I don't know exactly what type this would be or if it will work. After building a gamma engine from old vw cylinders (it did work), I noticed that the biggest problem I had was keeping the hot side hot and the cold side cold. The engine would not run long without water or an ice pack. My idea would consist of two separate displacement cylinders (like an alpha type)
but in line with each other with the open ends facing each other. A single connecting rod would pass through both cylinders and displacement pistons. The rod would extend out through the closed end of each cylinder. one end of the rod would be connected to a fly wheel. This would be like an alpha tybe set at 180 deg. There would be a fair amount of space between the two cylinders with only a small rod for heat to transfer. the rod could have a heat sink welded to it between the cylinders or could be made of a non conducting material. the cylinders could be connected with a tube and regenerator like an alpha but have a power cylinder tube branching off at the regenerator. The power cylinder would would be set at 90 deg. from the displacement rod. The hot cylinder piston could be a close fit piston or stepped with sealing rings at the end farthest from the heat source. I think this would probably be like a gamma type but with the advantage of heat not being able to travel to the cold side easily and possibly produce more power. The displacement pistons would be as light as possible and would not have to be as strong as alpha pistons. When I have an idea I usually build it and if it does not work then I wasted my time. I thought maybe some of you could give me some input before I waste my time on it.
Alpha type engine Idea/need input
Re: Alpha type engine Idea/need input
......There are no displacement cylinders in Alpha. This model idea, hot cyl pistons and displacement pistons. Heat sink to pushrod. Sealing rings for the hot piston....farthest away from the heat source. Draw up some diagrams to post for a better idea of your concept for critique. You need to study up on Stirling dynamics, their various types and descriptions of type. Stick with configurations that work! Build something that works, not build something because its "your idea". Ask yourself if you want to build a running engine.....or a doorstop. 
Re: Alpha type engine Idea/need input
Think of a normal alpha 180 deg. instead of 90 deg. The pistons would now be displacing air from one cylinder to the other. No compression would be taking place. It would be logical to refer to them as displacement pistons now. a power piston branching off at the regenerator. that is it. Hot and cold cylinders are separate which restricts radiant heat flow. It would help with cooling issues and allow for a greater temp difference. Maybe a three cylinder gamma perhaps. I hope this is a more simple explanation of the engine.
In my first description I was only trying to explain a way to reconfigure the two compression/displacement cylinders to operate from one rod instead of two.
In my first description I was only trying to explain a way to reconfigure the two compression/displacement cylinders to operate from one rod instead of two.
Re: Alpha type engine Idea/need input
derwood, you could make a V type motor, one cylinder with a hot cap the other one cold. The hot one needs a hot cap,Heylandt Crown on the piston. On a cylinder of the size your using (VW), you should have a tubular heat exchanger, that will involve brazing in proberbly in excess of twenty tubes in the hot end, and a similar number at the cold end. At least with a V type you only need a single crank on the crankshaft. Ian S C
Re: Alpha type engine Idea/need input
I can think of Alphas with parralel cylinders but not 180 deg. inline cylinders. Lets get our terms correct here. Compression cyl. do not exist in Stirling. You have the hot cyl with displacer piston and cold cylinder with power piston ( Gamma). Two power cylinders. (Alpha). A common cylinder with both displacer and power pistons (Beta). OK, you have dual piston displacer cyl. shuttling air back and forth.......to where? At what point along this dual piston displacer cyl is the power cyl. joined? How are you moving that air to the power cyl? Twin displacer cyl. on a common pushrod to your power cyl. with regenerator. Have to see where this regenerator and power cyl. is joined. Sound like you want the features of the Beta (inline displacer & power piston) The Alpha (regenerator) and the Gamma (separated power cylinder) into one engine. Mechanically, you have to have a 90 degree phazing between hot and cold cylinders at the crank/flywheel. I have 2 Gamma three cylinder model engines of different designs with the cylinders at 90 degrees and they are not done with one rod. The "three cylinder" term means here dual displacers and one power cyl or dual power cyl and one displacer.
Re: Alpha type engine Idea/need input
First of all, thanks for having this discussion with me. In order to build an efficient working model I have to understand the process. I guess I did not understand the process correctly. I thought that with a gamma, the displacement cylinder had a hot side and a cold side and that the air flowed freely around the displacement piston. Air to the hot side creates pressure inside the whole closed sytem and when that hot air is moved to the cold side a vacuum is created inside the whole closed system. I was under the impression that the take off to the power cylinder could come from the hot side, cold side or the middle of the displacement cylinder because the system was closed and the internal pressure was the same anywhere in the system at any given time. That is why I wanted to have two displacement cylinders with the piston cycle 180 deg. off. Air would be shuttled back and forth and the take off to the power cylinder/piston could come frome anywhere. preferably from the middle of the tubing connecting the two cylinders. I did not understand that air had to be moved to tha power cylinder. Thanks!
Last edited by derwood on Wed Dec 15, 2010 12:08 am, edited 1 time in total.
Re: Alpha type engine Idea/need input
You are at the right place, the internet, to discover the Stirlings secrets. Sometimes buying a kit or ready to run model Stirling (Ebay) can give you a greater insite with hands on study on why and how they run. Continue to read back pages in this forum for the agreements and arguments on Stirling principle. Here is some video of my three cylinder Stirlings.
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http://www.youtube.com/watch?v=Zi49e-fEz6ICode: Select all
http://www.youtube.com/watch?v=bx-nGakbe6gRe: Alpha type engine Idea/need input
Nice! Here is a sketch of what I was talking about
Re: Alpha type engine Idea/need input
Different!! I don't think it would work. Get rid of the cold cylinder, the power cylinder is the cold cylinder. To the hot side/ bottom in this case of the hot cylinder attach a hot cap as I discribed before. Both cylinders should be the same capacity, the easyest way is to have the same bore and stroke. The port from the hot cylinder is at the top of the compression part of the piston, ie below the hot cap.
You can make your motor with parallel cylinders, and ordenary cranks, or With a Ross Yoke. Or make it a V and a single crank. I think it would also be possible to make a co-axial type. Ian S C
You can make your motor with parallel cylinders, and ordenary cranks, or With a Ross Yoke. Or make it a V and a single crank. I think it would also be possible to make a co-axial type. Ian S C
Re: Alpha type engine Idea/need input
I think I'm possibly the only person who gets the idea here... as far as I can tell, what derwood is talking about is not really an alpha or gamma type engine... the closest thing I can think of would be the "moving cylinder" types, as in this design "displacer" doesn't make sense. This engine isn't any of the three traditional layouts... may I suggest "delta"? :P
In this engine, instead of a single cylinder with a hot and cold end, allowing heat to be conducted between the two, derwood is proposing a hot cylinder and cold cylinder similar to an alpha engine. However, rather than have the pistons at 90 degrees phase, he proposes having them in anti-phase so there is no net effect on them due to changing pressure. Rather, they move in opposite directions, shuttling the working fluid between the hot and cold cylinders through a regen. A separate power cylinder/piston is at 90 degrees phase to both is what extracts power from the changing pressure.
The important thing to consider here is that the pistons in the hot and cold cylinders aren't affected by the changing pressure (or rather are in opposite directions, so the effects cancel out) and merely serve to move the air between cylinders.
derwood, in answer to your question, I am convinced that your engine would run but I don't know how this design would compare to a traditional alpha engine. Perhaps having a larger throw for the displacing pistons and a smaller throw for the power piston would let it run on a lower temperature differential than an alpha, which are usually high temp engines. The way to tell is to build one!
In this engine, instead of a single cylinder with a hot and cold end, allowing heat to be conducted between the two, derwood is proposing a hot cylinder and cold cylinder similar to an alpha engine. However, rather than have the pistons at 90 degrees phase, he proposes having them in anti-phase so there is no net effect on them due to changing pressure. Rather, they move in opposite directions, shuttling the working fluid between the hot and cold cylinders through a regen. A separate power cylinder/piston is at 90 degrees phase to both is what extracts power from the changing pressure.
The important thing to consider here is that the pistons in the hot and cold cylinders aren't affected by the changing pressure (or rather are in opposite directions, so the effects cancel out) and merely serve to move the air between cylinders.
derwood, in answer to your question, I am convinced that your engine would run but I don't know how this design would compare to a traditional alpha engine. Perhaps having a larger throw for the displacing pistons and a smaller throw for the power piston would let it run on a lower temperature differential than an alpha, which are usually high temp engines. The way to tell is to build one!
Re: Alpha type engine Idea/need input
Drat, forgot my own diagram. Imagine the double-piston-dumbbell-thing and the power piston moving in 90 degree phase and I think you'll get it.
- twopistongamma.PNG (20.75 KiB) Viewed 13715 times
Re: Alpha type engine Idea/need input
This isn't going anywhere. You can't "tee off" a power cyl. between two like cylinders of hot and cold type with no volume change. The air tranfer tube has to end at the power cyl. That air at that point cools down lowering the internal preasure below atmoshperic with the greater external atmospheric preasure acting on the power piston. Your diagram illustrates horizontal pistons moving in tandem and in derwoods diagram vertical cylinders with pistons move 180 degrees. I agree they will shuttle air but with no volume change then where is the pressure change? Now you can heat the one cylinder and have a vessel (cylinders) full of hot air higher than external atmospheric pressure to push that mid point mounted power piston up its bore but without an explanation of why a cool down and pressure change at that point where the power cylinder is in the air tube there is no Stirling here. You have a cork (power piston) in a bottle (hot/cold cylinders) being heated up to pop its cork.PKM wrote: In this engine, instead of a single cylinder with a hot and cold end, allowing heat to be conducted between the two, derwood is proposing a hot cylinder and cold cylinder similar to an alpha engine. However, rather than have the pistons at 90 degrees phase, he proposes having them in anti-phase so there is no net effect on them due to changing pressure. Rather, they move in opposite directions, shuttling the working fluid between the hot and cold cylinders through a regen. A separate power cylinder/piston is at 90 degrees phase to both is what extracts power from the changing pressure.
The important thing to consider here is that the pistons in the hot and cold cylinders aren't affected by the changing pressure (or rather are in opposite directions, so the effects cancel out) and merely serve to move the air between cylinders.
Re: Alpha type engine Idea/need input
Pkm's drawing is exactly what I was trying to explain in my first description. It's a closed system. The power cylinder take off could come from any point in the system. The only reason I suggested this is because I want to seperate hot and cold (possibly cold side could now be air cooled). Also I thought it would run on lower heat unlike an alpha. It was not meant to compare to an alpha, but only to improve a gamma.PKM wrote:I think I'm possibly the only person who gets the idea here... as far as I can tell, what derwood is talking about is not really an alpha or gamma type engine... the closest thing I can think of would be the "moving cylinder" types, as in this design "displacer" doesn't make sense. This engine isn't any of the three traditional layouts... may I suggest "delta"? :P
In this engine, instead of a single cylinder with a hot and cold end, allowing heat to be conducted between the two, derwood is proposing a hot cylinder and cold cylinder similar to an alpha engine. However, rather than have the pistons at 90 degrees phase, he proposes having them in anti-phase so there is no net effect on them due to changing pressure. Rather, they move in opposite directions, shuttling the working fluid between the hot and cold cylinders through a regen. A separate power cylinder/piston is at 90 degrees phase to both is what extracts power from the changing pressure.
The important thing to consider here is that the pistons in the hot and cold cylinders aren't affected by the changing pressure (or rather are in opposite directions, so the effects cancel out) and merely serve to move the air between cylinders.
derwood, in answer to your question, I am convinced that your engine would run but I don't know how this design would compare to a traditional alpha engine. Perhaps having a larger throw for the displacing pistons and a smaller throw for the power piston would let it run on a lower temperature differential than an alpha, which are usually high temp engines. The way to tell is to build one!
Last edited by derwood on Wed Dec 15, 2010 3:39 pm, edited 2 times in total.
Re: Alpha type engine Idea/need input
Pressure change does not occur at the power piston in a gamma configuration. The power piston reacts to the change in pressure inside the whole closed sytem. In a gamma type most people place the power cylinder take off on the cold side so if what you are saying is correct then when air is moved to the hot side (displacer piston occupying the cold side), the power piston would not experience high pressure for it's up/out stroke. The power piston is pushed up/out so this proves that high pressure is not confined soley to the hot side and low pressure to the cold side. It is a closed system, low and high pressure is not moved to the power piston. It simply reacts to the change in pressure. I want to completely understand how a stirling works, so other peoples opinions are respected and expected.
Re: Alpha type engine Idea/need input
Are you sure there is no difference in pressure from hot to cold sides? A pressure change does happen in the sealed air sytem in Stirling and it does begin to happen at the power cylinder. Think about why this would be so.derwood wrote:Pressure change does not occur at the power piston in a gamma configuration. The power piston reacts to the change in pressure inside the whole closed sytem. .
You are going to find that in all Stirling types the cold end is the power cyl. Power piston is experiancing a pressure increase on the up stroke and the internal volume is increasing as both the displacer and power piston move in the same direction (for 90 degrees flywheel rotation).In a gamma type most people place the power cylinder take off on the cold side so if what you are saying is correct then when air is moved to the hot side (displacer piston occupying the cold side), the power piston would not experience high pressure for it's up/out stroke.
Thats not a good explaination and a wrong conclusion. The power piston moving up its bore is not the power stroke. Its not high pressure heated air pushing up the power piston causing the engine to run! And the air is not moved because its a sealed system? You say here that the air is not confined nor is it moved. Then whats the purpose of the displacer piston then? Air is being moved at different pressures.The power piston is pushed up/out so this proves that high pressure is not confined soley to the hot side and low pressure to the cold side. It is a closed system, low and high pressure is not moved to the power piston. It simply reacts to the change in pressure.