Drivetrain

A system is needed to transfer mechanical energy from the engine to the ground (are we including tires here? I always think a drivetrain discussion without talking about tires isnt complete -simon). The train takes the rotational mechanical energy from the engine and transfers it to the wheels.

Gearing

Gearing determines crawl speed, top speed and torque availability at any vehicle speed in between.

Need to also be mindful of how much tractive for you will be generating in any given gear. This plays with tire selection and helps determine what happens when the driver firewalls the go pedal.

This also plays into forces on the differential and driveline components.

Motorcycle Gearboxes

Motorcycle engines have internal sequential gearboxes. This is means that the gearing is located inside the crankcase. The oiling is managed by the engine's oil system. Typically these are 5 (YZ450) or 6 speeds (CBR600RR).

Clutch

Most motorcycles use a wet plate clutch pack whereas most cars use a single dry plate clutch. Wet plate clutch packs are immersed in oil (wet) and use multiple friction plates (pack).

The motorcycle clutch uses a set of linear springs or a diaphram (less common). When engaged, the springs squeeze a series of clutch plates tight enough to restrict relative rotation. This mechanically links the engine output to the crankshaft. When disengaged, the plates are under no pressure and have the ability to rotate freely relative to one another. This allows the engine to spin without outputting a torque.
[we should get a simple diagram of how the torque flows through the engine here]

Talk about slipper clutches

Continuously Variable Transmissions

These allow for an infinite combination of engine to wheel speeds. The benefits of this include allowing the engine to be run at peak power, peak efficiency, or peak torque at any vehicle speeds. The downsides are lower efficiency and a lower peak torque transfer.

Gear Selection

Main page: Shifter

should get own page, there's more to come -simon

Actuation

Mechanical

linkage or cable or both
mimics actuation used on motorcycle
+Cost [citation needed]
+Simplicity [citation needed]
+Robust [citation needed]
-Most implementations mean driver has to take hand off steering wheel [citation needed]
-Minimum shift time is longer [citation needed]
-Maximum shift time is longer [citation needed]
-Unable to convert to automatic

Electronic

solenoid
+OEM solutions available[1] (they can be expensive)
+simplest upgrade to automatic
I have no idea on shift times
-cost
-everyone knows electronics always go wrong

Pneumatic

pneumatic solenoid
Which gas to use

• N2
• compressed air
• CO2

Valving +OEM solutions available [2] +Actuation speeds [citation needed]
-safety (compressed gas can be dangerous)
-largest number of points of failures of all actuation methods [citation needed]
-inherently limited number of shifts per tank
-shift gas pressure can change when running low on gas

Automatic Shifting

not going to touch on driver controls (paddles or whatever)

Drive Mechanisms

There are two ways to get power from the engine to the tires: place the engine output on the same axis as the wheel(s) being driven (direct drive) or transmit the power from the engine to a parallel driven axis connected to the wheels (indirect drive). For combustion vehicles, indirect drives are the prevalent design as it allows for a flexibility of engine placement relative to wheels, a greater degree of drive ratios, and it often easier to implement. [citation or explanation needed]

Indirect Drive

Chain Drive

Should probably get own page, its so common, and theres so much to discuss - simon

Power transmission using a chain drive uses a drive sprocket on the engine connected by a chain to a driven sprocket on the rear axle(s). A chain drive is the most common system found in FS [citation needed?] for a few reasons: most motorcycles already use this system, and it is easy to convert the existing system to drive a formula car, the system is robust, and the minimum design work to implement a functional system is limited [explanation or citation needed] (explanation - low part count, oem sprockets available, no pretension, no slip, wide margin of error for design flaws except planar misalignment).

A chain and sprocket requires lubrication and a tensioning system.

There are two main types of chain: sealed and non-sealed. Sealed chains use o-rings to seal in a lubricant, great for daily driving. Non-sealed require more frequent lubrication application and are commonly used for motocross or low mileage applications. Motorcycle chains also vary in size; make sure the sprocket matches the chain. Choose the right chain size for the forces you expect to see. Chains can also be easily lengthened or shortened using quick release links.

Sprockets are usually made of steel or aluminum and can replaced cheaply to change the final drive ratio (link to fdr?). As the number of teeth decrease, the sprocket will approach a polygon instead of a circle. This is called the polygon effect or chordal action and results in a variation in speed output (Imagine driving on square wheels).[3]

If there is excessive sprocket wear, improperly installed quick release, no lubricant, or if the chain drive is not all in the same plane there WILL be a failure. Chain failures can be extremely dangerous for both the vehicle and nearby people. (more on failure modes/design flaws?)

+No slip possible in chain drive without failure [4]

Belt Drive

Power can also be transmitted with a belt and two pulleys. A belt and pulley does not require lubrication, but still needs a tensioning system (also needs to be pretensioned or else you'll get big slip). Pulleys are more expensive than sprockets [citation needed] and can be difficult to manufacture for most teams [citation or explanation needed, is it hard to design but easy to manufacture or both or easy to design but hard to manufacture?]. The chordal action is less apparent on belt drives because the pulley is more circular than a sprocket.
-system allows slip

CVT

can be done w belt or laminated chain(which could be argued to just be a belt)

Tensioning Systems

should probably get own page -simon

Shims

design judges HATE him, most structurally sound, most smoothbrain, likely the lightest
-assembly
+weight
-get laughed at by design judges bc they are all biased against it smh my head

Eccentric

big brain time
+rigidity
-design complexity
-limited finite number of tensioning options if using shear pins

Turnbuckle

-play
-wear
-packaging
-rigidity[citation needed]
+infinite adjustability
can be done w coarse/fine pitch instead of handedness (i completely forgot what the name is for this kind of turnbuckle, but they have less wear/play [citation needed] but allow a smaller range of motion)

Final Drive Ratio

The final drive ratio is the gearing reduction between the transmission output shaft and the differential. Changing the final drive to a smaller ratio will result in a lower top speed, close gearing, and higher acceleration. A larger ratio will result in a higher top speed, wide gearing, and lower acceleration. Talk about how to choose FDR - impact on number of shifts, acceleration, packaging, integrate w stock gearbox if not running all 5 or 6 stock gears (some teams only run with 3 or 4).

Traction Model

what it looks like, what it means (wheel spin, FDR is high or low, top speed, shift points), how to draw(excel, optimumL).

Differentials

Main page: Differential

Driveshafts

• CV Joints
  • tripods
• flex plates
• Half-shafts
  • material
• lateral play
• do we wanna talk about splines? - maybe just mention how splines should be outside the major shaft diameter. also, circlip grooves/failures
  • splines should what outside shaft diameter? think a word got skipped in there
  • revised
• Torque Steer baby - probably make another page for this for details on concept and derivation

Validation

In vehicle simulations, including driveline affects become important the more detailed the vehicle model gets. The brake torque and horsepower are not what is seen by the tire's contact patch. A physical measurement of driveline forces should be undertaken at some point. It is not likely needed to do this every year however it should be done at least once to correlate model to reality.

This is typically a rotating measurement and typically involves the use of strain gauges. Wireless amplifiers are often needed. Several companies make them available such as Texense, Izze Racing and Lord Microstrain.

--Can talk more about the measurement in the electronics section. Maybe keep this higher level? You could right a whole section just on measurement techniques, uncertainty analysis, error influence coefficients.I think it is worth calling out a couple companies so teams at least have some direction. In the case of wireless strain gauge amps you can go down a real rabbit hole and not find what you need. As far as the gauge install itself, I think that is a lot easier to self research.