pic: Prototype Drivetrain

[Akash Rastogi]

Pull the wheels out to the edges. Even if you didn't realize the physics behind this, just think "if it was an advantage to pull the wheels closer together, more teams would be doing it by now." Common sense goes a long way. Also I hope you plan to drive those Omni wheels.

Other than that I can't say much since I'm not one to judge about lightening patterns and structural integrity of sheetmetal parts just yet.

[LLogan]

I would advise you to drive the four omnis on the corners. Your tractive force is based off of the sum of the forces of friction on all of your wheels. With the design you have right now, you are essentially "wasting" the normal force on the corner wheels. Whatever weight you will have on those sections of the robot will not contribute to your pushing force, giving you less than what you would generally want.

[548swimmer]

Originally Posted by LLogan

I would advise you to drive the four omnis on the corners. Your tractive force is based off of the sum of the forces of friction on all of your wheels. With the design you have right now, you are essentially "wasting" the normal force on the corner wheels. Whatever weight you will have on those sections of the robot will not contribute to your pushing force, giving you less than what you would generally want.

Though the force is "wasted" the majority of the weight will be placed on the drive wheels due to where the CG is. Our current build leader, whom I have discussed this design with, guesstimates that roughly 75% of the weight will be put on the center wheels. Also, I believe that in previous posts I addressed the design goal of maneuverability. The omni's are there as casters, meant to prevent the robot from scratching the floors. There is also the suspension, that will transfer weight during a pushing match onto the center wheel.

[LLogan]

Originally Posted by 548swimmer

Though the force is "wasted" the majority of the weight will be placed on the drive wheels due to where the CG is. Our current build leader, whom I have discussed this design with, guesstimates that roughly 75% of the weight will be put on the center wheels. Also, I believe that in previous posts I addressed the design goal of maneuverability. The omni's are there as casters, meant to prevent the robot from scratching the floors. There is also the suspension, that will transfer weight during a pushing match onto the center wheel.

At the cost of 25% of your tractive force, you gain a theoretical slight advantage in turning. This should raise a very large red-flag. I don't think that losing 25% of your pushing force has ever been a good thing. The turn radius for a dropped center 6WD isn't zero, but it can be pretty close. Driving the omni wheels will not cost you much maneuverability at all. The suspension will not magically "transfer" weight to the center. In fact, a suspension is useful when you want to keep all of your wheels on the ground. A suspension makes sense in a mecanum drive, where you want to make sure that the normal force is distributed as evenly as possible, otherwise the perpendicular vectors don't cancel each other out and you cannot drive straight. The springs in your suspension will actually cause a reactive force and increase the normal force on your omnis, which is the exact opposite of what you want to happen.

I apologize if I'm making the assumption that your omni wheels are on an active suspension. But... I would be even more puzzled if you were to use a floating suspension.