pic: Ramp Video

[betsy888]

Looks like your center wheels are 2 individual omni wheels per side, each one slaved to either the fore or aft mecanum wheel. So basically the center wheels are commanded to have the same velocity profile as the front/back wheels. Is this accurate?
btw, awesome design and thanks for sharing your ideas. We're a second year team so still need lots of help!

[Chris is me]

Originally Posted by betsy888

Looks like your center wheels are 2 individual omni wheels per side, each one slaved to either the fore or aft mecanum wheel. So basically the center wheels are commanded to have the same velocity profile as the front/back wheels. Is this accurate?

There's a ball differential so if the front and back wheels are spinning in opposite directions, the omnis don't turn.

[betsy888]

Originally Posted by Chris is me

There's a ball differential so if the front and back wheels are spinning in opposite directions, the omnis don't turn.

Thanks so much for the feedback. Our team has decided against having an articulating 6-wheel approach due to the complexity and the limitations of our team but I must say I'm still curious. How does your ball-differential work? From what I understand of ball differentials, there is one drive gear and 2 driven axles. So I assume your center omni wheels are on the driven axles. But you have 2 driving chains coming from the omni wheels and only one drive gear. Do you have a special type of ball differential? Can you explain a bit more?

Thanks again! Good luck with your design. Congrats on getting the green light in Q&A!!

[joeweber]

Originally Posted by betsy888

How does your ball-differential work? From what I understand of ball differentials, there is one drive gear and 2 driven axles. So I assume your center omni wheels are on the driven axles. But you have 2 driving chains coming from the omni wheels and only one drive gear. Do you have a special type of ball differential? Can you explain a bit more?

The Mechanum wheels are driven, the chains drive sprokets on the ball differential, between the sprockets are steel balls that are inside a round flange with holes for the balls. The flange is attached to the drive shaft with the omni wheels. Pictures are on our wesite http://www.team1322.org/ideas.htm

[betsy888]

[quote=joeweber;902964]The Mechanum wheels are driven, the chains drive sprokets on the ball differential, between the sprockets are steel balls that are inside a round flange with holes for the balls. The flange is attached to the drive shaft with the omni wheels. Pictures are on our wesite http://www.team1322.org/ideas.htm

I think I know the source of my confustion. I assumed the omni wheels could move independent of each other. Now that I see your ball differential drawing and photos it looks like they are attached to the same shaft so must move together. If this is true, why do you have 2 omni wheels at each location, why not just one?
As always, thanks and good luck!

[EricH]

Originally Posted by betsy888

If this is true, why do you have 2 omni wheels at each location, why not just one?

It provides a smoother ride than having one single omni at each point. A number of teams have tried single; I believe most of them switched to double at some point.