rotor speed compared to e-shaft speed.
09-22-12, 09:18 AM
#1
rotor speed compared to e-shaft speed.
So i was doing some thinking.
The e-shaft spins 3 times per revolution of the rotor correct? Or is it the other way around?
Also is rotary engine speed measured according to the e-shaft speed or rotor speed?
If its measured by e-shaft speed and the rotors spin at 1/3 the speed. In theory at the 7000 rpm redline the rotors are actually only spinning at 2333 rpm.
Im trying to figure out if Im thinking this all correctly or if Im slightly off or completely off base.
Can anyone confirm anything? I just like to know that Im correct, and not just hope or think i am.
The e-shaft spins 3 times per revolution of the rotor correct? Or is it the other way around?
Also is rotary engine speed measured according to the e-shaft speed or rotor speed?
If its measured by e-shaft speed and the rotors spin at 1/3 the speed. In theory at the 7000 rpm redline the rotors are actually only spinning at 2333 rpm.
Im trying to figure out if Im thinking this all correctly or if Im slightly off or completely off base.
Can anyone confirm anything? I just like to know that Im correct, and not just hope or think i am.
09-22-12, 09:51 AM
#3
Correct.
each rotor has 3 combustions pulses per rotor rotation. So 2 rotors have 6 per rotor rotation.
Every 1/2 turn of the e shaft is a compression pulse (as the rotors are 180 deg apposed), 1 turn is 2 pulses, one from each rotor. So 3 turns of the e-shaft = 6 pulses.
3 to 1.
each rotor has 3 combustions pulses per rotor rotation. So 2 rotors have 6 per rotor rotation.
Every 1/2 turn of the e shaft is a compression pulse (as the rotors are 180 deg apposed), 1 turn is 2 pulses, one from each rotor. So 3 turns of the e-shaft = 6 pulses.
3 to 1.
09-26-12, 05:50 PM
#4
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the benefit of this is that instead of having strokes that are 180 degrees like a piston engine, the rotary has 270 degree strokes, so there is more time for each event.
the down side is that there is more time for compression leakage. if you couple that with a really long seal length vs a piston engine there are more places to leak.
this is why chamber sealing is super important.
the down side is that there is more time for compression leakage. if you couple that with a really long seal length vs a piston engine there are more places to leak.
this is why chamber sealing is super important.
09-26-12, 06:03 PM
#5
your tachometer is reading e-shaft speed not rotor speed, so you are correct about the rotor speeds based off the tachometer.
rotors spin much slower than pistons bounce but the drawback is the rotor is a huge mass of metal compared to pistons, even though they require less tolerant balancing.
rotors spin much slower than pistons bounce but the drawback is the rotor is a huge mass of metal compared to pistons, even though they require less tolerant balancing.
Last edited by RotaryEvolution; 09-26-12 at 06:06 PM.
09-26-12, 07:18 PM
#6
So how does the timing work? It fires once per plug every e-shaft rotation ?
I'm just confused as to how the cycle goes, trying to see the big picture to better understand. Really can't picture it in my head.
The 270 degrees you speak of (90 degrees per stroke, the one not being counted as a sealed stroke making it 360 -- 90 * 4 = 360)
the intake , ignition, and compression stroke are the sealed strokes? (not sure of order or if these are the right terms/strokes).
the exhaust stroke being the unsealed stroke since that's where everything is basically pushed out (though sealed by apex seals on both sides of that side of the rotor)
I'd probably need to see a good picture/animation to better understand, I'm a little slow admittedly-not stupid.
rotary > pistons
I'm just confused as to how the cycle goes, trying to see the big picture to better understand. Really can't picture it in my head.
The 270 degrees you speak of (90 degrees per stroke, the one not being counted as a sealed stroke making it 360 -- 90 * 4 = 360)
the intake , ignition, and compression stroke are the sealed strokes? (not sure of order or if these are the right terms/strokes).
the exhaust stroke being the unsealed stroke since that's where everything is basically pushed out (though sealed by apex seals on both sides of that side of the rotor)
I'd probably need to see a good picture/animation to better understand, I'm a little slow admittedly-not stupid.
rotary > pistons
09-26-12, 07:30 PM
#7
difficult to explain without a diagram, rotate the eshaft once and a single face on the rotor turns towards the plugs(TDC) and fires, turn it one more full turn and a second face on that same rotor now turns towards the plugs and fires, third is same as the first.
add in the second rotor is doing the same exact thing but is phased 180* degrees of crank rotation out of the first rotor so you have 2 firing sequences per full e-shat rotation.
add in the second rotor is doing the same exact thing but is phased 180* degrees of crank rotation out of the first rotor so you have 2 firing sequences per full e-shat rotation.
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09-26-12, 07:54 PM
#8
difficult to explain without a diagram, rotate the eshaft once and a single face on the rotor turns towards the plugs(TDC) and fires, turn it one more full turn and a second face on that same rotor now turns towards the plugs and fires, third is same as the first.
add in the second rotor is doing the same exact thing but is phased 180* degrees of crank rotation out of the first rotor so you have 2 firing sequences per full e-shat rotation.
add in the second rotor is doing the same exact thing but is phased 180* degrees of crank rotation out of the first rotor so you have 2 firing sequences per full e-shat rotation.
The motor I have is a s4 turbo motor from the junkyard, could be half junk or total junk who knows, I just want to take it apart and put it back together---learning more about how everything works, how to rebuild etc.
Rotaries are like math problems, they only seem complicated until you've figured out the complete theory behind how they work, I already know quite a but but not everything--yet.
09-26-12, 08:09 PM
#9
not exactly, even when you think you know it all you tear one apart and get a curve ball still.
these cars and engines are all unique in and of themselves, one to another they are never quite alike and each have their own temperaments. sometimes this makes for challenging days.
these cars and engines are all unique in and of themselves, one to another they are never quite alike and each have their own temperaments. sometimes this makes for challenging days.
Last edited by RotaryEvolution; 09-26-12 at 08:12 PM.
09-26-12, 10:38 PM
#10
"So how does the timing work? It fires once per plug every e-shaft rotation ?"
Yes basically. Each 180 deg of e shaft rotation (on a 2 rotor engine) there is a combustion event. 360 degs are 2 combustion events. But the rotors have only spun 1/3 of a time around.
Yes basically. Each 180 deg of e shaft rotation (on a 2 rotor engine) there is a combustion event. 360 degs are 2 combustion events. But the rotors have only spun 1/3 of a time around.
