Steam Engine/Correspondence
Main > Energy > Steam Engine
Steam Review
Tom Kimmel
May 2, 2011 to Tom Kimmel of SACA
I have been working with Marcin Jakubowski of the Open Source Ecology project lately to update a design for a steam engine. Marcin tells me that he had some discussion with you back in 2009 on an earlier version of this engine.
To refresh your memory, OSE is trying to develop a prototype steam engine that is:
- Easy to fabricate from stock materials (steel, cast iron, perhaps brass, etc).
- Modular such that it can easily be broken down for maintenance and repair
- Stackable so that multiple cylinders can be ganged to a common crankshaft for more power
The current design is similar to the older one (single action, uniflow), with the following improvements:
- Piston activated bump valve
- Steam entry at end of the cylinder, rather than the side
- An oil sprayer for lubrication
- A water drain to remove condensed water
We would welcome any comments you might have about these updates to the design. Several drawings can be viewed at http://openfarmtech.org/wiki/Steam_Engine_Design and I am included the mid-cycle drawing as an attachment. The design of the bump valve was influenced by comments on the SACA forums - the "chinese hat" shape that is self centering and less likely to be damaged by the bump pin.
Some questions to consider:
- How likely is this bump valve to work? What improvements could be made?
- We at thinking of making the bore 4" in diameter, in part so that we can use off-the-shelf piston rings. What impact does this have on the performance/function of the engine.
- Will the oil sprayer shown be sufficient to lubricate the engine?
- Should we leave the crankshaft end of the cylinder open or close to to keep dirt out?
- If we put a hand crank on the flywheel, would that be sufficient to start the engine?
- There is a cylinder liner shown in blue, what material would you suggest for it?
- What are we missing or should consider?
Tom replied on May 3, 2011
May 3, 2011 Dear Mark,
I am sending this message on to another club member who may reply with some comments. If anyone other than me responds they will know more than I do, so listen to them. Secondly, you are invited to come to my shop and look at steam engines and take them apart and look at my extensive blueprint collection. I suggest that a little research will go a long ways when designing steam engines. Thirdly, there is a great need for a manufactured steam engine. For stationary purposes it does not have to be light or small, just cheap and reliable, which makes the design and manufacture much easier.
And to answer some of your questions:
A hand crank will get the engine started rotating the right direction. Off the shelf re-built starters should be available that are cheap and reliable so making provision for a flywheel with teeth on the outer edge, in other words, using a used IC engine flywheel may be the better way to go. You will want a pretty good sized flywheel for this anyhow because of the high recompression on the up-stroke.
The cylinder liners should be cast iron and they should be an easily available one. There are custom made ones from India available from a company in Texas and on a good day I can find that address. The ones that the people who know what they are doing use are from a re-build kit for a small International four cylinder tractor. For a couple of hundred dollars you get four sleeves and four pistons. This is what Jim Tangeman used and what Art Gardiner used. They are the two smartest people I know. Jim took a six cylinder in-line Ford engine and cut the block off sideways from the crankcase and then turned it upside down and cut it in half. This left him with a 3 cylinder engine and a store bought crank and connecting rods. He then bolted these cylinder liners onto some type of a frame and had a very good and reliable boat engine that is still running. Art used the liners in a 3 cylinder Outboard motor and made a 100 hp engine for the dragster that Chuk drives. This way you have a cylinder liner and a piston and rings that all fit.
With regards to the bump valves that you are using, these are the same design more or less as the MSS people used on the Hirth snowmobile engine that is in the VW they made. The difference is that the sealing surface was machined spherical instead of conical. The advantage of that design, yours and the MSS one, are that the pin bashes against the part of the valve that is not part of the sealing surface, because the bashing deforms it. You can go with a round sphere if it is silica nitride from McMaster Carr. The true Chinese hat design done by Jay Carter, the next smartest person I know, is no where like the design you have. Therefore I suggest a little more research there.
An open or enclosed crank case is not a serious issue if we are talking stationary power. You do not want to get caught in the mechanism on the one hand and you want to watch it go around on the other hand, so it is a toss-up. Jim went with an open crank.
Lubrication is a serious issue and I suggest that smarter people than myself be asked that question.
The answer to your first question is that the bash valve design is a pretty good one and it will work as long as you have enough area for the steam to flow through. As for going with a 4” bore in order to get rings, I suggest that rings are available for every sized bore there is in the world, so the precise diameter is not an issue as far as rings go. What you will want is a good piston and connecting rod and the issue is how to get lubrication to the bearing at the little end. This is why most people go with a two cycle engine because there are needle bearings there. I would ask Jim T. what he used for lubrication at the little end.
People are working on all kinds of exotic materials, such as nitride coating of the cylinder as they do in drag racing to minimize friction and wear and others are going with carbon pistons in order to get around the lubrication issue, but the long term reliability of the carbon piston is unknown. Therefore I suggest that this engine start with conservative materials.
I suggest that you take a long look at the way the MSS people made the exhaust manifold for the uniflow engine. Theirs’ was the most clever and easiest and smartest of all the designs I have seen and it needs to be designed into the engine from the beginning. And finally I suggest a long day visiting Bill Ryan up north of Chicago who has years of experience making bash valve engines that go like the wind for at least short periods of time. I am going to be looking at a well-developed two cylinder double acting uniflow using poppet valves and a sliding cam shaft with castings made by a fellow over north of Detroit. I find it easier to use other people’s work than it is to do my own.
Sincerely, Tom Kimmel
Mark responded on May 3, 2011
Thank you for your prompt reply, Tom
I'd love to come and visit your shop some time. Where are you located?
I agree that more research is needed and perhaps some experimentation as well.
We certain agree that a manufactured steam engine would be a wonderful thing. Even better, perhaps, is a steam engine that one could build yourself give metal working tools like a lathe, mill, drill, etc.
With regards to starting the engine, having a toothed flywheel is a good idea. Starter motors can be had cheap or for free, so why not support that in the design? However, having an electric starter motor does require an electric power supply to run the motor, which adds a require that should be optional, if possible.
Concerning the cylinder liner, would it be possible to use a sheet of flexible stainless steel, curl it into a cylinder, and insert it into the cylinder chamber with out welding the seam? I understand that any gap would cause a steam blow-out, but purchasing cast iron liners adds to the cost of the engine, in addition to purchased pistons.
You make mention of the MSS people and the Hirth snowmobile engine. Can you tell me who the MSS people are? Perhaps a web link?
Could you provide an email address for Jay Carr? I'd like to ask him questions, if he can spare the time. Any links to bash valves that you have on hand would be quite useful.
I will look into exhaust manifold design. I've been considering that, but haven't included it in the design yet.
Who is Bill Ryan? I get out to Chicago occasionally and it would be nice to meet him.
Thank you again for your time, insight, and willingness to contribute, Tom. It is my belief that not only OSE will benefit from this, but many people across the world.
Tom Kimmel replied on May 3, 2011
May 3, 2011 Dear Mark, My shop is in Southwestern Michigan, a two hour drive from the Loop of Chicago. I suggest that your time would be better spent looking at the 100 or so steam engines in my collection than in trying to design one yourself. However, a person needs to think about them a lot and to try to design a few of them to begin to appreciate what one is looking at.
Secondly, as for a cylinder liner, one never wants to use stainless steel in any form because of the large grain size in the material that leads to spalling and galling when it is used for any sliding surface. This is why it helps to build on other people’s wisdom and experience. That mistake has been made a few times already.
Secondly, a standard automobile electrical system, 12 volts, is quite useful around a steam power plant. There is always a use for a few fans or solenoids or relays or water level sensors or even a little light so that gauges can be checked in the dark. It is possible to design a control system around a completely analog system, and that is the ideal toward which we aim, but in the meantime using a little electricity makes things go a lot faster.
As for contacting Jay Carter, he is pretty old now and busy and so I am hesitant to have some new steam person contact him and take up his time. He did the experimentation and had quart jars of bash valves that he had tried and that did not work.
Tom Kimmel
Mark responded on May 3, 2011
I've always enjoyed Chicago as a place to visit. Now there is another reason to go there. :)
Point taken about stainless steel. Thank you for sharing your knowledge. Sharing knowledge is part our mission at OSE, which is why I and others are taking the time to collect information and put it on our web site (wiki). With your permission, I will include our discussion as well.
Concerning Jay Carr, I understand what you are saying. I have no desire to impose on him or be a bother. Still, it seems a shame that so much acquired knowledge should fade away with time. Did he happen to write down his observations, experiments, etc? A web site would be perfect, but if it was ever published as a book, I'd be willing to purchase it. Did he happen to train an apprentice or some such who might be willing to talk with me?
Ken of SACA
May 3, 2011 reply to copy of Ken's messages
We haven't been introduced, so allow me to take some liberties. My name is Ken Helmick and I'm a resident of southeast Michigan. I am a recipient of e-mails to and from SACA President Tom Kimmel and am therefore assuming he'd like me to add my thoughts. Please excuse any abruptness that may occur in this mail, I'm in a lull between assignments (which may end any moment) and therefore may unintentionally come off as brusque in my hurry to finish before that occurs. For much the same reasons, this message may tend to be a bit unorganized.
The problem of designing and building a steam engine involves many parameters with initial decisions having huge influence on final design. Higher operating pressures and temperatures lead to potentially higher efficiency, but the design must be optimized to realize this potential else the energy and initial cost expended to generate this highly energetic steam is wasted.
Generally speaking, a uniflow engine has the potential of higher efficiency, but in order to achieve this the clearance and cutoff are necessarily tightly controlled and (preferably) the exhaust is sub-atmospheric. A counter flow engine has the relative advantage of being more easily operated across a wider variety of steam inlet conditions at the cost of higher engine complexity and potentially lower efficiency.
The issue of cylinder liners was bought up. Wrapping a sleeve and welding is not likely to yield a satisfactory engine for a whole variety of reasons I won't attempt to describe in detail. The methods I would employ would include:
- Fabricate wooden pattern and core box, sand cast iron cylinder, machine. I actually have such a pattern, core box and cast cylinder in my basement.
- Purchase engine sleeves off the shelf--one example of a manufacturer capable of supplying both finished and 'raw' centrifugally cast sleeves is LA Sleeve Co. http://www.lasleeve.com/master.html
- Purchase already honed hydraulic cylinder tubes and fabricate the engine around those. One of many suppliers is http://www.nationaltubesupply.com/stocklist/NTSC_Honed_Metal_Catalog.pdf
- Convert an existing IC engine or extensively utilize IC engine components. Some motorcycle engines have replacable cylinders (notably V twins) and could be readily modified, as can the original VW Beetle Boxer engine which can be purchased in any variety of original or aftermarket configurations and level of assembly.
Use of the centrifugally cast sleeve would require an external retaining cylinder which could be either cast or machined from stock metals. Honed hydraulic cylinders could be used the same way or, in the case of cylinders with heavier side walls, it may be possible to join upper and lower flanges as well as exhaust manifolds directly to the cylinder. If welding is employed, I'd likely stress-relieve the assembly and then re-hone lightly, just in case there is any slight thermal induced distortion to the bore.
One problem with bump valves is that of valve springs. If higher temperatures are contemplated, special springs must be wound from superalloys and correctly heat treated. This is well beyond the home machinist and probably some more pedestrian heat treat vendors. Conventional springs will rapidly fail under higher steam conditions. Another problem with bump valves is mass, the heavier they are, the more potential damage due to impact, this is why Jay Carter invented the light weight valve. Too many bump valve engines had very short life between failures.
At first blush, bump valves shouldn't work. The valve is open just as long before TDC as after and the combined effects of compression and steam pressure admission just before TDC should rob as almost as much power as steam admission and expansion after TDC. This would tend to imply that steam inertia advantageously provides for asymmetrical flow around TDC. The corollary is that the acceleration effects are tied to the amount of time the valve is open and, therefore, RPM must come into play very significantly. I'd postulate that depending on size, inlet geometry and pressure differential the engine rpm has an effect on how well the bump valve engine performs with performance and efficiency degrading both above and below some particular rpm 'sweet spot'.
Asymmetrical valve events for bump valves can be achieved by either staggering the cylinder according to the DeSaxe principle so that the cylinder axis does not intercept the crank axis or by offsetting the piston wrist pin. The second method is very common in modern IC engines although the wrist pin offset is done primarily to help the piston distribute the peak cylinder pressure against the side wall over a longer time period and thus reduce wear. In any case, offset should improve the bump valve engine operation but will lead to deteriorated performance (or even non operation) in reverse.
Besides the thought that bump valve engines probably are more efficient at some moderate rpm, there are other reasons for operating at higher speeds than traditional steam engines. Blowby around the piston rings is a significant loss of power and efficiency. This is proportional to both the mean effective pressure and the residence time in the cylinder. For high steam pressures, a very short cutoff lowers MEP to a point where blowby is less of a problem. Higher rpm provides less time for the blowby to occur. In addition, the short cutoff (high expansion) of most uniflow engines and associated low MEP reduces the amount of power generated per unit of cylinder volume. All things being equal, power goes up wirh rpm, so this is a way to gain back power lost by pursuing more efficient expansion. Fluid lubricated bearings employ hydrodynamic suspension (Langmuir theory of lubrication) to reduce friction and wear. The strength of the suspension film rises with shaft velocity, and so does the load the shaft can bear without bearing failure. Typically, lugging wears out more car engines than racing.
There is a potential alternative to the bump valve that is otherwise pretty similar in overall operating characteristics. Basically, this is a smaller piston valve mounted coaxially with, and upon, the engine piston. This piston valve opens to admit steam only around TDC and is otherwise closed...the same condition a bump valve attains. The disadvantage is more friction, extra rings or seals and the need for more precision in manufacture. The advantages are no springs to weaken from temperature and no hard impact leading to valve failure.
I would always enclose the crankcase of any higher rpm engine, smaller such engines are traditionally referred to as 'splash lubricated' for very good reasons.
I agree with Tom concerning piston rings, there is an incredible variety available in almost any size, configuration and material imaginable and this is about the last reason I would select a given engine diameter. I have chosen a 4 inch bore because it is about the largest diameter used in modern passenger automobile practice, not because of the rings. Possibly the supplier with the best selection is a local company, check their pdf download for diametric applications: http://www.hastingsmfg.com/
I don't know that I see an issue with an electric starter. The electric power supply can be incredibly simple. Older General Motors alternators are widely available and they have an integral voltage regulator. Simply connect the alternator to a 12 battery with standard automotive cables and a self regulating system is in place, explaining why these units are often seen in hotrods built up from other makes of cars. This also allows for niceties like electrical steam plant controls and a light to see what is going on in the dark.
A uniflow exhaust manifold could be very, very simple, depending on the cylinder. If using something like a honed heavy wall hydraulic tube or a cylinder with a liner, I'd consider haunting the steel supply houses and finding a piece of larger rectangular tube, say maybe something like 2 x 6 inches. Weld a cap on one open end of the tube and a flange on the other, bore a hole in the face equal to the cylinder OD, slide over the cylinder and lightly weld.
The crankshaft is the heart of the engine. All the loads focus on the crank and it is subject to compression, torsion, tension and shear loads as well as cyclic fatigue and potential damage from localized heating; proper design and fabrication is necessary to minimize destructive inertial unbalance loads, misalignment and bending. People have been making cranks for a long time, and almost anyone can do so, building a crank capable of trouble-free operation at high speed and power for long periods of time is another matter.
The average home machinist is typically not equipped for (nor capable of) building a multiple throw, one piece crankshaft capable of turning high rpm and decent torque for extended periods; this isn't an insult but reflects the high degree of specialization needed to produce such an item. The most certain and economical means of obtaining such an item are to buy a crank used in a mass produced engine.
If that isn't feasible, one route to consider is the built-up crank. These are found in many smaller engines such as those used in ATVs and snowmobiles. Since the crank is assembled, it is possible to use ball bearings in the connecting rods.
If a one piece crank is desired, the best route to go would be to either cast a rough out of a high grade of iron (still used in some V-8 engines) and machine it leaving the pins and mains a bit over sized. Another option would be turning the crank a bit over-sized from billet steel. Many engine rebuild shops have the equipment to accurately grind mains and pins (the pins are the hard part) as well as micro size (polish) to final dimension. Manufactured cranks tend to be fillet rolled to increase toughness, but this won't be feasible, so filleted pins would be needed along with matching bearings. Such bearings are stocked by racing crankshaft builders. Before having a rebuild shop grind and polish the crank, it should ideally be stress relieved and possibly nitride hardened; something available from job shops. The home machinist can balance a crank with a single throw (assuming he remembered to add counterweights to the design and fully understands the issues involved) but multiple pin cranks can only be balanced in a shop with a dynamic balancing machine---many hot rod shops have such capability
Even production cranks will need to be rebalanced if changes are made to the pistons, connecting rods and so on UNLESS the crank is of a symmetrical design. Typically, this would be radials, inline and boxer 4 cylinders, inline 6s, inline 8s and V-12 engines.
Hope these initial thoughts are of some help.
Regards, Ken
White Cliffs Solar Thermal Power Station
May 2, 2011 to Mal Williams of Australia NSW DOE
I am involved with a project to build a small, scalable steam engine for farm use. I came across an article by Erik Rossen (http://www.rossen.ch/solar/wcengine.html) that commented favorably on the solar steam engine developed by NSW DOE back in the eighties. Mr. Rossen mentioned that you might have an electronic form of the report, "White Cliffs Solar Thermal Power Station", Design, operation, and results. 242 pages, 1991. If possible, could you send me a copy? I'm very interested in the diesel engine conversion and the use of bump valves.
I am doing this work for the Open Source Ecology project (http://openfarmtech.org/wiki/Main_Page). Our intention is to design and prototype a set of 50 tools (the Global Village Construction Set) that would enable the development of high standard of living and local economy at a village scale in virtually any setting globally.
Old Messages, 2009
2000 to VK Desai of Tinytech Plants
Letter to VK Desai of Tinytech Plants (Tinytech are an Indian company that make steam engines)
Dear VK,
Can you share your knowledge of steam power with us?
In order to make our solar turbine a success, we need to build the steam engine at low cost - in house. If I do my own labor, use our machine shop, and use casting in house, then the price for the engine parts should be about $150 for a 3 hp engine. Do you think that is realistic?
Please share with me your basic design. Simple drawings on the back of an envelope would do. I am smart at studying design. Please just give me the essentials and material specifications.
Please respond, or put your notes up directly at:
http://openfarmtech.org/index.php?title=Steam_Engine_Construction_Set
If you have any pictures of steam engines in fabrication, please share.
Sincerely,
Marcin
2009, From nick to Mike Brown
Mr. Brown, I have been working lately on developing a simple horizontal uniflow steam of 3" x3.5" bore and stroke that is controlled by an electronic solenoid valve and a small programmabale logic controller. My full intention is to power this engine with a gasifier monotube style boiler and utilize the exhaust in a 750 gallon thermal storage tank for home heating purposes. In my research in this project I found reference to Skip Goebel's work through your site.
that Skip Goebel may already be building a boiler of similar design, if possible could you give me his contact info? I would also be interested to know if you have given any thought to developing an electronically valved steam engine? I intend to try an asco 1/2" direct acting steam valve that claims to cycle at 800cycles/min for a million plus cycles. I intend to run my engine at 100rpm which in theory may give my controll of the cutoff ratio in increments of .25. This obviously will not be efficient but I want to try the concept first. Perhaps you know more about what this actually would take? In any case I do appreciate your time to read this email and I hope you keep up the good work in small scale steam power development.
seek out mike brown steam engins on google
Response from Mike Brown Steam engines
Nick,
Skip Goebel is in Peru, do you have the DVD he did on building a prototype boiler?
I doubt if your solenoid valve will last six months on a steam engine.
Sorry, we don't get involved in other people's engineering projects (we average two emails like yours a day).
Best wishes, Mike
Skip Goebel Sensible Steam Peru s.a.c. Lima, Peru Lima 51 996 984 741 US· 559 922 2410 www.sensiblesteamperu.com
January 26, 2009, to Skip Goebel
To: info@sensiblesteamperu.com Sent: Monday, January 26, 2009 10:22:16 AM Subject: Wood Fired Monotube Boiler
I came across your site in studying the works of Skip Goebel in home powered steam systems. I intend to build a 3kW cogeneration DC system for home and experimental use. All my research leads me to conclude that Mr. Goebel may have pioneered this idea the furthest and I would be interested in purchasing any information that he has made available on the subject.
I'm not unfamilar with steam, I worked 2 years as Mechanical Engineer at a 400MW coal fired power plant, but am now envisioning working on something a little more decentralized. In any case I strongly feel the case for more self sufficient energy systems is here and given the fuel flexibility and reliability of the steam engine I wish to pursue this idea further. My plan is to construct a simple monotube fired 3kW mechanical valve steam engine to charge my DC battery bank and thermal storage tank. After I am comfortable with this design I would like to investigate the potential improvements of using a low cost programable logic controller for boiler control. Additonaly I am looking for a a high speed durable solenoid valve and the right steam valve to investigate the possibility of electronically conrtolling steam into the engine.
Right now I am thinking that I could use a control loop to continously vary the cutoff ratio of the steam engine for my governor. This would optimize efficiency by running with the lowest allowable cutoff ratio. In any case it seems at least feasible to think that in the future steam engines efficiencies can be improved by better steam control which is one more reason that this technology attracts me. So if Sensible Steam has any information avaialable by Skip Goebel on steam engine system construction and experiences with it I would be very eager to hear more about it how to get it.
January 31, 2009 to Alan Nelson
Sent: Saturday, January 31, 2009 12:30 PM To: Alan Nelson Subject: Atkomatic Solenoid Valve Response Times
Alan, I am looking at your atkomatic line of solenoid valves and would like to know if you offer anything suitable for the a 2-way continous duty pulse cycle valve for saturated steam up to 600 deg. The valve also needs to have a very fast response time of 75ms for open and 75 ms for close. Is there anything in the atkomatic line that might fulfill that response time requirement? If not do you know what other type of valve I might try looking at for that desired response time? Thank you for your time.
Regards, Marcin Jakubowski
Response from Alan Nelson
We do not have any valves capable of handling 600F steam.
Alan Nelson, Fluid Process Control Corporation