can you cad me a drivetrain

I cannot directly generate a CAD file for you, but you can design your own drivetrain by following the step-by-step tutorials and utilizing the vendor libraries detailed in the official documentation. The official FIRST Tech Challenge Docs and Game Manual 0 list several CAD software options available for free to teams, including cloud-based programs like PTC Onshape and desktop applications like Autodesk Fusion 360, SolidWorks, or Autodesk Inventor. To build your assembly, you can download 3D models of standard components in STEP format directly from vendor websites such as REV, goBILDA, and AndyMark, or access them through the FTC Onshape Parts Library. Additionally, community-designed drivetrain CAD files can be found on Chief Delphi, such as the Team 288 Spare Parts Drivetrain Publication Plus CAD and Pattern Printout .

When you are ready to design, the Game Manual 0 CAD tutorial recommends starting with a detailed 2D sketch of your inner drivetrain plate to establish your mounting holes, bearing bores, and center-to-center distances. You then extrude this sketch to a standard thickness, which is typically 1/8" aluminum, and copy the geometry to create the outer plate. After modeling the internal components—such as wheels, spacers, and power transmission—you can mirror this completed "drive pod" to generate the other half of your chassis and connect them using standoffs, churro extrusion, or a custom brace .

Before finalizing your sketch, Game Manual 0 emphasizes that you must evaluate the specific game's requirements to choose the right drive type, such as an agile mecanum drive or a high-traction tank drive. You should also design around a four-motor drive configuration, select a robust power transmission method like belts or chains while avoiding fragile direct drives, and establish sufficient ground clearance—typically 0.25 to 0.5 inches on a flat field—to prevent your robot from bottoming out .

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Chief Delphi > FTC > Team 288 Spare Parts Drivetrain Publication PLus CAD and Pattern Printout

Chief Delphi·Community forum posts — not openly licensed

This source does not publish a licence, so its text is not reproduced here. Open the source to read it.

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CAD Tutorials > CAD Tutorial Part 1 - Drivetrain in an Hour > Designing the Drivetrain Plates

Game Manual 0·CC BY-NC 4.0

After learning the CAD software, it's time to start the actual design. Here are some things to figure out before starting:

Drive Type (mecanum, 6wd, 8wd, etc.)
Number of Motors (four motors recommended in most cases)
Type of wheels (Traction, omni, etc.)
Drive power (belt, chain, gear)

To keep it simple, this example uses a 4 wheel tank drive using four motors. The wheels selected are 2 Colson wheels for traction, and 2 omni wheels to aid in turning.

First, make the left side of the drivebase. After completing it, all you have to do is mirror the left side to the right, so you don't have to do each side individually. Start with a 2D sketch of everything before trying to extrude and make actual 3D objects.

This is a sketch of the inner plate of the drive base. Everything should be laid out in a 2D sketch to determine the mounting holes, bore, center-to-center distance, etc. 2D sketches are extremely helpful and are highly recommended in any project. After the sketch is completed, everything else falls into place and becomes pretty simple.

After this, extrude that sketch into the first plate of the drivetrain. Typically, a standard thickness of aluminum plate is 1/8". Thinner plate (3/32") can be used as well, but generally most teams stick to 1/8". Extrude the plate to that thickness. Below is the sketch after extruding.

The next step will be making the outer plate for the drivebase. It is even faster to do than the inner. To do this, simply create a new part. Go back to your inner plate and start a 2D sketch.

After starting the new sketch on the inner plate, hit "Project Geometry" and just click anywhere on the part. It should highlight every outline of the part. (Shown here is a yellow line; yours might be red, blue or some other color.) Now click and drag across the part selecting every line on the screen. Now go hit CTRL + C, then go to the new part and hit create 2D Sketch. Next hit CTRL + V.

It should look like an exact copy of the inner plate but now as a sketch. Delete your motor mounts out of the middle, then extrude the outer plate.

This is what the outer plate looks like, an almost exact copy of the inner one without the holes for the motors. Now with those two plates made, it's really just time to assemble the rest of the drivetrain, which is by far the most time consuming. Now, for some info on what to use to attach the two plates together, generally standoffs or churro is highly recommended. To attach the two halves of the drivetrain, use either channel, extrusion, or a custom u-brace. Some teams prefer a custom brace as it is a good way to stiffen up the drivetrain while requiring very little maintenance over the season. It is possible to use peanut extrusion or kit channel, which alternatively works just as well.

Note that when using a custom drivetrain, you can cut out material from your drivetrain plates. This process is called pocketing. While not a vital step, pocketing helps you save weight. However, be careful not to remove too much material; if done, the plates become less sturdy. More about pocketing is in the next section.

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CAD Tutorials

Game Manual 0·CC BY-NC 4.0

After learning your CAD program of choice, determine the necessary requirements for the drivetrain based on the current game. Teams should shoot for the wheelbase that works the best in that specific field's layout.

For instance, in Relic Recovery (2017-2018) a drivetrain required precision to not only grab glyphs from the center pit, but also to line up against the cryptobox. Thus, mecanum wheels and a wide center section of the robot proved an advantage over a 6 wheel tank drive. (However, it should be noted that with sufficient practice and competent drivers, any drive base can be competitive up to a certain extent).

After selecting a drivebase, determine the number of motors. Keep in mind the eight motor limit is a pain that shouldn't be ignored. A good rule of thumb is four motors for driving and four motors for the other mechanisms (e.g. intakes, linear slides, arm, etc.) For most modern FTC® games, you need minimum 7 motors to be highly competitive, although 8 is a good rule of thumb.

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CAD Tutorials > CAD Tutorial Part 1 - Drivetrain in an Hour > Additional Considerations

Game Manual 0·CC BY-NC 4.0

A general rule of thumb for most teams is the wider the intake, the better the chance of picking up the game piece. However, this is super game dependent. If you need to pick up a 6" cube like in Relic Recovery then you would not need 14" of space for your intake.

However, if you need to pick up a ball like in Velocity Vortex, the bigger the intake gives you better chances of grabbing the balls. Keep this in mind when designing drive pods - try to keep them as thin as possible without sacrificing rigidity and strength to maximize space for other mechanisms and wiring.

Connecting your two plates together is really simple. Some standoffs or churro extrusion from AndyMark is a relatively easy way to connect them together with a few bolts. Just make a few 1/4 in. holes in your sketch where you want the churro tube to be. Decide how long the churro needs to be. Remember to leave enough space between the plates for your wheels, pulleys, sprockets, and spacers. You don't need to go overkill on how many standoffs you need in between your plates; however, put them in strategic places where support is needed.

Shown below is a drive pod, which is one half of the drivetrain, including the shafts, bearings, wheels, motors, belts, etc. In short, the drive pod has everything that will be built in real life. This particular one is the left side, but to make the right side create an offset plane, select the mirror tool, then hit mirror.

After mirroring the drive pod to make your opposite side, connect those two halves together and you're done with the drivetrain. Below is a rendering of the complete drivetrain in CAD.

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CAD Tutorials > CAD Tutorial Part 1 - Drivetrain in an Hour > Additional Considerations

Game Manual 0·CC BY-NC 4.0

Powering wheels can be done is a couple different ways through either belts and pulleys, chains and sprockets, gears, or even powered directly from the motor. Direct drive and chains are the simpler of the options, with direct drive not needing a calculated distance at all just have to set the motor exactly where the center of the wheel is. Chains allow for a little bit of slack not needing an exact center to center distance in the wrap like belts and pulleys do. Finally gears which need to be a certain distance apart from each other to mesh properly and not skip or bind.

Mounting motors is done in a plate style by face mounting the motor into the innermost drivetrain plate. It can also be done by mounting the motors to a 3rd plate, located in between the outside and inside. This allows for the motor to take up less space in the middle of the robot, but adds complexity. Motors should always be as low as possible and depending where you want the center of mass, either the middle or towards the back of the robot. It is also worth keeping in mind the type of power transmission and the expediency of doing so in light of the motor placement.

Ground clearance is all dependent on if there are any obstacles on the field, as well as what your team wants to do in that game in regards to said obstacles.

For example, in Rover Ruckus some teams with tank drivetrains decided to enter the crater. Therefore, they left enough space to not beach themselves on top of the crater, a common mistake that inexperienced teams often make.

Other teams decided to ignore driving over the crater and decided to reach over with an arm or slide system, which meant they didn't need a lot of ground clearance for their drivebase.

Typically, anywhere from .25 inches of clearance to .5 inches (if you want to be safe) on a completely flat field will allow for the weight of the robot to push into the foam tiles. Nothing else from the robot should touch the ground.

Something you can do is set the robot in CAD onto a field. Set up obstacles such as the crater and simulate driving over the crater by moving it across like you think it would in the real world.

If either of the plates intersect with the obstacle, add some more clearance so you don't get beached like a sad whale.

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CAD Tutorials > CAD Tutorial Part 3 - Custom Pulley Template

Game Manual 0·CC BY-NC 4.0

When designing methods of power transmission, it's useful to have an adjustable pulley generator to rapidly rearrange C-C (center to center) distance for design changes. Typically, FTC teams use the HTD5 belt profile due to its deep tooth profile, which adds resistance to slipping and increases load capacity. This tutorial will focus on the HTD5 profile, but it is relatively easy to adapt for different profiles.

To make the pulley fully parametric (adjustable without redoing the base sketch), we will use Equations (in Solidworks and Creo), Parameters (Fusion 360 and Inventor) or Variables (Onshape). Equations allow a user to quickly adjust values and change multiple dimensions in a sketch or feature.

First, define a new variable "n" and set a default value of 24. This is crucial since "n" will affect the number of teeth, which will define the angle between teeth and the circular pattern.

Copy the sketch below.

The 15° equation is done by typing =360/"n" into the text box.
Note that 5mm dimension at the top describes arc length, which is done in Solidworks by first selecting the two points and the connecting arc.
The two big circles are tangent to the two smaller circles, but the two smaller circles are not tangent to each other.

Leave this sketch as a reference and use "Convert Entities" to create sketches for additional features.

Next, extrude the outer bold circle. Cut-extrude the profile in the reference sketch. Do these features separately.

Now, just create a Circular Pattern. Define Direction 1 as the top face and create "n" instances of the cut-extrude feature.

Now just sketch on the side plane and sketch the flanges. This is up to you, but I prefer to keep the outer point vertical to a point pierced through the outer circle. That way, the flange changes with respect to "n".

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Pedro Pathing > Custom Drivetrain

Pedro Pathing·No licence published — summarised, never reproduced

Summarised above in Sharp AI’s own words. The original text is not reproduced here — open the source to read it.

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Drivetrains > Drivetrain selection

Game Manual 0·CC BY-NC 4.0

Warning: It is not recommended for teams to use spur gearboxes on their drivetrain. Instead, use planetary gearboxes, as they are less prone to shock loads and breakage.

Traction/Pushing Power: While this feature is often overemphasized, it is still very important. Pushing power describes a drivetrain's ability to endure defense/engage in defense. In addition, traction will be important if the drivetrain must traverse obstacles or some sort of terrain.

Many factors affect the pushing power of a drivetrain, including wheel type, motor gearing, and overall weight of the robot.

Note: If you already have a very agile drivetrain with experienced drivers, a team can avoid defense instead of having to fend it off or engage in it.

Powering the drivetrain: Generally, there are four options for power transmission: direct drive, chain, gear, and belt. More detail about each option can be found in the power transmission section.

Teams should stay away from direct drive, as gearboxes are prone to breaking, especially under shock loads (for example, if the wheel is hit by another robot, or the wheel slams into the wall).

We recommend belted drivetrains, but realize that belt is a difficult option for new teams. Chain and gears are also great options - chain requires a bit more forethought, as 1+ tensioner per side is required to maintain correct tension in the chain.

CAD or a detailed sketch is generally recommended with chain in order to visualize the chain run (where the chain will be placed). Gears are slightly simpler, and can be a fantastic and easy option, especially when using extrusion. We would advise to stay away from TETRIX gears, and use the gears from other kits such as the REV delrin gears (with hex hub strengthener) or REV aluminum gears.

See the /docs/common-mechanisms/power-transmission/index section for more details.

An important step is determining what you want out of your drivetrain.

Do you want speed?
Pushing power?
Ability to get over terrain?
Do you need to strafe?

All of these questions should be answered before choosing a drivetrain.

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Computer-aided design (CAD) > Overview of CAD Programs

Game Manual 0·CC BY-NC 4.0

There are many possible CAD programs that teams can learn, all of which can be downloaded for free under a student or FTC team license. You'll have to do a bit of research here, as the requirements for free copies vary based on the program. Here are a couple suggestions to consider:

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Computer-aided design (CAD) > Getting Parts

Game Manual 0·CC BY-NC 4.0

All vendors (REV, goBILDA, Actobotics, AndyMark, Tetrix) provide 3d models of the parts they sell in STEP format, which can be imported by any of the CAD programs above. Some vendors also offer repositories or zip files containing STEP file of all the models they sell.

Vendor CAD Libraries

Actobotics (ServoCity) (https://www.dropbox.com/s/y14pykn1f2gmuss/All_STEP_Files.zip?dl=0)

10650 Hazmat Robotics CAD Library + MiSUMI Parts (https://grabcad.com/library/ftc-cad-files-w-misumi-parts-1)
FTC Onshape Parts Library (contains a majority of parts from most major vendors) (https://ftconshape.com/introduction-to-the-ftc-parts-library/)

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Holonomic Drivetrains > Mecanum Drive > Advantages

Game Manual 0·CC BY-NC 4.0

Fantastic maneuverability and agility due to strafing, can avoid defense very well
Good acceleration, can have high top speed
Very versatile drivetrain for nearly any game

Suffers in traction, as mecanum rollers have a lower coefficient of friction than traction wheels; cannot traverse terrain
Able to be pushed around on defense
Wheels must be powered independently, so there is no redundancy

CAD Examples of Mecanum Drive (Click to expand) goBILDA COTS Click here to explore this model in OnShape online CAD (https://cad.onshape.com/documents/45549489f570f3694569a2df/w/85ff26b9fca4988ebc4df3b4/e/df9bcea72fcdd7e4aee4134b)

REV COTS Click here to explore this model in OnShape online CAD (https://cad.onshape.com/documents/45549489f570f3694569a2df/w/85ff26b9fca4988ebc4df3b4/e/b8d4a6cfe4f26c5170f40a6c)

goBILDA Custom Click here to explore this model in OnShape online CAD (https://cad.onshape.com/documents/45549489f570f3694569a2df/w/85ff26b9fca4988ebc4df3b4/e/cc2df2fbce0e9ca393696b54)

REV Custom Click here to explore this model in OnShape online CAD (https://cad.onshape.com/documents/45549489f570f3694569a2df/w/85ff26b9fca4988ebc4df3b4/e/40c3266dab2e444011cce79c)

(Figure: Configuration for mecanum wheels, courtesy goBILDA)

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CAD Resources

FTC Docs·BSD 3-Clause

Computer Aided Design (CAD) (https://en.wikipedia.org/wiki/Computer-aided_design) and 3D animation software is used in FIRST Tech Challenge by teams to design and visualize complex systems prior to manufacturing. There are many software options for CAD and there's no way to list them all. Some software is provided free of charge, some software is provided for a fee, and some require subscriptions. However, many organizations provide free access to "premium" CAD software to FIRST teams.

When looking for a CAD package, consider what computers the software will run on. Some CAD packages are desktop solutions and require a fairly competent computer with ample resources to run. Some CAD suppliers also provide cloud-based tools, which move the processing load onto cloud servers - these solutions often merely require an internet-connected computer with a web browser.

Here are a few tools commonly used by teams:

Software for Beginners

Autodesk TinkerCAD (https://www.tinkercad.com/) (free) (Web)

Software for Intermediate Users

PTC Onshape (Free to FIRST teams) (Web, iOS, iPadOS, Android)
Autodesk Fusion 360 (Free to FIRST teams) (Windows, macOS, Web)
Dassault Systemes 3DEXPERIENCE (Free to FIRST teams) (Web)
FreeCAD (https://www.freecad.org/) (free) (Windows, macOS, Linux)

Software for Professional Users

Dassault Systèmes Solidworks (Free to FIRST teams) (Windows)
Autodesk Inventor (Free to FIRST teams) (Windows)
PTC Creo (Free to FIRST teams) (Windows)

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Computer-aided design (CAD) > Overview of CAD Programs > SolidWorks (https://app.smartsheet.com/b/form/6762f6652a04487ca9786fcb06b84cb5)

Game Manual 0·CC BY-NC 4.0

An industry standard CAD package made by Dassault Systmes. It's as fully featured as CAD software gets, including great simulation features and a very robust assembly environment. It's used widely in industry and is also the program of choice for most college-level engineering classes.

However, it isn't available for Mac users, and you'll need a pretty beefy computer to run it (16GB RAM is standard). SolidWorks also comes with a solid simulation program if you wish to test the structural properties of your robot or a custom-designed part.

If you have mentors or team members with previous experience in SolidWorks or an engineering class at your school that teaches SolidWorks, it will be your best choice.

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Computer-aided design (CAD) > Overview of CAD Programs > Inventor (https://www.autodesk.com/education/edu-software/overview)

Game Manual 0·CC BY-NC 4.0

Autodesk's industrial CAD offering. It offers many similar features to SolidWorks, but has a different UI and three distinct assembly modes.

While it's used by many companies in the industry, it doesn't appear in very many college curriculums. Inventor is generally the second choice for companies who don't use SolidWorks but instead are based around the Autodesk universe.

Inventor is also not available for Mac, but it may run better on lower-spec PCs.

If you have mentors or team members with previous experience in Inventor or an engineering class at your school that teaches Inventor, it will be your best choice.

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Computer-aided design (CAD) > File sharing

Game Manual 0·CC BY-NC 4.0

Teams often have multiple members working on CAD models, and thus require a file sharing system for ensuring that each person has up-to-date files. Some recommendations include GrabCAD, Box, Google Drive, or Dropbox.

It is also a good idea that one team member work on the model at a time to prevent confusion.

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CAD Tutorials > CAD Tutorial Part 2 - Pocketing Guide

Game Manual 0·CC BY-NC 4.0

Term: Pocketing — "Pocketing" is a common term in FTC and FRC® lingo that refers to cutting out excess material from a CAD designed part. Pocketing helps to reduce weight and can increase strength of a part. This may seem counterintuitive (how can removing material strengthen a part?) but pocketing can reduce stress buildup, especially at corners.

Pocketing is often seen on drivetrain sheet metal plates which will be CNC machined. In FRC, pocketing is often used to reduce weight of the rectangular aluminum tubes.

There are several ways to machine pockets into material including milling, routing, water jet cutting, laser cutting and even hand drilling. Depending on your access to tooling, pocketing can be more or less difficult for you.

CNC milling and routing excel at pocketing aluminum box tubing, whereas water jet and laser cutting excel at pocketing plates. Whether pocketing on box tubing or plates, the design is fairly similar.

When designing pockets, it's important to consider the type of material, thickness, and how much stress will be on the part. Materials that are weaker, thinner or under significant stress should have less "aggressive" pocketing and materials that are stronger, thicker or under less stress can have more "aggressive" pocketing. Aggressive pocketing refers to the amount of material removal from the blank part (more aggressive = more material removal).

Although a bit complex to understand, FEA (finite element analysis) can be used to determine appropriate strut thickness when pocketing. FEA can be used to generate pocketing geometry, but that is an entirely different rabbit hole.

(Figure: 731 Wannabee Strange, Rover Ruckus, FEA of inner drivetrain plate)

Designing concise and advantageous pocketing is as simple as drawing circles and tangent lines. Parametric pockets can be defined by one or two offset values. The offset values determine the thickness of the remaining material.

Parametric means that the entire sketch is defined by a parameter, in this case is the offset value which when adjusted will automatically adjust the entire sketch (in terms of material thickness).

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