Race car clucthes
Discussion
Right, settle an argument.
Do pretty much all race cars that have H-gate transmission work without using the clutch.
That is, do the drivers rev match and just 'slam it into gear' without a clucth?
http://forum.racesimcentral.com/showpost.php?p=390...
This is the statement, and I don't think its true, no way can someone rev match good enough to never need a clutch and especially when racing.
Do pretty much all race cars that have H-gate transmission work without using the clutch.
That is, do the drivers rev match and just 'slam it into gear' without a clucth?
http://forum.racesimcentral.com/showpost.php?p=390...
This is the statement, and I don't think its true, no way can someone rev match good enough to never need a clutch and especially when racing.
Edited by Cerberus90 on Thursday 13th August 21:25
i would say depends on the driver, some do some don't.
http://www.youtube.com/watch?v=UpSDK84XVIg
http://www.youtube.com/watch?v=N9vEI-ijTdU
http://www.youtube.com/watch?v=lwv0EVYasq0
http://www.youtube.com/watch?v=lwv0EVYasq0
http://www.youtube.com/watch?v=azpqTZ6WeJk
http://www.youtube.com/watch?v=UpSDK84XVIg
http://www.youtube.com/watch?v=N9vEI-ijTdU
http://www.youtube.com/watch?v=lwv0EVYasq0
http://www.youtube.com/watch?v=lwv0EVYasq0
http://www.youtube.com/watch?v=azpqTZ6WeJk
They use the clutch sometimes in V8 supercars using a sequential box, although mostly while downshifting:
http://www.youtube.com/watch?v=qdWSyrqEnE4&fea...
And heres Colin Turkington using the clutch in his BMW during the warmup lap, not sure if its the same when racing:
http://www.youtube.com/watch?v=rkeHfC7ZIrI
http://www.youtube.com/watch?v=qdWSyrqEnE4&fea...
And heres Colin Turkington using the clutch in his BMW during the warmup lap, not sure if its the same when racing:
http://www.youtube.com/watch?v=rkeHfC7ZIrI
Basically it depends on the driver.
If the car has a dog box (dog rings instead of synchros, but still H gate) then it is possible to change gear without the clutch. However, by doing so you tend to speed up the wear of the dogs. Most drivers I have worked with will prefer to use the clutch.
With sequential dog boxes (as used in BTCC etc) the clutch is not used for upshift, instead there is a switch hooked up to the gear lever which cuts the throttle for a fe milli seconds for the shift to occur. When going back down the box most drivers will use the clutch to help 'soften' the downshifts and prolong the life of the gearbox and aid general reliability.
If the car has a dog box (dog rings instead of synchros, but still H gate) then it is possible to change gear without the clutch. However, by doing so you tend to speed up the wear of the dogs. Most drivers I have worked with will prefer to use the clutch.
With sequential dog boxes (as used in BTCC etc) the clutch is not used for upshift, instead there is a switch hooked up to the gear lever which cuts the throttle for a fe milli seconds for the shift to occur. When going back down the box most drivers will use the clutch to help 'soften' the downshifts and prolong the life of the gearbox and aid general reliability.
As said above, it depends. There are many factors.
Robustness of the device itself, of course:
What sorts of loads are going through the rings (the things that engage and disengage)?
How long is the race or, perhaps more accurately, for how many shifts does the box have to last?
Which ratios to be used (higher gears easier to match)?
What's the budget for maintenance/rebuilds?
etc...
You could do with a real expert PHer, such as John Felstead, to asnwer the question.
Btw, the linked post refers to "straight-cut gears". The gears themselves are in constant mesh, so they aren't the things that need to be synchronised. They can have straight-cut teeth, or helical (angled) teeth.
The dog rings are the things that engage and disengage for gear selection. You can have them with or without synchros.
Edited to get "PHer" right!
Robustness of the device itself, of course:
What sorts of loads are going through the rings (the things that engage and disengage)?
How long is the race or, perhaps more accurately, for how many shifts does the box have to last?
Which ratios to be used (higher gears easier to match)?
What's the budget for maintenance/rebuilds?
etc...
You could do with a real expert PHer, such as John Felstead, to asnwer the question.
Btw, the linked post refers to "straight-cut gears". The gears themselves are in constant mesh, so they aren't the things that need to be synchronised. They can have straight-cut teeth, or helical (angled) teeth.
The dog rings are the things that engage and disengage for gear selection. You can have them with or without synchros.
Edited to get "PHer" right!
Edited by flemke on Thursday 13th August 22:00
Cerberus90 said:
http://forum.racesimcentral.com/showpost.php?p=390...
Quoted from the above
Like it or not, that is how most race car transmissions work. The gears in the gearbox are straight cut, meaning they have to engage and disengage as quickly as possible to avoid touching only the outer parts of the teeth - as the forces might tear these teeth off (a so called 'stripped gear' would occur). I'm not 100% of WHY and how all this works, but the outcome is that the clutch is only used to get going, and to avoid stalling when having an off from the track. They just slam them into gear, while trying to rev match best they can with the right foot on the throttle. Using left foot to brake.
The guy is talking nonsense.Quoted from the above
Like it or not, that is how most race car transmissions work. The gears in the gearbox are straight cut, meaning they have to engage and disengage as quickly as possible to avoid touching only the outer parts of the teeth - as the forces might tear these teeth off (a so called 'stripped gear' would occur). I'm not 100% of WHY and how all this works, but the outcome is that the clutch is only used to get going, and to avoid stalling when having an off from the track. They just slam them into gear, while trying to rev match best they can with the right foot on the throttle. Using left foot to brake.
Straight cut has nothing to do with the gear engagement system, it refers to the tooth cut pattern of the gears. You can have syncromesh or dog engaged straight cut gears. Road car boxes use helical cut gears to reduce noise, Race boxes tend to use straight cut gears because they put no side load on the gear, so you lose less torque to the wheels, but they are noisy.
With all types of gear engagement, it helps to rev match, but it's more beneficial with a dog gear arrangement because you are engaging two sets of dogs (dogs are angled protrusions on the side of the gear and the side of the clutch ring that interlock to provide drive from the gear to the hub and then to the pinion shaft), with a syncromesh you have a system that automatically rev matches the hub to the gear before final drive engagement takes place. The problem with syncro engagement in a race environment is the speed the two parts can match speed is slower than ideal, so you can beat the syncro and force the engagement of drive before the hub and gear have speed matched, this wears the syncro assembly quickly and you can end up with a crunching gear change and the gear popping back out as the drive teeth on the syncro hub are worn out of shape.
As to the clutch question, it depends on the gearbox and size of the gears involved (ie the momentum in the gear assembly), some gearboxes need the use of the clutch both up and down, others can get away with downshift only use of the clutch, others once on the move can get away with no clutch use. The most modern sophisticated kit that has electronics involved can have no driver input for the clutch, but on a lot of these the electronics is activating the clutch and rev matching the engine, just the driver doesn't need to get involved.
johnfelstead said:
Cerberus90 said:
http://forum.racesimcentral.com/showpost.php?p=390...
Quoted from the above
Like it or not, that is how most race car transmissions work. The gears in the gearbox are straight cut, meaning they have to engage and disengage as quickly as possible to avoid touching only the outer parts of the teeth - as the forces might tear these teeth off (a so called 'stripped gear' would occur). I'm not 100% of WHY and how all this works, but the outcome is that the clutch is only used to get going, and to avoid stalling when having an off from the track. They just slam them into gear, while trying to rev match best they can with the right foot on the throttle. Using left foot to brake.
The guy is talking nonsense.Quoted from the above
Like it or not, that is how most race car transmissions work. The gears in the gearbox are straight cut, meaning they have to engage and disengage as quickly as possible to avoid touching only the outer parts of the teeth - as the forces might tear these teeth off (a so called 'stripped gear' would occur). I'm not 100% of WHY and how all this works, but the outcome is that the clutch is only used to get going, and to avoid stalling when having an off from the track. They just slam them into gear, while trying to rev match best they can with the right foot on the throttle. Using left foot to brake.
Straight cut has nothing to do with the gear engagement system, it refers to the tooth cut pattern of the gears. You can have syncromesh or dog engaged straight cut gears. Road car boxes use helical cut gears to reduce noise, Race boxes tend to use straight cut gears because they put no side load on the gear, so you lose less torque to the wheels, but they are noisy.
With all types of gear engagement, it helps to rev match, but it's more beneficial with a dog gear arrangement because you are engaging two sets of dogs (dogs are angled protrusions on the side of the gear and the side of the clutch ring that interlock to provide drive from the gear to the hub and then to the pinion shaft), with a syncromesh you have a system that automatically rev matches the hub to the gear before final drive engagement takes place. The problem with syncro engagement in a race environment is the speed the two parts can match speed is slower than ideal, so you can beat the syncro and force the engagement of drive before the hub and gear have speed matched, this wears the syncro assembly quickly and you can end up with a crunching gear change and the gear popping back out as the drive teeth on the syncro hub are worn out of shape.
As to the clutch question, it depends on the gearbox and size of the gears involved (ie the momentum in the gear assembly), some gearboxes need the use of the clutch both up and down, others can get away with downshift only use of the clutch, others once on the move can get away with no clutch use. The most modern sophisticated kit that has electronics involved can have no driver input for the clutch, but on a lot of these the electronics is activating the clutch and rev matching the engine, just the driver doesn't need to get involved.
A point that might have been mentioned is that there is no need for the gears
to 'engage and disengage'.
The pairs of gears are always meshed together. What happens is the that dog rings shift in and out of engagement to lock one gear or another into transmission.
For the definitive method of shifting gear read the article by Willam Hewland, copied below:
By William Hewland.
July 2000
The following is some info regarding shifting gear and face dog wear. I am in the fortunate position where I have a good amount of knowledge on the subject, as I understand the mechanical side and the user (driver) side equally well.
N.B. For succesful gear shifting, remember that it is critical to ensure that all mechanical elements between the drivers hand and the dog faces are in good order and properly set. This includes the gear linkage in the chassis!
Successful up-shifting, (defined as fast and non dog-damaging) will be achieved by fully moving the dog ring as rapidly as possible from one gear to the next, preferably with the engine's driving load removed until the shift is completed. (The opposite is true of a synchromesh gearbox as used in passenger cars, where slow movement helps). It should be remembered that it is not possible to damage the dogs when fully engaged (in gear). The damage can only take place when initiating contact during a shift, (the `danger zone`) therefore this element must be made as short as possible. If a driver moves the gear lever slowly, or if the linkage is not rigid and effective, dog wear will occur. We always recommend lightweight yet solid rod linkage, not cables ideally.
I list below the different methods of up-shifting that are used in racing most commonly. The best at the top, the worst at the bottom:
Automated (semi automated). The movement of the dog ring is powered and the engine is cut / re-instated in a co-ordinated manner. Gear-shifts take milliseconds. This system produces zero dog wear when set up well. It is not applicable to most cars, but it illustrates that speed of shift is a good thing.
Manual with engine cut. This system is almost as good as an automated one as long as the driver pulls the lever very quickly. Again it is not applicable to many cars, but it illustrates that speed of shift is a good thing. A `cheat` version of this is to shift on the engine rev limiter, which can work well. With this system it is especially important to move the lever ultra fast, otherwise the engine will be reinstated during partial dog engagement, causing damage. The damage can usually be felt by the driver.
Manual.
Best method: With no assistance from the engine management, the driver must lift off the throttle sufficiently to allow the dog ring to be pulled out of engagement. He should then stay off the throttle long enough to allow the dog ring to engage with the next gear. In practice, the driver can move the gear lever faster than he can move his foot off and back on to the throttle. Therefore the effective method is to apply load to the gear lever with your hand and then lift the throttle foot off and back on to the pedal as fast as physically possible. In lifting your foot, the loaded gear lever will almost involuntarily flick to the next gear before the foot is re-applied to the throttle.
Another method is to load the gear lever with your hand, stay flat on the throttle and dab the clutch to release the dog ring. The overall effect on the gear shift is similar to the above method, but clutch wear may become a big issue.
The worst method (most destructive and definitely slowest) is to attempt to change gear in a `passenger car / synchromesh` way, i.e. lifting off the throttle, dipping the clutch, moving the gear lever, letting the clutch up and re-instating the throttle. The method causes unnecessary clutch wear, does absolutely nothing to help come out of gear and usually causes dog wear whilst engaging the next gear. This wear is due to several reasons. Firstly, it is impossible for a driver to co-ordinate the complicated sequence of all five physical movements accurately. Consequently the engagement dogs often find themselves engaging whilst the throttle is applied. The lever is usually pulled more slowly as it was not pre-loaded, lengthening the `danger zone`.
Successful down-shifting, has similar rules applied regarding speed of shift. Unloading the dogs is done in the opposite manner obviously. Whilst braking, the dogs must be unloaded by either touching the throttle pedal or- my preferred method- by dipping the clutch. However, one sharp dab of clutch or throttle is appropriate per shift. Continued pressure on either will cause dog damage for different reasons. `Blipping the throttle` just before engagement is advisable if the rev drops between gears are over 1300 rpm, as this will aid engagement and stabilise the car.
TOP TIP for ease of downshifting: Make the downshifts as late as possible in your braking zone (i.e. at lower road speed), because the rev drops between each gear are then lower. So many drivers make the mistake of downshifting as soon as they begin braking, causing gearbox wear, engine damage and `disruption` to the driving wheels.
to 'engage and disengage'.
The pairs of gears are always meshed together. What happens is the that dog rings shift in and out of engagement to lock one gear or another into transmission.
For the definitive method of shifting gear read the article by Willam Hewland, copied below:
By William Hewland.
July 2000
The following is some info regarding shifting gear and face dog wear. I am in the fortunate position where I have a good amount of knowledge on the subject, as I understand the mechanical side and the user (driver) side equally well.
N.B. For succesful gear shifting, remember that it is critical to ensure that all mechanical elements between the drivers hand and the dog faces are in good order and properly set. This includes the gear linkage in the chassis!
Successful up-shifting, (defined as fast and non dog-damaging) will be achieved by fully moving the dog ring as rapidly as possible from one gear to the next, preferably with the engine's driving load removed until the shift is completed. (The opposite is true of a synchromesh gearbox as used in passenger cars, where slow movement helps). It should be remembered that it is not possible to damage the dogs when fully engaged (in gear). The damage can only take place when initiating contact during a shift, (the `danger zone`) therefore this element must be made as short as possible. If a driver moves the gear lever slowly, or if the linkage is not rigid and effective, dog wear will occur. We always recommend lightweight yet solid rod linkage, not cables ideally.
I list below the different methods of up-shifting that are used in racing most commonly. The best at the top, the worst at the bottom:
Automated (semi automated). The movement of the dog ring is powered and the engine is cut / re-instated in a co-ordinated manner. Gear-shifts take milliseconds. This system produces zero dog wear when set up well. It is not applicable to most cars, but it illustrates that speed of shift is a good thing.
Manual with engine cut. This system is almost as good as an automated one as long as the driver pulls the lever very quickly. Again it is not applicable to many cars, but it illustrates that speed of shift is a good thing. A `cheat` version of this is to shift on the engine rev limiter, which can work well. With this system it is especially important to move the lever ultra fast, otherwise the engine will be reinstated during partial dog engagement, causing damage. The damage can usually be felt by the driver.
Manual.
Best method: With no assistance from the engine management, the driver must lift off the throttle sufficiently to allow the dog ring to be pulled out of engagement. He should then stay off the throttle long enough to allow the dog ring to engage with the next gear. In practice, the driver can move the gear lever faster than he can move his foot off and back on to the throttle. Therefore the effective method is to apply load to the gear lever with your hand and then lift the throttle foot off and back on to the pedal as fast as physically possible. In lifting your foot, the loaded gear lever will almost involuntarily flick to the next gear before the foot is re-applied to the throttle.
Another method is to load the gear lever with your hand, stay flat on the throttle and dab the clutch to release the dog ring. The overall effect on the gear shift is similar to the above method, but clutch wear may become a big issue.
The worst method (most destructive and definitely slowest) is to attempt to change gear in a `passenger car / synchromesh` way, i.e. lifting off the throttle, dipping the clutch, moving the gear lever, letting the clutch up and re-instating the throttle. The method causes unnecessary clutch wear, does absolutely nothing to help come out of gear and usually causes dog wear whilst engaging the next gear. This wear is due to several reasons. Firstly, it is impossible for a driver to co-ordinate the complicated sequence of all five physical movements accurately. Consequently the engagement dogs often find themselves engaging whilst the throttle is applied. The lever is usually pulled more slowly as it was not pre-loaded, lengthening the `danger zone`.
Successful down-shifting, has similar rules applied regarding speed of shift. Unloading the dogs is done in the opposite manner obviously. Whilst braking, the dogs must be unloaded by either touching the throttle pedal or- my preferred method- by dipping the clutch. However, one sharp dab of clutch or throttle is appropriate per shift. Continued pressure on either will cause dog damage for different reasons. `Blipping the throttle` just before engagement is advisable if the rev drops between gears are over 1300 rpm, as this will aid engagement and stabilise the car.
TOP TIP for ease of downshifting: Make the downshifts as late as possible in your braking zone (i.e. at lower road speed), because the rev drops between each gear are then lower. So many drivers make the mistake of downshifting as soon as they begin braking, causing gearbox wear, engine damage and `disruption` to the driving wheels.
DSM2 said:
A point that might have been mentioned is that there is no need for the gears
to 'engage and disengage'.
The pairs of gears are always meshed together. What happens is the that dog rings shift in and out of engagement to lock one gear or another into transmission.
For the definitive method of shifting gear read the article by Willam Hewland, copied below:
worth pointing out this only applied to DOG (engagement) boxes, this has NOTHING to do with the gears being straight-cut/helical/semi-helical/etc.to 'engage and disengage'.
The pairs of gears are always meshed together. What happens is the that dog rings shift in and out of engagement to lock one gear or another into transmission.
For the definitive method of shifting gear read the article by Willam Hewland, copied below:
- *SNIP***
do this with a syncro (engagement) box and you will kill the syncro's.
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