Seamless Gearboxes (aka blowing in the shifts)

[Tommy Cookers]

below 15000, or above 15000 ?

for ignition retard giving hot blowing ?

[timbo]

below 15000, or above 15000 ?

for ignition retard giving hot blowing ?

I checked the rules and it says above 15k, so my idea is not very valid, however, I found this:

Engine high rev limits may vary for differing conditions provided all are significantly above the
peak of the engine torque curve. However, a lower rev limit may be used when :
-
The gearbox is in neutral.

I think this might be the thing teams are exploiting. Between shifts they have lower limiter settings, and they achieve engine limiting in such way that provides more exhaust flow.

[autogyro]

below 15000, or above 15000 ?

for ignition retard giving hot blowing ?

I checked the rules and it says above 15k, so my idea is not very valid, however, I found this:

Engine high rev limits may vary for differing conditions provided all are significantly above the
peak of the engine torque curve. However, a lower rev limit may be used when :
-
The gearbox is in neutral.

I think this might be the thing teams are exploiting. Between shifts they have lower limiter settings, and they achieve engine limiting in such way that provides more exhaust flow.

If they are it proves there is a neutral 'gap' in the current so called 'seamless' gearboxes.

[xxChrisxx]

It seems that certain F1 teams are increasing the gearshift 'GAP' to allow use of the engine being 'disengaged from the gearbox' during the shifts, to blow a higher volume of exhaust gas over the diffuser during deceleration and corner entry.

The 'GAP' in the gearshift allows this to be done because there is zero or minus torque being transffered during the shifts.

So mush for all the 'seamless' gearbox BS.

Not to make too fine a point of it but torque interupt only really hampers acceleration, F1 boxes don't have a torque interrupt on an upshift because the higher gear overdrives the lower one.

This means using the current system can't have non interruped downshift, but why should one care if no engine power is being delivered when one is slowing down?

[rjsa]

If they wanted to fix the blown diffuser they would, the solution wouldn't go the way of the gearbox. Just clarify the exhaust rules and have the damn thing spitting straight back. They just won't.

[autogyro]

It seems that certain F1 teams are increasing the gearshift 'GAP' to allow use of the engine being 'disengaged from the gearbox' during the shifts, to blow a higher volume of exhaust gas over the diffuser during deceleration and corner entry.

The 'GAP' in the gearshift allows this to be done because there is zero or minus torque being transffered during the shifts.

So mush for all the 'seamless' gearbox BS.

Not to make too fine a point of it but torque interupt only really hampers acceleration, F1 boxes don't have a torque interrupt on an upshift because the higher gear overdrives the lower one.

This means using the current system can't have non interruped downshift, but why should one care if no engine power is being delivered when one is slowing down?

Ill tell Adrian Newey he's wrong then.

[Tommy Cookers]

Unfortunately for 2014 the FIA is allowing 8 speed gearboxes and I think I can see why now.

IIRC that is 8 overall (end-to-end) ratios throughout the 2014 season
(so presumably there is only one final drive ratio available)
with a one-off departure option in-season (Monaco related?)

so some races might see drivers using 1-2-3-4-5-6, some 2-3-4-5-6-7, and some 3-4-5-6-7-8 in the '8 speed' gearboxes ?
so, loosely speaking, they will typically be used as 6 speed gearboxes

although, given the fixed rate of fuelling above 10500 rpm, the engine man would prefer a 'real' 8 speed box, or 9, or 10 ?
to keep the engine around this speed almost constantly

[timbo]

If they are it proves there is a neutral 'gap' in the current so called 'seamless' gearboxes.

Most likely there is. However it is not there because they can't make a gearbox without gap, but because they need that gap for aero reasons.

[machin]

This is off topic, but I can't allow these phrases to be posted without identifying the flaws, simply to avoid people going away thinking that physics is more complicated that it really is....

First gear has to accelerate the car from stationary which takes lots of power to establish inertia.

A vehicle's inertia is a measure of its mass, and, in the case of rotational inertia (applicable to the car's wheels, engine, brake discs, props shaft, etc) the placement of that mass about the component's centre of rotation. For a given gear ratio it is a fixed value whether the car is stationary, moving at a constant speed, or accelerating. There is no such thing as "Establishing inertia". Fundamentally the equation F=mA (or A=F/m) is what determines vehicle performance.

A good start is much easier with a lower first gear.

The easiest start in a vehicle with a high power:grip ratio is achieved when using a longer (lower ratio) first gear since this reduces the motive force at the driven wheels; there is no chance of spinning the driven wheels since there is insufficient force to break traction, for this reason motoring groups recommend pulling away in 2nd or 3rd gear in icy conditions. The fastest start is achieved when the motive force at the driven wheels exactly equals the tyre's traction capacity... try increasing the force any more than the tyre's limit (e.g. by opening the throttle more or using a shorter (higher ratio) gear) will simply result in wheel spin and a loss of acceleration. If you decrease the force below the tyre's traction limit (by using a longer (lower ratio) gear, or reducing the throttle opening a bit) you are simply giving yourself less force to accelerate the car, and remember A=F/m.

People shouldn't be confused by "crawler" gears which are fitted to some cars; generally off-road vehicles. These are very short (high ratio) gears which are expressely used to limit the maximum rotational speed of the driven wheels; this is ideal for travelling at a constant slow speed on low friction surfaces, but the maximum low speed acceleration of the vehicle is still limited by the tyre's traction limit.

[xxChrisxx]

So mush for all the 'seamless' gearbox BS.

Not to make too fine a point of it but torque interupt only really hampers acceleration, F1 boxes don't have a torque interrupt on an upshift because the higher gear overdrives the lower one.

This means using the current system can't have non interruped downshift, but why should one care if no engine power is being delivered when one is slowing down?

Ill tell Adrian Newey he's wrong then.

Here is an extract from a letter I received from Adrian Newey when he was technical director at McLaren in1999.

"The current layout may be crude but it is light, small and has a good efficiency with only a very short torque interruption during gear changes".

Signed Adrian Newey.

Not really answering the question that is it. Also, you state yourself that the response was in 99. Not really surprising that he mentions a brief torque interrupt as it predates the current in use shifting system by about half a decade+.

[autogyro]

The easiest start in a vehicle with a high power:grip ratio is achieved when using a longer (lower ratio) first gear since this reduces the motive force at the driven wheels; there is no chance of spinning the driven wheels since there is insufficient force to break traction, for this reason motoring groups recommend pulling away in 2nd or 3rd gear in icy conditions. The fastest start is achieved when the motive force at the driven wheels exactly equals the tyre's traction capacity... try increasing the force any more than the tyre's limit (e.g. by opening the throttle more or using a shorter (higher ratio) gear) will simply result in wheel spin and a loss of acceleration. If you decrease the force below the tyre's traction limit (by using a longer (lower ratio) gear, or reducing the throttle opening a bit) you are simply giving yourself less force to accelerate the car, and remember A=F/m.

People shouldn't be confused by "crawler" gears which are fitted to some cars; generally off-road vehicles. These are very short (high ratio) gears which are expressely used to limit the maximum rotational speed of the driven wheels; this is ideal for travelling at a constant slow speed on low friction surfaces, but the maximum low speed acceleration of the vehicle is still limited by the tyre's traction limit.

I agree but using a higher first gear will result in higher engine rpm than is ideal to achieve maximum tyre grip from that ratio without engine stall. The higher gear will therefore practicaly assure wheel spin in a powerful light F1 car, which will be less controllable than for a lower ratio.
There is a bigger chance of wheel spin because of the high ratio and less of a chance to regain grip.
A poor start.


The time between two points for a stationary vehicle is zero.

[Richard]

avoid people going away thinking that physics is more complicated that it really is....

Thanks. The joy of physics is that it is wonderfully simple and elegant.

I sometimes think its a failing of the human brain that we tend to over complicate matters, we try to see patterns in everything, try to see shapes in the shadows. I guess that was a useful evolutionary trait for foraging and avoiding sabre tooth tigers in the bushes. However its a real obstacle at times, most acutely when it assessing probabilities.

So back to topic...

As I understand it, this method contrives to exaggerate the gap between gears in the downshift, and then uses that freewheel moment to blip the engine to blow the exhaust? Would that be rather disruptive because the rear downforce will be spiky? Or is shifting down the gears so rapid that the gap between pulses at each gear change is short enough to keep the momentum of the air flowing through the diffuser with little disruption?


ox

[bhall]

Just looking through the regs - again - there's a considerable amount of room to play with.

9.8.1 Automatic gear changes are considered a driver aid and are therefore not permitted.

For the purposes of gear changing, the clutch and throttle need not be under the control of the driver.

9.8.4 The maximum permitted duration for down changes and up changes is 300ms and 200ms respectively. The maximum permitted delay for the latter is 80ms from the time of the driver request to the original gear being disengaged.

The duration of a gear change is defined as the time from the request being made to the point at which all gear change processes are terminated. If for any reason the gear change cannot be completed in that time the car must be left in neutral or the original gear.

[timbo]

So we have 300ms max. As the whole braking event takes mere seconds, that's quite a long time indeed!

[Richard]

So we have 300ms max. As the whole braking event takes mere seconds, that's quite a long time indeed!

If you stack them up with say 300ms between each, then changing from 7 to say 3 = 4*(300+300) = 1.8 sec. If the driver can sync that with late braking then that'd give more downforce on the corner entry?

It'd only help on tight corners, they'd not get any benefit on fast bends or a sequence like Eau Rouge or the Susuka S