26-01-2013 22:04

Re: pic: Team 3992 DriveTrain

Looks nice! Any reason why you're using such large mecanum wheels?

26-01-2013 22:10

dcarr

Re: pic: Team 3992 DriveTrain

Are those 8" or larger?

26-01-2013 22:35

ksafin

Re: pic: Team 3992 DriveTrain

They're 8".

We figured we'd go for the 8 inchers to get more distance.

We wanted to couple a decent speed with good maneuverability to be able to go across the field quickly, and evade defenders.

26-01-2013 22:43

Littleboy

Re: pic: Team 3992 DriveTrain

What does it weigh?

26-01-2013 23:04

ksafin

Re: pic: Team 3992 DriveTrain

Roughly 40 lbs with all the controls & motors.

Luckily the sheet metal version of this that we'll have later is much lighter.

27-01-2013 03:35

James Tonthat

Re: pic: Team 3992 DriveTrain

Seems like you're geared pretty aggressively on those gearboxes (4.7:1) on 8" wheels.

Also, aren't the mecanums mounted incorrectly? It's been a while but don't the wheels need to make an 'X' when viewed from the top?

27-01-2013 11:48

Gregor

Re: pic: Team 3992 DriveTrain

From what I can tell, you are using CIMple boxes, the kit sprockets (39 and 42 tooth), and 8" mecanums.

This gears you for a very nifty 30 fps. Consider halving that, on even a third of that. That is far too fast for an FRC bot, and will be near uncontrollable for your drivers.

A quick fix would be to switch to Toughbox minis with a 12.75:1 or a 10.71:1 ratio.

27-01-2013 12:22

omsahmad

Re: pic: Team 3992 DriveTrain

We got the same wheels this year too, and I am anxious to try them out.

Just a heads up, I think you have your wheels on wrong. Supposedly it compromises the performance when they are in this orientation. From the top they should make an "X" pattern.

27-01-2013 17:17

PAR_WIG1350

Re: pic: Team 3992 DriveTrain

It actually makes it impossible to turn in place if they are on wrong. When configured improperly, the individual forces from each wheel are applied along lines nearly intersecting the axis of rotation resulting in little or no torque to turn the robot.

27-01-2013 18:19

ksafin

Re: pic: Team 3992 DriveTrain

We actually did have issues getting the robot to turn and do any Mecanum-like movements yesterday. This was a picture taken after I finished assembling it and putting on controls, but prior to our testing the code.

You all are correct, and the wheels will be fixed accordingly tomorrow.

27-01-2013 18:47

kingbrandon14

Re: pic: Team 3992 DriveTrain

That's got to be one of the heaviest looking drivetrains I've ever seen. But hey, at least it's durable!
Oh, and an easy way to remember which way the mecanum wheels face, is that the diagonal rollers make an invisible X (they point at the ones diagonally from them).