Thank You Princess Auto

18 03 2013
The Ravens Racing Team would like to thank Princess Auto on Ages Drive in Ottawa for donating over $2,000 worth of tools to be used in the Team’s shop and in the newly designed pit cart which will be used at competition this year. A good set of tools are essential to the build of a hybrid race car and with Princess Auto’s generous donation this years team will have the luxury of working with the best quality tools you can find in the Ottawa area. To all the staff and Terry at Princess Auto, we look forward to working with you in the future and representing your brand with a top contending car at the Formula Hybrid Competition this year.
Picture: Mark Cohen from the Ravens Racing Team accepting two shopping carts full of tools from Terry Legere of Princess Auto
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Thank You Swagelok

18 03 2013

The Ravens Racing Team would like to thank Swagelok for their generous donation of $1500 on January 28, 2013. Swagelok has also agreed to retrofit the RR13 (this years car) with all the necessary plumbing and fitting requirements for the brake system to be used at this years international competition in Loudon, New Hampshire. Kirk and Christian, we look forward to you driving the car at this years sponsor appreciation day!

Underneath Picture:
Bob De Snoo accepting a cheque from Swagelok on behalf of the Ravens Racing Team during an info session put on by Christian and Kirk from Swagelok.
swagelok




Flexures: Spherical Bearings Be Warned

7 02 2013

Like most autocross cars, our car uses spherical bearings to attach the a-arms and z-arms to the frame.  A new design currently under development will replace these bearings with flexures, solid components that allow for movement in the vertical direction without moving parts. This design is undergoing physical testing to validate the FEA simulations and to ensure that the car will withstand the forces that occur during a race. Our team is simulating this component using both Pro Engineer and real world MTS testing to analyze the stress distributions and to ensure the component performs to specification.  So far the flexures have performed exactly as predicted by simulation and are slated for implementation on the next iteration of the car.  See the figures below for a selection of the FEA simulations and MTS testing.

flexure

Figure 1: Flexure (This is designed to bend along the thin section)

yielding

Figure 2: Yield Simulation (Red indicates areas of high stress)

buckling

Figure 3: Buckling Simulation

mts testing

Figure 4: MTS Testing (Testing the critical buckling load)

surface strees top

 Figure 5: Surface stresses due to bending for front upper arm

Fatigue upper

Figure 6: Fatigue life of the flexures on the front upper arms





Revving it Up with Powertrain

30 03 2011

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.





Uprights for Support

29 03 2011

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.





Dynamics

21 03 2011

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





Structural Frame Design

14 03 2011

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.