Introduction: Go Fetch!

An adapted hands-free fetch device for individuals with upper limb mobility limitations looking to interact with their canine companions in engaging ways.


Canine companions are an important part of every pet owner's life, especially of those who depend on assistance from their canine companions to carry out daily activities. More specifically, for individuals with mobility limitations, having a canine companion means having constant support, company, and assistance to retrieve certain items, and overall increase the individual's independence by decreasing their dependence on other people. Time to play is important in enriching the life of the canine while also maintaining a healthy relationship between the canine and the individual. Common methods of enriching play that involves both the owner and the canine is the game of fetch. In general, fetch is a type of game that requires extensive upper-body mobility which makes it difficult for those with upper limb limitations to comfortably participate. Simply because of one's limitations, an individual and the canine companion should not have to compromise their quality of life.

Problem Statement:

Individuals with upper limb limitations may be unable to play fetch with their canine companion due to restitutions to their mobility. Devices that currently exist that offer owners the opportunity to play fetch with their canine companion “hands-free” are unaffordable and have not been adapted for those with limited mobility. Our target audience is people with upper limb disabilities who have canine companions. Our device will allow our target audience to play fetch with their canine companions while comfortably using the limited movement of their upper limbs.

Competitor Analysis:

Throughout the research process, we noticed that a lot of the product ball launchers we found shared similar features, some of which we wanted to use and others that we thought needed reform. Many of the dog ball launchers included a compact shape, and this was something that we used as a model for our first design. Since our client has mobile impairments, we wanted a device that could be held or supported by him without causing trouble or frustration. We noticed that most of the ball launchers also had a hole in the top of the device in which a ball could be placed before launch. We also decided to keep this design for our product because it enables our client to easily reload the machine. Rather than the bowl-shaped opening seen in most of these products, we decided to have a smaller opening, yet one closer to the client. We improved upon the bowl-shaped opening by extending a PVC pipe, through which the ball could be loaded. The PVC pipe makes the opening closer to our client, who will have more ease trying to utilize the launcher. We noticed that a majority of the products also used a personally manufactured tennis ball, which is much smaller in size than standard tennis balls. We decided to use standard tennis balls because it will be more fitting for the large companion dog that our client has. Most of the tennis ball launchers were power operated as well. We looked into different ways of powering our device, and we found that using a rechargeable battery or power outlet would be a nice feature. However, rechargeable batteries are pretty expensive and can be a hassle to use. Instead, we looked into using a battery-operated machine. So far, it has been working well, but we are looking into using a rechargeable battery in our product which may benefit our client as he can recharge the battery instead of replacing it altogether. The last design critique that we have for all of the products is usability. For most, the flipping of a small switch on the side of the machine will be enough to activate it. However, those with mobility impairments may find it difficult to press the small buttons on the sides of the machines. To combat this conflict, we decided to use a large button for operating the device. The button will serve as an on/off switch for the device.


Generally, our approach was to use flywheels and motors to power a tennis ball to be launched at a minimum distance of 15ft. Additionally, we felt that it was important to prioritize developing the device to be independently usable, easily activated, and durable for long term use. To achieve these goals we produced and tested various prototypes until we developed a version of our device that met our MVP. This version met most of our level 1 and 2 requirements and can be further iterated to add more functionality and safety features.


  • (2x) Three-inch Compliant Wheels ($14)
  • (2x) 3/8" Hex Shaft ($8)
  • Three-inch Inner Diameter PVC ($27.91)
  • (4x) 3/8” Flanged Hex Bearings ($24)
  • (4x) 18 Tooth 3/8” Hex Sprockets ($24)
  • 25 Chain ($23)
  • (10x) 3/8” Hex Shaft Collars ($60)
  • 775 Motor with VersaPlanetary Gearbox ($84.96)
  • On/Off Rocker Switch ($7.99)
  • (16x) D Cell Batteries ($14.00)
  • Large 12V Battery ($22.00)

Supplies can be purchased from the following sites:

As well as...

  • Home Depot (PVC Pipes)
  • Amazon (Electrical parts)


  • Joiner
  • Planer
  • Dremel
  • Drill
  • Allen wrenches
  • File
  • Screwdriver
  • Chain break
  • Multitool
  • Soldering Iron

Step 1: Build Process

  1. First, refer to the CAD files for the basic components of the mechanism.
  2. Make the basic individual components of the launcher as follows:
    1. Assemble the motor gearbox with the instructions provided by VexPro
    2. 3D print 2 polycord pulleys (TBL1_006)
    3. Make 2 of the Versa Mounting plate(TBL1_005) part using a joiner, planer, table saw, and drill.
    4. Make 1 of the Spacer Plate (TBL_007) part using a drill press, table saw, and bandsaw.
    5. Make 2 of the Mounting Plate (TBL_002) part using a drill press, table saw and bandsaw.
    6. Cut hex shafts to about 8 inches long and sand as needed.
    7. Cut slots in either side of the PVC tube that is larger than the height of the wheels and a little smaller than the diameter (3 in) of the wheels.
  3. Put together the wheels, mounting plates, motor pulleys, hex shafts, bearing, sprockets, and PVC tube as follows:
    1. Put a wheel with 1 shaft collar on either side onto both hex shafts.
    2. Put bearings inside each of the holes in the mounting plate.
    3. Attach the space plate to one mounting plate using screws after lining up the hex shaft holes.
    4. Add the versa mounting plates to the spacer plate by fitting them into the rectangular gaps on the side of the spacer plate. Fasten with screws.
    5. Put a shaft collar and a sprocket onto the motor shaft. Place the motor in between the versa mounting plates and line up the screw holes. Fasten together using 10-32 screws.
    6. Put the hex shafts through the bearings.
    7. Add polycord pulleys and shaft collars to the bottom of the hex shaft (side without the motor).
    8. Put another sprocket on the top of one of the shafts (the side with the motor) and attach the chain to both sprockets.
  4. Put in spacers as needed between the tube and the mounting plates.
  5. Put all the pieces back together and insert screws.
  6. Attach the battery holders, motor, and the switch

Step 2: Usage

  1. First, place and mount the device in a comfortable and easily accessible location on your mobility device and ensure tennis balls are also accessible.
  2. Prepare your canine for tennis ball launch, as the launch will occur quickly after the tennis ball is loaded. This can occur by having you canine stand out of the initial launch zone of the tennis ball. In other words ensure your canine is not initially positioned directly in front of the device.
  3. Activate the device by switching the rocker switch to the "on" position.
  4. Load the launcher with one tennis ball.
  5. Immediately after the ball is launched deactivate the device by switching the rocker switch to the "off" position.
  6. Wait for canine to retrieve the tennis ball and repeat steps 2-5.
  7. Once your play session is completed, ensure that you turn off the device by checking to make sure the switch is in the "off" position (similar to after each launch) to deactivate the device.


  • If the device is mounted on the side of your chair, the width of the chair and the device will be wider than the user may be used to so be careful when moving through narrow areas such as doorways and hallways.
  • Before launching the tennis ball ensure canine is not directly in front of the device as the tennis ball may hit the canine causing possible injury. Position canine next to the device or at least 10ft distance away from the device so when the ball is launched the dog is far enough away that it surpasses the height of the dog (this will vary based on the height of the dog, it is safer to have the dog positioned to the side of the device).
  • Ensure to deactivate the device after every launch and every use (follow the steps for usage as needed).

Step 3: Maintenance & Care


Ensure the usage of only standard size tennis balls ( approximately 3inch diameter) as any other size tennis ball or any other dog toy could potentially get stuck inside the device and damage mechanical parts during retrieval of stuck parts.


Cleaning of the device can occur by disconnecting the main PVC section from the small curved edge. Once these two sections are separated the device can be washed using any disinfectant/soap but do not run underwater, instead rub in the product using a cloth. After cleaning and complete drying of the device, reattach parts securely and prepare for its next use!

Part Replacement:

  • 8 D-Cell Batteries will have to be replaced on a more regular basis (length of battery life varies based on how often the device is used).
  • If any mechanical parts are broken or are suspected to be broken, return the device to Jeffrey Wilcox (contact: ) for repair.

Step 4: Improvements and Extentions

One could extend upon our most recent iteration of the “Go Fetch!” device by looking into improving both aesthetic and functional components of the device. Aesthetically, improvements made to the appearance of the PVC using paint would aid in making the device less chunky and material looking. Functionally, one could look into developing the button activation component. The device can be extended further by developing a component that allows for the device to easily change launch angles and launch distances for the user to adjust based on their setting and canines play preferences. Other extensions include precautions and characteristics that can be implemented to ensure maximum safety for both the owner and their canine and aid in long term usage of the device.