pic: 2605 Mecanum Drive
 

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Do you have something keeping the belts tensioned apart from the screws to tighten the cim down. If it doesn't I think it will gradually get loose and the belts might fall off. What I'm thinking of is something like the WCP cam tensioner.

Re: pic: 2605 Mecanum Drive
 

Really love the simplicity of this, and it's a perfect use for your encoder mounts.

What's the overall reduction, and what size wheels are those?

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We've done chain drivetrains like this and found that they slip unless you use something like star washers on the bolts. This was sixteenth inch sheet metal though, these tubes might work better.

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+1 on the slippage issue. That was our primary problem last year. Add a WCP cam or something to keep it tensioned or it will slip.

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I believe the reduction is 9:1, and those are 6 inch AndyMark Wheels (not HD). We'll be cutting a smaller reduction soon, because these gears actually pinch the belts on the ground and cause problems.

Thanks for the input! We'll look into adding a cam next to each motor.

Re: pic: 2605 Mecanum Drive
 

At 9:1 with 6" wheels the bot free speed is already on the high side for this year's game, no?

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We had the exact same gearing and wheel size last year, and it was only a moderate speed on the field.

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Am I the only one a little worried about the side load you're putting on those CIMs? Direct belt drive off a CIM just doesn't seem like a great idea, even if they're super robust

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9:1 on a 6 inch wheel is 15.4 fps free speed. Twins Inc indicated they're going to gear it even faster. Some would say that's a bit too fast for this year's game. How fast do you plan to gear your bot this year?

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We usually gear for around a 15 to 17 fps free speed but then we use code to tone it down a bit so that when you push the joystick forward you only get 50 to 70% of the full speed. We have a turbo button on the joystick that the driver has to push for full speed. Works well.

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With mecanums it's not a bad idea to gear a bit on the fast side anyways. Even though your wheels are spinning at a particular speed, doesn't mean your robot will move at the same speed - especially if your mecanum rollers don't have a lot of friction, which is ideal for moving sideways.

It's one of the strangest things to see a mecanum drivetrain drive, and watch the wheels spin faster than the robot is travelling... :mad:

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Physics Quiz:

Imagine you have 2 robots which are identical in every way, except that Robot A is geared for 8 fps, and Robot B is geared for 16fps but has the voltage limited to 50%.

Describe the performance differences between the 2 robots: acceleration, motor heating, battery drainage, pushing force, fine control of slow maneuvers, etc.

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Do you have a video you could post.

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I imagine that the bot with the higher gear ratio, bot A, (or lower fps) would have more control and less acceleration than B. But also more heating, and power consumption because of more motor use/rpm. Or am I mixing things?