Effective Drive Base

[JosephBurns35]

i have also thought of a 6wd base but i am leaning for a 4wd with 8in stickes in the front and 8in omnies in the back this allows for the traction that you will need to go over the bumps it has its drawbacks you have yo go over stright othrwise you will just slide the back sideways. it is also very manoverable used the drive system in 2008
you can easily overcome the botoming out issues by putting a type of rub rail system on the robot like the sample ones had or moving your wheals front to back and even the size of them will help im open to sugestions

[Michael Ogden]

On mecanum wheels: I saw a video of one team (who will remain anonymous) having issues steering with a mecanum drive. If that doesn't turn your mind away from mecanum, AndyMark is coming out with a lighter version of mecanum wheels on Jan. 22.

[carbuff2228]

no mecanum if properly installed will work fine. Are team went with them this year and we think they will work fine for getting over the bumps

[Chris is me]

Originally Posted by carbuff2228

no mecanum if properly installed will work fine. Are team went with them this year and we think they will work fine for getting over the bumps

Have you driven a mecanum drive over the bump yet?

[fsgond]

Originally Posted by Michael Ogden

On mecanum wheels: I saw a video of one team (who will remain anonymous) having issues steering with a mecanum drive. If that doesn't turn your mind away from mecanum, AndyMark is coming out with a lighter version of mecanum wheels on Jan. 22.

Mecanum when programmed, design and driven correctly have great agility and maneuverability, arguably as good as swerve. Obviously the video that you saw was not a good representation of what good mecanum can do.

Originally Posted by fsgond

Mecanum when programmed, design and driven correctly have great agility and maneuverability, arguably as good as swerve. Obviously the video that you saw was not a good representation of what good mecanum can do.

A properly built Mecanum system is one of the most impressive drive systems out there. That being said, it has absolutely no pushing power. If your team rates maneuverability over brute strength, Mecanum is the way to go. However, a large majority of teams don't utilize a Mecanum's trues strength: Translating and rotating at the same time. It takes a skilled programmer and a very aware driver to really use a Mecanum system to full effect.

[Chris is me]

To some extent, every mecanum bot I see makes me second guess my own engineering decisions. I made a thread about that. To another extent, every mecanum I see makes me grin, knowing that my team's robot is best equipped to harass them to no end.

[Al Skierkiewicz]

Originally Posted by JosephBurns35

you can easily overcome the botoming out issues by putting a type of rub rail system on the robot like the sample ones had or moving your wheals front to back and even the size of them will help im open to sugestions

Joe,
Please be careful in suggesting this or implementing something that violates the robot rules. You can't have metal in contact with the carpet as part of your regular drive design.

[Brandon Holley]

Originally Posted by Al Skierkiewicz

Joe,
Please be careful in suggesting this or implementing something that violates the robot rules. You can't have metal in contact with the carpet as part of your regular drive design.

Also going off what Al is saying...

Make sure that this kind of system WILL WORK! I saw many teams in 2006 that decided to put some kind of slick rail on the underside of the robot. When the robots attempted to climb the ramp, they would either a. not make it at all b. make it after several attempts, usually ending with a half field ram of the ramp or c. end up on their back side. Just a word of caution.

-Brando

[JosephBurns35]

Originally Posted by Al Skierkiewicz

Joe,
Please be careful in suggesting this or implementing something that violates the robot rules. You can't have metal in contact with the carpet as part of your regular drive design.

this i not what i ment in the sample with woody and dean thay showed the plastic and bunge cord things on the robots by the weals they can also be used as somthing to slide you across the bump to prevent hanging up

[Kevin Sevcik]

Checking your assumptions at the door is definitely important. For instance, the Aim High ramp was only 30 degrees to a nice flat with a wall behind it. The Bump (caps make it scarier) is 45 degrees up, to a flat with a 45 degree faceplant just waiting for the unwary or timid driver.

Before picking a drivetrain, you should consider how it's going to rest on the slope, what that implies for your CoM, and what a sudden stop will do to you on the down slope. Or a sudden start on the upslope. You may want to mock up a bump and throw a drivetrain at it to see the effects momentum can have on your robot. I can tell you that a robot with more than 3 contact points per side should worry about having a CoM higher than 12". The case for a 6 wheeler is going to depend on the wheel sizes and separations, though it should be somewhat better.

EDIT: As Martin Taylor pointed out, numerous contact points on a side means you significantly raise your CoM before your robot tips onto the flat of the bump. Which would be survivable if the flat was, say, 24" long. But a 12" flat isn't a large landing pad. If you have a CoM over 12" in the center of your bot, then once you tip over to the flat of the bump, your CoM is already past the far side of the flat. Which means you just keep tipping forwards. Which means you're going to faceplant on the far side of the bump. Moving your CoM rearward helps, but not as much as you'd think. Accelerating off the backside of the bump will probably spare you the faceplant at the price of an even rougher landing.

[hyperdude]

Something I don't think has been mentioned yet, but is important:

At the kickoff, after the Game Animation, Dean and Woodie demonstrated the difference between using the "slick" wheels and "stick" wheels when it came to the vision tracking.

If we use the "slick" wheels, the robot will have an easy time sliding around lining up with the vision target. However, it pretty much can't make it over the bump (gets stuck at the top)

If we use "stick" wheels, we can make it right over the bump, but it can't move sideways to line up with the target.


So if we go with treads, what kind of sideways motion is there to be expected? Sure, treads can go right up and over the bump, but you'd have to resort to tank-drive driving to line up with anything. Not exactly an effective solution, at least in my mind.

[DanDon]

Originally Posted by hyperdude

Something I don't think has been mentioned yet, but is important:

At the kickoff, after the Game Animation, Dean and Woodie demonstrated the difference between using the "slick" wheels and "stick" wheels when it came to the vision tracking.

If we use the "slick" wheels, the robot will have an easy time sliding around lining up with the vision target. However, it pretty much can't make it over the bump (gets stuck at the top)

If we use "stick" wheels, we can make it right over the bump, but it can't move sideways to line up with the target.


So if we go with treads, what kind of sideways motion is there to be expected? Sure, treads can go right up and over the bump, but you'd have to resort to tank-drive driving to line up with anything. Not exactly an effective solution, at least in my mind.

I've had no problem with tank-drive steering in regards to vision tracking in 2006 or 2007.

[Nathan2974]

Originally Posted by Kevin Sevcik

The Bump (caps make it scarier) is 45 degrees up, to a flat with a 45 degree faceplant just waiting for the unwary or timid driver.

I just wanted to point out that the actual grade of the bump is approximately 38.7 degrees (or something to that effect) using simple trigonometry based on the height and width provided by FIRST.

[hipsterjr]

We designed these articulating drive pods back in 2005 and have been waiting for a game like this to use them.