prolonged running on the pond - which location makes re-watering by hand-pump a bit difficult. But that is only a simple pond-cooled condenser.
Maybe steam-car condensers are useful designs for you?
K


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## besty771 (Aug 17, 2020)

Charles Lamont said:


> ...I am tempted to quote Tom Lehrer: "Life is like a sewer ... you get out of it what you put in".


First Flanders and Swan, then Tom Lehrer...  Thankyou, this place just gets better and better


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## windy (Jan 24, 2021)

Sadly have called it a day with the model flash steamer health restrictions have raised its head.
The model has been over its recorded speed many time but aerodynamics has caused problems.
Hopefully the new owner an ex flash steam record holder will break my record.
Am making a full size version of the power plant to power a wheeled vehicle hopefully before I pop my clogs.
Have been interested in full size record attempts for many years and am a member of the speed attempt community at Elvington and Melbourne drag racing.
Sneaky friends unknown to me arranged a memorable ride for me on a classic BSA C10 in 2019 that bike was the same as my first road bike in 1959.
I had not ridden a motorcycle for over 30 years.


A change from my 207.9mph UK fastest motorcycle one way run in 1974 very happy days.
At the present time 300mph is the goal for some UK competitors a few are over 270mph with power to spare.


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## Steamchick (Jan 25, 2021)

You need a friendly tv producer - like Guy Martin and Fred Dibner acquired - to really tell us your autobiography. I would buy the box-set!
K2


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## windy (Jan 25, 2021)

Thank you Bert Monro for the following quote.
My Offerings to the God of Speed
Many of us have the above this is mine with my flash steam hydroplane.
Had many crashes and repaired or built a fresh hull my last hull was very strong and survived over 130 mph crashes
My first crankshaft to a published design broke then made a stronger one that cracked my latest one has stood up to very high rpm and a lot of very fast runs.
Made many pistons and ported liners the quickest was a cast iron slipper piston with a dykes ring.
Played about with a few designs of cylinder heads the record one was the best until a high speed crash and quick cooling.
A minute crack in the valve seat appeared was hard to spot until hot.
The same happened in the steam generator tubing a series of longitude cracks happened they did not leak at 2500 psi cold as soon as warm pressure dropped.
Am assuming a bad batch of stainless tube my other batches were ok.
Cams and follower had a hard life and stellited the follower eventually which with solid lube providing clearance correct worked well.
Propeller breakages were common prop riders have to stand a lot of hammer.
Prop skegs smashed at times when propeller broke with prop shaft being bent as well.
Hope the K9 new owner can go quicker than 130 mph.
This video shows generator popping and pumps not seating correctly.
The last part shows a flying boat at about 135mph?

.


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## windy (Jan 25, 2021)

Have read these informative posts with interest I am not that good at the theory so here are my settings etc. on my poppet valve uniflow 14cc 129.33mph record engine.
I found that when the compression ratio was as high as I could get there was a large speed increase .
The poppet valve timing opens 7°BTDC closes 47°ATDC Uniflow exhaust opens 57°BBDC closes 57°ABDC when engine cold a few degrees were added.
Engine clearances were very critical due to expansion when hot the inlet steam pipe to manifold was red hot.
Am not sure of efficiency of propeller but estimate at 130mph engine rpm 11,000.
When power unit at record speed and hydro takes off for a very short while revs shoot to between 15.000rpm to 20,000rpm.
Do not know steam pressure.
There are so many other things involved with hydroplanes, aerodynamics, propellers and the various angles they have to be set an extra power increase can raise more problems.
I enjoyed all the speed meetings I was at over many years  engine problems or crashes were just part of the course in speed attempts whether model or full size.


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## Steamchick (Jan 26, 2021)

I am a fan of yours since I saw your demo at the Harrogate show some years back... I'll buy the book and video box-set when you publish!
K2


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## windy (Jan 27, 2021)

Steamchick said:


> I am a fan of yours since I saw your demo at the Harrogate show some years back... I'll buy the book and video box-set when you publish!
> K2


Remember this in 2014 Bob in the background it was his series of articles in Model Engineer that inspired me to play with flash steam hydroplanes.


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## Richard Hed (Jan 27, 2021)

windy said:


> Remember this in 2014 Bob in the background it was his series of articles in Model Engineer that inspired me to play with flash steam hydroplanes.
> View attachment 122544


Do you know what kind of fuel he is using?  I hopes those containers below are not full of highly flamable materials.


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## Steamchick (Jan 27, 2021)

Hi Windy, yes, that's what "ignited  my interest"!
Richard , it was probably one of paraffin, one of water, and one of vodka, to steady the nerves!
K2


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## windy (Jan 27, 2021)

Steamchick said:


> Hi Windy, yes, that's what "ignited  my interest"!
> Richard , it was probably one of paraffin, one of water, and one of vodka, to steady the nerves!
> K2


It was disguised  Guinness the stronger alcohol with up to 80% Nitro was used in my motorcycle them old Triumph engines took a lot of hammer.
If this virus lockdown eases there are many speed and record attempts at Elvington this year a photo of a record attempt Triumph based bike I laid on at Elvington a couple of years ago.
Not much original, home made crankshaft, barrels and much more the previous version was on a TV program about UK record attempts at Bonneville


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## Richard Hed (Jan 27, 2021)

windy said:


> It was disguised  Guinness the stronger alcohol with up to 80% Nitro was used in my motorcycle them old Triumph engines took a lot of hammer.
> If this virus lockdown eases there are many speed and record attempts at Elvington this year a photo of a record attempt Triumph based bike I laid on at Elvington a couple of years ago.
> Not much original, home made crankshaft, barrels and much more the previous version was on a TV program about UK record attempts at Bonneville


Just out of curiosity, as I know nothing about racing or speed record breaking machines, Would it not actually reduce air friction if there were a fairing about the front and side of the motorcycle, sort of like the sides of a fish?  Would also protect a bit if you spilled.


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## windy (Jan 27, 2021)

Richard 
You are correct about fairings or full streamlining I do not know if that machine will have one on.
There are so many different record classes apart from capacity,
To list a few naked, part streamline, full streamline, petrol, methanol, nitro, supercharged with combinations of fuel there are so many variations.
My 1974 built machine would do 190mph plus with no fairing it was run like that because of high side winds.
With a fairing estimated terminal speed was 215mph average 207.9mph.
A couple of pictures one naked at 190+ wind sock horizontal across the course and what happens when things go wrong.


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## Richard Hed (Jan 27, 2021)

windy said:


> Richard
> You are correct about fairings or full streamlining I do not know if that machine will have one on.
> There are so many different record classes apart from capacity,
> To list a few naked, part streamline, full streamline, petrol, methanol, nitro, supercharged with combinations of fuel there are so many variations.
> ...


Whoa, If I get up to 90 I'm soiling myself!


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## windy (Jun 16, 2022)

Had a few delays with health issues but still experimenting with full size flash steamer had a few problems with steam generator burners but sorted them.
Generator is 12 inches diameter and would not self ignite when hot the exhaust outlet was too large cooling it down.
Restricted exhaust outlet and seems fine am only using a small hand pump for initial tests the liquid on bottom burner is a drop of high temperature oil from a connection I lubricated.
New exhaust similar to my proven model design now being made.


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## dazz (Jun 16, 2022)

Hi
Take a look at Dan Gelbart's uniflow steam engine here.
It sounds terrible, but is the best uniflow design I know of.  If I was going to build a uniflow steam engine, I would build to the Dan Gelbart design.


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## Basil (Jul 26, 2022)

windy said:


> Had a few delays with health issues but still experimenting with full size flash steamer had a few problems with steam generator burners but sorted them.
> Generator is 12 inches diameter and would not self ignite when hot the exhaust outlet was too large cooling it down.
> Restricted exhaust outlet and seems fine am only using a small hand pump for initial tests the liquid on bottom burner is a drop of high temperature oil from a connection I lubricated.
> New exhaust similar to my proven model design now being made.


Hi Windy, Nice work!  Could you show me what your spot welder looks like.


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