ATLAS F1   Volume 6, Issue 46

  Taking the Lid Off F1

Formula One Technical Analysis

  by Will Gray, England

Last year, Atlas F1 ran a series of articles that investigated the technical areas involved in design, development, and construction of an F1 car. Now, a year later, Will Gray picks up where he left off, and dives deeper into the technical analysis of Formula One.

Part 8B. Use the Force: Transmission

A good engine must be installed well to perform to its ultimate ability, and it must output its power to the wheels in the best manner possible. The chain of events is as follows: The engine is connected to the flywheel, which is linked to the drive shaft via the clutch plates. The drive shaft goes into the gearbox, which is connected to the axles (and therefore the wheels) through the differential. Let's take it piece by piece!

The gearbox is perhaps the most important link in this chain of mechanical events, as it is the most adaptable. The full torque (rotational force) and power produced by the engine cannot go directly to the wheels - it is useless unless it is controlled, and without the gearbox to tone the power down, the wheels would just spin on the track with the car going nowhere. The power produced by the engine is delivered to the gearbox through the driveshaft which, by the very nature of its job, must rotate at the rotational speed (rpm) of the engine.

Because of this, it has to be strong to resist the severe twisting forces placed upon it, and there have been hundreds of retirements put down to driveshaft failure - some teams played with carbon fibre versions to save weight, but in the early days they simply couldn't get them strong enough. At the end of this driveshaft is a gear wheel, which is the initial wheel in the gearbox. As this gear wheel is also spinning at the speed of the engine internals, the gearbox's job is to take the rotation of the crankshaft in the engine, and convert it to an axle (and wheel) rotation speed that the tyre and track adhesion can cope with.

The gearbox consists of a number of different sized gear wheels - a common F1 gearbox will have six or seven different gears, and each one will convert the rpm of the engine to a different wheel rotation speed. First gear will give a slow rotation speed, which will rise up through the gears until, in sixth or seventh gear, there will hardly be any reduction of the engine power (or gear resistance) at all.

Part of the set-up options on the car are the gear ratios, and by modifying these, teams can dictate how much power is received by the wheels in each gear. In a road car, it is easy to see the resistive nature of the gears - if you are in fourth gear and don't press the accelerator, the car will slow; in third, it will slow at a quicker rate. Therefore, it is easy to understand that gears can be used for both braking and accelerating - although if a driver use his engine as a brake, he can put more stress upon it and make it more likely to fail.

Having explained how the gears work, the next thing to consider is how to change between them. We all know this is done using the clutch, but why? Well, with the gear wheel on the end of the drive shaft rotating in the gearbox, it is not going to be easy to move it through the gearbox to meet up with another gear. Any attempt to do so will result in that nerve-jangling, ear-bashing, grinding noise heard all too often from a poorly driven car! That noise is the noise of the rotating gear wheel on the drive shaft grinding against one of the gears in the gearbox - carry on with that, and you're going to by left with a gearbox full of metal shreds! This is why the drivetrain in a car incorporates a clutch.

It consists of two (or more) plates which, when held together with a strong compressive force, provide a perfect connection between driveshaft and engine. When the clutch paddle is pulled (in F1 terms, the clutch is a paddle on the steering wheel), the compressive force on the clutch plates is released and the plate that is connected to the engine can spin to its heart's content, while the one attached to the driveshaft and gear wheels in the gearbox remains still. This allows a new gear to be selected before the clutch pedal is let free, and the pressure on the clutch plates holds them together once more.

In the world of the semi-automatic gearbox, of course, there is no need for the driver to even think about this - his electronics do it all for him! All the driver is required to input is when he wants to change up or down a gear, and the electronics controlling the gearbox and clutch do the rest. The advantages here, over and above the fact that the driver can keep his hands on the wheel at all times, is that the whole process can be done in a split second (much quicker than a manual clutch could be operated) and also that the wear on the clutch pads is less because it is never held half-on, and so this increases reliability. Again, teams have tried to use carbon fibre for clutch material, with limited success.

On the other end of the gearbox lives the differential - an essential part of the drivetrain where drivability is concerned. As it travels around a corner, the car will map out a curved path the width of the car itself. The inside arc of the path will be of tighter radius than the outside one, and so the wheel on the outside will have to travel further and so rotate at a different speed to the wheel on the inside. If the two wheels were directly connected, the loaded wheel (on the outer, longer arc) would force the inner wheel to rotate at the same speed, and the tyre would scrub along the ground. To solve this, the 'limited-slip differential' is used.

This allows the wheels to roll at separate speeds to each other when the car is entering the corner, then as the driver comes back on the power, the differential will slowly lock up to avoid the inside wheel spinning. Of course, like most things on a Formula One car, this is all electronically controlled, and can be programmed into the car - in fact, until it was recently banned, there was a button on the steering wheel which drivers could press to manually lock or release the diff as they pleased, enabling them to get better traction out of the corners.

Finally, from the differential, the power is transferred to the wheels by the axles, which must be extremely strong to cope with the loadings. They stick through the wheel uprights (or hubs), and present small screw studs onto which the wheel is slipped and a nut is tightened in place. The drivetrain is a complex chain of many fragile parts, and if things go wrong, you can always expect this area to be mentioned. That is because although each part is carefully designed, the forces going through them can be, at times, very unexpected - and if one part breaks, that's it, because every bit is crucial as every other in getting the power down to the ground.

Will Gray© 2000 Kaizar.Com, Incorporated.
Send comments to: Terms & Conditions