Gearbox
First we will explain basics of the gearbox and how he work in "normal" cars. Racing cars have more sophisticated gearboxes, and especially Formula one. They are optimized for faster operation and higher forces. More about that later.
The gearbox has an input and an output. There is always some number of gear ratios, in modern cars from 4 to 7, and one reverse gear ratio. The forward gears are all constant-mesh. That means that the gear teeth for all ratios are always engaged with each other at all times. Instead of sliding a gear out of engagement with another gear, the gear is disengaged by disconnecting it from the shaft that it is on. Only one gear ratio pair can be connected to the shaft at one time. The reverse gear is an actual non-constant-mesh sliding gear whose teeth actually slide out of engagement when it's not being used.
Each forward gear can be coupled to its shaft by a sliding locking coupler. This coupler connects splines on the shaft to splines on the gear. The coupler needs to be at the same speed as the gear splines to avoid grinding. When people refer to "grinding the gears", it is actually the splines that are grinding, not the gear teeth. To synchronize the coupler with the gear splines, there is an intermediate device called a synchro-mesh or "dog ring".
One of Webster's definitions for „dog“ is „Any of various devices for holding, gripping or fastening something, as one consisting of a spike or bar of metal with a ring, hook, claw or lug at the end.“
Hold your hands out with fingers spread and your finger tips pointed toward each other. Now move your hands together such that your fingers slip between the fingers of the other hand. Now try to rotate one hand within the other. That is the concept of „Dog ring engagement.“ The fingers or dogs of one hand are engaged with the fingers or dogs of the other hand - they are hooked together.
The synchro-mesh is a lightweight ring with spline teeth on one side, and a conical friction surface on the other side. It is positioned between the sliding coupler and the gear splines. The gear also has a conical friction surface that mates with the surface of the synchro-mesh.
When a gear is to be engaged, the shift linkage selects a sliding coupler to connect to a gear. At this point, the coupler and the gear to be engaged are usually spinning at different speeds. As the coupler starts to slide, it first engages the spline teeth of the synchro-mesh ring. Because the synchro-mesh is lightweight, it can virtually instantly change speed to match the sliding coupler that was just forced into engagement with it. He then becomes part of the coupler. As the coupler continues to slide towards the gear splines, the friction surface of the synchro-mesh ring is pressed into contact with the friction surface of the gear assembly. This friction causes the transmission's input shaft (which at this point is hopefully disconnected from the engine by the clutch) to be accelerated (or decelerated) so that the coupler and the gear are spinning at the same speed when their spline teeth finally engage.
A synchro-mesh is limited in how much mass it can accelerate and how fast it can do it.
A true racing transmission may not have synchronizers at all. The transmission may be equipped with very strong dog rings that are simply jammed together. And on many early transmissions there were no dogs to help with gear alignment, the gears themselves were simply put together - with various degrees of success and grinding depending on the expertise of the driver.
And now when we understand how simple gearbox work, let's talk about more complex stuff!
The two primary functions of any gear case are to rigidly mount the bearings of any gear shafts, such that the gears maintain accurate meshing under the parting loads induced as they transmit torque, to keep dirt out, and to keep lubricating oil in. Additionally, the case must locate selector mechanisms and oil pumps, and have access panels to permit assembly. As designed into almost any modern racing car, the case also forms part of the primary chassis structure, mounting the rear suspension and feeding the suspension loads to the rear face of the engine. Spare space within the gear case may be used to accommodate oil for the engine, the gearbox if it is dry-sumped, the hydraulics, and the mandatory catch tank. Finally in recent years, the gearboxes used in the leading Formulae must mount a rear impact absorbing structure, normally integrated into the detachable rear cover for the final drive/differential, which also mounts the rear wing structure.
"Simple" gearbox, as explained before, is not in use in racing any more. Only most basic racing categories are using it. In Formula 1 this kind of gearbox is not in use more than 20 years. Sequential gearbox is stuff of the day in our sport, take rally, DTM, Formula 1, almost all open wheel classes, WTCC, Indy, truck racing...
Ferrari 640 with Mansel driving
Ferrari 640 was the first F1 car using a semiautomatic sequential gearbox 1989 in the Brasilian GP. Car was driven by Nigel Mensel.
John Bernard, in this time Ferrari technical director, proposed this innovation 1988, and was accepted and adopted for first time in 1989. Idea was to speed up gear change to maximum, and get read of clutch pedal. First idea in time of development was to have one lever on right hand side of the driver, on the place of "old" "H" gear shift lever. Driver will move this lever only backward and forward to go trough gears (sound familiar?). During development period Bernard got better idea. He put two buttons on each side of the steering wheel to prevent driver to move hands from the steering wheel.
Later, they change this idea to two paddles behind a wheel. They added third, clutch paddle little bit offset and smaller then first two. Left side paddle was used for downshift, and right paddle for up shift. Clutch paddle was smaller because this one is in use only during the start, stop and in some emergency situations. During normal race clutch was operated automatically, together with gear change forks with help of electronically controlled electrohydraulc system.
Paddles behind a wheel
Ferrari 640 steering wheel with inovative paddles behind the wheel
Ferrari 640 inovative sequential gearbox.
Note that diffuser is very crude and simple.
Note also wooden rear wing suport.
Selector drum of an modern sequential gearbox
Honda RA106 Formula 1 Gear Selector Barrel
FIA technical rules allow gearbox's with 4 to 7 forward speed and one reverse gear. Reverse gear is mandated. The driver initiates gear changes using paddles, and electro-hydraulics perform the actual change as well as throttle and clutch control.
Since the Ferrari 640 F1 showed the performance benefits of semi-automatic gearboxes back in 1989, all F1 teams adopted that idea. Development has been astonishing: they've become smaller, lighter (because of the use of advanced materials, particularly in the gears and casing). And, most importantly, they become faster. Talking about "old" F1 sequential gearbox (two or three years ago), they become so fast that "normal" person can't understand and can't believe if that is possible. Complete gear change happened in 10-15 millisecond.
In this time:
- Driver gives a command to up or downshift.
- Electronic control system check position of the clutch, engine speed and wheel speed (using different sensors in engine and differential)
- Initiating clutch opening (electronics give a signal to electrohydraulic system to operate solenoid valve, valve open and relise high pressure oil into hydraulic piston, piston push clutch discs to open position)
- Changing the gear. Disengaging old one and then engaging new, selected gear. (electronic give a signal to electrohydraulic system to operate solenoid valves to operate gear selector forks and to adjust proper gear to desired position)
- ECU is checking new proper position of gears, and comparing this data with engine and wheels speed in this instant (using different sensors in motor and differential. If driver select wrong speed, gear change will not be done)
- Closing the clutch if item 5 is OK (electronic give a signal to electrohydraulic system to close solenoid valve and to rilise hydraulic oil from piston and to close the clutch)
- If item 5 is not OK, electronic control system will try to engage proper gear, or to return to originally engaged gear.
All this checking is necessary because of high speed of the system. If anything goes wrong during gear change process, anything, we can see white smoke behind car or blocked rear wheels and spin.
2008 Honda Formula 1 Gear Selector Hub
But only in the last few years we can see some very serious, inventive thinking been applied to developing a step change in the way gearboxes work. This 10-15 milliseconds explained before, for them is to much of lost time. They want something better and faster. F1 engineer are never satisfied (that's why they are F1 engineers), and they started to think about seamless gearshift.
Despite the systems having been in use for several years, there is still little information coming from the teams on how they work. What is known is that the systems retain the conventional two-shaft gearbox and single clutch. A double clutch would provide a seamless shift, but this is banned under the current rules. No F1 engineer wants to talk about that. Every team has his own way to do the job.
While almost all teams have seamless boxes, the choice of gear case material varies, with the choice being between aluminum, magnesium, titanium or carbon fiber, along with the additional choice of hybrids of the metals bonded with carbon fiber. Gear case stiffness and weight are very important. Back part of rear suspension wishbones and dampers are connected to the 'box and stiffness is a paramount. Also, back crash structure is fitted on gearbox. 'Box is located behind engine on relatively high position and behind rear wheels axel, and that is the reason why weight is also very important.
In 2007, only Honda and McLaren ran full carbon fiber cases, and Ferrari evolved their titanium skeleton with bonded carbon skins. All of the other teams ran a metallic (Magnesium, Titanium) gearbox, albeit with some level of carbon fiber bonded to specific areas for stiffness.
Magnesium gearbox
Titanium gearbox
Hybrid technology gearbox
Carbon fiber gearbox designed 1998 by John Barnard for Arrows
All materials have his pros and cons. Carbon fiber is very light but torsional stiffness can be a problem. Aluminum has a torsional stiffness, but weight and durability is a problem. Titanium is stiff, light and durable, but extremely expensive material and hard to work with. Anyway, carbon fiber is lighter then titanium.
Ferrari use titanium skeleton with bonded carbon panels. In this way, they are using positive sides of both materials. Light and extremely stiff. Bay the way, this type of 'box casing was again invented by John Bernard and for first time used by Ferrari F1 team. I think it was 1988.
Shape of gearbox is extremely important because they are a part of back side aerodynamic package, and part of diffuser. In 2005, the gearboxes had to become smaller because there was less space available due to the new aerodynamics regulations. The change from V10 to V8 engines has allowed the teams to extend box little bit.
Formula 1 engineers don't allow themselves to get excited about gearboxes. They instruct the design office to package it to a certain size, to optimize the aerodynamics around the back end - then, provided it doesn't break every second race (Red Bull in 2007), job is not done.
People who've got it right don't have much time to congratulate themselves: 2008 technical regs call for 4 race gearbox, and new electronics provided by McLaren/Microsoft.
After that, 2009 technical regulations confirm use of kinetic engine recovery systems, and expect gearboxes to last even more races. Technical regulations for 2011 say that gearboxes will have to last five races instead of four previously. Gearbox technology is going to have to move on yet again.
Formula 1 Gearbox from 2009 season with rear crash structure. You can see rear suspension elements attached to gearbox, and on the top you can see rockers, dampers, pushrod element and torsion bar.
A gearbox is a carefully cultured, very secret high-tech product, and its 400 individual parts are all specially produced for each team- right down to the bearings and seals. Naturally, that all has its price: a Formula 1 gearbox, according to expert estimates, costs about 150,000 euros.
Until 2009 reliability of the individual parts varies: while the gear wheels were replaced after every race, the gearbox housing normally lasts for the whole season orclose to that.
Many of the internals come from outside suppliers such as Xtrac and Hewland.
Founded by Mike Hewland in 1957, Hewland Engineering invented the bespoke racing car gearbox and it has supplied the worlds racing car constructors ever since.
Today, Hewland supplies 21st century motorsport transmissions to an amazing client list, spanning a worldwide and diverse array of racing series.
F1 gearbox used by Ferrari during seasson 2000
A little bit of history
Gearbox designe by John Barnard
CFRP is an excellent material for tanks, covers, and impact structures, but is not so good at accepting point loads. Joints, bearing housings and suspension mountings all need very careful detail design to spread the concentrated loads into the material and, as he has demonstrated many times over his years at Chaparral, McLaren, Ferrari, Benetton and Arrows, John revels in and excels at detail design.
John has never been particularly happy with cast magnesium, and had already got rid of it for uprights back in 1975, on the Parnelli Formula 1 car. When he joined Ferrari for the second time in 1993, they were using a magnesium case, longitudinal gearbox, with the gears behind the final drive, and employing the paddle shifting system that John had pioneered during his previous tenure there. The casting technology at that time produced magnesium with the possibility of porosity and variable wall thickness, due to problems of positioning the cores accurately during the casting process. Designers had to increase the structurally optimum wall thickness to allow for these deficiencies and, along with magnesium's well-known reduction in stiffness above about 100°C, this resulted in a combined bell-housing/engine oil tank/gearbox case weight of around 27.5Kg. The loads put through the gear case as part of the chassis of the car, and the flexing of the hot case often generated fatigue-cracking around stress raisers in a new design, and even cases to a proven design needed replacing after half a season at the most.
John wanted to do something different for the 1994 car. "I looked at a transverse layout, to see if I could line up the bearings of the gear shafts and final drive/differential into planes and move the weight ahead of the rear wheels. In that way I could hang them on flat plates and hence fabricate the gear case. I wanted to do it in CFRP, but had no confidence to hang the bearings in that material. Instead we used steel." The gear case was made up as a fabricated steel box, with the sides machined out of 25mm plate, CNC-milled down to 1.2mm wall thickness and ribs. The gear case weighed only a little less than the magnesium one it replaced, which was a disappointment. "In mid-season we switched to titanium instead of steel, and gained an immediate 40% weight reduction." Manufactured at Barnard's Ferrari Design and Development base in the UK (now B3 Technologies), they had to get to grips with welding titanium in inert gas tanks. "There were few problems: to avoid distortion during welding thin sections, it had to be done in the right order and allowed to cool between steps." Machining the titanium plates required considerable investment in CNC machine tools, but otherwise John claims this approach is not more expensive than traditional techniques. Process time is longer however, and cannot compete with casting rates.
The weight reduction at the rear of the car was most valuable, but the increased hot stiffness also meant better gear reliability. As the gears do not displace significantly under load, they can be ground to truer profiles for greater efficiency and durability.
The '94 transverse gearbox was the first to use John's internal-spline dog-ring arrangement. The three face dogs on each gear engaged with internal dogs, which themselves had splines on their inner diameter to engage with the shaft. The width saving was around 6mm per dog-ring, to give an overall width reduction of 18mm. He has used this arrangement ever since. For 1995, the fabricated titanium gear case bolted to a CFRP bell-housing/oil tank, onto which the suspension units were mounted and into which the majority of the suspension loads were fed. There were some initial problems with cracking and oil leaks at the suspension mounting points on the CFRP oil tank. These were caused by insufficient overlaps at the joints, and after the tank was lined with a tank slushing compound no further leaks occurred. The '94 and '95 gearboxes were a 3-bearing arrangement, but in 1996 John went to a 2-bearing design. This year was also the first in which a CFRP rear impact crash structure was fitted, albeit one year ahead of the FIA requirement. The same basic arrangement - CFPR bell-housing/titanium fabricated gear case/CFRP rear case and impact structure - has been in use at Ferrari ever since, but in longitudinal layout since 1998.
With 4 years of successful experience of the CFRP/titanium gearbox construction under his belt, John decided to take the next step when he joined Arrows to design their 1998 car. He was not the only Technical Director to believe the time was right for a full CFRP gearbox case: Alan Jenkins committed the fledgling Stewart team to one too. Both boxes were longitudinal, and both had bonded in transverse bulkheads to carry the gear-shafts' bearings. However, where the Arrow's case employed titanium for the bulkheads, the Stewart used aluminum, and the different success of the two designs is rooted in this variation. While Arrows continue to use Barnard's basic arrangement, Stewart, now Jaguar, have reverted to magnesium after a lot of trouble with the joints between the aluminum bulkheads and the CFRP casing, in spite of eventually solving the problems. John: "The bonded joints are the key to building a successful gear case in CFRP. The joints must have fully machined mating faces and the correct surface preparation. We experienced no leakage problems with the joints (the bulkheads keep the oil in), and I suspect it was Stewart's choice of aluminum, which has over twice the thermal expansion of titanium, that caused them problems. The coefficient of thermal expansion of CFRP is very low, and when the box heats up to its running temperature of over 100°C, quite a lot of stress can build up in the joint between the two materials."
Carbon fiber gearbox designed 1998 by John Barnard for Arrows
One problem occurred in initial testing of the gearboxes, which was so hard to diagnose that it nearly led to the abandonment of the CFRP design, even though it eventually transpired that the problem was unconnected to the use of the material. The gear-engagement dogs were chipping such that the gear-change deteriorated quickly and failure followed shortly after. The problem was eventually traced to .001" (40 micron) undersize gear hubs, on which the dog-rings moved. This caused the dog-rings to tilt slightly when located in the out-of-gear position, and allowed the dogs to touch the corresponding dogs on the gear, which then chipped. John: "It was a classic example of how novel features in a design tend to be blamed for any shortcomings, even though the cause may be rooted in conventional engineering processes."
The CFRP main case weighed under 9kg, and the rear case, including rear impact structure, weighed 4kg, the two assembled together totalling 14kg. This compared well with the equivalent magnesium cases that they replaced, which weighed 25kg. The saving at the rear of the car translated into more available ballast to be mounted forward, in an era when every effort was being made to move weight forward to make the wide front tires work. The all-CFRP design gets rid of the joint between the bell housing and the gear case, increasing overall stiffness. A surprising advantage was that the oil in the box ran cooler - 100°C instead of the more usual 130°C. Part of this is due to the greater efficiency of the correctly meshed gears, but John also believes that the insulating properties of the carbon fibre/Bismalamide resin casing prevented heat being transferred from the hot air stream from the radiators and around the exhaust pipes to the oil. Altogether the Arrows gear cases have been reliable, lasting more than a season.
Carbon fiber gearbox designed 1998 by John Barnard for Arrows
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