manual transmission shifting, whats normal?
07-12-2015, 09:14 PM
#31
Rennlist Member
07-12-2015, 09:27 PM
#32
Former Sponsor
Slightly off topic curiosity question:
How much noise should a "normal" torque tube make?
I know my clutch works well, because if I'm in neutral and depress the clutch pedal, I can hear the TT stop. If I release (engage) it, I can hear the TT spin again.
There's no "grinding" to it, nothing abnormal sounding, it's not even loud. I need to be either inside the garage or right next to my house to hear it (the sound reflects off the wall). Out in the open, I can only hear it if I listen closely (and I know what to listen for).
I've considered it normal because it sounds to me like a normal "stuff spinning" noise.
How much noise should a "normal" torque tube make?
I know my clutch works well, because if I'm in neutral and depress the clutch pedal, I can hear the TT stop. If I release (engage) it, I can hear the TT spin again.
There's no "grinding" to it, nothing abnormal sounding, it's not even loud. I need to be either inside the garage or right next to my house to hear it (the sound reflects off the wall). Out in the open, I can only hear it if I listen closely (and I know what to listen for).
I've considered it normal because it sounds to me like a normal "stuff spinning" noise.
07-14-2015, 12:28 AM
#34
Former Sponsor
greg, you are still not listening..... just stop for a second and think about it.
you said: The syncros work only by friction....pure energy absorbers. They don't care about force. but then you say, you are aware that friction IS a force...... Hmmmmm
energy is not force..... right?
I get that the energy , or power , or best said, rate of change of KE, to slow and stop the driveline is the same, in the same period of time, but at the point of sychro ring contact , there are two different speeds . 5th gear for example is 1:1.... so the force is the force to slow and stop the driveline. However, in 1st, the force is NOT the same, because the mechanical advantage is different. you LOSE the mechanical advantage in 1st, slowing the driveline. just as you GAIN the mechanical advantage by driving the gear box from the input gear to the output shaft.
that said, the friction force is proportionally higher for 1st gear sychros vs the 5th gear synchros. think about this before you respond because I don't think you are correct. I could be wrong but I could be right!
Now, think about two things. the force required to stop the driveline connected to the INPUT shaft of the transmission by putting transmission in 5th (1:1) gear OR putting it in 1st gear. 4:1 reduction (actually its the opposite)
Its ok to be wrong here Greg... really! If Im wrong, ill buy you lunch!
let me summarize...... if it takes 5lbs of force at the synchro to slow the driveline down in 5th gear (1:1) then, in 1st gear it will take 20lbs of force to create the same friction at the synchros due to the actually, 1:4 gear ration facing the input shaft. this increased force is what wears the synchro!
you know I like analogies..... two same mass vehicles powered by an F1 car engine and a Semi engine, need 1000hp to accelerate... they both use 1000hp to accelerate over some speed range.........the F1 has only 200ftlbs of torque, the semi might have 1000ftlbs acting on the driveline. if they both use a driveline rated for 300ft-lbs, which one is going to break, even though the same mass is being accelerated at the same rate. (same as the synchros slowing the drive line) .
you said: The syncros work only by friction....pure energy absorbers. They don't care about force. but then you say, you are aware that friction IS a force...... Hmmmmm
energy is not force..... right?
I get that the energy , or power , or best said, rate of change of KE, to slow and stop the driveline is the same, in the same period of time, but at the point of sychro ring contact , there are two different speeds . 5th gear for example is 1:1.... so the force is the force to slow and stop the driveline. However, in 1st, the force is NOT the same, because the mechanical advantage is different. you LOSE the mechanical advantage in 1st, slowing the driveline. just as you GAIN the mechanical advantage by driving the gear box from the input gear to the output shaft.
that said, the friction force is proportionally higher for 1st gear sychros vs the 5th gear synchros. think about this before you respond because I don't think you are correct. I could be wrong but I could be right!
Now, think about two things. the force required to stop the driveline connected to the INPUT shaft of the transmission by putting transmission in 5th (1:1) gear OR putting it in 1st gear. 4:1 reduction (actually its the opposite)
Its ok to be wrong here Greg... really! If Im wrong, ill buy you lunch!
let me summarize...... if it takes 5lbs of force at the synchro to slow the driveline down in 5th gear (1:1) then, in 1st gear it will take 20lbs of force to create the same friction at the synchros due to the actually, 1:4 gear ration facing the input shaft. this increased force is what wears the synchro!
you know I like analogies..... two same mass vehicles powered by an F1 car engine and a Semi engine, need 1000hp to accelerate... they both use 1000hp to accelerate over some speed range.........the F1 has only 200ftlbs of torque, the semi might have 1000ftlbs acting on the driveline. if they both use a driveline rated for 300ft-lbs, which one is going to break, even though the same mass is being accelerated at the same rate. (same as the synchros slowing the drive line) .
To me (keep in mind that I'm just a dumb mechanic) that the fact that 1st gear is spinning at a slower speed that any of the other gears, 1st gear should be the easiest gear to stop. However, I can also see that first gear synchro would have to do the same amount of work as the 5th gear synchro in a shorter time, if everything had to happen over the same exact period of time....which means one would have to "push" on the slider touching the synchro harder to stop it in the same amount of time (this is the "force" that I was talking about, BTW.) That being said, 5th gear synchro would be moving at a higher speed and it seems like there would be more wear at the contact point of the engaging teeth....simply because of this increased speed.
I keep going back to the fact that the energy required to stop the same mass should be the same, regardless of what gear is chosen.....unless I completely missed the entire thing about a moving mass and energy, in physics.
I've got a couple world class physicists that own 928s. I'll ask them how the gear ratio influences the energy required to stop the mass....although I'm going to have a really tough time when stopping the same exact mass requires a different amount of energy.
I think they are going to laugh at me for even considering such a thing.....