Car Body Modification
There is also a small amount of modification that needs to be done to the body itself before any parts can be installed. For reference pictures please refer to the Media page.
- First of all, the radio receiver will no longer be needed, since the servos will be controlled by the PC. This is fairly straightforward, as there are just 4 hex screws that need to be removed, and then the rest of the receiver is free to remove. This part is no longer needed, so it can be stored somewhere or stored in e-waste. See red highlighting on image below for further clarification.
- The ESC will also need to be removed. First, detach the battery cables(they may be fairly tight, and require a bit of force to pull apart). Now, simply unscrew it from the body, and store somewhere temporarily, as we will be needing this part later. See bright green highlighting on image below for further clarification.
- Remove the battery. Place one piece of velcro on the battery and one piece of velcro on the underside of the car, centered and mounted vertically. This is the new location of the car battery. This leaves some unneeded plastic pieces on the top side of the car. The top piece that is held in place with a cotter pin simply slides out, so do that first (you probably already removed this to take out the battery). Now unscrew the two pieces holding the plastic mount in place and remove that mount. This part can be disposed of. Another small part that needs to be removed is the metal stud that the battery pin was attached to. You will need to find a correct sized wrench and remove this and dispose of it. See pink highlighting on image below for further clarification.
- Now, there are 2 “extensions” on each side of the chassis which provide rigidity to the shell. These screw holes will be needed to mount the body plate, so we need to remove these pieces that are currently occupying these holes. The screws are underneath of the car. Remove them and then “unclip” the plastic extensions. We will not be needing these parts. See dark green highlighting on image below for further clarification.
- This should complete the modification to the top of the plate, however, we will also need to modify the suspension in order for the vehicle to support the weight of our soon to be added components. The Bill of Materials includes a set of replacement springs. In that set, there is a wide range of spring rates, however we will want the stiffest option, the black springs. The stock springs were measured to have an approximate spring rate of 3.5 lb/in in the front and 3.2 lb/in in the rear. The red replacement springs have spring rates of 6.2 lb/in and 5.8 lb/in respectively. If it is determined that the vehicle needs stiffer springs than the red ones currently equipped, then the black springs can be installed, which have a spring rate of 7 lb/in and 6.6 lb/in.
Be sure all parts are accounted for before continuing with assembly including modifications made to the Waterjet parts described on the CAD and Waterjet Files page
- PC Assembly
- Assembling the PC is a simple process given that you have all of the required parts listed on the BOM. Follow the instructions that are supplied with the motherboard if you are not familiar with attaching a processor and memory to a motherboard. Additionally, we are going to want to attach the power supply that has already been modified(see earlier section). The power supply is a 20 pin connector, while the motherboard uses a 24 pin connector. Connect the power supply to the motherboard in the orientation that results in the power input cables facing away from the motherboard, and the leftmost 4 pins on the motherboard are unused. You are also going to need to connect the ATX_12V cable that is also part of the power supply. This is more straightforward.
- Body Plate
- The order of attaching all of the individual components to the body plate and to the car itself is a process that relies heavily on the order of installation. Some of the components will be attached to the plate before the plate is attached to the body, and some can be installed after the plate is installed. If any of this is unclear, take a look at the assembles car pictures on this wiki
- Battery Holder
- In order to install the battery holder, which should have already been bent into the correct shape, all that you need to do is use a pair of: M3 x 1/2” Hex Flat Cap Screw and M3 nuts
- Simply attach the battery holder to the body plate with this hardware
- Solid State Drive
- The SSD is installed underneath of where the PC will be, so that needs to be put in before we install the PC
- Simply attach the SSD with a set of four: 6-32 x 1/4 hex machine screws
- Power Switch
- The power switch is secured to the body plate with a set of two :M3 x 12 socket cap screws and matching nuts
- The wire will need to be routed underneath of the body plate and will attach to the motherboard in the red highlighted pins next to the power supply.
- Servo Controller
- Use a set of 2-56 x 5/8″ screws along with matching nuts to secure the servo controller at the front of the body plate. Also make sure to use a pair of plastic nuts as spacers to keep the servo controller board from making direct contact with the metal plate
- The mini USB port of the servo controller should be facing away from the steering servo.
- Speed Encoder Board
- The Phidgets speed encoder is secured to the body plate in a similar fashion as the servo controller. The hardware required to mount the board to the plate should come included with the package from Phidgets. This includes 4 machine screws, 4 matching nuts, and 4 plastic spacers. You may notice that the first version of the car uses different hardware.
- The orientation of the encoder board should be so that the mini USB is facing the rear of the vehicle.
- The PC is the final piece that needs to be attached to the plate before the plate is attached to the car body
- First, attach the 4 sandwich mounts to the motherboard with the stud facing upwards and secure it with a 6-32 nut
- place the Aluminum Unthreaded Spacer 5/16” OD, 9/32” Length #6 between the sandwich mount and the body plate, and secure this with a 6-32 screw from underneath of the body plate.
- Attach Plate to Body
- Use the 4 Body plate screws(item 24 on BOM) to secure the plate to the car body
- This may be difficult to do, as the motherboard gets in the way while screwing these in
- The Rear left body screw also secures on side of the ESC to the plate.
- The heat sink side of the ESC will be towards the rear of the car.
- use the 4-40 x 5/8″ body plate screws to attach the ESC
- Battery Holder
PrimeSense Sensor Mounting
- The PrimeSense Camera has had two holes drilled in the base (3/16″ spaced 60 mm) to match the spacing on the plywood plate that is epoxied to the underside of the body shell. The two holes will also need to be drilled into the body shell. A set of 8-32 bolts and nuts secures the sensor to the vehicle. See CAD drawing for further details.
- Attach the multiplexer on the right side of the car, closer to the rear. Make sure when placing the multiplexer on the body plate that there is enough room to plug in each of the servo leads.Test the multiplexer before attaching it to the car, if the using the multiplexer generates some jittery behavior replace it with a different one. Using the Multiplexer:
- Attach servo leads from the ESC and wheel servo to the OUTPUT pins
- Attach servo leads from the servo controller to INPUT B
- Attach ch3 from the receiver to ch8 of INPUT A on the multiplexer (this lets the multiplexer know to take default input from the receiver)
- Attach CH1 and CH2 from the receiver to CH1 and CH2 respectively of INPUT A on the multiplexer
- Make sure that the battery is oriented so that the cables are facing the left side of the car.
- The battery can be slightly moved to the left or right to achieve optimal weight distribution
*Any time that the battery is in use, it is crucial that the Lipo battery voltage alarm is attached to the balancer cable.