Stirlingengineforum.com

....You should throw the caculator away and start building the engine. Those who get lost in the math just end up with a pile of parts and going back to the chauk board doesn't advance the construction process. You have the hot cyl. and displacer missing? Start cutting metal. Make the displacer about .060-.080in. smaller than the cyl. bore. It will shuttle enough air. You engine isn't going to care about deadspace if you proceed with a pratical approach to clearances in the diameter and length of a displacer for your engine....and running Stirling models allows some generous leadway in clearances if your parts are off optimum by calculation.

True Longboy, absolutely true, I'm no lost in calculations, was only to do answer and to do do consideration on (in a good way done, and interesting) "provocation" of your friend.
For this (less calculation: make) also I recall the book "Making Stirling Engines" by Andy Ross; that contains a lot of building precious indications, and indication of priority and advices.
About other to be do, I'm working about.
Fer.

Longboy wrote:....You should throw the caculator away and start building the engine. Those who get lost in the math just end up with a pile of parts and going back to the chauk board doesn't advance the construction process. You have the hot cyl. and displacer missing? Start cutting metal. Make the displacer about .060-.080in. smaller than the cyl. bore. It will shuttle enough air. You engine isn't going to care about deadspace if you proceed with a pratical approach to clearances in the diameter and length of a displacer for your engine....and running Stirling models allows some generous leadway in clearances if your parts are off optimum by calculation.

If one wants to get lost in the math, the best book I've come across is "Principles and Applications of Stirling Engines" by C. D. West (ISBN: 0442292732). Its no longer in print, but I found one at my local library. This book goes through the math, but does it in a very practical way, where it makes sense of all of the terms. In fact, West emphasizes the definition of standard terms so that every one can understand what the other is saying. West is the inventor of the Fluidyne, (liquid piston stirling), by the way, which another of his books covers.

Ferraccio wrote:I'm Ferraccio from Italy.
Compliments for your remarkable work, in materials and in images!

Thank you, but most of the work isn't mine. The picture is one I found on the internet, and the digital renderings were done by a friend of mine. I will post pictures of the actual unit soon.

Ferraccio wrote: Before to give answer please a question: becouse this title for the discussion?
We have supported strange theory-men for many time, without delete. Property of delete is only in hands of Coordinator, and this operation is only for evident disturbs.

The title is a bit of a joke. I got a notice from the administrator that if I didn't post something in a certain number of days, the account would be deleted.

Ferraccio wrote: I personally think that we aren't able to redo calculations of yet built engine, as you well know, (sincerely I think you have "copied" your engine, and not "calculated") is a lot simpler draw-and-built on the basis on the existing engine, than to project "ex novo" and calculate it.

Exactly. I don't claim this is my original design. It is essentially a copy of a Delameter or Ericsson engine. Not trying to reinvent the wheel here. The engine was sitting uncompleted on a shelf in the basement of a nearby university. It had been picked up at a flea market some years ago with the displacer piston and it's chamber missing. I am simply trying to finish it. This is why I was attempting to calculate the sizes for the missing parts. The formula I used above are from Reverend Stirling's patent. Believe me, if I had access to the actual missing parts to copy, I wouldn't be trying to calculate anything.

Ferraccio wrote: Is an engine with a beautiful aesthetic of 1800.
Instead I am more critical to its efficiency, and the engineering approach to buil: each lever that moves is really nice. but it's lost work, each pin wheel is friction, which reduces the power.
Briefly, the moving parts are nice, but most of the work ends simply there.
is an interesting work of industrial architecture.

While this may be true, as i stated before, I am not trying to reinvent the wheel or trying to maximize efficiency for that matter. This is a scale model of a proven design (given a 100 year old design), and there is no reason that it should not run and produce some power. I am sure a rhombic or wobble plate would be more efficient, but that is not what I have presently, nor do I have the resources, time, or motivation to machine an entirely new engine from scratch when i have a workable model which is 75% complete.

Ian S C wrote:I think you say the displacer is 4.025", I would suggest that this is a bit short, 6" is nearer the mark. In your diagram can the cylinder be arranged so that the water jacket is a little nearer to the top of the table, this also would lower thehot end, and the center of gravity (help to stop it falling over). Ian S C

Thanks, I believe you are correct. I managed to find a scale cutaway drawing of an Ericsson engine, and your suggestions seem to fit with the measurements.
I suppose I could cut the unit apart and shorten it, but as you can see in the pic of the manufactured model that i posted, this seems to be the norm for the scale models. I find it strange that there is such a large area which is neither heated nor cooled directly. I will keep your suggestion in mind when analyzing the model once it is complete. The only reason I could see for the space to be there is to give some room to install some sort of regenerator, but I am not sure.

theropod2 wrote: I would buy a reproduction of the 8" Rider-Ericsson today if one were available. With modern materials and construction methods these engines could last a very long time and supply power for a great many applications. These simple engines would be easy for anyone with a basic mechanical ability to repair and or maintain, whereas some of the newer designs I see, but can't buy, need a specialist to keep running.
Lately I've read on our forum how this theoretical ideal must be reached, that a specific material is the only suitable one for a given application or one objection after another until actually building a power producing engine is out of reach of most here. If we take a different approach and start with a proven design and build on that we will have made much more progress than arguing about stuff that doesn't matter to the average Joe.

I'd buy one too. I'd love to see a relatively small engine that could run off waste industrial heat (or maybe even waste home heat) that would produce enough power to turn a small generator and back feed to the grid. Costs could be kept low by using a proven design (lower engineering costs), fuel costs would be essentially nil (waste heat), and maintenance costs would be kept down by the units simplicity (no special training required). If the costs of modern materials didn't drive the price through the roof, and the unit could be made to run more efficiently than the century old design through use of those materials, the unit could pay for itself in a few years time by my estimates.

Ferraccio wrote: I agree with you that many involved in the usual engines "wire and tin cans", or nearly so, and do not make engines that produce a little work "measured".

I agree, but I don't think their goal was to produce power in the first place. They are toys and those building them are well aware of it.

Ferraccio wrote: When I addressed to the problem "Stirling" I have documented, talking to friends of the forum, then I read the book of Andy Ross, "Making Stirling engines", available on the web through Jimlarsen, all this in the light of my knowledge of the designer .
I examined the difference in energy yield of different architectures (alpha, beta and gamma).
I have examined the effect on yields with the pressurization, and resulting complications in structural (to design equipment under pressure was my job).
Then I applied my knowledge, and those that emerged from the data studied, to find solutions to reduce friction, promote heat exchange, and produce the insulation where it should.

I have read the Andy Ross book too, as well as read several dozen academic papers on the subject, and am in the process of doing research on the subject similar to what you have done.
I agree with you that all of the above would need to be addressed to truly bring a Stirling powered engine into the 21st century.

Ferraccio wrote: Conclusions:
Has no sense to design a Stirling engine that produces energy appreciably without addressing "high technology" and pressurization.
Try to do as I did, you and I realize, these are NOT my beliefs, are facts.

This is where I disagree. i guess it depends on what you mean by "produces energy appreciably". Personally, 1 or 2 hp would be plenty for my needs. While I am am sure pressurization and modern materials would make that kind of number much easier to obtain, I see no need for "high technology". Computer monitoring might be nice to have, but it is hardly necessary in a 1hp engine. I also see no need for super exotic materials or specialized manufacturing processes.

Ferraccio wrote: In 1800 they produced precisely machinery to produce 2500 W that weighed three hundred pounds.

They did? Who?

Ferraccio wrote: This largely explains BECOUSE today quite all Stirling engines built by "amateur" are simple, and none addresses the issue of power, and why those who have developed, a high price, for the right technologies are careful not to publish them.

You'll get no argument from me here. Those that have the deep pockets to explore high technology and exotic materials have every right to protect any intellectual property that they have developed as a result of their investment.

Ferraccio wrote: If you want to look simple and easy engines, with low maintenance I suggest you look at the Lister engine, and Indian Listeroids.

Not really the same thing, but they are interesting.

Ferraccio wrote:
If you want a Stirling engine, and also talk about power, and energy that must be measured, you have to go up in the machining of grooves 1/30 of an inch, tolerances of 1/2000" and the use of nickel and stainless steels, sorry.
Of course I'm allowable to discuss about this with you, and to all that like.
Ferraccio

You say that like it is impossible. None of those tolerances or materials are really very difficult to deal with in a modern industrial setting. the 5 tenthousanths (1/2000) is pretty tight, but not undoable. I have access to equipment that would be up to the task. What parts are you talking about specifically?

Ian S C wrote:Look at GENOASTIRLING.
Modern materials, modern bearings proberbly double the power of the equivalent 19th century motor.
Not really related, I do some work at a local museum where we have an old water turbine, the rotor is about 30" in diameter,producing about 3hp with a 16ft head. I'v been told that with modern materials a turbine about a foot in dia would give about the same power, the revs on the new turbine would be much higher, the old one runs at a little over 120rpm (just out of interest the drive is via a pair of bevel gears, the one on the turbine shaft has wooden teeth, while the driven gear is cast iron, these gears are 30" in dia). Ian S C

This is what i was trying to say before. Application of modern materials, and some engineering updates, could make one of the old engines workable. I don't think we are talking a compact, super efficient powerplant turning out megawatts, but a small motor/generator setup backfeeding power to the grid...

Awesome. I love hydropower. If I lived in a mountainous area, I'd be all over a Pelton.

Longboy wrote:....You should throw the caculator away and start building the engine. Those who get lost in the math just end up with a pile of parts and going back to the chauk board doesn't advance the construction process. You have the hot cyl. and displacer missing? Start cutting metal. Make the displacer about .060-.080in. smaller than the cyl. bore. It will shuttle enough air. You engine isn't going to care about deadspace if you proceed with a pratical approach to clearances in the diameter and length of a displacer for your engine....and running Stirling models allows some generous leadway in clearances if your parts are off optimum by calculation.

Thanks. That's essentially what i am doing now that i have a basic idea of where to start. I plan on making a few "mock ups" and testing them out.

nate wrote:If one wants to get lost in the math, the best book I've come across is "Principles and Applications of Stirling Engines" by C. D. West (ISBN: 0442292732). Its no longer in print, but I found one at my local library. This book goes through the math, but does it in a very practical way, where it makes sense of all of the terms. In fact, West emphasizes the definition of standard terms so that every one can understand what the other is saying. West is the inventor of the Fluidyne, (liquid piston stirling), by the way, which another of his books covers.

Cool. I am going to have to find a copy. Too bad they seem to be pretty pricey. I am a fool for any kind of deep calculation stuff (physicist with a math minor).

The turbine is a Francis inward flow type, unlike a pelton wheel that uses the velocity of the water through a nozzle, these turbines utilise the weight of water at low velocity, and large amounts(in the 19th century it was the high tech replacement for a waterwheel). We just have problems with a shortage of water, more so since last years earthquake damaged the bed of the dam so that it does'nt hold water so well. Another bit of machinery of a similar vintage to the peak time of hot air engine use. Ian S C

Meanwhile, I apologize if I did not understand (my english is very poor) you're restoring an engine with parts missing, and then you had what was to size. Have patience.

I step directly to the things that I consider important and on which you disagree.

I make some considerations.
1) The engine is an external combustion, so the primary problem is to transfer the heat inside, ...and outside in the cold point, easy task with a small engine, when the size increases the exchange surface increases with the square of the scale, while the internal volumes increases with the cube. So if the internal volume of displacement is about eight times the heat transfer surfaces are only four times.
The exchange is in crisis, we must (by increasing the size of the motor) to increase much more than direct proportion the surface of exchange.
2) the Stirling engine has a unit power density (on unit displacement) much lower than internal combustion engines, so you need to have large engines to power of order of kW, ...then the provisions of item 1.
3) In the forum at the time I called to check the validity of the empirical formula of "Beale" (see proposed by Sesusa), this "today" formula has a reasonable approach, is based on a statistical analysis of many Stirling engines that were built recently: with the parameters: expected power, pressure and speed; this gives you the necessary capacity, the key is the number of Beale.
The number of Beale is the "quality of the engine"; with a number of Beale level of 0,15 is considered "really excellent performance engine" (only a few best, and high-efficiency engines reached such level), with the 0,11 is considered a "good level engine".
Consider to change the pressure (means: absolute - the atmospheric is 0,1) and you will understand what it means to take out power, (see which displacement is necessary to pull out of 8 kw in atmospheric pressure).
4) One way to upgrade the power is to raise the temperature of the hot heat, AISI 304 is ok, if you make an engine that has to go an hour sometimes, if you make an engine that operates at high temperature (always) have to go on special stainless steel alloys or free-steel nickel alloys.
The increased "heat exchange" with inside fins, (in good engines) needs slots 0.7 - 0.9 mm width, 5-10 mm deep, in lengths 70-150 mm, is not the usual mechanics, if you go in larger engines you may have to use also hundreds of solded or welded micro-tubes (internal diameters of one millimeter). The thing gets worse every time you increase the size of the engine (see point 1).
Without this you may go on Beale number: on range 0,05

5) Seals, (and related processes).
The decent Stirling engines must not have piston rings for sealing, possibly never in the displacer (if sealing there is need), this means to use ONLY metal on metal (or porcelain on porcelain, or Teflon on teflon)), with tolerance "in the range " of by me said, but also smaller, (for continuous use) and do not use lubricants at all, (that incinerate and forming sludge). All this is not a mechanical low-level, and not with "common materials".

I should note that the engines described in the book by Ross have technology that do not seem at all "low", ... hundreds of thin internal slots, use of nickel thin foil..., and despite this, possible powers do not seem so very high.
We are out of "low" technology of the Lister clones with pistons made ​​with a hand-lathe, running at 900 rpm and can be removed using two wrenches.

That's why I indicated that was my path, and I invited you to follow me, if there are different conclusions I would like to know!
What I said do not means that I've to teach to those who have concluded in their pocket, what they should do.

The fact is that the conclusions allowable "simple" and "easy" there are not, e and those that I see are not simple.
Fer




I

References for Beale Formula:
http://www.sesusa.org/SEDAF2.htm
downloadable in:
"The Beale Equation Spread Sheet (Excel97)" is a excel file, editable.
Fer