Build directions for H drive

Hi all. I’m a new coach with Vex and I’ve seen a few robots using the h drive train in order to move left and right as well as front and back. I haven’t been able to find any sort of directions online to help our students figure out how to build something like this at the elementary level. If anyone has something like this to help, I’d appreciate it! Thanks!

good source here

What language are you using to program, RobotC, Modkit, etc…?

We’re starting out with Modkit this year.

Thanks for this link. I have the same question as well. Are there any step by step instructions that can be used by an elementary school level team? The photos at the link are great, but my kids might get frustrated trying to build from those alone.

I understand this is an old thread, but anyway, how do you access that article on robolink? It’s asking me for a password.

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From a build concept perspective, here’s a quick guide. Start with a normal tank drive. I’d make two identical sides by attaching wheels between a set of c-channels, making sure to use pillow blocks (bearing flats) any time the axles pass through metal.

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In order to power the wheels, attach motors on the insides of the c-channel.

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From here, attach both sides of the base with cross bars, leaving enough room in between the bars for your fifth wheel.

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Power the middle wheel similarly to the others

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This is just the concept, so youll encounter a couple issues to work through when building but hopefully it gives you a basic understanding of H drives.

Things to play with:
If you don’t have 5 motors, you can use 3 and chain the tank drive motors together.
The cross bars will not be on the same level as the tank drive channels, so you’ll need to figure out how to mount the middle wheel lower than the cross bars.
Moving the middle wheel and cross bars farther back (instead of in the center) can cause a swivel effect, especially if the front wheels are not Omni wheels.
Just the 2 crossbars won’t be enough to hold your tank drive sides together, so you can add more cross pieces that don’t span the entire robot.

I hope this is helpful.

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If you really want to access the article, there is an archived copy of the text made before the site became paywalled, but without the original pictures it is not very usable: http://web.archive.org/www.robolink.com/lesson-2-drive-systems

However, VEX provides an excellent set of downloadable build instructions for VEX IQ: https://www.vexrobotics.com/vexiq/resources/robot-builds

There is also an overview of various drivetrain types and build tutorials:

https://help.vex.com/article/412-how-to-select-a-vex-iq-drivetrain

https://www.vexrobotics.com/vexiq/education/iq-curriculum/mechanisms/drivetrains

They discuss various drivetrain types and provide build instructions for some, but not for the H-Drive.

@ThirdDegree did a great job outlining H drive build concepts. If you want to see an example of the built VEX IQ H-Drive, this thread provides pictures and some discussion:

The biggest issue with building H-Drive is that you have to balance the load between all wheels to ensure good traction, which is much harder with IQ than with VRC, because of the difference in the field material.

VRC plays on the soft foam tiles, that deform under the weight of the robot and that helps all five wheels to have contact with the field, even with less than perfect drivetrain builds.

That is one of the reasons why the help.vex.com article doesn’t recommend H Drive for beginner teams.

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Thanks a lot for the links, I’m scouring the web for material on drivetrains to present to my rookie team, and I have a feeling they’ll want to build a H-drive, but sounds like it may be a risky proposition.

I also found a ppt with this variant, and there was a recent post on this site where somebody showcased a similar build with very positive results.

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