pic: Versadrop Decadrive



After the vexpro product release I decided that I wanted to make a decadrive using the new versadrop modules. The center omni wheels are powered by cims mounted to the frame and with the reduction taking place inside the tubing. Overall Inventor puts the drive train at 32 lbs. This was designed to either use COTS parts or parts that could be easily made on a drill press or manual mill. Some parts still need adjusting but it’s mostly finished. Any feedback would be appreciated. CAD A Fond Farewell to GrabCAD Workbench - GrabCAD Blog

Looks good! Really like the use of COTS parts as opposed to custom parts.

I just have a few questions…

  • What is the speed of the drivetrain?
  • Are you going to add a belly pan to the chassis?
  • Why are you using two CIMs for the strafing module? The reason I’m asking this is because I did make a similar drivetrain in the past, and I ended up using only one CIM for the strafe module.
  • Is there anyway to add a smaller diameter traction wheel? If that happens, then you have two speeds, and one could be used for a pushing match.

Speeds about 14 on omni and 7 on traction
A belly pan will probably be added in later
I have the two cims there so I have the option to have two or use a minicim or just use one. So basically its for flexibility.
The versadrop doesn’t seem to play nice with different size wheels. It achieves different speeds on traction and omnis through another reduction via sprockets.

Oh wow, I must’ve forgotten about the sprocket reductions on the Versadrop at the time I wrote the reply. Well, great job on this drivetrain :smiley:

Just wondering, do the VersaDrop modules allow for connection to a gearbox via chain or belt? I don’t really see the benefits to DecaDrive over Octocanum without having each side of the robot connected to one gearbox.

Looks neat! I hope we see a lot of these types of drivetrains next year… the availability of these parts is a good way to speed up the evolution of drive bases and find optimal configurations.

Vexpro has some examples on their site that show how this can be done. The VersaDrop is really just a frame that you can attach axles/sprockets/gears to, so you can do all kinds of neat things with it.

Here’s one example
and another

If that’s true, why would you not use chains to connect the two sides for better power distribution? I thought that was the main benefit of butterfly drive over octocanum.

The main reason that it doesn’t have a chain or belt linking the two sides right now is the center bars. With chain that’s not so bad to do. But our team has been looking at belts which makes it slightly harder to design and maintain due to needing to remove the center bars if a belt needs to be replaced.
<sidenote> like this the design can be quickly switched to mecanum wheels if we wanted to test various drive options early in the season.

You could make access holes in the center bars for the chain to run through. I think you can also remove one of the center bars and perhaps offset the strafing wheel to make room for a gearbox connected to the modules by chain. However, I would stick with having 4 gearboxes as opposed to 2 gearboxes connected by chain. My reasoning is that it’s more about the speeds you are getting with this drivetrain. In addition, 2 gearboxes connected by chain may require more material.

Right now the center strafe is placed to be roughly under the center a gravity. One of the bars is a piece of c just so that i wasn’t cantilevering the whole strafe mechanism. There is the option to do a lot of different ways to connect the modules to act as one but i will probably still stick with independently driven. I could use gearboxes and run chain and other similar ideas but that adds quite a bit to material weight and cost which all of which i was trying to minimize. In reality if this design is used and how it is used will depend quite a bit on the game.