GLOSSARY – GEAR SYSTEM COMPONENTS
BEVEL GEARS
Bevel gears are the ones you use when you need to change direction. They’ve got angled teeth and work at a 90-degree angle to each other, often found in differentials to send power to the wheels. In motorsports, bevel gears are crucial for getting power from the gearbox to the drivetrain without losing efficiency. PPG uses precision-cut bevel gears in some systems to ensure smooth power transfer, especially in all-wheel-drive setups where every ounce of grip counts!
CLUTCH PACK
A clutch pack is a stack of discs that work together to connect the engine to the gearbox, often found in automatic or semi-automatic systems. When the discs press together, they transfer power; when they separate, they let you shift gears. In motorsports, clutch packs are designed for quick engagement to handle rapid shifts without slipping. PPG uses advanced clutch packs in some sequential systems, giving you the grip you need for those split-second gear changes!
COUNTERSHAFT (LAYSHAFT)
The countershaft, or layshaft if you’re feeling fancy, is like the middleman in a gearbox. It’s a shaft that sits between the input and output shafts, holding gears that mesh with others to create different gear ratios. When you shift, the countershaft helps transfer power smoothly. In motorsports, a strong countershaft is key because it takes a lot of stress during rapid shifts. PPG designs countershafts to handle the abuse of high-power engines, keeping your shifts tight and reliable.
DIFFERENTIAL GEAR
The differential gear is what lets your wheels spin at different speeds, especially when you’re cornering. It’s often connected to the gearbox in a car to help with turns—without it, your wheels would skid and wear out faster. In motorsports, a good differential can make all the difference in handling. PPG offers limited-slip differentials in some gear systems, giving you better traction out of corners and keeping your lap times tight!
DOG RINGS
You hear everyone talk about dog rings and wonder what exactly are they? Well in very simple terms they are the parts that move when you change gear between the two gears. They are the front line in making sure you get the next gear or not! So they are pretty important for the operation of a gearbox, they determine how a gearbox gets a gear and also releases a gear. PPG have some very unique features that other unscrupulous companies have tried to copy to their failure…… The way we design and heat treat our dog rings and dog gears sets us apart so much, it is not uncommon to hear of PPG gear systems having covered several years racing without any significant wear being visible. We design our systems to last and this is one of many reasons they do so in so many high power, drift, race and rally applications.
DRIVE BY WIRE (DBW)
A mechanical linkage between the accelerator pedal and throttle butterfly has always existed, be it a cable or rod linkage. With modern ECU systems, theses manual systems have been replaced by sophisticated electronic control modules, sensors and actuators performing the task operated via control signals. This system is also referred to as “Drive By Wire” or “Fly By Wire”. There are several reasons why electronic throttle actuation is preferable to a conventional throttle cable:
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Chassis ECU systems are able to control all of the throttle operation.
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The use of throttle actuation ensures that the engine only receives the correct amount of throttle opening for any given situation.
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Allows optimised start procedures for traction & launch control strategies.
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Closed loop gearbox shift management, throttle blipping, flat shift. The use of such a system has advantages over the conventional cable versatility, removing the mechanical element of a throttle cable and substituting with fast responding electronics reduces the number of moving parts (and associated wear) and therefore requires minimum adjustment and maintenance. Greater accuracy of data improves the performance of the chassis, which in turn provides better response, performance & repeatability.
FLAPPY PADDLES – PADDLE SHIFT
Used and seen a lot in modern DCT cars today. The paddles in motorsport applications are used to shift or actuate the next gear, either up shift or downshift. This function via a small switch mounted into the paddle assembly. When a signal is sent, the ECU reacts to its input and signals the gearbox to change gear. This function works to actuate the gear shift pneumatic cylinder mounted on the gearbox.
GEAR LEVER
The simple gear levers we supply are billet aluminium construction with over sized pivot bearings which allow precise low friction bearings to be incorporated in the design. We offer two versions of lever, actuation above and below the pivot. This gives the option to pull or push the lever to change gear, depending on the sequential system fitted. PPG gear levers are designed for each application.
GEAR RATIO
Gear ratio is the magic number that tells you how many times one gear spins compared to another. A 3:1 ratio means the smaller gear spins three times for every one spin of the bigger gear. In motorsports, gear ratios are everything—they control how fast you accelerate and your top speed. Lower ratios give you more torque for quick starts, while higher ratios are for cruising at high speeds. PPG gear systems let teams fine-tune ratios to match the track, ensuring you’re always in the power band!
GEARBOX COOLING SYSTEM
Gearboxes get hot—really hot—especially in motorsports! A gearbox cooling system uses oil coolers, fans, or heat exchangers to keep temperatures in check. If your gears overheat, they can wear out or even seize up mid-race. PPG gear systems often include integrated cooling solutions, like oil channels and external coolers, to keep things running smoothly even after hours of flat-out racing!
GEARBOX GCU
A gearbox GCU is a dedicated control system for gear shift parameters. Many motorsports systems have integrated GCU functionality to undertake the calibrations and controls in a single solution. Many mid-market ECU systems do not have the ability to control closed loop gear functions, also paddle-shift controls are not covered. In this scenario a GCU can interface with the engine ECU and undertake the closed loop functions of sequential lever and paddle-gear systems, thus making it possible to retain existing chassis ECU systems without the need to reprogram and rewrite.
HELICAL CUT GEARS
Helical cut tooth profiles are common in OEM applications in DCT & DCT transmissions. The profile offers great contact area in larger gears and quiet operation for passenger comfort. We design a lot of our larger gear systems using helical tooth profiles as they offer large contact surfaces and quiet operational characteristics. They maintain good strength and longevity in service.
INPUT SHAFT
The input shaft is the first stop for power coming from the engine into the gearbox. It’s connected to the clutch or torque converter and spins the gears inside the gearbox to get things moving. In motorsports, the input shaft takes a lot of abuse from high torque and rapid shifts. PPG designs input shafts to be ultra-tough, ensuring they can handle the power of even the most aggressive race engines without snapping!
MME - K.M.P. – SHIFTEC – GEARTRONICS - MOTEC
When building a motorsport chassis or fast road car there is a requirement to integrate new sensors, gearboxes, & ECU systems. This is overcome via the use of a custom wiring harness. Theses types of harness’ can be a full chassis loom or what we called an “overlay loom”. When we supply a sequential gear system we supply a specific harness that is a generic design that will allow the customer to integrate a gear system and our sensors into their application. Motorsport wiring harness’s use high quality connector and wiring, which offers increased performance in highly demanding environments containing heat, vibration and water.
LOAD CELLS – STRAIN GAUGE
A load cell is a sensor that converts force (nm) into a voltage output. This allows the load cell to be optimised and calibrated for force input and voltage output. PPG supply load cells configured to operate for up shift and downshift operation, this means that the 0-5vDC output is split into two voltage ranges, 2.5-0v for downshift and 2.5-5v for upshift. The strain gauge (load cell) is a pull (up) or push (down) on the gear lever. Sensors can be supplied for the various force ranges. The Load cell supply is optimised for a centered voltage range and can be ensured the components will work exactly as advised in the field. PPG use exclusively KA Sensors for all load cell applications, custom calibrated and designed for each application in the PPG sequential gearbox range.
LUBRICATION SYSTEM
Lubrication is the lifeblood of any gearbox! It’s the oil or grease that keeps gears spinning smoothly, reduces heat, and prevents wear. In a high-performance gearbox, good lubrication is a must—without it, your gears would grind and overheat in minutes. Motorsports teams use special synthetic oils that can handle extreme heat and speed. PPG gear systems are designed with advanced lubrication channels to keep oil flowing to every gear, even during the most intense races!
OVERDRIVE GEAR
An overdrive gear is like a “chill mode” for your gearbox. It’s a gear ratio that lets the wheels spin faster than the engine, reducing engine RPM at high speeds. This saves fuel and lowers wear on the engine, but in motorsports, overdrive isn’t always the star—it’s more for road cars cruising on the highway. That said, some PPG systems include overdrive options for endurance racing, where fuel efficiency can make or break a 24-hour race!
PNEUMATIC GEAR SHIFT CYLINDER
Air actuators are compact and low weight. Air actuators produce very high force output from a very small physical size & weight. Actuators produce approximately 75kg (750N) force when operated at 8.0Bar (120psi). Pneumatic cylinders do not suffer reductions in force output whilst the temperature increases and require little additional thermal management considerations. Pneumatic systems only place small requirements of kinetic energy from the vehicle’s electrical system during the shift phase. The air compressor requires minimal electrical power and current long term and consume less than 1amp per shift.
ROTARY GEAR POSITION SENSOR
A sensor that allows a rotary movement to be converted to a voltage or PWM (Digital). All sensors however were not created equal. At PPG Performance Gearboxes we have pioneered the use of contactless rotary sensors in sequential gear systems, this allows the sensor to avoid reading any vibrations and the sensor itself has the ability to be configured and used in many positions. The ECU is then used to convert the rotary position into a linear position, which in turn allows the ECU to characterise the positions in which to return power. You know the position you can decide the best point to remove and return power. PPG use exclusively Gill Blade 360° Sensors – 10bit resolution and allows data capture at high frequencies, which yields real time benefits for ECU calibration and has full health check and configurable software. The sensors are hermetically sealed and are long term temperature and stable in operation by their operational life.
SEQUENTIAL ACTUATOR
The sequential actuator is a key component of our sequential gear system. Its contains our unique rotary position sensor (BLADE 360°) along with a lock out system for neutral and reverse selection. This device is responsible for the transfer of motion in the system, in many PPG applications it converts a linear motion to a rotary motion….. its rather clever!
SEQUENTIAL BARREL
The “barrel” as it referred to in the motorsport world, is the item that holds the gear selectors in place and transfers motion from the sequential actuator, to rotate and select gears. This rotation can perform several actions at any time. Typically, the selector forks follow a track that allows the selectors to follow a path that is predefined around the barrel.
SHIFT FORK
The shift fork is a small but mighty part that moves gears into place when you shift. It slides the gears along the shaft to engage or disengage them, working with the gear lever or actuators in flappy paddle systems. In motorsports, shift forks need to be tough and precise for lightning-fast shifts. PPG shift forks are made from high-strength materials to handle the rapid, high-force shifts you need on the track without ever missing a beat!
STRAIGHT CUT GEARS
Straight cut tooth profiles in very simple terms is the angle of the gear tooth profile. Straight cut is associated with strength and noise in terms of the profile. Not all gear sets are made with straight cut in motorsports however, helical cut which is usually 12-20° degrees from the norm for OEM gear systems. We at PPG use helical in a lot of our applications so as to provide a quieter profile which in turn makes the gear more able to accommodate for endurance and road-based cars.
SYNCHRO GEARS
Synchro, or synchromesh as it's widely known. The dictionary defines it as a device in a transmission system that automatically brings the gears being meshed to about the same speed of rotation before the shift occurs. Basically it stops the gearbox from crashing or smashing gears! Our dog rings in our dog boxes replace the synchro systems in order to be stronger, with quicker engagement when shifted fast. Did you know it is the synchro hub that move when you change gear and not the gears themselves!
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