Why a triangle?
10-31-2005, 06:07 PM
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Why a triangle?
I am very much perplexed as to why rotaries use a triangular shaped rotor rather than a square shaped or an octoganal shape or any other type of shape. It would allow for more usable "cylinders". Additionally, it wouldn't require an additional rotor out of phase to halt the vibrations because the crankshaft would be centered and the rotor would be moving in the same direction and angles at all times. I think the square shaped rotor would be best because it allows for an intake area, spark plug area, gas injector area, and an exhaust port area. If you don't understand what I am saying, I created two quick sketches:
10-31-2005, 06:13 PM
#2
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Because our cars would look goofy if we had an octogon shape on our hood. 
10-31-2005, 06:17 PM
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I believe a triangle is used because there is more area for the air/fual mixture...look how little there is in your octigonal example, and also how little there is in the square example. Think of is this way....octogomal a lot of small combustion putts....triangle less putts...but more powerful ones.
pa..pa..pa..pa..pa..pa..pa..pa
compated to
pummm....pummm.....pummm......
pa..pa..pa..pa..pa..pa..pa..pa
compated to
pummm....pummm.....pummm......
10-31-2005, 06:23 PM
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There is actually a "square rotary" currently in development:
http://auto.howstuffworks.com/quasiturbine.htm
http://auto.howstuffworks.com/quasiturbine.htm
10-31-2005, 06:27 PM
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If you look at a picture of a rotor then you will see that its not a perfect triangle. Triangular in shapes yes, but the outer perimeter lines are curved outwards.
10-31-2005, 06:54 PM
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this says it best
http://www.theautochannel.com/news/2...04/202357.html
Wankel thoroughly investigated shapes for both the rotor and the housing of the engine to bear his name, discovering over 800 possible shapes. The majority were impractical, but Wankel thoroughly investigated nearly 150 basic configurations and many variations on each - long before computer simulation was possible. And you were wondering why development took so long....
Early Wankel engines were of a design called ``drehkolbenmaschine'' (DKM) in which an inner rotating housing and rotor move around a fixed central shaft. It was remarkably smooth in operation, and could run at fantastic speeds - over 20,000 rpm - but the engine needed to be disassembled in order to change the spark plugs, This was not a good characteristic for a production powerplant. So the ``kreiskolbenmotor'' (KKM) was developed. In the KKM, the rotor and output shaft rotate inside a fixed housing. Spark plugs are easily accessible on the housing. Intake and exhaust are by ports on the housing, similar in principle to a two-stroke piston engine. All current working Wankels are of KKM design.
The rotor design that worked best was shaped like a triangle with convex edges, while the shape of the interior of the housing is a vaguely figure-eight shape called a two-lobed epitrochoid. The Wankel engine operates on the same four-phase cycle as any other internal combustion engine, with intake, compression, ignition, and exhaust. Unlike a piston engine, but similarly to a gas turbine, each phase takes place in a different area of the engine. The output shaft rotates at three times the rate of the rotor, and there is one ignition pulse for each rotation of the output shaft.
Early Wankel engines were of a design called ``drehkolbenmaschine'' (DKM) in which an inner rotating housing and rotor move around a fixed central shaft. It was remarkably smooth in operation, and could run at fantastic speeds - over 20,000 rpm - but the engine needed to be disassembled in order to change the spark plugs, This was not a good characteristic for a production powerplant. So the ``kreiskolbenmotor'' (KKM) was developed. In the KKM, the rotor and output shaft rotate inside a fixed housing. Spark plugs are easily accessible on the housing. Intake and exhaust are by ports on the housing, similar in principle to a two-stroke piston engine. All current working Wankels are of KKM design.
The rotor design that worked best was shaped like a triangle with convex edges, while the shape of the interior of the housing is a vaguely figure-eight shape called a two-lobed epitrochoid. The Wankel engine operates on the same four-phase cycle as any other internal combustion engine, with intake, compression, ignition, and exhaust. Unlike a piston engine, but similarly to a gas turbine, each phase takes place in a different area of the engine. The output shaft rotates at three times the rate of the rotor, and there is one ignition pulse for each rotation of the output shaft.
10-31-2005, 07:08 PM
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Originally Posted by zoom44
you know there are other people around here that can answer questions with correct information.
........... 
Last edited by juikster; 10-31-2005 at 07:13 PM.
10-31-2005, 07:21 PM
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this says it best
Quote:
Wankel thoroughly investigated shapes for both the rotor and the housing of the engine to bear his name, discovering over 800 possible shapes. The majority were impractical, but Wankel thoroughly investigated nearly 150 basic configurations and many variations on each - long before computer simulation was possible. And you were wondering why development took so long....
Early Wankel engines were of a design called ``drehkolbenmaschine'' (DKM) in which an inner rotating housing and rotor move around a fixed central shaft. It was remarkably smooth in operation, and could run at fantastic speeds - over 20,000 rpm - but the engine needed to be disassembled in order to change the spark plugs, This was not a good characteristic for a production powerplant. So the ``kreiskolbenmotor'' (KKM) was developed. In the KKM, the rotor and output shaft rotate inside a fixed housing. Spark plugs are easily accessible on the housing. Intake and exhaust are by ports on the housing, similar in principle to a two-stroke piston engine. All current working Wankels are of KKM design.
The rotor design that worked best was shaped like a triangle with convex edges, while the shape of the interior of the housing is a vaguely figure-eight shape called a two-lobed epitrochoid. The Wankel engine operates on the same four-phase cycle as any other internal combustion engine, with intake, compression, ignition, and exhaust. Unlike a piston engine, but similarly to a gas turbine, each phase takes place in a different area of the engine. The output shaft rotates at three times the rate of the rotor, and there is one ignition pulse for each rotation of the output shaft.
http://www.theautochannel.com/news/.../04/202357.html
Quote:
Wankel thoroughly investigated shapes for both the rotor and the housing of the engine to bear his name, discovering over 800 possible shapes. The majority were impractical, but Wankel thoroughly investigated nearly 150 basic configurations and many variations on each - long before computer simulation was possible. And you were wondering why development took so long....
Early Wankel engines were of a design called ``drehkolbenmaschine'' (DKM) in which an inner rotating housing and rotor move around a fixed central shaft. It was remarkably smooth in operation, and could run at fantastic speeds - over 20,000 rpm - but the engine needed to be disassembled in order to change the spark plugs, This was not a good characteristic for a production powerplant. So the ``kreiskolbenmotor'' (KKM) was developed. In the KKM, the rotor and output shaft rotate inside a fixed housing. Spark plugs are easily accessible on the housing. Intake and exhaust are by ports on the housing, similar in principle to a two-stroke piston engine. All current working Wankels are of KKM design.
The rotor design that worked best was shaped like a triangle with convex edges, while the shape of the interior of the housing is a vaguely figure-eight shape called a two-lobed epitrochoid. The Wankel engine operates on the same four-phase cycle as any other internal combustion engine, with intake, compression, ignition, and exhaust. Unlike a piston engine, but similarly to a gas turbine, each phase takes place in a different area of the engine. The output shaft rotates at three times the rate of the rotor, and there is one ignition pulse for each rotation of the output shaft.
http://www.theautochannel.com/news/.../04/202357.html
Now here is my next question. Why not use carriages (like those found on Quasiturbnie engines) on the current rotaries because that would eliminate the need for apex seals and reduce oil consumption.
10-31-2005, 10:01 PM
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someone on here has a link to a rotary book that talks about this stuff. when i get on the correct computer ill try to find it for you (or someone else that knows what the hell im talking about can help out). the book is old and is a acrobat file, maybe truemagellen is the guy w/the file?
Last edited by buzzardsluck; 10-31-2005 at 10:22 PM.
11-01-2005, 01:27 PM
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for the book...
http://rx7.pw.cx/documents/rotary%20...to%20re-ky.pdf
for why ours is not a carriage.. why would it be?? if you made the sides of the triangle carriages with pivots on the end... it still wouldn't flex in anyway.... or change shape..
remember a^2+b^2=c^2 ? if you're just thinking about just using the rollers on carriages over apex seals... take a look at how much harder it is to make a rotor that is not a solid block of metal.. we take pride in having a motor with few moving parts...
another thing wrong with the carriage design is that as the rotor housing wears away... the carriages will no longer seat tightly against the side walls... since from the current designs they dont have any adjustments or ways to expand... where as the apex seals do have springs in them and allow them to come out more and more as the rotor housing expands... keeping compression
now as to why the shape is a triangle... i thought about this as well.... and if you look at the combustion cycle, the triangle shape is the minimum number of sides needed to carry out all 4 phases of a combustion cycle... (intake,compression,expansion,exhaust)
with a quasi turbine... 4 phases 4 sides... it still works out well... but when you get further into 5 or more sided shapes... you'll have sides of the rotor that aren't doing anything at all... which translates to a bigger rotor doing less work and carrying more mass around. It would sorta be like using our triangle rotors and disabling 1 side of it... giving only 2/3 the power for 1 rotor... not cool...
http://rx7.pw.cx/documents/rotary%20...to%20re-ky.pdf
for why ours is not a carriage.. why would it be?? if you made the sides of the triangle carriages with pivots on the end... it still wouldn't flex in anyway.... or change shape..
remember a^2+b^2=c^2 ? if you're just thinking about just using the rollers on carriages over apex seals... take a look at how much harder it is to make a rotor that is not a solid block of metal.. we take pride in having a motor with few moving parts...
another thing wrong with the carriage design is that as the rotor housing wears away... the carriages will no longer seat tightly against the side walls... since from the current designs they dont have any adjustments or ways to expand... where as the apex seals do have springs in them and allow them to come out more and more as the rotor housing expands... keeping compression
now as to why the shape is a triangle... i thought about this as well.... and if you look at the combustion cycle, the triangle shape is the minimum number of sides needed to carry out all 4 phases of a combustion cycle... (intake,compression,expansion,exhaust)
with a quasi turbine... 4 phases 4 sides... it still works out well... but when you get further into 5 or more sided shapes... you'll have sides of the rotor that aren't doing anything at all... which translates to a bigger rotor doing less work and carrying more mass around. It would sorta be like using our triangle rotors and disabling 1 side of it... giving only 2/3 the power for 1 rotor... not cool...
11-01-2005, 05:54 PM
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Originally Posted by zoom44
you know there are other people around here that can answer questions with correct information.
Might save it up for later.....
I still love ya, RG.
11-01-2005, 05:58 PM
#21
Bummed, but bring on OU!
Originally Posted by zoom44
where is your compression done?
Edit: damn 1003 posts, i didn't even notice crossing 1000
Last edited by therm8; 11-01-2005 at 06:01 PM.
11-01-2005, 06:03 PM
#22
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Originally Posted by Gomez
I stumbled over an RG mistake just today, in fact. I didn't correct it.
Might save it up for later..... I still love ya, RG.
Might save it up for later.....
I still love ya, RG.
I don't make mistakes. I have happy little accidents!
11-01-2005, 07:06 PM
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No, I haven't been following the bearing thread. It's another one....in the Tech Garage. Hint...it's a current thread, but your post is weeks old....
.
You don't slip up often, we mortals need to grab onto any small bone thrown our way....lol.
.You don't slip up often, we mortals need to grab onto any small bone thrown our way....lol.
11-01-2005, 10:22 PM
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circle?? Circle??
actually i thought about this one too... its called a radial engine... pistons mounted in a circular pattern... thats how you could do a circular shape...
actually i thought about this one too... its called a radial engine... pistons mounted in a circular pattern... thats how you could do a circular shape...
