https://mega.co.nz/#F!NU4nkSJL!LS-wOHcu1YtxZi5YFgLWiA - MECANUM WHEEL FILES AND ASSEMBLY

Problem : Our robot used regular tank drive which only drove forward and backwards, we knew that we had to change this because of how difficult it had become to accurately maneuver throughout the field.

Solution: In our brain storming back in september we came up with the idea of using mecanum wheels to introduce a side to side motion along with the forward and backward motion which we already had. This would improve our maneuverability all over the field.

Obstacles:

We cant buy regular mecanum wheels for the competition.
We were restrained from using the tetrix mecanum wheels.
We would need to CAD/Design the wheels our selves
We would need to redesign the chassis of our robot.

Step 1: Pros/Cons

Many other teams asked us why we didn't just use the omni wheels provided in our kits, although they offer the same maneuverability we found key benefits in using mecanum wheels.

Mecanum Wheels-
Maneuverable
70% forward push force (key for pushing other robots around/ and not being pushed around)
An individual and unique feature of our robot.

Omni Wheels-
Maneuverable
50% forward push force
easily pushed around
Almost every team has Omni Drive (not a unique feature)

The deciding factor was that we could get more pushing force with our mecanum wheels, we knew that in this game we could not afford to be pushed around, especially with our unique scoring mechanism.

Step 2: Stress Analysis

To determine whether or not nylon 5 powder printing provided by shapeways would be strong enough for our mecanum wheels, we conducted stress tests on our cad model through Inventor (an Autodesk program). We realized that with out our own 3d printer we had one shot to get the print for shapeways right. If we messed up it would be an expensive mistake. Each wheel would cost us upwards of 50 dollars.

Step 3: Initial Prototype

Because our ftc team does not have its own 3d printer we had to rely on an outside sponsor for the use of theres. Before sending our cad models for the wheel bases to shapeways we got a quote for how much our wheel rollers would cost. The cost was our determining factor for why we decided to give this task to one of our sponsors. We decided against printing the wheel bases through our sponsor because of the ridges which are present in the additive manufacturing of ABS plastic.

Step 4: Mounting the Wheels

in order for the mecanum robot to have a sturdy chassis, we created our own inside c-channels to connect the tetrix parts. The metal bar on the outside is to support the axle of the wheels from bending. With the mecanum wheel mounted on black oxide axles, it is to ensure that there is no way for the wheels to be bent out of shape. we used tetrix motos to power thme and geared them with a one to one gear ratio for an even spread of strength and speed.