pic: 2605 Mecanum Drive

[Twins Inc.]

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[JorgeReyes]

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.

[Gregor]

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?

[Bryce Paputa]

Originally Posted by JorgeReyes

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.

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.

[asid61]

+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.

[Twins Inc.]

Originally Posted by Gregor

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

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.

Originally Posted by JorgeReyes

What I'm thinking of is something like the WCP cam tensioner.

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

[Ether]

Originally Posted by Twins Inc.

I believe the reduction is 9:1, and those are 6 inch AndyMark Wheels (not HD). We'll be cutting a smaller reduction soon...

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

[Jay O'Donnell]

Originally Posted by Ether

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

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

[Kevin Sevcik]

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

[Ether]

Originally Posted by Jay O'Donnell

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

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?

[holygrail]

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.

[Mr. Lim]

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...

[Ether]

Originally Posted by holygrail

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.

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.

[Ether]

Originally Posted by Mr. Lim

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

Do you have a video you could post.

[Twins Inc.]

Originally Posted by Ether

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.

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?