pic: 1640 Pivot Module

[Brandon Holley]

Originally Posted by Dillon Carey

This is the roughly the same method we used this year, only we still had a delrin ring on the bottom for extreme side loads, since this year involved a lot of force on the wheels when hitting the bump, and instead of 2 bearings we used 1 needle roller bearing on the vertical shaft. This worked extremely well.
Most of the time the delrin disk at the bottom didn't even do anything and under normal playing conditions there was very little turning friction.

Ditto the use of a needle bearing. As long as the thrust load is handled with something like a delrin ring like Dillon mentioned, the needle bearing is an effective quick and dirty solution.

-Brando

[Al Skierkiewicz]

Guys,
The distance from floor to top of module is nearly the same for both our designs. (BTW, we do not use a coaxial drive, opting instead for motors in the module) We have run checks of current draw on the steering motors during a pushing match and found that without the bottom bearing (ours is near the floor) the motor current skyrockets as additional side load is applied to the bearings. It is unavoidable. Obviously, different bearing types produce different frictions, your mileage may vary. Without something to limit the side movement of the module, a strong robot is likely to move the bottom of the drive module at least a 1/4" or more if the wheels are sticky. Something has to give, and with both the steering and drive running in the assembly, something may bind and momentarily fail to perform as desired.
One lost match can screw up your whole day.

[Clem1640]

To Dillon Carey,
We used Labview for the programming. Since each wheel is independently driven and steered, the software development was not trivial. On the other hand, with a choice of crab and snake drive, and two different robot twist modes (around the drive-train centerpoint and around the possessed ball centerpoint), we have a remarkably agile and maneuverable robot. It was worth the effort.

This is basically a fly-by-wire robot.

[Dillon Carey]

Originally Posted by Clem1640

To Dillon Carey,
We used Labview for the programming. Since each wheel is independently driven and steered, the software development was not trivial. On the other hand, with a choice of crab and snake drive, and two different robot twist modes (around the drive-train centerpoint and around the possessed ball centerpoint), we have a remarkably agile and maneuverable robot. It was worth the effort.

This is basically a fly-by-wire robot.

We also programmed our robot in labview. Although since we had them all steered together and the left and right side powered separately we only had 2 different modes. Swerve and 6 wheel.

If you would like any help with code or a copy of our how we programed our bot just send me a personal message.

[Dillon Carey]

Brando,
We used needle thrust bearings to handle the thrust load. the delrin ring went around the bottom of the module, which had an aluminum ring on it. This ring was there only for extreme load situations. Like Al said without bottom support things tend to bind under extreme load.

But I do believe with the correct bearing and support you can nearly remove the lower bearing without much increased turning friction under load. Ex: in a pushing match, if your module is supported enough to have almost no binding until your traction brakes then you should be able to get away without supporting the bottom of the module.