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The Joe Kart Operator Manual

Team 5

Morgan Templeton

Mike Fitzpatrick

Marek Wartenberg

Joey Toce NSF Project Contact: Katrina Toce, 114 LePage Dr. Southington, CT 06489 (860) 621- 8616

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Important Safety Instructions:

This product is meant for outdoor use only. Never use the Joe-Kart indoors or on indoor surfaces, including carpeting.

This product is designed for use on moderate off road surfaces. Grass and packed dirt are ideal surfaces. Never use on rough terrain.

This product should never be used in rain, snow, ice mud or any other inclement weather.

This product is not designed to ride on wet surfaces. Never immerse any part of the Joe-Kart in water. Water can damage the electronics, and can cause serious injury to the passengers.

This product is only to be used on off road surfaces. It is not designed to be ridden on roads or other paved surfaces.

Never ride the Joe-Kart on public roads, streets, alleys or other public property. Never use the Joe-Kart near motor vehicles.

Never ride the Joe-Kart in areas where it can cause harm to other people, animals or property.

Avoid use near small children.

The Joe-Kart is designed for two passengers. The total weight of passengers should not exceed 300 pounds. Passengers who cannot fit comfortably should not use the Joe-Kart.

The Joe-Kart should only be operated when the remote is on and in range.

Use of the Joe-Kart should be done under the supervision of an adult, who has control of the remote.

The supervising adult must read the operator’s manual and thoroughly understand the controls of the Joe-Kart.

The operator and passengers should have previous experience and thorough knowledge of the controls. It is the responsibility of the supervising adult to make sure that the passenger is thoroughly trained and ready for use of the go-kart.

The Joe-Kart is a machine and should be treated with care and respect while operating, working on or near. If used improperly, injury can occur.

The passengers should always wear protective gear. Clothes toed shoes should always be worn. Long sleeves and pants should always be worn. Loose clothing should never be worn when riding or working on the Joe-Kart.

A helmet should always be worn.

TO REDUCE THE RISK OF INJURY, ADULT SUPERVISION IS REQUIRED. THE JOE-KART SHOULD NEVER BE USED WITHOUT ADULT SUPERVISION. NEVER USE THE JOE-KART ON STEEP INCLINES, STEPS, OR ROUGH TERRAIN. NEVER USE THE JOE-KART NEAR WATER AND DO NOT ALLOW IT TO GET WET. ALWAYS WEAR THE APPROPRIATE ATTIRE WHEN OPERATING. NEVER ALLOW MORE THAN TWO RIDERS AT A TIME.

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Parts and Accessories:

Rack and pinion

Steering Position transducer

Steering gear motor

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Tie rods

Front wheels

Front guard

Dashboard

Foot rests

Passenger Seat

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Client Seat

Wire Conduit

Control Box

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4QD Speed Controller

Steering Speed Controller

Braking Speed Controller

Receiver

Batteries

Brake Motor

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Brake Caliper

Brake Disc

Brake Position Transducer

Rear Axle

Drive Motor

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Transmission Box

Rear Wheels

Roll Cage

Remote Control

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Features:

Wireless Remote Control

Battery Powered

Two Passengers

Adjustable Custom Seat

Dashboard Controls o Steering o Braking o Driving

Remote Kill Switch

Power Steering

Power Braking

Transmission

Forward and Reverse

Table of Contents

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1. Introduction……………………………………………………………………11 1.1 General Overview…………………………………………………..11 1.2 Operating the Joe-Kart……………………………………………14 2. Maintenance………………………………………………………………….18 2.1 Mechanical Maintenance………………………………………..18 2.1.1 Chassis………………………………………………………18 2.1.2 Steering……………………………………………………..18 2.1.3 Batteries………………………………………………….19 2.1.4 Control Box………………………………………………19 2.1.5 Seats………………………………………………………19 2.1.6 Foot Straps……………………………………………….19 2.1.7 Front Guard……………………………………………...19 2.1.8 Tires………………………………………………………...19 2.1.9 Transmission Box…………………………………………20 2.1.10 Rear Axle………………………………………………..20 2.2 Electrical……………………………………………………………20 2.2.1 Batteries…………………………………………………..20 2.2.2 Control Box……………………………………………….20 2.2.3 Remote Control…………………………………………21 2.2.4 Wires……………………………………………………….21 2.3 Environmental……………………………………………………….21 3. Technical Description………………………………………………………22 3.1 Chassis……………………………………………………………….22 3.2 Seats…………………………………………………………………22 3.3 Steering Mechanism………………………………………………25 3.4 Drive System………………………………………………………..28 3.5 Braking System……………………………………………………..31 3.6 Batteries……………………………………………………………..34 3.7 Control Box………………………………………………………….35 3.8 Control Systems…………………………………………………….38 3.9 Remote Control…………………………………………………….37 4. Troubleshooting………………………………………………………………40

1. Introduction

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1.1General Overview

The Joe-Kart used a prefabricated frame which had several modifications done so that it could meet the needs of the client. The chassis was purchased from Northern Tool. The frame is made of steel and had a steering, and braking system in place. These were both removed and replaced. It also came equipped with a steel roll cage. The Joe-Kart is powered by three deep cycle marine batteries. Each system, steering, braking, and drive, are all run off these batteries. The drive motor uses two of these batteries in series. The other two systems run off of the third battery. The batteries have switches so that power can be turned off when not in use. Each of these independent systems is driven by electric motors, which interface the user and the mechanical systems. The Joe-Kart is designed for two passengers. There is a specially designed seat as well as regular bucket seat. The specially designed seat also has foot straps attached to the floor so that the passenger does not kick any important mechanical or electrical systems. This seat has a harness attached to it so the passenger is secure in the seat. The bucket seat has a regular seat belt to keep that passenger safe as well. The steering system uses a rack and pinion powered by a Dayton DC gear motor. The rack and pinion is connected to the wheels via tie-rods. The steering system also uses a linear potentiometer attached to the rack and pinion as a feedback sensor. This allows the wheels to move back to a straight position when the joystick is released. The linear potentiometer also controls how much the wheels can be turned so that no damage is done the go-kart. The steering system can be seen in Fig. 1

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Figure. 1. Steering System

The braking system uses a disc caliper and brake disc attached to a Dayton DC gear motor. This system also uses a linear potentiometer to determine the amount of braking. The brake sensor allows the brake to retract when the brake control is released. The braking system can be seen in Fig. 2

Figure 2. Braking System

The drive system uses a Magmotor attached to a transmission box to drive the rear axle. The Magmotor uses 24 volts which is provided by two

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batteries in series. The transmission box with the Magmotor can be seen in Fig.3.

Figure 3. Transmission box with Magmotor

There are two different ways to control the Joe-Kart. A remote control is available so that parents do not have to be in the go-kart. There is also an option to put the remote in the go-kart and control it while riding in it. The remote has a kill switch which will cut all power to the go-kart. The Joe-Kart also has the option to go in reverse via a switch.

1.2 Operating the Joe-Kart

The Joe-Kart should never be used without the supervision of an adult. It is recommended that the Joe-Kart is not used during any precipitation, or in wet environments. Use in wet environments can cause serious damage to the Joe-Kart and possible injury to the users. Before starting the Joe-Kart, make sure that all the batteries are fully charged. When the Joe-Kart is not in use the batteries should be connected to a charger. Failure to properly charge the batteries could result in serious injury. Make sure that the power switches are in the off position. Also make sure that the forward/reverse switch is in the forward position. BE AWARE OF FORWARD/REVERSE POSITION. Check the transmission oil level and make sure all systems are connected properly. Make sure that there is no mud or dirt on any of the systems. If it is not clean, clean the systems before use. If any problems are identified, refer to the maintenance section.

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Before riding in the Joe-Kart, the supervisor needs to be familiar with the controls. They also need to be comfortable with the handling of the Joe-Kart. Previous experience with remote controlled cars is preferable. Both passengers should be seated in the Joe-Kart before any power is turned on. The passengers should be properly seated with the correct harnesses buckled. Both passengers should have all the necessary safety equipment including helmets. The seats and harnesses can be seen in Fig. 4. When both passengers are ready, the power can be turned on. To turn on the power on, the supervisor must turn the battery switches to the on position as seen in Fig. 5. The supervisor must also turn the ignition switch which can also be seen in Fig.6. The supervisor also needs to check the forward/reverse switch and make sure that it is in the correct position.

Figure. 4. Seats with harnesses

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Figure 5. Battery Switches

Figure 6. Ignition switch and Forward/Reverse Switch

If the supervisor is to ride in the go-kart, the remote should be mounted to the dashboard. If the supervisor is not riding in the go-kart, the remote should be kept with them at all times. To make the remote functional the power switch on the remote needs to be in the on position. Make sure the emergency kill switch is not on. If the emergency kill switch is on, the status LED will be solid green. If it is not on, and the remote is fully functional, the status LED will blink green. If the kill switch is on, the remote will not function. The remote can be seen in Fig. 7.

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Figure 7. Remote Control

To use the remote, both hands need to hold the remote. On the left side is the acceleration and braking. These are labeled on the remote. To accelerate the go-kart, press the joystick forward. To stop the go-kart, push the joystick back towards you. These functions will operate the same, regardless of forward/reverse functionality. If the go-kart is switched to reverse, it will accelerate in reverse when acceleration is pressed. Braking will operate the same; regardless of forward or reverse, it will stop the rear axle. On the right side of the remote is the steering joystick. To turn the go-kart right, push the joystick to the right. The steering will only turn to a certain point. If held to the right, the joystick for an extended period of time, the wheels will not turn anymore once the linear potentiometer is at full stroke. Once the joystick is released, the wheels will move back to the straight position. The same is true with the left. If the joystick is held to the left, the wheels will turn to the left, but only to the end of the stroke. They will not continue to move once at full stroke. Once the joystick is released, the wheels will move back to the straight position. The remote is also equipped with an emergency stop button. If pressed this button will stop all function in the go-kart. To regain function, the button must be released. If it is not released the status LED will be a solid green. Once functioning again, the LED will flash green. The emergency kill switch should be used only in emergencies. Do not use to stop or power down the go-kart. This can cause damage to the go-kart.

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While operating the Joe-Kart do not use on rough terrain. Use on rough terrain can cause loosening of parts and wires. If anything does become loose, refer to the technical description section to fix it. The Joe-Kart should also not be used in wet environments or during any precipitation. If the go-kart does get wet it can damage the sensitive electronics. While operating, avoid very sharp turns and short stops. Rough use such as this can cause damage to the go-kart and injury to the passengers. Once operation is complete, make sure that the following steps are done in order to prevent damage to any of the systems. First, make sure the forward/reverse switch is in the forward position for the next use. Then turn of the ignition switch and remove the key. Do not leave the key in the ignition. The supervisor should then turn off the power switches to shut down the batteries. The remote power should be turned off last. Once all power is shut down, press the emergency kill switch to ensure the nothing will happen unexpectedly. The passengers can now remove the harnesses and protective gear and exit the go-kart. Remove any mud or dirt from the go-kart and make sure that it is clean to ensure that all parts will work correctly the next time. Store the go-kart in a dry place where it will not be exposed to moisture. Any exposure to moisture will severely damage the Joe-Kart. Cover the Joe-Kart using a tarp or cloth to ensure that no debris can get into the Joe-Kart while not is use. Attach the batteries to battery chargers to keep them at full power. The batteries will drain quickly while in use, so keep them charged when not in use to prevent them from dying during use. By following the proper shut down and storage procedures, the Joe-Kart will have a much longer life and the maintenance will be greatly reduced.

2. Maintenance

2.1 Mechanical Maintenance

2.1.1 Chassis

To properly maintain the chassis, make sure that it is cleaned regularly. Do not let loose dirt accumulate on the floor or in other areas. Loose dirt can get into the other systems and cause damage. Check the chassis regularly to make sure that no welds have come loose. In the event that

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a weld has come loose, do not use the go-kart until it can be re-welded by a professional.

2.1.2 Steering

Before operation, check all the connections for the linear potentiometer, the rack and pinion and the tie rods. Also make sure that the motor mount has not come loose in any way. If any connection has come loose, tighten using the appropriate tools. Make sure the wheels are maintained in a straight position. If the wheels are not straight, straighten out by twisting the tie rods in the appropriate direction.

2.1.2 Braking

Check the braking motor mount and the caliper mount before operation. If either has come loose, tighten using the appropriate tools. Also check the mounting of the linear potentiometer and tighten if necessary.

2.1.3 Batteries

Before and after each use, make sure the batteries are secured to the chassis using the straps. If the batteries come loose tighten the straps. Be aware of loosening during operation. If the straps come loose during operation, stop and tighten the straps.

2.1.4 Control box

Also make sure that the control box is tightly secured to the chassis. Too much movement of the control box can cause serious damage to the electronics. The control box uses three bolts. Before, during and after use make sure that all three bolts are secure.

2.1.5 Seats

Make sure that both seats are secure to the chassis. Use on rough terrain or rough use can cause the seats to come loose. Tighten all the bolts on both seats regularly. The sliding tracks on the specialized seat may need to be lubricated periodically for ease of sliding. Use silicon spray to lubricate the tracks.

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2.1.6 Foot straps

Check the foot straps before and after each use. Make sure the springs are in place and all the bolts are secure.

2.1.7 Front guard

Avoid damage to the front guard. If bent too severely, it can interfere with the steering system. If it becomes bent do not use go-kart until it can be completely cleared from steering. The top guard also needs to be checked for loose bolts every month.

2.1.8 Tires

The tires should be checked regularly for wear. If the tires are too worn, it is recommended that they be changed. The back tires are larger than the front tires and when replacing tires, be sure to keep the correct tires in the correct place.

2.1.9 Transmission box

The transmission box should not move, but check every year as a precaution. The grease coating the gears should be checked every 100 hours of use. At this point it is at the owner’s discretion whether to clean and re-coat, simply re-coat or leave the gears as they are. Although this is at the owner discretion it is advised that the gears be CLEANED AND RE-COATED with grease at each inspection to maximize life of the gears.

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Figure 8. Filling the transmission box

2.1.10 Rear Axle

The drive motor is mounted underneath the chassis. Make sure that the U-bolt around the motor is secured to the chassis. Also make sure that the rear axle is secure. Check these bolts before every use.

2.2 Electrical

2.2.1 Batteries

Make sure the battery terminal connectors are secured and have good electrical contact. Do not let dirt near the battery terminals. Also make sure the battery switches are connected properly.

2.2.2 Control Box

The control box is where most of the electrical components are housed. It is not advised to move anything in the control box; however, the control box should be checked before and after each use to make sure that no wires are exposed and that no bare wires are touching. If any bare wires are touching, make sure that all power is disconnected before touching the wires. If anything needs to be adjusted, refer to the technical description and troubleshooting section before changing anything.

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2.2.3 Remote Control

The remote control runs on three “D” batteries. When the batteries are low the status light will indicate low battery. Replace the batteries at least once a year. To replace the batteries, loosen the four screws on the bottom of the remote and remove the panel. Take out the existing batteries and dispose of them. Put three new batteries in. Do not reuse any of the old batteries.

2.2.4 Wires

All wires should be contained in the conduit and not exposed. Check to make sure there are no exposed wires on the chassis. Do not use the go kart if there are any exposed wires. Turn off all power before touching the wires. Only someone with experience should try to re-wire if a wire comes loose. Refer to the wiring diagram in the technical description to wire the go-kart.

2.3 Environmental

The easiest way to maintain the go-kart is to use it in the appropriate environment and treat it with care. Do not drive on rough surfaces and do not turn or brake suddenly. This behavior will lead to problems with maintaining it. Do not use the Joe-Kart in any wet environments including mud. Clean off any mud or dirt that gets on the go-kart. Store in a dry place with a cover so that nothing happens while not in use. Do not store other things on top of the go-kart.

3. Technical Description The Joe-Kart consists of many subunits that are connected together. Each subunit will be reviewed, giving an in depth description of each system along with a picture of the subunit described. The final prototype can be seen in Fig. 9.

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Figure 9. Completed Joe-Kart

3.1 Chassis

The chassis option selected for the optimal design is the prefabricated Stingray complete go kart chassis kit from Northern Tool. This chassis has dimensions of 72 x 43.5 x 47.25 in (l x w x h) and is meant for two people. This double seat model was chosen because it allows for the client’s parents to ride along.

3.2 Seats

Instead of a single bench seat the Joe-Kart implements two separate seats; one specialized for the client, the other for the passenger. The passenger seat is standard bucket seat on the left side of the go-kart, depicted in Fig 10. This seat is equipped with the seatbelt provided to ensure passenger safety.

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Figure 10. Passenger Bucket Seat

The specialized seat is based on his existing wheelchair seat, providing all the similar adjustable supports such as head and neck, trunk, waist and groin. The specialized seat also has foot rests and foot straps to safely keep the client seated and protected. A seat from an old wheelchair was used. This seat is very similar to the client’s current wheelchair and can be seen in Fig.11 with the modifications. It had the appropriate supports that are needed and also comes with a harness. The seat needed to be modified so that it can be attached to the chassis. The client’s seat is on the right side of the go-kart. This allows the left handed controls to be in the center of the go-kart.

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Figure 11. Client seat

This seat is adjustable so that it will be able to grow with him. Furthermore, it is permanently fixed to the go kart on adjustable sliding tracks easing entry into the kart as well as accounting for future growth. To move the seat forward or back, pull up on the lever and push the seat back or pull it forward. The frame of the seat can be seen in Figure 12. The adjustable tracks are attached under the frame.

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Figure 12. Seat frame

3.3 Steering Mechanism

The steering mechanism for the go-kart needed to be designed to be quick and responsive to handle optimum maneuverability while also being able to withstand the forces exerted on the system while it executes turns while in motion. Since the client lacks the motor control to be able to steer the go-kart manually, the steering system is powered and controlled by a gear motor which powers a rack and pinion. The rack and pinion is connected to the wheel brackets via tie rods. The linear displacement of the rack due to the rotation of the pinion will result in a translational movement of the wheels which will steer the car left and right. The steering system can be seen in Fig. 13.

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Figure 13: Steering System

Motor

The Dayton DC gear motor (Part #: 1L469) is used in the design to drive the rotation of the rack and pinion. The gear motor is capable of producing 50 lb-in of torque at 90 RPM. It has a source voltage of 12V and a current rating of 9 amps. The gear motor is mounted on the frame of the go kart. It gives rotational power to the rack and pinion through a gearing reduction that will connect the drive shaft of the gear motor to the 36 spline input shaft which is also connected to the rack and pinion. This output to the rack and pinion is more than enough to provide quick and responsive handling for the steering system of the go kart.

Rack and Pinion

The rack and pinion depicted in Fig. 14 is used to take the rotational energy produced by the gear motor and translate it into a linear displacement of the rack which ultimately results in the right and left turning of the wheels. The rack and pinion system used for this go kart is an 11” Rack and Pinion steering unit. This product is designed for go karts and small dune buggies and will provide not only the necessary performance for efficient turning, but also durability for a higher quality and more rugged steering system. The rack and pinion ratio is 12:1 which equates to 1.5 turn of the pinion to a 4 inch displacement of the rack. The rack is made of billet aluminum and is equipped with steel gears and a sealed bearing. The rack also comes with a 3/8” male tie rod ends which can be screwed into the sides of the rack to allow for the adjoining of the

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tie rods. The rack also comes with a 5/8” 36 spline input shaft. This spline can be connected to a couple which is sold separately. This coupler acts as the connection between the rack and pinion and the steering column, or in the case of this go kart, the gear motor.

Figure 14: 11” Rack and Pinion System in go-kart

The motorized steering system is mounted off center of the go kart in order to maximize leg room for both passengers. The tie rods used in this go kart are 6061-T6 high strength aluminum tie roads from McMaster-Carr (Part #: 6516K23). The tie rods contain a 3/8” thread size which is ideal for the female rod ends which are used to attach the tie rods to the rack and pinion on one end and to the rod arm of the wheel spindle. Linear Position Transducer

In order for the microcontroller to be able to track the linear displacement of the rack and pinion, a linear position transducer was installed to move with the rack and pinion. The linear position transducer used in the steering system is a Celesco CLP Linear Potentiometer shown below in Fig. 15.These transducers have been proven time and again in the automotive and robotics industry and provide precise accuracy of measurement in a durable long lasting design. This transducer acts like a variable resistor which changes the voltage output to the microcontroller due to the linear displacement of the actuating tie rod. The best aspect about this product is that the pivot heads in the transducer can be attached male and female rod ends of the rack and pinion and tie rods. The transducer has a 6” stroke length and was calibrated upon installation to have a set potentiometric resistance at a zero point. Any movement of the actuating shaft inside the housing will change the internal resistance of the transducer and ultimately change the output voltage to the microcontroller. The receiver will read the voltage difference as a change in the linear position of the rack and pinion. The

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implantation of the linear actuator is crucial because the rack and pinion has no electrical component to interface with the microcontroller to help give information of the linear displacement.

Figure 15: Celecso CLWG Linear Position Potentiometer in steering system

Speed Controller

A speed control must be used in order to control the gear motor which drives the steering system. The speed controller that is used in this system is the 24V IFI Victor 883. This drive motor has been engineeried to be implemented in many robotics applications especially within drive and steering systems. The Victor 883 comes with a PWM signal driver which helps ensure that it is compatible with the incoming RF signal from the receiver. This speed controller can operate at higher currents with a continuous current rating of 25A which makes it ideal for the steering system. Also, the low voltage drop and high switching speed helps feed maximum power to the motor. The switching speed will help in the constant forward to reverse rotation of the motor that will occur during normal steering and will make the steering system even more responsive. The speed controller is mounted in the control box.

3.4 Drive System

Motor

The motor that is used to power the go kart is the C40-300 MagMotor shown in Fig. 16. Magmotors have been engineered specifically for use in robotics combat competitions and also for use in electrically driven scooters and go karts. The C40-300 MagMotor is an electric motor that can produce 3.8 horsepower and 3840 oz-in of torque while putting out 4000 RPM at a maximum voltage of 24V. This is an extremely powerful motor and is ideal for the design of the go kart. The MagMotor has many benefits including a high efficiency at higher RPM and also an easy mounting system that gives it versatility in the placement of the motor in

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the go kart. It also comes with build in capacitors between the brushes in order to reduce RF noise. This is a very crucial feature considering the amount of RF communication that is already implemented into the design. The motor has a 1.75” drive shaft that is 5/8” in diameter with a 3/16” keyway which allows the shaft to be integrated with a custom sprocket to initiate the proper gear reduction. The motor will draw a lot of current trying to move the go kart if it was attached to the sprocket on the axle directly which will drain the power source quickly. By having a gear reduction in place, the motor accelerates at a faster rate with increased torque. The other advantage is that since this motor is very powerful, the gear reduction will allow it to perform at a safer speed and also run more efficiently at a lower RPM. This will save a lot of power which will ultimately lead to longer continuous operation times.

Figure 16: C40-300 MagMotor with Transmission Box

Speed Controller

Just as the gear motor needed a speed controller to gauge the voltage input, the drive motor needs one as well. However, since the drive motor will be drawing a much higher current the speed controller for the drive motor must be much more robust a durable to handle the high current load. The speed controller used to drive the main motor is a 4QD-300 speed controller designed by SLT Technology, Inc. This motor controller is compatible with the 24V MagMotor described previously and is powerful enough to withstand current draws of up to 300 Amps. The 4QD-300 is a notoriously very durable speed controller and is equipped with many fail safes in order to ensure maximum reliability and prolonged use. This

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speed controller is optimally designed for joystick input which is ideal considering the main method of control for this motor is going to be two single axis joysticks. Also, an external potentiometer is mounted on the controller to give the owner manual top speed control. This is a good additional feature for the client since as he becomes older; his parents may think he could be ready for some more speed. The 4QD-300 also has the ability to execute direction switching for drive braking giving it the ability to change the direction switch and break while moving forward at full speed. This is a very convenient feature to have for the go kart however, considering this speed controller is mainly used is smaller robotics applications, a rotary breaking system will still be installed as a safety precaution. The speed controller is also placed in the control box.

Transmission Box It will be necessary to design and fabricate a transmission box to transfer torque from the motor shown above to the differential axle we will install. This will be done through a specific gear ratio to increase the torque applied to the axle. The transmission box designed and modeled has a 7.5:1 gear ratio, broken down between two sets of interacting gears. The first is a 16 tooth gear attached directly to the motor shaft interacting with a 40 tooth gear providing a 2.5:1 ratio. The 40 tooth gear is mounted on a shaft with another 16 tooth gear spinning with the same torque. The second 16 tooth gear is interacting with a 48 tooth gear mounded onto the axle providing a 3:1 gear ratio ultimately delivering a 7.5:1 from the motor to the axle. Figures 19 and 20 show the gear box. Figure 17 shows the placement on the chassis and Figure 18 shows the inside of the transmission box. The transmission box should never be taken apart.

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Figure 17. Placement of transmission box on chassis

Figure 18. Inside of Transmission box

3.5 Braking System

The same problem with the steering controls is also present in the implementation of the braking system for the go kart. On a standard go kart, a brake line attaches the brake pedal to the brake calipers. When the pedal is pushed down, the leverage pulls the brake cable which compresses the calipers on to the brake rotor which slows down the go cart. The client does not possess the capability to be able to push down a brake pedal which means that this process is going to have to be done mechanically. This system implements gear motor and motor drivers that is controlled by the receiver in order to safely and effectively apply brakes to the moving go kart.

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Braking Mechanics Since safety is the number one concern when it comes to the design and construction of this go kart, the entire braking system is designed with very acute detail. The motor driver will take signals from the receiver and send them to the gear motor via PWM which allows for a variable compression force to be exerted on the brakes. In the case of this gear motor, maximum RPM and voltage input are not as much as a factor as the maximum torque and current draw are. The gear motor will be controlled by a motor driver that will be responsible for driving voltage to the motor which will pull the calipers together. The motor driver also has to be able to reverse the polarity of the signal to allow the motor to release the caliper compression on the brake rotor. The braking system also needs an electro mechanical feedback system to help govern the rotation of the motor which is where the linear transducer comes into the design again. The fortunate thing about the braking system on this go-kart is that the rotary braking system can have assistance from the speed controller that controls the MagMotor because this speed controller comes with a regenerative braking feature. However, we limited the amount of work done by the speed controller because regenerative braking requires a lot of current. This can deplete the power sources more quickly and ultimately give the go-kart a smaller time of operation per charge cycle.

Braking Motor

The braking is powered by a gear motor just like the steering system. The braking motor can be seen in Fig. 19. The gear motor has a rated voltage of 12V and current rating of 6.5 Amps. The gear motor provides a continuous output torque of 500 in-lb at an RPM of 6. The brake line is attached to the drive shaft of the motor and when the brakes are applied, the motor will rotate and pull on the brake line. This will close the brake pads on to the brake rotor and will slow down the go kart. Upon release of the brake, the motor driver will send a reverse polarity voltage to the motor causing the motor to rotate in the opposite direction to release the calipers from the rotor.

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Figure 19: Braking Gear Motor

Braking Motor Driver

The IFI Victor 883 motor driver that is used in the steering system is also used in the braking system. This motor driver not only excels in performance in steering systems but also has unmatched performance in braking systems. The efficiency of the IFI motor driver at high voltage and current capacities makes it ideal for the braking system because the motor is going to be resisting a lot of rotational force. This means that the gear motor will be drawing an ample amount of current in order for it to keep tension on the brake line to compress the calipers on the brake rotor. The motor driver is rated to be able withstand that current draw. That notion, along with its ability to control forward and reverse rotational movement, makes the IFI Victor 833 the ideal motor driver for the system. This motor controller is also located in the control box.

Braking Position Transducer

A typical braking system on a go kart relies on a brake pedal to apply a mechanical advantage to the brake lines to close the calipers on to the brake disc. Due to the lack of motor control of the client, this process cannot be feasibly executed. Therefore, an electromechanical system is used to gauge the position of the brake line with respect to the neutral position. This was done with a linear position transducer just like in the steering system. The linear position transducer used in this system is the Celesco MLP Miniature Potentiometer. This linear potentiometer will vary the feedback voltage to the braking microcontroller in order to give input as to the overall distance the brake line has moved which ultimately

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coveys the compression of the brake pads on the disc rotor. The stroke length for the brake line is not be nearly as large as it was for the steering system. This linear potentiometer has a stroke length of 4 inches which will be enough of a stroke length to close the brake pads on the rotor while providing it with a wide variance of voltage output for a feedback signal.

Brake Caliper

The brake caliper that is used in the go kart is a Comet Industries DC Series Disc Caliper Brake. This brake can be an aftermarket addition or direct replacement for comparable brake discs on its size. The caliper has a total of 16 different lever positions which provide a multitude of different installation options on the go-kart. An integrated actuation design features a positive stop lever so that a return spring can be used without causing braking in the opposite direction of pull which is ideal in our system. The brake can also be fine tuned via a hex screw adjustment system. Also, a mounting bracket provides a larger degree of freedom when considering the implantation of the caliper on the chassis.

3.6 Batteries

The go-kart uses three deep cycle batteries. These batteries have an output voltage of 12V. Two batteries will be put in series to create 24 V which will power the drive motor. These batteries will be 500 CCA each. The third battery will power the steering, braking, and all other systems. This battery is larger and has 665 CCA. Any battery that satisfies these needs can be used. This way if a battery needed to be replaced by the client, they would be able to get them. The terminals are configured with dual wing nut terminals. All three batteries are on the back of the go-kart. They are held in place with brackets and buckles. This will prevent any movement of the batteries. The battery set-up can be seen in Fig.20.

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Figure 20. Batteries on go-kart

3.7 Control Box

All of the electrical components need to be secured in a control box. This box contains all of the major electrical components including the remote receiver, and the speed controllers. This box will be made from metal and will be secured to the chassis. This box is located behind the seats so it is easily accessible if anything needs to be changed. Containing all of the electrical components will prevent them from being damaged in the case of collision. It will also insulate the components to protect the client and other users. All of the wiring is also insulated, housed in a conduit and secured to the chassis, so that it does not harm the client. The wiring is tightly secured to the chassis in such a way that they cannot be tripped over or pulled up. An ignition switch as well as a forward/reverse switch has also been wired in towards the front of the go-kart. The ignition switch powers the 4QD speed controller. The control box also houses the battery switches. These switches can be used to give power to the go-kart. When the go-kart is not in use the switches can be turned off to save power. The control box can be seen in Fig. 21.

Figure 21. Control Box

The wiring diagram for the control box can be seen in Fig. 22. All wires do come into or out of the control box and this is a complete wiring diagram. The appropriate voltages and currents are included in the wiring diagram.

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Figure 22. Wiring Diagram for Joe-Kart

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3.8 Control Systems

The go-kart has two different ways to control it. This first is a remote control with two single axis joysticks. One controls steering, and the other controls speed, and braking. To put the go-kart in reverse, there is a switch. When the go-kart is put in reverse, all of the functions will work the same; however, when the acceleration is pushed, it will go backwards.

The remote can also be mounted into the chassis to create a second method of control. This dashboard is mounted to the chassis via a mounting arm. This mounting arm can move side to side and front to back. This will allow the parents to use the controls or point them to the client. It also allows the controls to be out of the clients reach so that he does not accidentally hit something.

3.9 Remote Control

The remote control was custom built by Miratron Inc, Portland, Oregon. The transmitter used will be the T-1 model. The remote control runs off of 3 “D” batteries and is also be equipped with a tether cable. When connected momentarily, this tether cable allows the transmitter to “learn” the receiver address. This also allows for replacement of the transmitter without replacing the receiver. The remote will have a range of up to 500 feet and is enclosed in high impact polystyrene for durability. It will have two single axis joystick controls. One joystick controls the acceleration and braking of the go-kart. The second controls the steering. The remote will always be able to overpower the on board controls. This will allow the guardian the most amount of control over the go-kart, while still allowing the client to operate it. The remote will also have a small LED which will light up when the battery of the remote is at 40% power. The design of the remote is shown in Fig. 23. The data sheet for the T-1 transmitter can be found in Appendix B.

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Figure 23. Remote Control

The receiver will also be provided by Miratron Inc, Portland, Oregon. The receiver is the R-4 radio receiver model. The receiver takes inputs from the remote transmitter, and also has inputs directly from the button controls. The receiver is programmed to run the steering, the braking as well as the drive motors. The receiver is able to act as the microcontroller eliminating the need for external microcontrollers and embedded code. The receiver is encased in black nylon and is compact so that it can fit into small spaces. The data sheet for the R-4 receiver can be found in Appendix A and the wiring diagram can be seen in Fig. 24. If there are any problems with the remote or the receiver, contact Miratron, Inc, directly at 503-352-0654.

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Figure 24. Wiring Diagram for Receiver

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Remote Kill Switch

The remote control is also equipped with a kill switch. This kill switch is a mushroom button located in the top center of the remote control. This kill switch will stop any movement of the go-kart. The kill switch will also shut down all power to the go-kart. The kill switch will be red, and is marked “E-Stop” so that it is easy spotted, and the user is aware of its location.

4. Troubleshooting Problem: No Power to any or all of the systems Possible Causes:

1. Batteries are not connected 2. Batteries are dead

Possible Solutions: 1. Connect batteries at terminals and check to make sure the switches are

wired correctly. 2. Charge Batteries

Problem: Power is on, but nothing is happening Possible Causes:

1. Remote is not on 2. Remote has low battery 3. Remote is out of range 4. Emergency kill switch is activated

Possible Solutions: 1. Turn remote on 2. Change batteries in remote 3. Make sure remote is within 500 feet of go-kart 4. Take off the emergency kill switch

Problem: Steering is erratic Possible Causes:

1. Steering wheel input for receiver does not have the proper voltage applied a. It needs to have a constant 2.5V applied

2. Rack and Pinion is not connected correctly 3. Battery does not have enough power to steer 4. Linear potentiometer has been damaged

Possible Solutions: 1. Check the voltage divider circuit for loose wires 2. Check the rack and pinion for proper connection

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3. Charge or replace batteries 4. Check linear potentiometer, if damaged it needs to be replaced

Problem: Batteries die quickly Possible Causes:

1. Battery Switches are not being turned to the off position 2. Batteries are not being fully charged 3. Batteries need to be replaced

Possible Solutions: 1. Turn battery switches to off position when not in use 2. Charge each batteries on a slow charge for at least eight (8) hours 3. Replace batteries

Problem: Batteries are moving too much while driving Possible Causes:

1. Battery straps are not tight enough Possible Solution:

1. Tighten straps 2. If a reoccurring problem, replace straps and ratchet buckles

Problem: You hear rattling noises in the back of the go-kart Possible Causes:

1. Control Box is loose 2. Components in control box are loose 3. Batteries are loose 4. Rear axle is loose 5. Drive motor is loose 6. Brake motor is loose

Possible Solutions: 1. Tighten control box to chassis 2. Check all components in control box and tighten any loose ones 3. Tighten or replace battery straps 4. Tighten bolts for rear axle 5. Tighten U-bolt for drive motor 6. Tighten brake motor and check brake

Problem: You hear rattling in the front of the go-kart Possible Causes:

1. Steering motor is loose 2. Rack and pinion is not connected to steering motor

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3. Rack and pinion is not connected to tie rods 4. Front or top guard is loose

Possible Solutions: 1. Tighten steering motor 2. Make sure rack and pinion is connected to motor and tighten set screws 3. Check the tie rods and make sure they are connected properly 4. Check front guard and make sure linear potentiometer has not been

damaged.

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Appendix A: Operators Manual for Miratron Reciever

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Appendix B: Operators Manual for Miratron Remote

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