928 Technical discussion - Theories, experiences, physics, and solutions.
#16
#17
Nordschleife Master
HP is power. Which is force applied over time.
One is static (measured in foot-pounds) and the other is dynamic (measured in foot-pounds per minute) The measurements can be different - metric (newton-meters) or different units (seconds vs minutes, inches vs feet, ounces vs pounds)
Obviously, HP is dependent on torque, but it also is a function of speed. If two engines produce the same amount of torque, but one spins twice as fast as the other, the faster engine produces twice as much HP.
The only effect gearing has on HP is how much power is lost to the drivetrain running it through the gears as opposed to direct drive. Any changes to the torque due to gearing are accompanied by an equal but opposite change of the speed.
Think about a water pump. A big, slow engine with a lot of torque (think truck diesel) will drive a pretty big pump, in terms of amount of water per rev.
A smaller faster motor will have less torque (think sportbike engine). That means it will be able to pump less water per revolution, but will make a lot more revs in a given time than the big diesel.
Which one will fill a pool faster? The one with more HP.
#18
Rennlist Member
Thread Starter
Good description. I would add that the gear boxes effect on HP is its ability to allow for the effective use of the HP. wide spaced gears don't allow for this.. (you go from max hp range to very low HP range, so average HP utilized and available is less)
so, gears , as I always say, don't make HP they allow for more effective use of the HP available..." efficiency", is more about the losses through the transmission ... entirely different concept
I like the analogy of HP to that of a Battleship and torque being the weapons on board while HP is the destructive potential of the battlship.
You can have two battleships that have the same destructive power, but different sizes. the smaller one will have more little guns and the bigger one will have less guns but larger in size. same distructive power analogous to Same hp or same potential for acceleration for a given mass. (grossly different engine torque, but same rear wheel torque at any vehicle speed compared to another same car with the same HP)
so, gears , as I always say, don't make HP they allow for more effective use of the HP available..." efficiency", is more about the losses through the transmission ... entirely different concept
I like the analogy of HP to that of a Battleship and torque being the weapons on board while HP is the destructive potential of the battlship.
You can have two battleships that have the same destructive power, but different sizes. the smaller one will have more little guns and the bigger one will have less guns but larger in size. same distructive power analogous to Same hp or same potential for acceleration for a given mass. (grossly different engine torque, but same rear wheel torque at any vehicle speed compared to another same car with the same HP)
Torque is force.
HP is power. Which is force applied over time.
One is static (measured in foot-pounds) and the other is dynamic (measured in foot-pounds per minute) The measurements can be different - metric (newton-meters) or different units (seconds vs minutes, inches vs feet, ounces vs pounds)
Obviously, HP is dependent on torque, but it also is a function of speed. If two engines produce the same amount of torque, but one spins twice as fast as the other, the faster engine produces twice as much HP.
The only effect gearing has on HP is how much power is lost to the drivetrain running it through the gears as opposed to direct drive. Any changes to the torque due to gearing are accompanied by an equal but opposite change of the speed.
Think about a water pump. A big, slow engine with a lot of torque (think truck diesel) will drive a pretty big pump, in terms of amount of water per rev.
A smaller faster motor will have less torque (think sportbike engine). That means it will be able to pump less water per revolution, but will make a lot more revs in a given time than the big diesel.
Which one will fill a pool faster? The one with more HP.
HP is power. Which is force applied over time.
One is static (measured in foot-pounds) and the other is dynamic (measured in foot-pounds per minute) The measurements can be different - metric (newton-meters) or different units (seconds vs minutes, inches vs feet, ounces vs pounds)
Obviously, HP is dependent on torque, but it also is a function of speed. If two engines produce the same amount of torque, but one spins twice as fast as the other, the faster engine produces twice as much HP.
The only effect gearing has on HP is how much power is lost to the drivetrain running it through the gears as opposed to direct drive. Any changes to the torque due to gearing are accompanied by an equal but opposite change of the speed.
Think about a water pump. A big, slow engine with a lot of torque (think truck diesel) will drive a pretty big pump, in terms of amount of water per rev.
A smaller faster motor will have less torque (think sportbike engine). That means it will be able to pump less water per revolution, but will make a lot more revs in a given time than the big diesel.
Which one will fill a pool faster? The one with more HP.
#19
Rennlist Member
Thread Starter
The force on the drive train is limited by the amount of traction the rear tires have, on one end, and the force that the clutch can hold on the other end.
This amounts to 400-450 ft. lbs....on the very best of days.
There is no other magically "Kibort" force involved.
But you will argue that until the sun doesn't rise...just because you don't like to be wrong.
No one here has the energy to argue with you until the end of time....so we just give up. Once we give up, you immediately think that makes your ridiculous statements fact.
That's why this thread is a complete waste of time!
This amounts to 400-450 ft. lbs....on the very best of days.
There is no other magically "Kibort" force involved.
But you will argue that until the sun doesn't rise...just because you don't like to be wrong.
No one here has the energy to argue with you until the end of time....so we just give up. Once we give up, you immediately think that makes your ridiculous statements fact.
That's why this thread is a complete waste of time!
yes, the stock clutch can produce this much clamping force, but stiction is much higher.
We are not talking magic here Greg... its a simple calculation. if you EVER get a tire chirp from a mis rev downshift from 4th to 3rd, that force (the traction force you reference) is mutlipled by the gear box.
you said it, it was above your "paygrade" so im trying to give you a little information. there are not mystery forces here. simply the force of traction and the gear box reflecting the the torque to the driveline. yes, it willl be limited by the clutch clamping, but you are forgetting one other significant force. that of the mass of the driveline and clutch pressure plate and INT plate, all spinning at 4500rpm, being quicly rev'ed to 6000rpm on a missmatch downshift.
That alone is a force to be calculated by someone above your paygrade.
the point is, there are forces far greater than you are giving credit to. the fact that the tires can "chirp" on a mis matched downshift, proves that the forces exist on the driveline, its a fact.... otherwise there would be magical forces creating the chirping tire from a mss matched downshift.
(keep in mind greg, the forces are different in 1st and 2nd gear.. the only way to exceed the engine torque with a missmatch downshift is from 4th to 3rd, or 5th to 4th)
i have tested the stock clutch with my stroker for hours before i took it to the track. with 420rear wheel torque, it was not able to slip. But, at the race track with a WOT, fast shift from 2nd to 3rd, it would slip. so, at the track, i replaced it with (what i think is your brilliant design) the high torque stock pressure plate. it worked and has worked for many years now with no slipping and the ability to speedshift and clamp with out slipping as well.
the point is, there are instantaneous forces, no different than a fuse... ( a 30amp fuse can take 40-60amps for a few seconds with no problem. any longer and it blows). the clutch has stiction, and even though the clamping force might be around 400ftlbs, it can hold for a bit higher forces as i have seen.
Just look at the short shafts and input shafts that have broken with out clutch slipping. those are rated and and proved to work at much higher torque values. Anderson ran his motor and trans for many years putting down big torque and with hard downshifts, it still survived.
match reving is so easy and essential to reduce the chance that higher than rated torque forces will be applied to the drivline, thus protecting the input 5th gear, couplings and short shafts. hard downshifts can break CV joints as its like applying drag launch forces on the CV joints and shafts every time you downshift. we have all seen those break on occasion. usually, they are related to not matching RPM on the downshift as well. now that force IS related directly to traction forces... (different than the mis RPM downshift forces on the driveline and now you understand why.... I hope)
#21
Rennlist Member
#22
Rennlist Member
Thread Starter
Greg.... also look at the forces of a non- pre reved shift from 4th to 3rd (or really any gear in this case)
spinning up from 4000rpm to 6000rpm , a 25lb intplate and pressure plate is about 16,000J (thats joules Greg.. you can look that term up)
And, thats about 22hp or 22ftlbs if the speed is around 5300rpm...... if that quick gear slection goes from 4th to 3rd in less than 1/10th of a second.... thats 220hp or near 220ftls of torque all on the synchros! also a source of why things wear out and get "crunchy". this is why it is so important to pre rev and do it without a full pedal depression as then you get the effect of double clutching when you rev with the clutch in before you select a gear.
spinning up from 4000rpm to 6000rpm , a 25lb intplate and pressure plate is about 16,000J (thats joules Greg.. you can look that term up)
And, thats about 22hp or 22ftlbs if the speed is around 5300rpm...... if that quick gear slection goes from 4th to 3rd in less than 1/10th of a second.... thats 220hp or near 220ftls of torque all on the synchros! also a source of why things wear out and get "crunchy". this is why it is so important to pre rev and do it without a full pedal depression as then you get the effect of double clutching when you rev with the clutch in before you select a gear.
#23
Hell, I had to go back and look at that. There's just something in the pic that takes the attention away from the words.
#24
Rennlist Member
This ad, however, was real:
#25
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
My very limited experience in situations such as the one pictured: "Pre Owed" is absolutely the best word. And it never ends.
#26
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