Racing Brake Pad / Brake system discussion/questions
07-28-2014, 01:12 AM
#316
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Thread Starter
kaiB,
I was discussing this with several people and it seems you might not have the gip on reality of the dynamics of the syncho's as you think.
From a known expert in transmissions and building race cars and engines:
(You have to look at the last sentence, to not only show that there isnt a debate here, but you are "completely" wrong.)
that's the problem with this discussion. so many people making suggestions and providing information without either a clue of understanding, or leaving out several of the main dominant factors.
Anyway, here is what he wrote.
Well....the writer certainly seems really sure of what he thinks....
However, the closer one can match the speed of the gear that is going to be engaged to the speed of the syncro it is being used to engage that gear, it's pretty obvious that wear is going to go down at an incredible rate.
Simply look at a common downshift:
The pinion is obviously rotating at the speed required by the ring gear, for the speed the vehicle is going....they are all mechanically connected and unable to be disconnected (unless something breaks.)
The layshaft, 5th gear, the torque tube shaft, the clutch disc, and the engine are all turning the speed required for the gear currently selected.
When a downshift is desired, the layshaft, 5th gear, the torque tube shaft, the clutch, and the engine rpms must be increased.
Once the clutch is depressed, the engine is temporarily out of the equation....but the clutch, the torque tube shaft, 5th gear, the layshaft, and the "new lower ratio" gear must all have their speed increased. Without increasing that rpm with the engine, the only way to do this is by the syncro increasing the speed as it slides over the "new lower ratio gear".
Pretty simple stuff.
Obviously, the less work the syncro needs to do (increasing the speed with the engine, instead of totally by the syncro) the less wear there will be on that syncro.
I have no idea of who made the statement that "matching has NO effect on the syncro at all. None, zero, nada, zip", but his understanding of what is happening isn't nearly as good as his writing....
Respectively, he's completely wrong.
I was discussing this with several people and it seems you might not have the gip on reality of the dynamics of the syncho's as you think.
From a known expert in transmissions and building race cars and engines:
(You have to look at the last sentence, to not only show that there isnt a debate here, but you are "completely" wrong.)
that's the problem with this discussion. so many people making suggestions and providing information without either a clue of understanding, or leaving out several of the main dominant factors.
Anyway, here is what he wrote.
Well....the writer certainly seems really sure of what he thinks....
However, the closer one can match the speed of the gear that is going to be engaged to the speed of the syncro it is being used to engage that gear, it's pretty obvious that wear is going to go down at an incredible rate.
Simply look at a common downshift:
The pinion is obviously rotating at the speed required by the ring gear, for the speed the vehicle is going....they are all mechanically connected and unable to be disconnected (unless something breaks.)
The layshaft, 5th gear, the torque tube shaft, the clutch disc, and the engine are all turning the speed required for the gear currently selected.
When a downshift is desired, the layshaft, 5th gear, the torque tube shaft, the clutch, and the engine rpms must be increased.
Once the clutch is depressed, the engine is temporarily out of the equation....but the clutch, the torque tube shaft, 5th gear, the layshaft, and the "new lower ratio" gear must all have their speed increased. Without increasing that rpm with the engine, the only way to do this is by the syncro increasing the speed as it slides over the "new lower ratio gear".
Pretty simple stuff.
Obviously, the less work the syncro needs to do (increasing the speed with the engine, instead of totally by the syncro) the less wear there will be on that syncro.
I have no idea of who made the statement that "matching has NO effect on the syncro at all. None, zero, nada, zip", but his understanding of what is happening isn't nearly as good as his writing....
Respectively, he's completely wrong.
Rev-matching has NO effect on the synchros at all. None, zero, nada, zip. It does not help wear on the synchros, it does not help them do their job and it does nothing more than match engine speed to road speed.
A properly executed double clutch WILL spin the synchros up and help the tranny out.
Two different operations, two different effects. As a small matter of fact, in cars with super light flywheels and tiny clutches, two distinct blips are often necessary during double clutching: One with the clutch engaged (while in neutral) to spin up the tranny and then another a split second later (just prior to the second engagement) to affect rev-matching.
The odd thing is the fact that you actually KNOW all of this. I now believe you have either a reading comprehension problem, an attention issue, drink while posting, or otherwise don't care what others have to say; you merely stab words into the little reply box in an effort to continue the direction of whatever tangential debate the threads lead you.
A properly executed double clutch WILL spin the synchros up and help the tranny out.
Two different operations, two different effects. As a small matter of fact, in cars with super light flywheels and tiny clutches, two distinct blips are often necessary during double clutching: One with the clutch engaged (while in neutral) to spin up the tranny and then another a split second later (just prior to the second engagement) to affect rev-matching.
The odd thing is the fact that you actually KNOW all of this. I now believe you have either a reading comprehension problem, an attention issue, drink while posting, or otherwise don't care what others have to say; you merely stab words into the little reply box in an effort to continue the direction of whatever tangential debate the threads lead you.
07-28-2014, 02:00 AM
#317
Rennlist Member
Thread Starter
I understand what you are saying. However, i do think there is a major factor when you have the driveline pre-reved, before it goes through neutral and then into gear, that the driveline is spun up, greatly lessening the load on the synchros to do the job. I totally understand your point. the driveline is disconnected from the engine. all the force to spin up the driveline to match the new speed is on the sychros and new gear slected. BUT, you are leaving out one key element. everyone starts to let out the clutch as you pass through neutral. this spins up the driveline and you have smooth shifts. again, double clutching was for those big clunky drive lines and straight cut gears.
do an experiment. go 60mph and get the transmission from 3rd gear to second by letting the RPM just fall with the clutch pushed in. watch it grind or if in great shape, it will clunk. Now do it again with the RPM held at 5k after it passes through neutral, then let the clutch pedal out slowly after changing gears. should also go "clunk". now, do it like you are racing. big difference.
the racing downshift, spins up the driveline as you pass through neutral and start using the synchros to clean up any rpm differences, lowering the wear of them.
that's my final answer.
do an experiment. go 60mph and get the transmission from 3rd gear to second by letting the RPM just fall with the clutch pushed in. watch it grind or if in great shape, it will clunk. Now do it again with the RPM held at 5k after it passes through neutral, then let the clutch pedal out slowly after changing gears. should also go "clunk". now, do it like you are racing. big difference.
the racing downshift, spins up the driveline as you pass through neutral and start using the synchros to clean up any rpm differences, lowering the wear of them.
that's my final answer.
07-28-2014, 04:57 AM
#318
I can't believe I am getting sucked in again.
I'll quote your expert in transmissions:
Once the clutch is depressed, the engine is temporarily out of the equation....but the clutch, the torque tube shaft, 5th gear, the layshaft, and the "new lower ratio" gear must all have their speed increased. Without increasing that rpm with the engine, the only way to do this is by the syncro increasing the speed as it slides over the "new lower ratio gear".
Look at the text again. Tell us how you are going to increase the speed of all that stuff if you don't double clutch and rev match? Without double clutching and rev matching, the synchros have to do all the work.
The only way to reduce the workload of the synchros is to double clutch and rev match.
I'll quote your expert in transmissions:
Once the clutch is depressed, the engine is temporarily out of the equation....but the clutch, the torque tube shaft, 5th gear, the layshaft, and the "new lower ratio" gear must all have their speed increased. Without increasing that rpm with the engine, the only way to do this is by the syncro increasing the speed as it slides over the "new lower ratio gear".
Look at the text again. Tell us how you are going to increase the speed of all that stuff if you don't double clutch and rev match? Without double clutching and rev matching, the synchros have to do all the work.
The only way to reduce the workload of the synchros is to double clutch and rev match.
07-28-2014, 08:26 AM
#319
Rennlist Member
Thread Starter
I can't believe I am getting sucked in again.
I'll quote your expert in transmissions:
Once the clutch is depressed, the engine is temporarily out of the equation....but the clutch, the torque tube shaft, 5th gear, the layshaft, and the "new lower ratio" gear must all have their speed increased. Without increasing that rpm with the engine, the only way to do this is by the syncro increasing the speed as it slides over the "new lower ratio gear".
Look at the text again. Tell us how you are going to increase the speed of all that stuff if you don't double clutch and rev match? Without double clutching and rev matching, the synchros have to do all the work.
The only way to reduce the workload of the synchros is to double clutch and rev match.
I'll quote your expert in transmissions:
Once the clutch is depressed, the engine is temporarily out of the equation....but the clutch, the torque tube shaft, 5th gear, the layshaft, and the "new lower ratio" gear must all have their speed increased. Without increasing that rpm with the engine, the only way to do this is by the syncro increasing the speed as it slides over the "new lower ratio gear".
Look at the text again. Tell us how you are going to increase the speed of all that stuff if you don't double clutch and rev match? Without double clutching and rev matching, the synchros have to do all the work.
The only way to reduce the workload of the synchros is to double clutch and rev match.
I believe that the fluid nature of the synchronized shift, allows the engine to spin up the torque tube, 5th gear shaft, and gears, before you actually engage the gear. its a timing thing, and that's how you lighten the load significantly on the actual transmission synchros. it has the effect of double clutching but you are not double clutching. it has to do with the timing of every so slightly letting the clutch out as you are going through neutral, which spins up the driveline, quickly and before the synchros finish the job. its the only explanation why a non reved shift attempt will grind the heck out of the synchros and gears, while a match rev shift, doesnt. it takes very little clutch friction to spin up the drive shaft, while still being relatively disconnected to the engine.
07-28-2014, 10:02 AM
#321
The Penguin King
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Danica....
07-28-2014, 10:53 AM
#324
07-28-2014, 10:56 AM
#325
Mr. Excitement
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07-28-2014, 10:56 AM
#326
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Anything...
Brakes are for slowing the car down, way cheaper than synchros (or dog rings and dogs...).
I work with historic cars 70-75% of the time, and have for thirty years.
I don't know ANYONE, except the Pre-War (that's World War II, youngsters), that "double declutch" downshifts.
Brakes are for slowing the car down, way cheaper than synchros (or dog rings and dogs...).
I work with historic cars 70-75% of the time, and have for thirty years.
I don't know ANYONE, except the Pre-War (that's World War II, youngsters), that "double declutch" downshifts.
__________________
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www.peterkrause.net
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"Combining the Art and Science of Driving Fast!"
Specializing in Professional, Private Driver Performance Evaluation and Optimization
Consultation Available Remotely and at VIRginia International Raceway
-Peter Krause
www.peterkrause.net
www.gofasternow.com
"Combining the Art and Science of Driving Fast!"
Specializing in Professional, Private Driver Performance Evaluation and Optimization
Consultation Available Remotely and at VIRginia International Raceway
07-28-2014, 10:59 AM
#327
Rennlist Member
Anything...
Brakes are for slowing the car down, way cheaper than synchros (or dog rings and dogs...).
I work with historic cars 70-75% of the time, and have for thirty years.
I don't know ANYONE, except the Pre-War (that's World War II, youngsters), that "double declutch" downshifts.
Brakes are for slowing the car down, way cheaper than synchros (or dog rings and dogs...).
I work with historic cars 70-75% of the time, and have for thirty years.
I don't know ANYONE, except the Pre-War (that's World War II, youngsters), that "double declutch" downshifts.
07-28-2014, 11:16 AM
#328
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Anything...
Brakes are for slowing the car down, way cheaper than synchros (or dog rings and dogs...).
I work with historic cars 70-75% of the time, and have for thirty years.
I don't know ANYONE, except the Pre-War (that's World War II, youngsters), that "double declutch" downshifts.
Brakes are for slowing the car down, way cheaper than synchros (or dog rings and dogs...).
I work with historic cars 70-75% of the time, and have for thirty years.
I don't know ANYONE, except the Pre-War (that's World War II, youngsters), that "double declutch" downshifts.
You don't know anybody who needs first gear in an older Healey, TR or MG...or a worn out old farm truck? No need to answer.
Dad never D/C'd in his Triumph when he was racing and taught me precisely what you mentioned above, but he used it on the old Benz on the streets, his Singer and he taught me how to when I was 12.
This thread, like virtually all Kibort threads, was entertaining....
07-28-2014, 12:30 PM
#329
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Possibly my favorite in car video of all time is Peter Brock narrating a lap of Bathurst to the tv commentators in 1986, one arm on the window sill, sliding up Mt Panorama at full chat, carrying on conversation as if he were relaxing next to a pool.
You can see his downshifts from 5-4 are single clutched, but 4-3 and 3-2 where the synchros have to make up a larger rev difference he double-clutches. Great stuff.
07-28-2014, 12:54 PM
#330
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Brock's in a league of his own. He can do anything he wants.
Kibort? Not so much!
Kibort? Not so much!