Gear Ratios

[Venom]

How is the gear ratio calculated? I assume it is the radious of pulleys inside the gearbox that transfer motion.

If I'm right (let me know ) then most teams change ratios for specific tracks and in order to do that they have to change gearbox or take it apart as it is very complicated piece of machinery right.

So, what happens in 2008 and the gearboxes have to last forur races? How will teams adjust gear ratios for each track?

[DaveKillens]

Gear ratio is calculated by counting the gear teeth. For instance, the driving gear may have 23 teeth, while the driven gear may have 32 teeth.
The teams run a lot of computer simulations to try to predict the upcoming race, and usually set the ratios before they arrive at the track. But with the new rule, I guess we shalll soon see everyone running seven speed gearboxes.

[Ciro Pabón]

To clarify the above explanation a little, the gear ratio is the number of revolutions that makes the exit axle of the gearbox while the axle connected to the engine makes one revolution.

You can find it out by dividing the number of teeth of the gear connected to the wheels by the number of teeth of the gear connected to the engine.

When you are chosing your gear ratios, you want to run the engine around the point of maximum torque, which is a fairly narrow window of rpm. Besides, you want to be able to reach your maximum speed. So, the rule of thumb is: a low speed circuit will have lower gear ratios (actually, greater numbers) than a high speed circuit. In a windy circuit you may give a little of your maximum speed or you can spread a little more your gear ratios to gain more accelerating power. It is the same as in your bycicle: a mountain bike has lower gear ratios than a race bike. You can accelerate faster in the first, you can go faster in the second.

The ideal would be to have a variable gear box: this gearbox would change your gear ratio automatically and continously to keep the engine at the maximum torque attainable. But this kind of gearboxes are forbidden, so you want as much gears as possible. There is a limit: every time you are in the middle of a change of gears, your car is idle.

The word ratio comes from the latin word for relationship or reason (ratio), not from the word for radius (radii). Finally, there are no pulleys inside a gearbox, only gears. If they were inside, we could call it the pulleybox.

[Reca]

When you are chosing your gear ratios, you want to run the engine around the point of maximum torque

Not “around maximum torque” but “around maximum power rpm”.

The ideal would be to have a variable gear box: this gearbox would change your gear ratio automatically and continously to keep the engine at the maximum torque attainable

Again, to keep the engine at the rpm of maximum power attainable, not torque. To maximise torque at the wheels you have to keep the engine at maximum power rpm.

[lob4star]

does any one know where you can find out what types of gear ratios are used in f1 car.
odiously there isn’t going to be ratios for ever track i just wanted to know an averaged figure for the different gears as i have been looking around for a bit but cant find anything.

[DaveKillens]

Usually, gear ratios are selected based on the powertrain power delivery, and the speeds of the individual corners. For each track, there should be different ratios. Ideally, for each corner you launch out of, you want the engine in the meat of it's powerband, still able to rev a little more, but with maximum torque. And of course, as you shift from one gear to the next, ideally you want the next higher gear to be well into generous torque, to continue to accelerate as best as possible. If engineers were given free rein with no rules constraint, we might see someone with a 18 speed gearbox. But of course, practical limitations on the size and complexity of the gearbox, as well as the rules limit the engineers using a seven or six speed gearbox. And of course, different tracks require different speeds. For instance, gear ratios for Monaco would not work at Monza, and vice versa. Usually, ratio selection is a compromise.

[ginsu]

I think some of the best experience you can get with gear ratios comes from bicycling. I know humans have a very specific cadence (rpm) with which they operate

The best cadence is a balance between leg speed and pedal pressure, but as a cyclist puts more energy into the task, both increase. So, the non-cyclist will pedal at 60 rpm going 10 miles an hour, the tourist will spin at 80 rpm going 15 miles an hour, and the racer will twirl at 100 rpm going 20 miles an hour.

Because the cadence only varies by 40rpm that makes gear ratios even more important than in a car. I find myself constantly shifting when I bicycle to keep the cadence within a specific range, especially because muscles can tire so easily. This is the same reason you see diesel trucks with obscene numbers of gear ratios, because the diesel engine only operates effectively in a narrow RPM range. I think you can say that the number of gear ratios are a function of the powerband of the engine operating them. Alas, Renault only needed 6 gears in 2005.

[m3_lover]

I got this information from my car and driver dated 0ctober 2000

The Jaguar R1

Final-drive ratio 3.83:1, programmed electrohydraluic limited slip

Transfer-gear ratio 1.35-1

Gear Ratio Mph/1000 rpm Max. speed in gears
1 2.29 6.0 107 mph (18000 rpm)
2 2.00 6.8 123 mph (18000 rpm)
3 1.79 7.6 137 mph (18000 rpm)
4 1.65 8.3 149 mph (18000 rpm)
5 1.56 8.8 158 mph (18000 rpm)
6 1.47 9.3 167 mph (18000 rpm)

Also this was a good tid bit too and I quote

"Every aspect of the v-10 is a study in such compromises. Increase the revs in search of more power and internal friction also rises, along with fuel comsumption. Install a thermostat set for a cooler temperature to increase the intake-charge density, and you need a bigger radiatior, which adds to aerodynamic drag. Make the engine stronger and more durable, and you make it heaver."

[lob4star]

great thanks for the ratios .