We are using 4-inch mecanum wheels connected to 200 rpm motors by a 5/3 rear ratio for an output rmp of 333. How will this stand up to other drivetrains? Why does no one else use mecanum wheels?
Although mecanum wheels can go omnidirectional, it is not too good in every cases. For this season and even 2023-2024 season, the game is more likely a defensive game, and you need a tank drive for strong force to push enemy bots. However, each drivetrain require different strategies, so if you wanna use mecanum drivetrain, you should have a good strategy.
VEX Robotics competitive areas tend to have extreme aggression with both loads of offense and defense. The friction from mecanum wheels means that all you need is one 400RPM 3.25” wheel 6 motor tank drivetrain that can ruin your day with aggressive defense.
However, for skills, mecanums shine. You can use mecanum wheels in skills to leverage movements that traditionally cannot be done as easily or as precise as tank drive (i.e. horizontal course correction during a pure pursuit maneuver). Your robot can do a lot more without worry of defense during skills which is why mecanums can give you a massive leg up when it comes to skills.
But yet again it is for sure a tradeoff.
- Mecanum wheels → Can strafe but has added friction. Good for skills, not as good during matches
- Tank drive → Cannot strafe but excessively reduced friction. Works “good enough” for skills, and dominant during matches.
Tank drives are a 90% solution in VEX matches, whereas mecanum wheels are either a 100% (in skills) or a 60% solution in VEX matches.
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Good points above. Another major issue with mecanum is their width. In games with large game objects (like mobile goals), the very wide wheels (especially if gearing for speed) force a larger drivebase than you might desire for weight and maneuverability.
The difference is 2-3" less space between the drivebase sides – it is a lot.
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We are able to put the drivetrain motors inside the wheel cage. Any thoughts on this?
I am noticing a lot of defensive playing, do you think the extra traction will help with that, or be purely negative for mobility?