Drivetrains Project

[jrp62]

Here are the artifacts from a project the Bumble Bees did a the start of this season. We provided instructions for each team to build a different type of drivetrain, and then tested and compared all of them. This project was really fun, the kids learned a lot, and it opened their minds to different design options. I’m hoping that other mentors can share projects or activities that they have done with their teams.

At the time we had five teams, so there are five different designs. Of course you could run the project with fewer teams. One other type of drivetrain that could be added is a crab drive. If there is interest I will create instructions for it.

The designs are fairly simple and are intended for participants without much experience. However, you should be able to build the clawbot before trying this. Each drivetrain should take about 2 or 4 hours to build, depending on experience. Take your time. Expect to make mistakes and have to do some rework. Don’t get frustrated, rework is part of the process.

Before you start make sure that you have all the needed parts. Some of the designs require more than the Super Kit. The additional parts you may need come in either the Competition Add-On Kit (for chains, tank treads, and omni wheels), the Foundation Add-on Kit (for more plates beams and corner connectors), or separately (additional omni wheels).

The instructions were made using last season’s parts. Consider using the new plastic shafts instead of the metal shafts in the instructions.

Hopefully you will find the instructions useful, but there is no claim that they are professional quality, and certainly not perfect. If you find an error feel free to go ahead and update the source document (they are editable to anyone with the link). Or send me a message and I’ll make the update.

Although it is possible to use the Driver Control program, it won’t be easy with the 4 motor drivetrains. Below is a link to sample Robot C code that will make driving much easier. To use the sample code you will need to have Robot C installed, click on the link to get a trial version.

Editable Design docs: https://drive.google.com/drive/u/0/#…EJwMFo5TnFIeEU
Code: https://drive.google.com/drive/u/0/#…W1Wd1FKUHY3d3c
Robot C Download: http://www.robotc.net/download/vexrobotics/

Once you have the drivetrains built you are ready to run them through a series of tests. The following tests: Tug of War, Drag Race, Catch the Other Robot (round track), Obstacle Course, Mine Field. Ideally each test would show the strengths of a different drivetrain.

Tug of War: Connect two robots together back to back with Vex IQ chain or tank tread. On GO the robots pull in opposite directions. The first robot to pull past a predetermined finish line wins. Set the finish line so that one robot must pull the other about 2 ft or 1/2 meter. Use a bracket ranking system to determine which robot is the best.

Drag Race: Line up all robots behind a starting line facing the same direction. On GO all robots drive forward as fast as they can in a straight line to the finish line. Set the finish line 10 or 15 feet (~4 meters) from the starting line.

Catch the Other Robot: This is a round track race with 2 robots. They start directly opposite to each other on track and go around in the same direction. The robot that can catch the other robot wins. Use a bracket ranking system to determine which robot is best. Results will vary base on driver skill, especially for the slide drive.

Obstacle Course: Setup a course that requires robot to go around, over, under, or move objects to get through. Same course for all robots, so you must make something that can be reset. We used a Vex IQ field with different IQ parts stuck in the holes. Keep track of the best time. Results will vary base on driver skill.

Mine Field: Setup a course that robot must get through without bumping into anything. We used a field for this too and placed blocks so that it progressively harder to maneuver past them. Track how far each robot gets before it touches a block, and how long it takes to get to the end, if they get that far. Results may vary based on driver skill, especially for the slide drive. Note, that robots will a smaller foot print also have an advantage.

Mentoring Notes:

• Have the students compare their drivetrain design with the others. [LIST]
• How are they different? [LIST]
• Mechanically #motors, types of wheels, gear differences, wheel orientation, size, height, center of gravity...

Which designs are good at what?

Which are better at pushing, speed, turning, going over stuff, are easier to control?

Other factors - easy of building, durable, battery consumption, programming difficulty

Create a grid or matrix that compares the drivetrain type with capabilities and limitations [/LIST]

Make sure the teams understand that this is just a project

• Let the students know before they start that the robot drivetrain that they will be building will be taken apart when the project is over. They will be proud of their work, and will want to keep it forever. However, the parts will be needed for other projects, and chances are that some other drivetrain is a better fit for this year’s competition. It is also an important lesson not stop striving to improve, and making changes is part of improving.
• Conversely, they shouldn't be disappointed if their robot does not perform well in some or many of the challenges. They can pick a better design for their own competition robot.

After going through all the challenges with the robot design they were given, encourage your team to think of ways to improve their drivetrain.

Have them write down their thoughts in their engineering notebooks and if time permits let them try the changes. [/LIST]

PowerTurtleDrivetrainBuildInstructions.pdf (1.59 MB)

DragsterDirvetrain.pdf (2.06 MB)

TankDriveBuildInstructions.pdf (1.8 MB)

SlideDriveBuildInstructions.pdf (8.67 MB)

6OmniWheelBuildInstructions.pdf (9.46 MB)

[jrp62]

Here are some pictures of the challenges.

[pengthom]

This is great! Thank you so much for sharing. I hope that one day I can share some similar projects with the community!

[Gameoa]

Please do not revive old threads. This happened 4 years ago

[jrp62]

This was a fun project and is still applicable today. What has changed? Most of the kids in those pictures are now in high school. Other than that, not much. This was before colored parts were available, as well as Modkit, but it wouldn’t be hard to adapt the content for 2019, or from VexIQ to EDR or Lego. The forum thread is still valid too. It’s not the same as a post where someone is looking for a solution to a Windows Vista download problem, gets their answer and is done.

We did this as a part of an after school program, where time was tight. It is better suited for a class that meets frequently. Also, it is not something that you would want to do every year. The kids that have done it before know what to expect and are not as excited the 2nd time around.

[rhowbot]

crab drive. If there is interest I will create instructions

Please.
And thank you for responding. Instead of a reflexive “don’t revive”, this should be wiki/pinned/faq.

@Gameoa, What is automatically wrong with “reviving”? I have searched, delved into past forum posts for days, did not see this, but so happy it surfaced. Don’t want to start a back-and-forth, I get the complaint when the come-lately comment is pointless, but that is not this.

[jrp62]

The crab drive was quite difficult in VexIQ . This one works: https://www.youtube.com/watch?v=m-zREfLMo2I but would not be practical for a competition robot. It uses 5 motors just for the drivetrain.

Below are some pictures of a later version, using turntables and the differential part that they now sell. It reduced the number of motors to three. This one sort of worked, but it was not promising, and interest waned.

All in all, I would not recommend attempting to build a crab drive as part of a lesson or group project. This is a good “advance study” project for someone who is really into it and can work on their own.

[Lucas_Lira]

@jrp62 !!

Hello

Congratulations on the publication!
Great content, I’m thinking of translating these montage and adding to Fusion 360 could I do that?

[rhowbot]

Cool, thanks! Swerve drive. Been messing with that. Chains.

[jrp62]

@Lucas_Lira You are certainly welcomed to do that. Have at it.

Depending on how you want to use the content that you will be creating, you might want to consider using RobotMesh mimics instead of Fusion 360. Especially if the students will be working in the CAD environment, like using Fusion to see the design and make changes to it.

Good luck and please post your finished results.

[jrp62]

Here are some updates to the build instructions. In color no less. As I recall there were some issues with the parts listed in the original instructions.

What’s interesting to me is that when I originally posted this article, there was no response whatsoever. Nothing. I remember thinking, “OK that was a waste of time”. The forum has changed since then. Back then there were no like buttons and no statistics on how many people looked at something. So if no one replied you could only assume there was no interest. With the new forum I can see that this was viewed over 3,000 times! And there were no responses until today.

L2 - ChainOmnisDrivetrainBuildInstructions.pdf (9.6 MB)
L2-4SideSlideDrivetrainBuildInstructions.pdf (4.7 MB)
L1-PowerTurtleDrivetrainBuildInstructions.pdf (12.8 MB)
L1 - Clawbot.pdf (9.3 MB)
L2-TankDrivetrainBuildInstructions.pdf (4.0 MB)
L1-Dragster Drivetrain Build Instructions.pdf (6.9 MB)

[Gameoa]

I see now that my immediate response was awfully heavy handed for the light-hearted comment made on this thread, and either I should have made my initial reasoning more clear, or not have posted at all.

In retrospect, I still think it was out-of-place and unneeded to post a comment simply saying thank you to a post from 4 years ago. Such comments would probably be better in a PM especially considering the age.

Is this thread useful, probably, I can not properly gauge the value of it from my complete lack of Vex IQ experience, but it would most likely come in handy if I were participating in Vex IQ.

Should I have posted my initial response, no. While I have a reason for posting, this reason was not adequate enough to warrant a response, especially a heavy handed one.

I hope this clarifies everything

[Lucas_Lira]

Perfect!

Once you have something developed go back here in this same publication to share!

Greetings!

[rhowbot]

I hope this clarifies everything

All good. Forum needs FAQ. Wiki doesn’t cut it. The regular posts move down the timestream as they should, but there is no way to capture the timeless bits. Wiki seems to include off-topic. FAQ needs to be curated, all signal, no noise.

[Lucas_Lira]

Hello ! I’m coming back again in this news topic!

This is the first piece developed in the CAD platform is available for download!

This way you can perform animations and other functions as well!

The Power Turtle Drivetrain - VEX Robotics

See you later!

[jrp62]

Looking good!

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