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Flex Wheels for V5

What Are Flex Wheels?

Flex wheels are soft wheels that are designed to be compliant, and are useful for a variety of applications, such as:

  • Picking up hard plastic game objects
  • Picking up objects that have an irregular shape (e.g., cubes, discs, etc.)
  • Driving over field obstacles where regular drive wheels may have difficulty

Flex Wheels were originally designed for the VEXpro product line, which primarily uses 1/2" hex or 1-1/8" round bore for most applications. However, V5 uses 1/8" and 1/4" square shafts. In order to use Flex Wheels on a V5 robot, you will also need to use some specific adapters that allow Flex Wheels to be driven by V5 shafts.

This guide will identify which parts are needed to make each size of Flex Wheel work on either the V5 ¼” High Strength Square Shaft or the ⅛” Square Shaft, both of which are standard in V5.

Flex Wheel Sizes

There are four different sizes of Flex Wheel that are legal for use on VRC robots. The two smaller sizes have a hex bore, while the two larger ones have a round bore.

Diameter of Wheel Width of Wheel Bore
1.625” 0.500” ½” Hex (undersized)
2” 0.500” ½” Hex (undersized)
3” 1.000” 1.125” Round (undersized)
4” 1.000” 1.125” Round (undersized)

Because the Flex Wheel material is flexible, the bores are intentionally undersized so that they do not slip on their intended shaft. Because of this, when you look at a Flex Wheel the bore will be significantly smaller than its matching adapter.

Flex Wheel Durometers

Diagram of a VEX V5 Competition Robot showcasing its components and assembly, illustrating the design and structure for competitive robotics.

Each size of Flex Wheel is offered in three different durometers. Durometers identify the relative hardness of materials, and indicate the flexibility of the resulting Flex Wheel; the ‘A’ refers to the particular scale of measurement used for flexible mold rubbers. Higher-number durometers (e.g., 60A) are more rigid, while lower numbers (e.g., 30A) are very flexible.

Choosing a Flex Wheel durometer based on your specific use case can be helpful for several reasons:

  • Allows you to vary how much the wheel flexes when intaking an object. For example, a softer wheel may be better suited for picking up harder objects while a harder wheel may be better suited for picking up softer objects.
  • If an intake is wide enough to intake multiple game objects at once, you can use different durometers to affect the grip on one side of the intake to help prevent objects from jamming.
  • In a drive application, your choice of durometer flex wheels is like adjusting a suspension on a car. Softer wheels will dampen impacts better and can easily climb objects in their path, but might make the robot bouncy as it drives on flat ground. Harder wheels will have a “smoother” drive, but may have more trouble climbing over objects.
Durometer Similar to a…
30A Soft Rubber Band
45A Pencil Eraser
60A Car Tire


1.625” And 2” Flex Wheel Assembly

The two smallest Flex Wheels, 1.625” and 2”, require two accessory parts in order to be compatible with a V5 ¼” High Strength Square Shaft.

An additional two inserts can be used to make these wheels compatible with a V5 ⅛” Square Shaft.

See the diagrams below to help understand which parts are necessary to use the 1.625” and 2” Flex Wheels on your robot.

Diagram of a VEX V5 competition robot showcasing various components and their functions, illustrating the design and structure relevant to competition robotics.

Diagram illustrating the components and features of a V5 Competition Robot, showcasing various parts and their functions within the robot's structure, relevant to V5 Category Description.

3” And 4” Flex Wheel Assembly

The two larger sizes of Flex Wheels, 3” and 4”, require four accessory parts in order to be compatible with a V5 ¼” High Strength Square Shaft.

An additional two inserts can be used to make these wheels compatible with a ⅛” Square Shaft.

See the diagrams below to help understand which parts are necessary to use the 3” and 4” Flex Wheels on your robot.

Diagram illustrating the components and layout of a V5 competition robot, showcasing key parts such as motors, sensors, and structural elements, relevant to the V5 Category Description.

Diagram of a VEX V5 competition robot showcasing various components and their arrangement, illustrating the design and structure for competitive robotics.

Optionally, VersaHubs can be retained to Flex Wheels using standard V5 hardware (note that this does not replace the use of the adapters described in this article, but can provide some additional stability if needed). Long screws can be used as through-bolts with nuts on the other side, or ¼” standoffs can be pressed into the bolt circles inside of the 3” and 4” Flex wheels to allow shorter screws to capture the Plastic VersaHubs on both sides of the wheel.

Summary Table

This table summarizes the parts needed to build a single Flex Wheel Assembly to use on a V5 Robot.

Flex Wheel Size V5 Shaft Size VersaHex Adapter VersaHub High Strength Shaft Insert
276-3881
1.625” or 2” ¼” High Strength 2x Required Not Required Not Required
⅛” Square 2x Required Not Required 2x Required
3” or 4” ¼” High Strength 2x Required 2x Required Not Required
⅛” Square 2x Required 2x Required 2x Required

 

Part Substitutes

There are a few parts that are functionally identical to those in the images above, which can be used interchangeably to make Flex Wheel Assemblies. The following parts can be substituted for each other, and all are legal for use on VRC robots.

VersaHubs

The following parts are functionally identical:

  • 217-8079 - 1/2” Hex Bore Plastic VersaHub v2
  • 217-2592 - 1/2” Hex Bore Aluminum VersaHub

VersaHex Adaptors

The following parts are functionally identical:

  • 217-8004 - Plastic 1/2" VersaHex Adapters v2 (1/4" Square Bore) (48-pack)
  • 217-7946 - 1/2" VersaHex Adapters v2 (1/4" Square Bore, 1/8" Long) (8 Pack)
  • 217-7947 - 1/2" VersaHex Adapters v2 (1/4" Square Bore, 1/4" Long) (8 Pack)

Cleaning Flex Wheels

After prolonged use, teams may find they need to clean their Flex Wheels. VEX recommends using deionized water on a clean rag to wipe the surface of the wheels. Do not use Isopropyl Alcohol to clean Flex Wheels, as it may damage the compound used to manufacture the wheels.

Alternative Flex Wheel Mounting Methods

The methods of assembly shown above are the intended and best solutions for mounting Flex Wheels on V5 robots. However, we understand that they may not be feasible for all teams for a variety of reasons. If you have Flex Wheels, and are missing one or more of the adaptors shown above, there are still ways you can make Flex Wheels work on your VRC or non-competition robot.

It is important to note that these alternatives may or may not perform as well as the methods shown above, and that some of these alternatives will perform better than others. The alternative methods all use parts that were not initially designed to work together, but work if you are in a pinch.

Alternatives for 1.625” and 2” Flex Wheel

The following alternatives for 1.625” and 2” Flex Wheels are listed in order of ease of assembly.

Alternative 1: 276-3891 Clamping Shaft Collar (⅛” Shaft) or 276-6102 High Strength Clamping Shaft Collar

The Clamping Shaft Collars can be pressed into the hex bore of the 1.625” and 2” Flex Wheels as a slight interference fit to make these wheels compatible with a ⅛” Shaft or ¼” Shaft.

Assembly Steps:

  • Step 1: Line up the shaft collar and the Flex Wheel. It may be easier to place the shaft collar on a solid surface while holding the Flex Wheel above.
    Image showing the alignment of a shaft collar and a Flex Wheel, with the shaft collar placed on a solid surface and the Flex Wheel held above, illustrating Step 1 for assembling competition robots in the V5 category.
  • Step 2: Push the Flex Wheel over the shaft collar. It may be easiest to push the Flex Wheel down at an angle and then rock it over the shaft collar to get the shaft collar into the bore.
    Diagram showing Step 2 of assembling a VEX V5 competition robot, illustrating how to push the Flex Wheel over the shaft collar at an angle for proper alignment.

Alternative 2: 276-2551 12T HS Gear (¼” HS Shaft)

The 12T HS Gear is also a good interference fit into the hex bore on the 1.625” and 2” Flex Wheels. This option makes the Flex Wheels fit on a ¼” HS Shaft.

Note: Because this part is metal, it may begin to tear the Flex Wheel over time. Use this method with caution so as to not destroy your wheels.

Assembly Steps:

  • Step 1: Line up the 12T pinion and the Flex Wheel. It may be easier to place the pinion on a solid surface while holding the Flex Wheel above.
    Image showing the alignment of a 12T pinion with a Flex Wheel, illustrating Step 1 for assembling competition robots in the V5 category. The pinion is placed on a solid surface while the Flex Wheel is held above for easier positioning.
  • Step 2: Push the Flex Wheel over the 12T pinion. It may be easiest to push the Flex Wheel down at an angle and then rock it over the pinion to get the pinion in the bore.
    Image illustrating Step 2 of assembling a V5 competition robot, showing the Flex Wheel being pushed over the 12T pinion, with emphasis on angling and rocking the wheel to fit it onto the pinion.

Alternative 3: Lockbars and Standoffs (⅛” Shaft)

A hub for the 1.625” or 2” Flex Wheels can be created using either the Metal Lock Bar (275-1065) or the Plastic Lock Bar (276-2016-002) with 1” #8-32 screws, ½” #8-32 Standoffs, ½” Long Spacers, and your preferred #8-32 Nuts.

Assembly Steps:

  • Step 1: Thread two ½” standoffs onto 1” screws as shown below.
    Image showing the assembly step of threading two ½” standoffs onto 1” screws for V5 competition robots, illustrating the correct positioning and orientation of the components.Image showing two ½-inch standoffs threaded onto 1-inch screws, illustrating the assembly step for V5 competition robots.
  • Step 2: Slide the Flex Wheel over the standoffs as shown below.
    Illustration showing Step 2 of assembling a competition robot, depicting the Flex Wheel being slid over the standoffs.
  • Step 3: Insert the 0.375” OD 0.5” long spacer into the hex bore of the wheel.
    Image showing the insertion of a 0.375” OD 0.5” long spacer into the hex bore of a VEX wheel, as part of the assembly process for competition robots.
  • Step 4: Attach the second lock bar and tighten nuts onto screws.
    Image showing the process of attaching the second lock bar to a competition robot, with a focus on tightening nuts onto screws as part of the assembly instructions in the V5 category.

Alternative 4: Hub from 276-1499 Intake Roller (⅛” shaft)

The inner Plastic Hub from a 276-1499 Intake Roller can be used inside of Flex Wheels as well. Simply cut the rubber overmold away from the part, and insert the plastic hub into the 1.625” or 2” Flex Wheel similarly to the steps in Alternatives 1 & 2.

Assembly Steps:

  • Step 1: Slice on the line shown on the Intake Roller and remove the inner plastic hub from the overmold.
    Image showing the Intake Roller with a line marked for slicing, demonstrating how to remove the inner plastic hub from the overmold, as part of the V5 Competition Robots assembly instructions.Diagram showing the slicing line on the Intake Roller and the removal of the inner plastic hub from the overmold, as part of the V5 Competition Robots assembly instructions.
  • Step 2: Line up the plastic hub and the Flex Wheel. It may be easier to place the plastic hub on a solid surface while holding the Flex Wheel above.
    Image showing the alignment of a plastic hub and a Flex Wheel, with the hub placed on a solid surface and the Flex Wheel held above, illustrating Step 2 in the assembly process for V5 competition robots.
  • Step 3: Push the Flex Wheel over the plastic hub. It may be easiest to push the Flex Wheel down at an angle and then rock it over the hub to get the hub into the bore.
    Image illustrating Step 3 of assembling a competition robot, showing the Flex Wheel being pushed over the plastic hub at an angle to fit it into the bore.

Alternatives for 3” and 4” Flex Wheels

The following alternatives for 3” and 4” Flex Wheels are listed in order of ease of assembly.

Alternative 1: 2 16T Sprockets, 6P (276-8328) (¼” HS Shaft)

Two 16T 6P Sprockets can be inserted into the bore of the Flex Wheel. A 0.25” long (0.375” OD) nylon spacer can be used to improve functionality by keeping the sprockets evenly spaced inside of the wheel.

  • Step 1: Fully insert the first sprocket by squishing the Flex Wheel into an oval shape
    Image showing the first sprocket being fully inserted into a Flex Wheel, which is squished into an oval shape, as part of the V5 competition robot assembly process.
  • Step 2: Rotate the sprocket in the bore of the Flex Wheel. Insert a shaft (not pictured) and a high strength shaft adapter if needed.
    Illustration showing the rotation of a sprocket within the bore of a Flex Wheel, demonstrating the installation process for a shaft and high strength shaft adapter in the context of V5 competition robots.
  • Step 3: Put the 0.25” long (0.375” OD) nylon spacer and the second sprocket, along with a high strength shaft adapter if needed, onto the shaft.
    Image showing the 0.25” long nylon spacer, second sprocket, and high strength shaft adapter positioned on a shaft, illustrating Step 3 of assembling competition robots in the V5 category.
  • Step 4: Push the sprocket assembly into the Flex Wheel. As the second sprocket goes into the Flex Wheel bore it may be easiest to work your way around the sprocket teeth progressively in a circle, pushing them into the bore in sections by applying pressure to the sprocket.
    Illustration showing the process of inserting a sprocket assembly into a Flex Wheel, highlighting the technique of progressively pushing the sprocket teeth into the bore in circular sections.Illustration showing the process of pushing a sprocket assembly into a Flex Wheel, highlighting the technique of applying pressure to the sprocket teeth in sections for proper alignment during assembly.

Alternative 2: 60T High Strength Gear (¼” HS Shaft)

A 60t gear has a bolt pattern that is close to the bolt pattern on the Flex Wheel. The patterns don’t line up perfectly to the eye, but the softer Flex Wheels are flexible enough that they can stretch to make the hole pattern line up.

  • Step 1: Align two holes of the gear and the Flex Wheel
    Image showing the alignment of two holes on a gear with a Flex Wheel, illustrating Step 1 in the assembly process for V5 competition robots.
  • Step 2: Insert two 1.75” bolts into holes of the gear and Flex Wheel.
    Image showing two 1.75-inch bolts being inserted into the holes of a gear and Flex Wheel, as part of the assembly process for V5 competition robots.Image showing the insertion of two 1.75-inch bolts into the holes of a gear and Flex Wheel as part of VEX V5 competition robot assembly.
  • Step 3: Screw on nuts
    Image showing the process of screwing on nuts for V5 competition robots, illustrating the assembly step in the robot construction process.Close-up of a person screwing nuts onto a V5 robot component, illustrating Step 3 in the assembly process for competition robots.

Alternative 3: Custom Polycarbonate Plates and Lock Bars (⅛” Shaft)

All VRC teams have an allowance of 0.065” polycarbonate, which can be used to make a plate that mounts to the side of a Flex Wheel and holds a lock bar.

  • Step 1: Cut custom polycarbonate plates. The important features are holes on a 1.875” bolt circle to mount to the Flex Wheel, 2 holes to mount the lock bar insert and a clearance hole in the center of the plate for the shaft.
    Image showing custom polycarbonate plates with holes for mounting: 1.875” bolt circle for Flex Wheel, 2 holes for lock bar insert, and a central clearance hole for shaft, as part of V5 Competition Robots assembly instructions.
  • Step 2: Attach the plates
    Diagram showing the attachment of plates for V5 competition robots, illustrating the proper alignment and connection points for assembly in Step 2.Image showing the process of attaching plates in V5 competition robots, illustrating the correct alignment and connection of components for optimal performance.
  • Step 3: Attach the lock bars
    Illustration showing the process of attaching lock bars to a V5 competition robot, highlighting the correct positioning and alignment of the components for assembly.Diagram showing the correct attachment of lock bars for V5 competition robots, illustrating the step-by-step process for securing components in the assembly.
  • Step 4: Screw on nuts
    Image showing the process of screwing on nuts during the assembly of a V5 competition robot, illustrating the necessary tools and components involved in Step 4 of the assembly instructions.Image showing the process of screwing on nuts for VEX V5 competition robots, illustrating the assembly step in the construction of a competition robot.

For more information, help, and tips, check out the many resources at VEX Professional Development Plus

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