pic: Side view of third try drive.

[Mr_I]

Okay, I'm confused about something (trust me, this isn't an unusual condition): The advantage of mecanum is that you can make the bot go sideways by rotating front and back wheels in different directions. If you chain them together by tying them to the middle wheel, aren't you defeating this potential?

[Joe G.]

I believe the plan is for the ball differential mounted on the center shaft to only allow power transfer when the 2 chains are moving in the same direction (when the robot is moving forward or backwards.) When the chains are moving opposite each other, when it is driving sideways, the ball differential will slip, no power will be transferred to the center wheel, and the chains will be allowed to move independently.

[NickE]

Originally Posted by Mr_I

Okay, I'm confused about something (trust me, this isn't an unusual condition): The advantage of mecanum is that you can make the bot go sideways by rotating front and back wheels in different directions. If you chain them together by tying them to the middle wheel, aren't you defeating this potential?

I believe they're implementing this design for these reasons:

Originally Posted by rocketperson44

For the most part, it acts as a standard mecanum drive, but the central wheels in combination with a suspension system provide additional forward traction and climbing ability.

[joeweber]

Here is a link to the first utube video of the drive. Maybee this will help with understanding the system. http://www.youtube.com/watch?v=urFsD0gA1D4

[Daniel_LaFleur]

Originally Posted by Mr_I

Okay, I'm confused about something (trust me, this isn't an unusual condition): The advantage of mecanum is that you can make the bot go sideways by rotating front and back wheels in different directions. If you chain them together by tying them to the middle wheel, aren't you defeating this potential?

Don't worry about being confused, this is a very advanced drive/suspension system.

(Correct me if I'm wrong with any details)

The 2 chains are not attached together. They are attached to a ball differential which allows them to drive the center (Omni) wheel when moving together and disengages them when the chains are driving in opposite directions (mechanum straifing).

There is also a pivot along the center axel through the omni wheels which allow the robot to keep all of the mechanums in contact with the driving surface even while cliimbing a ramp.

My only question is can it climb a ramp at any angle other than straight on? or will it slide sidewards if not aligned properly?

[joeweber]

Originally Posted by Daniel_LaFleur

Don't worry about being confused, this is a very advanced drive/suspension system.

(Correct me if I'm wrong with any details)

The 2 chains are not attached together. They are attached to a ball differential which allows them to drive the center (Omni) wheel when moving together and disengages them when the chains are driving in opposite directions (mechanum straifing).

There is also a pivot along the center axel through the omni wheels which allow the robot to keep all of the mechanums in contact with the driving surface even while cliimbing a ramp.

My only question is can it climb a ramp at any angle other than straight on? or will it slide sidewards if not aligned properly?

You are correct the chains are not attached together. Follow some of the links from previous post for video and photos.

Yes it can climb ramps on an angle and does it very well but to make it work on angles we had to add a second set of suspension to the front.

[Mr_I]

Thanks to all for the explanation. No, I did not realize the ball differential was in use (or even existed!). Very cool, but I honestly hope you won't need this in competition this year, because there are few teams that would be able to do this!

(Note: I don't mind being educated -- I figure it's part of my job in life to ask the questions that bunches of other people might have but are too shy to pose.)

[joeweber]

Originally Posted by Mr_I

Very cool, but I honestly hope you won't need this in competition this year, because there are few teams that would be able to do this!

Actually this system is very easy to build. The ball differental was the hardest part and we made it in house with no probblem. I also believe F.I.R.S.T. wants us to come up with new designs, thats the fun part. We have an addtional design we are working on for this that we will post when completed.

We have posted all parts of our design and anybody can build it. Below is the parts to the ball differental.

[lbarger]

I am impressed.

Excellent work.