Stirling Engine Q&A Q101-Q150

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Q&A from April 27, 1998 to December 22, 1998.

Q150: Would it be possible to power both a heat circulating fan and a fuel transport system for a pelletized wood fuel furnace such as are currently generally availible? Would these accessories run off of the waste heat only, or would considerable extra fuel be required?
P.S. - Yours is a most interesting and informative website, thank you!
22 December, 1998

A150: I don't know your aimed application, but I think that everything is possible, maybe.

Q149: Good day! I have some questions as followed:
1. Would you please tell me about the proper working temperature & mean pressure of ESE01?
2. Why do you use the short offset(->4mm) between connecting rod and the center of flywheel? Could I increase it?
Thanks in advance.
10 December, 1998

A149: The hot wall temperature is about 700 degree C, and the mean pressure is atmosphere.
You can increase the offset. But I think that a long offset is not better for the medical syringes.

Q148: Hello, I am a final year Mechanical Engineering student in the uk, I am interested in using a stirling engine as a cooling device for a medical application.
I was wondering if you could give me some more information on the engine designs you have, particularly some specifications on how much heat they can remove etc. The device would only need to cool a body by at most 5 degrees C. Would any of yours be suitable for this or do you know of any other sites which might be more relevant.
20 November, 1998

A148: It is difficult to answer this question for me. Stirling Engine Home Page Academic edition may be useful for you.

Q147: Could you please, let me know the volume relationship between cylinder and displacer for your newest rotary displacer Stirling engine, and how can the RPM be increased for that engine?
What cuold be the ideal compression ratio for that type of engine ?
Very best regards
3 November, 1998

A147: Sorry, I cannot answer to this question soon.
The rotary displacer Stirling engine reached about 600 rpm.

Q146: Is there any commercially produced sterling engines on the market? what size? Where? How Much?
1 November, 1998

A146: Please try to find the information from "Other Stirling engine web sites" page.

Q145: In the two piston version, why is the cold cylinder always so small? It looks like it displaces just as much air as the hot cylinder. The stroke appears to be just as long as well.
1 November, 1998

A145: Please see Q134.

Q144: One person sugjested steam as part of the medium inside the cylinders to help change its density why not try alcohol, ether, some refrigerant gas, or some similar liquid with a very low boiling point. We don't need to explain to each other the physics of evaporation,condensation, and expanding and condensing in relation to the thermal properties involved. I wish I knew what has already been tried and the results. I think it would be great fun to have a Stirling-powered small fishing boat.
30 October, 1998

A144: I don't have enough information. I have heard that one labolatory on Tokyo University studied about the steam Stirling engine before several years. Sorry, I don't know the result.

Q143: Hi My Name is Eder Franz an Im on the HTL in Salzburg(Austria) and our Teacher gave us som plans of a Sterling Engine.
We have to make in in our norm. Can you help me? Are there some austrian plans of a Sterlin Engine avaliable.
25 October, 1998

A143: Sorry, I don't have the Austrian plans.

Q142: Even though I did'nt read all of the Q.&A. on this page,I wonder about the adaptability of a radial design similar to early airplane engines or perhaps a Wankel (Mazda) style "piston" and chamber? These things are great brain candy!
23 October, 1998

A142: I think that such mechanisms can be used to the model Stirling engine. But the radial designed engine is not suitable for the model, because it has many heating points. Also, the Wankel piston engine is not suitable them, because a few gas leakage is affected to the engine performance.

Q141: Thank you for answering my question. Do you know any commercial organization which supplies Design, Part Drawings and Parts for a FREE PISTON STIRLING ENGINE with about 2 to 3 HP power? This is for a teaching project.
14 October, 1998

A141: I don't know about the free piston Stirling engine well. I recommend to contact to Sunpower Inc.

Q140: Your web site is very informative & educational. I just built the LSE-01 and tried to run it with a candle. I am not sure if I need more heat or if it is the way I built it. It has the same dimensions as your LSE-01 except it uses 10cc syringes and a 5mm stroke. The flywheel is also a little heavier. The engine has no air leaks and will revolve about 4 times when flicked with the side plug removed. Do you think I should apply more heat or reduce the stroke to make it work ?
13 October, 1998

A140: You should apply more heat for the LSE-01. I use an alcohol lamp or handy-type propane gas burnner as the heat source.

Q139: This is one of the best Web sites I've ever run across. It covers a difficult subject very well. Your enthusiasm is infectious. I think this is a tremendous resource. Thank you so very much.
12 October, 1998

A139: You are welcome.

Q138: I am building a two-piston type Stirling engine with "L" shape. In the case of the model engines, it looks that a hot cylinder volume is bigger than cold cylinder. Why?
Is a big and heavy flywheel better than a small and light one?
6 October, 1998

A138: I don't know your engine type. I think that the heater volume is heat transfer area, not volume. In the case of most type of the model engine, it has a cap type heater in order to increase the heat transfer area, not to increase the volume.
Too big flywheel is not good. A high speed Stirling engine (more 3000 rpm) needs a very small and light flywheel. A big and heavy flywheel causes to increase friction loss of the bearings.

Q137: My questions is about the use of glass syringes. Why is the glass syringe perfered? What is the deminsion tolarance of the glass cylender to the glass piston? Can a different material be used?
Thank you and I am enjoying your web page.
30 September, 1998

A137: I cannot answer your question enough. The grass syringe is very suitable for the model Stirling engines. Because it is a low cost, high seal performance, a few friction loss and endurance for high temprature. I have not find the different material with the same performance yet.

Q136: We have a plan to build a model Stirling engine in our university. But we don't have a lathe and a milling machine. Can we build the model engine in earnest?
18 September, 1998

A136: In your case, it is difficult to build the high speed model Stirling engine shown in my web site. Especially, a heater cap made by stainless steel cannot be processed. I recommend to adopt your original engine design.

Q135: Have you ever designed any "v" shaped engines, if so would you be able to send me any photos of them as i am building an engine as a college project. Your site has been very useful and your two piston engine was very useful, thankyou.
18 September, 1998

A135: I have not designed the V-shaped engine. In my opinion, the V-shaped engine has a big connected volume between two cylinders, so it is not suitable type for the model Stirling engines.

Q134: I am looking for data on a rotary type engine using the stirling cycle.
the engine looks like a turbine with a displacer at its side to cool and heat the air. any infromation is of use.
11 September, 1998

A134: Is not the engine my rotary displacer type Stirling engine in my web site? If so, I don't have any information.

Q133: I can work the Can Stirling engine today. Thank you for your usefyl information.
I have a question. How many the most suitable for a ratio of the diameter of the displacer piston and the diameter of the can cylinder? If you have any results of discussion, please tell me it.
27 September, 1998

A133: I have not discuss the ratio well. But, in the case of the Can engine, a bigger diameter of the piston is better, without any touch to the cylinder.

Q132: Thank you for your comprehensive Stirling page. I am interested i Stirling heat engine of 10 MWe for power plants in order not to produce steam. Can you have more about some details especially for hot side connected with heat source if an heat exchanger is used there or some adresses for such a power Stirling engine manufacturers .
Thank you for your interest.
27 August, 1998

A132: I cannot answer to your request enough. I have never heard the 10 MWe (13600 PS) Stirling engine. It is too big power for one Stirling engine. I seem that the Stirling engine is not suitable for the power plant.
In my opinion, one of the problems for the big power engine is the heat exchangers. When a thermal efficiency is 30 %, the heater must have 33 MW capacity, and the cooler must have 23 MW capacity. And they must have enough strong structure to endure high pressure. It is not easy and I don't know their design methods.
A high performance Stirling engine has been developed at SOLO, Germany. The url is;
But the power is only 10 kW.

Q131: i sorry for the bad english to all and you verry good at last a site that,s giving some info about a machine im looking for years as here in europe the goverments and busines keeping that info away from people brr if you make a machine you dont buy there taxes expensive energie.
i will build the model and give you a e-mail how and what funny and fine you do translate in english lukky us greetings from this side of the ocean.
24 August, 1998

A131: Thank you. I hope that you succeed the model Stirling project.

Q130: I am very impressed by your web site. Do you earn your living by playing with Stirling Engines? Have you earned a PhD in "Stirlingology"? If not, I think you truly deserve an honorary one, at least. Keep up the excellent and inspiring work.
20 August, 1998

A130: The model Stirling engine is one of the most interesting my hobbies. But recently I have not spent a long time for it, after my daughter has been born.
I received the doctorate in March 1998 with the "Stirlingology". But it is not the model engine in my web site. I have researched and developed more practical used Stirling engine for the doctorate.

Q129: Most impressed with your site. I built my first (and only) stirling engine from back in 1978 when I was in collage and I had a reprint copy of the Model Engineer.
I built it because it made no sense at all that that thing could actually work. (I won a bet too). Most imformative web site and full of the kind of enthusiasm that inspires others.
31 July, 1998

A129: Thank you very much.

Q128: I want to know if there is an stirling water-pump ?
29 July, 1998

A128: I know that the Bomin Solar has been developed the Stirling water pump. It is very high performance, but it has not been sold yet. Please refer Q117.

Q127: Please inform me about any references of artificial hearts with the Stirling engines.
27 July, 1998

A127: For examples,
M. A. White, R. P. Johnston, W. E. Carr, S. G. Emigh, L. C. Krogness, P. Riggle, Fully Implantable Stirling Engine for Artificial Heart Power, 17th Intersociety Energy Conversion Engineering Conference, Vol.4, p.1778-1783, 1982.
You can get more references, when you try to find them.

Q126: I'm looking for a wood fired steam generator 20 to 30 KW do you have any ideas ?
26 July, 1998

A126: Sorry, I don't have any good ideas yet. As one of the related information, Prof. Carlsen, at Technical University of Denmark has developed a 40 kW Stirling engine for wood fuel. I seem that the engine is very high performance, though it has been not practical use yet. Its main specification is;
Bore x Stroke: 140 x 74 mm,
Number of Cylinders: 4,
Mean Pressure: 4.0 MPa (Helium),
Engine Weight: 1200 kg.
The reference is;
H. Carlsen, 40 kW Stirling Engine for Solid Fuel, 31st Intersociety Energy Conversion Engineering Conference, Vol.2, p.1301-1306, 1996.

Q125: My name is Ushir Mehta. I am 12 years old.
I am very interested in heat pwered stirling engines.
I am about to make one as soon as i get wood.
Just a couple questions.
1)For the desighn of the can stirling engin; is there anything ither that would i could use throughout the whole engine?
2)How does a stirling engine work?
3)How many RPM's can i get the Can Stirling Engine to go up to?
25 July, 1998

A125: I answer to your question, though it may be not enough.
1) In the case of the whole model Stilring engine, you must be careful in few gas leakage and a few mechanical loss.
2) I prepared another web page for you. Please connect to;
3) On the case of the Can Stirling engine, you can get about 100 rpm. When the mechanical loss of the engine is decreased with your original idea, you can get more high speed.

Q124: Very informative homepage, I have copied drawings so that I can made the models my self. keep up the good work.
23 July, 1998

A124: Thank you.

Q123: I am 11 years old. I want to use the model Stirling engine in the handicraft homework of my school. Please inform me another Stirling engine, which is used every material to get easily.
Please consider another Stirling engine using hot water which I can build. Your web pages are very good, but please explain how to build more detail.
22 July, 1998

A123: Thank you for your e-mail. Sorry, I don't have another Stirling engine with easy construction as you said. I will make them under your opinion.
I think that Mr. Tsuchida's home page (in Japanese) is very useful for you.

Q122: I didn't have time to read all the Q&A and apologize if this is in duplication. Has anyone tried building a Stirling engine partially buried underground to develop the differences in temp? I know that the ground(underground) stays cool in the summer and retains heat in the winter. I don't know how much difference in temperature you would need but it seems like you could get 10 degrees F between the air outside and the dirt 2-3 feet underground. Any feedback??
21 July, 1998

A122: I have not heard the Stirling engine partially buried underground. As you said, the engine can operate with 10 degrees F temperature difference. But, I wonder that the engine cannot get enough power for practical, because the temperature difference is too low. I think that we need to dig the ground of 10m x 10m square, when we get electrical energy for one small bulb.
If we can find any other suitable applications, the engine is very useful in the world.

Q121: Hi, I've seen a Stirling-Engine that pumps water solar driven. It consists of a window with a lenght of about 1.5m and a height of 1m. Behind the window there was a deep black flat-piston that drove a mechanical construction to pump the water. The piston was attached to the window on the upper side and swung around that bearing point. It looks like a book, slightly opened in head-stand (like a reversed V) with a page flipping in it. The whole construction was attended to help people in warm countries to pump water. And the point is, it really worked...
Have you ever heard about such an engine? Are there any plans available?
12 July, 1998

A121: I think that the engine which you saw is a Stirling engine of Bomin Solar ( I have seen the engine in the Netherlands on 1993. I impressed its high performance.
Bomin Solar is aiming it commercial use, so you cannot get the plans of the engine, maybe. But you can get other plans of the model low temperature Stirling engine in following web site.
This web site shows smaller engine than the Bomin's engine. But I think that this model engine has the same of basic construction.

Q120: How many time do you build a model Stirling engine? Do you have any good method to build it?
9 July, 1998

A120: I need one or two days for building easy Stirling engine like LSE-01. I need two or three weeks for building complex engine like the model boat use. I don't know any good method for building them. Please build them steadily.

Q119: We are working on a low temperature cycle with Helium as working gas.
Do you know any sources for datas in Helium technologie and values for this gas?
Please send us a adress or the datas, if possible.
6 July, 1998

A119: I don't have enough information about the development of the low temperature difference Stirling engine. In my opinion, the engine has a high performance, because a flow loss in heat exchangers decreases. But, in the case of the low speed engine, the engine cannot get enough high performance, because the gas leakage from the power piston increases.
Are Properties of the working gas Gas constant, specific heat, heat conduction, viscosity and others? Sorry, I don't know their information except Japanese.

Q118: My mechanical engineering is restricted to 2 cycle lawnmower engine overhauls. I saw a circa 1896 Stirling engine at the Mid-West Old Threaser's Reunion 25 years ago. I figured the design lost to the internal combustion engine. Know you any recent studies on the economic practiality of Stirling engine applications? Have any studies been done for utilization in areas where geothermal sources met the sea?
3 July, 1998

A118: Recently, Stirling engine using biomass fuel and heat pump for air conditioning use are developed lively.
We had developed the low temperature difference Stirling engine using the geothermal source till March 1998 in Saitama university (Prof. Iwamoto). But our engine had been experimental use. I think that it need enough time for practical use.

Q117: Thank you for your very informative web site. The animations are especially clear and I have learned much.
My question: how many grams is the clay mass in the can engine?
11 June, 1998

A117: The clay mass is about 50 to 100 grams, maybe. But you must adjust it suitably after you complete to built the engine. I think that you will be able to find the suitable grams easily.

Q116: How reliable is a stirling engine?
Is it possible to produce a 10kWe current from a 350 Wth heat source, using a Stirling engine ?
What is the average specific mass of such a device ?
Thank You very much.
8 June, 1998

A116: Sorry, I cannot answer to the first question well. I think that several commercialized Stirling engines have high reliabilities.
On the second question, is the heat input 350 kW? If so, the thermal efficiency is 10 kW / 350 kW = 3 %. It is not difficult value for the high temperature difference Stirling engine. The engine weight becomes about 50 to 100 kg, maybe.

Q115: I am interested in building an engine with a rotary displacer. I was wondering if you had noticed an appreciable decrease in the rate of thermal transfer due to the lack of turbidity (hence mixing) in the rotary vs. reciprocating versions. It seems as though you wouldn't get as efficient an heat exchange when the air moves from side to side. Thank you for your reply.
1 June, 1998

A115: Yes, the rotary displacer type Stirling engine has a low heat transfer performance, as you said. When we hope more high performance engine, we should reform the heat exchangers.
As one of the early ways, in order to increase the heat transfer area, several fins are made on the rotary displacer and its wall. But I think that it is not best way.
I think that the best way is a suitable controlled gas flow, though I cannot find how to do.

Q114: Beautiful Stirling side at the moment building a low temp. Stirling engine. I like to change the original design to a ringbom one. But how do find the diameter of the displacer rod. Is it related to any other part??
D displacer is 140 mm Stroke 10 mm
D piston 8 mm Stroke 11 mm
31 May, 1998

A114: In the case of the Ringbom type Stirling engine, A diameter of the displacer rod is very important. Because the movement of the displacer piston is caused by the pressure force of the displacer rod. I think that you must adjust it with considerasion of displacer weight carefully, though I have not build such type engine yet.

Q113: Backin the 70's or 80's I remember an article that described a 20Kw sterling (helium pressurized) that Winnabago put in their motorhomes. Does anyone know the maker of this unit?
25 May, 1998

A113: I don't have any information about Winnabago. Can anyone answer this question?

Q112: When a Stirling refrigerator is rotated in the opposite direction, How is the temparature in expansion and compression space?
22 May, 1998

A112: When the Stirling engine is rotated in the same direction of the engine operation, a heater of the engine and the expansion space become cold, and a cooler of the engine and compression space become hot. In the case of the opposite direction, they become opposite.

Q111: I would like to build an alpha type Stirling engine. But I would not like to use the glass syringes. How can I use the materials for them? I think that seal characteristics become a problem.
21 May, 1998

A111: You can build the alpha type Stirling engine using the pistons and cylinders made of aluminum, stainless steel or brass. If you use such metal materials, it is important to seal characteristics when the engine is heated and operated (not room temperture).

Q110: I am designing a model Stirling engine. It is two cylinders double acting type Stirling engine. How you think such engine type?
21 May, 1998

A110: It is very interesting. But I seem that a pair of heaters and coolers are located separately. When distance of the pair is too long, it is not made good use of a good characteristics of the double acting type engine. Because the engine does not become compact.

Q109: I'm a French student who's looking for informations about producing electricity from heat thanks to Stirling engines. My hot fluid will be 300 deg C pressurized water and I did not make my choice of the 150 deg C cold fluid.
I want to produce a 10kWe direct current (120 Volt) from this heat source and I need the following informations :
- what would be the average efficiency of the power conversion ?
- what would be the average specific mass of this device ?
- what would be its total mass ?
- who would be my best contacts (manufacturers, researchers...)?
Thanks in advance.
20 May, 1998

A109: It is difficult to answer this question for me. I have not seen the high power Stirling engine using such lower temparature heat source. I wonder that it is possible to realize, or not. As my feeling, the engine weight become more 10 ton. Sorry, I cannot answer enough.

Q108: It is possiable to use the cut off tip of a latex dishwashing glove to form your dsplacment type power piston...simply streach the glove tip over a hollow plastic bottle cap or one inch diameter plastic pipe and mount to one side of your displacer container (beef stew can) the displacer is of thin cardboard and held in the center of the can by a thin brass rod the diplacer is driven by a crank arm attached to a verticle double can lid flywheel between the center displacer rod and the outer stew can rim latex dishwashing glove thumb tip power piston the power piston is mearly duct taped to another thin rod and is alloweed to osccillate up and down in a guide a flat balsa stick connects both the latex glove tip power piston and displacers verticle brass rods to the between them flywheels crankshaft the design requires only plyers to build and is far more robust then the fishing thread can motor its very easy to work on...@I have no way to submit a photo over a webtv lin!
K but I wish I could it has operated for hours without stopping or failing using the thumb tip piston that has a one and a half inch stroke...its easy to demo the piston put a cut off latex dishwashing glove thumb tip over a short piece of one inch diameter plastic pipe and gently blow or suck on it with your moth asif inflating a toy balloon...the thumb tip will go concaveby suction and convex by pressure instantly remember its the preformed shape of the glove tip that makes it oscillate like a piston not the elastic streachiness of the thick latex material that requires far more pressure ....the engine is simple and has no hard to find parts and no machining whatso ever and is far sturdier then the original can motor you describe i have run it at one to two hundred r.p.m. For hours using an electric stove top with exact speed control related to the stoves electric temperature dial setting ive had it to 500 degrees with no burning of the light wieght hollow carboard displacer!
...I think its a very good demo design for students as the power piston is almost fool proof and can be removed instantly to inspect the diplacer motion by simply pulling the latex glove tip from its plastic mounting tube....most students have no machine tools but this design is as elegant as any machined stirling engine....the power piston is safe and completly leak proof...the engine can be made in only a few hours and will last years...I wish I could provide a photo...I dont want to ever here again about some one not succeding in there first attempt to make a Stirling displacement engine this designs fool proof and almost cannot fail to work on any electric stove top or regulatable hot plate ...bunseen burners or gas stoves are not suitable to my design and I believe introduce an uneeded fire hazard...if you want exact deminsions I will provide them no student should be deprived of the joy of watching a stirling engines flywheel turn...nor should they require a machine sho!
14 May, 1998

Q107: I have herad that an event of the Stirling engineswill be held near Tokyo, Japan. Do you have any information about it?
12 May, 1998

A107: The event named 2nd Stirling Techno-rally will be held on 14 and 15 November, 1998 at Wako, Saitama (Honda Co.). The dead line of the participation is 10 September, 1998.

Q106: I would like to build a displacer type Stirling engine. And I want to get a high power without very high temperature heat source. How many temparature difference doed it need?
12 May, 1998
Japanese student

A106: It is too difficult to answer this question. Please select the hot heat source (exp. hot water, exhaust gas of motor cycle, solar energy, combustion of trash or gas burner). Of course, the engine can get the high power when the higher temparature heat source is used. I recommend that you estimate the temparature difference and predict the engine power, after selection of the heat source.

Q105: Thanks for the wonderfull site. I built the LSE01 using 12mm pistons. The laboratory equipment suppliers here in South Africa call them PLUNGERS. They are very accurate and I am sure that it made the project possible with the least effort.
My LSE01 runs at about 2000 to 3000 rpm depending on the size of the heat source. I used 2.5 mm ID ball bearings.
I "park" the machine with both pistons as high as possible (minimum volume)and find it easier to re-start with very little heat. Please let me know why?
I am going to build a V-4 and send you a picture.
Your site is very good and I hope it will be there for very long!
10 May, 1998

A105: Generaly, the Stirling engine with higher compression ratio (minimum volume) has a big power. On the other hand, the mechanical loss of the engine is not changed by the compression ratio. The engine is operating with the balance of the power and the mechanical loss. So, the engine with higher compression ratio can operate easily and re-start with littler heat.

Q104: how much percent of the total energy of a stirling engine is produced by the displacer piston? I think you did a fantastic job by producing such beautiful machines
greetings from Holland
5 May, 1998
The Neterlands

A104: The displacer piston produces few thermal energy. Because the pressure difference between above and below of the displacer piston is very small. And volume change by the displacer piston is very small (it is happened by the displacer rod only).
When the pressure loss in the heat exchangers is defined the energy of the displacer piston, it is about 2~5 % of the total engine energy.

Q103: Thank you for the informations on the Stirling-machine. I want to built a LSE01 and i have got two 30cc syringes gratis (:-)
Here is my question:
Can i change simply the proportions of the components for the bigger syringes or is there something to notice?
28 April, 1998

A103: I seem that a diameter of the 30 cc syringe is about 20 mm. You can change simply the proportion of the LSE-01. As the notices;
(1)A force to the crank mechanism increases strongly. So, you may use oversized bearings, crank pins, piston pins and a output shaft.
(2)The big sized syringe is too fragile. So, I recommend that you change a structure of a piston holder on hot side. It is better to locate the piston holder outside of the glass syringe. Because the thermal expansion ratio of aluminum is too larger than that of glass.

Q102: Your Pages are very interesting! Many Thanks for it.
My Question: Have you some experience with an engine of higher performance? (about >=250 W).
I'm planning to build me an engine for producing electric current. For the engine should work for me only, i'm searching for an easy to make and low cost Plan. I studied your plans of model engines, and i'm thinking of making one of them in bigger size. Did You still develop on then rotary displacer model? I think its a great concept.
27 April, 1998

A102: Yes, There is a 2 kW class Stirling engine at Ship research Institute that I am working now. I had experimented using the engine until several years ago. However, it is not suitable for the personal made engine, because it has very complex structure.
I have not developed the rotary displacer model recently. In my opinion, it is difficult that the rotary displacer model has such bigger power, because it is hard to get a high temperature difference. I seem that the engine type is suitable for the low temperature difference engine.

Q101: I have worked on designing the miniature Stirling Cycle Refrigerators for a couple of years. Stirling Cycle refrigerators are operated by electricial power. Do you think If is possible to bulid a combined machine which uses a miniature Stirling engine to operate a miniature Stirling refrigerator?
27 April, 1998
The Netherlands

A101: Yes, I think it is possible to build the Stirling-Stirling combined machine, though I have not try it yet. When the machine is completed, can it make ice or cold water using a solar energy? It is very good!

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Koichi Hirata

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