Carleton University Ravens Racing

Axle Design

This is the first year that Ravens Racing will be designing an All-Wheel Drive car.  The rear axle is driven by a gas-powered motor and each front wheel will be driven by a separate electric motor.  With an electric motor driving each wheel in the front, the need for a differential is eliminated.  A chain drive system will increase the torque from the electric motors.  The front gear ratio is 3.38:1, which when combined with performance curves of our electric motors, puts us alongside the top teams at competition for electrical power.  The front axle is unique in that it must supply power to driven front wheels that turn.  In order to do this there must be two types of CV joints; a plunging joint that allows the half-shafts to move longitudinally and vertically, as well as a high-angle joint that allows the wheels to turn while still transferring power.  For the RR11 we will be using a tripod style joint as our inboard plunging joint, and an Rzeppa high angle CV Joint as the outboard joint.   The rear axle will use a cam and pawl type locking differential.  The gas powered motor also uses a chain drive system to increase the torque applied to the wheels.  The rear gear ratio is 3.07.

Internal combustion Engine Integration

This being the first year entering a hybrid race car in competition, a lot of changes have been made to the car. This year we chose to go with an all wheel drive race car that has a gas powered engine to drive the rear wheels and a pair of electric motors to power the front wheels.  However competition rules regulate the engine to have a maximum displacement of 250cc. A 2008 yamaha WR250x supermoto motorcycle was purchased as a donor for the engine and electrical system.

Since the engine was removed from a motorcycle, various components have to be modified and retrofitted to fit the race cars frame and driver controls. The shifter in the engine has been modified from the standard foot pedal to a cable and hand shifter system. The throttle and clutch cables are changed from a hand throttle and  lever, both to foot pedals.

The engine was taken to a local motorcycle dealer for a dynamometer test to see what kind of performance the engine was capable of. It was found that it has 25hp and 16 lbs/ft of torque. In comparison to last years race car with a 510cc engine, this years 250cc engine produces about the same performance values.

Hybrid Electric Drive

The hybrid design of the vehicle utilizes a parallel configuration where the power plants work independently from each other. This allows for us to take advantage of the benefits of both the internal combustion, which provides maximum torque at high speeds, and the electric motors which operates better at lower speeds. The electric portion of the vehicle is powered by two permanent-magnet DC Agni 95R motors capable of producing up to 26kW of power and 53Nm of torque. The motors are powered from six Odyssey Extreme Racing AGM batteries configured in series and capable of producing  72V and up to 800A of current.

The electric control system of the vehicle receives all inputs from the driver and sensors, calculates the desired response, and outputs the signal to the appropriate device. The brain of this system is a self-programmed based Arduino microcontroller. The control algorithm is programmed in C and monitors the temperature of the electric devices and outputs the desired response of electric motor torque output.

The spindle assembly is the group of parts used to hold the wheel, uprights and the drive shafts of the car. It consists of five major components: the spindle, spindle back plates, stud pins, wheel lock nuts and a newly added part a bushing. The main purpose of the upright is to provide a secure mounting location for the control arms, wheel bearings, draglinks, and toe-links. This year the uprights underwent a major design change in construction. Contrary to years past the uprights this year have been constructed of aluminum 6061-T6 stock extrusions machined to size and welded together to improve load paths, reduce cost and reduce material wastage. Also a heat treatment was applied to recover material strength post weld.

Test coupons were also prepared and tested successfully to verify weld integrity and successful heat treatment. The newly added brass bushing to the spindle assembly has been added to reduce ware of mating surfaces that has been a recurring problem in the past.

Tires: A race car must generate large forces in order to achieve the desired lateral and longitudinal accelerations. This is a result of Newton’s Second Law of Motion. All such forces are generated by friction between the tires and the road surface. Maximizing this friction, or grip, between the tires and the road improves the cornering, acceleration, and braking performance of a vehicle. Extensive analysis has been done to evaluate several tire options for the Ravens Racing cars and to determine how to set them up so that they are operating at the peak of their capabilities. This analysis involves determining the best rubber compound, tread width, inflation pressure, and wheel alignment for maximizing the performance of the vehicle. For the 2011 Formula Hybrid competition, 20.5×7.0-13 Hoosier bias ply road racing slicks have been selected. These tires employ an extremely soft rubber compound to provide grip levels far beyond those of consumer street tires.

Shocks, Springs, and Anti-roll Bars: Similar to previous years, the RR11 car’s suspension will feature an independent, double, unequal length control arm setup that utilizes a system of pushrods and bellcranks to transfer the wheel loads to the horizontally mounted springs and dampers. Front and rear anti-roll bars will also be implemented on the car in the form of a t-bar to reduce body roll and aid in cornering. This year’s design will feature a spring and bellcrank combination that will allow the car achieve a slightly lower ride rate while the t-bars will be sized to deliver a stiffer roll rate than used in the past. Manufacturing of the suspension components has already begun. The springs and dampers have been received and the bellcranks are built and ready to be installed on the car. Manufacturing of the t-bars is expected to be completed shortly.

Figure 1: Suspension components including damper, coil spring, and bellcranks

Kinematics: A Short-Long Arm (SLA) suspension system has been carried over from previous years since the SLA design is generally considered to be the most flexible to tune. Motion of RR11 Suspension system is simulated using suspension simulation software such as OptimumK. Static wheel alignment settings for optimum performance and stability have been determined from the results of simulation and load transfer calculations.

Compliance: Carleton University Formula Hybrid has added the study of compliance to its race team this year to better understand load-induced deformation in our race car designs. As the design evolves each year, Raven’s Racing pushes performance limits higher with each step. In order to achieve the highest level of competitiveness, the dynamic behavior of the car must be understood in great depth. Compliance is the study of how the vehicle is deforming under racing loads. With this knowledge, designs can be fine tuned, and modified to perform above the competition. Progress has been made in the design and operation of a static test apparatus used to simulate dynamic loads on the car. It enables our team to study and analyze compliance effects. Initial testing has been carried out on RR10 to determine the compliance camber, and body roll hysteresis as a function of lateral loads. The testing was successful in gathering data that can be used for design and tuning modifications.

Figure 2: Compliance test setup using tension cable and load cell

The frame is an integral part of the any vehicle, and the design of the frame is important for several reasons. The frame is the main component that contributes to the stiffness of a vehicle. This effects how the vehicle responds to the driver’s inputs. Therefore, the stiffness of the frame plays a crucial role in maximizing the dynamic performance of the vehicle. In order to determine the stiffness of the frame, a torque load must be applied to it. The loading conditions are:
• The frame is fixed at the rear, at the differential mounting plate. The nodes lie in one vertical plane that is perpendicular to the centerline of the car.
• Two forces, measuring 500 lbf are applied in opposite direction, to simulate a moment at the front bell crank nodes.

The stiffness of the frame is calculated using the following formula:

Where,
S → Stiffness [ft•lbf/deg];
F → Force applied on either side of the frame [lbf];
A → Torque arm, horizontal distance from the centerline of the car to the point of application of the force [ft];
v → Vertical displacement of the point where the force is applied [ft];

Further analysis was also performed in order to determine the relative torsional stiffness of the various section of the frame. Determining the torsional stiffness of the various sections is an essential step when optimization is performed. By measuring the displacement of points at the same vertical height from the ground at the intersection of the different belts, the torsional stiffness of each section was determined. From the results it can be noticed that the front suspension section and the side impact sections have approximately the same relative stiffness. Since stiffness is a function of length, shorter sections will have higher values of stiffness. It can also be noticed that the rear section has a much lower stiffness than the other section. This is primarily due to the fact that the engine is not incorporated in this simulation and that a big portion of this section’s stiffness is due to the engine and the engine bracing.

This year has been a transition year for the Ravens Racing team, eager to compete for the first time at the Formula Hybrid SAE Competition after memorable showings at the Formula SAE Michigan Competition. They have come a long way; practically redesigning the vehicle system to gear towards a gas-electric hybrid system, but sleepless nights are yet to come. Slowly but surely…

In Pursuit of a Rolling Chassis

Thank you to everyone who made it out for unveiling.

Below are a few videos and pictures from the day.

This slideshow requires JavaScript.

It’s that time of year again! The Ravens Racing team will be unveiling their Formula SAE race car as part of their fourth year project this Monday March 29th. It will be taking place from noon to 1:00 pm in the University Centre Atrium with speeches from the FSAE team commencing at 12:15 pm.
Drop by and have a look!

• Date: March 29, 2010
• Where: University Centre Atrium
• When: 12:00 (noon) to 1:00 pm

~Ravens Racing Team

Students from the Ravens Racing Team went to Dymech Engineering Inc to help build our RR10 car frame. With help from Dymech Engineering, our frame was completed in January. Pictures of our team members in action can be found here.

Ravens Racing is committed to performance and safety. The mechanical properties of the frame are critical design criteria for a winning race car. Maximizing frame strength and torsional rigidity while minimizing weight is a very important racing trade-off. In the fall of 2009, torsional stiffness tests were conducted on the Ravens Racing 2009 fully assembled frame, the same frame that competed in May 2009 at Michigan. Using laser levels, digital angle deflection measuring devices and a custom test rig the frame was twisted at the spindles with the suspension fully locked out. This “hub-to-hub” torsional test allowed the applied torque to be related to the angle of twist of the frame under each applied torque. From the data gained from these tests the torisonal stiffness of the frame could be computed and was found to be similar to a performance high end sports car. When compared to the results of the finite element analysis performed on the frame using modern engineering structural computer software the test results were found to compare closely, thereby validating the experimental torsional stiffness data. Ravens Racing understands the structure of their car which will allow them to make improvements especially in areas of suspension performance and handling.

Ravens Racing 2009 Frame (Fully Assembled) in the torsional stiffness custom test rig.

The Ravens Racing team worked with Axis Rapid Prototypes to create the injector body for the RR10 car. The injector body is made out of duraform, which is a type of plastic used for rapid prototyping. The purpose of the injector body is to connect the plenum to the intake port of the engine and inject the fuel. Before it can be installed on the car, it will require a layer of Permatex sealanet to ensure it does not leak fuel (on top of the cyanoacrylate that was already added by Axis Rapide Prototypes), and a layer of carbon fibre reinforcement on the side that connects the part to engine. The injector body can be seen here: