Supershifters and Mechanum wheels

[bs7280]

Sorry about the "H" I though that I had fixed all of them.

What was wrong with the mecanum super shifter combo? or what was wrong with just the mecanum wheels?

if one were to make a swerve drive, what ratio would be best for the speed/power combo (as I saw a lot of options on andymark)? I feel like part of our shoving problems came from our omni wheels (so that takes care of its self). I am tempted to try and make one as a summer project.

could you please go into team 254's drive-train, or at least just something to use as a search query.

thanks so much! -3734

[Anupam Goli]

Originally Posted by bs7280

Sorry about the "H" I though that I had fixed all of them.

What was wrong with the mecanum super shifter combo? or what was wrong with just the mecanum wheels?

if one were to make a swerve drive, what ratio would be best for the speed/power combo (as I saw a lot of options on andymark)? I feel like part of our shoving problems came from our omni wheels (so that takes care of its self). I am tempted to try and make one as a summer project.

could you please go into team 254's drive-train, or at least just something to use as a search query.

thanks so much! -3734

I personally have something against mecanum wheels (insert dead horse to be beaten), but what I'm really trying to get at is to start simple and learn from your mistakes. It's easy to jump around ideas and only implement them halfway, but you learn more about engineering and gain more experience when you iterate your design to the best possible iteration. Do the changes I mentioned with your kit drive before exploring swerve and mecanum. If a team can't master the kit base and the standard 6 wheel drive base, they certainly don't have the resources or time to master an omnidirectional mecanum or swerve drive. If you want to learn more, A simple search in the whitepapers for a drivetrain design can help.

[Ether]

Well we got rid of the "h". Now if only we could get rid of that extra "c" :-)

[bs7280]

I will admit that our loaded could have been much better for sure. it was about as wide as a frisbee, not very helpful. We made some changes at competition that allowed us to have a "flapper" that would allow us more surface area to collect frisbees, but anyways, lesson learned there (practice more).

We could try making those changes (as well as checking which need to be fixed) once we meet again. I definatly will push for the gearbox change. If it helps, it could turn its self way better than any human could (on carpet) without us lifting it up.

I like that philosophy. Next year we are going to drive and make some competition pieces so we can get a better idea of what problems we are having.

EDIT:
Almost forgot to mention. Our center of gravity is centered very well (climber is in the middle) and the main problem from driving is that the front and back wheels of the tank drive where having a lot of lateral resistance on the carpet. enough so that no person could push it. So when it tried to turn, that was what it was fighting.

[Anupam Goli]

Could you possible provide some pictures of the drivetrain? Ideally, there should be a lot of resistance in the direction perpendicular to the forward-backward motion. The key to being able to turn a long robot is to have that drop in the center wheels. This way, the robot is on the front 2 and mid 2 or the back 2 and mid 2 wheels, never on all 6. This reduces the length of the drivebase effectively in half, requiring less torque for the robot to turn in place.

Also, make sure you look at all of the other issues before putting in a new transmission in the drivetrain.

[bs7280]

Originally Posted by Wing

Could you possible provide some pictures of the drivetrain? Ideally, there should be a lot of resistance in the direction perpendicular to the forward-backward motion. The key to being able to turn a long robot is to have that drop in the center wheels. This way, the robot is on the front 2 and mid 2 or the back 2 and mid 2 wheels, never on all 6. This reduces the length of the drivebase effectively in half, requiring less torque for the robot to turn in place.

Also, make sure you look at all of the other issues before putting in a new transmission in the drivetrain.

Thank you for the advice! I am pretty sure that you are right, in that our center wheel is not lowered. we are meeting tonight and I will be sure to check it out and grab some pictures.

Also keep in mind that we are only going to make minor changes to our competition bot if any (no major drive train changes) like flipping the frame. In the off-season we intended to experiment with frames (among other things) that are not intended to compete. We have good programmers, tools (mills,cnc,lathe) etc... that if we were optimistic we might attempt to build one of the complex drive trains as a prototype.

[FrankJ]

Ether: A big reason that I am an engineer is that mom knew I would fail miserably as an English major & starve.

For all of you that plan to major in engineering for the same reason.... Being able to communicate is really really important.

[jbsmithtx]

I think several people her have fallacies with mecanum. Our team decided week one to use them this year, and we did spend a little too much time perfecting it, but in the end it turned out for the better. We were a feeder station/shooter and we found the mecanum great for lining up. This was the problem we had last year. Even with all the summer practice I got with last years bot (hours upon hours) it still was not all that great. So our team debated week one and saw the omindirectional system as very advantageous, versus the challenge last year. Our original intent was to dive under the pyramids and such, but we never got to end up doing that because of the slight variations in pyramids. However, during competition when our shooter failed, we were plenty good at defense. (Youtube video. Not sure how much defense is shown.. http://www.youtube.com/watch?v=3M_YGV9kKP8). We actually pushed several teams with the kitbot around. We did find it easier to drive aroudn them though. We discovered (all too late), that speed would have definitely helped. I think a lot of teams underestimate speed. When are robot can drive around you, or simply quickly out maneuver you with a mecanum, it really makes a lot of things easier. Our teams has nothing bad to say about our mecanum, just make sure that you use a gyro to help with all the subtle problems. We used 6" AM mecs with TB minis

Also forgot to include that when we decided to add a climber, rather than messing with other systems, we were able to mount our climbers on the side and strafe onto the bar