Effective Drive Base

[=Martin=Taylor=]

When I first started analyzing the game I figured that a basic 6 WD robot with 8" wheels could easily climb the bumps. In this configuration there is no bottoming out issues, and the CG can be kept quite low.

However, we discovered a critical flaw when we tested this.

When a 6 WD robot climbs a ramp*, the center wheel acts as a pivot as the robot climbs over the crest. This results in half the robot being lifted into the air Highly unstable!

Take a look at the demo bots in the game vid (The non-animated ones of course!). They all have FOUR wheels. This is a much more stable configuration b/c all four wheels remain in contact as the robot climbs. There are no sudden rocking movements forwards or back.

Of course, as Dean himself pointed out, 4 WD robots don't turn very well...

*or a tracked drive

[teampronto]

Originally Posted by =Martin=Taylor=

When I first started analyzing the game I figured that a basic 6 WD robot with 8" wheels could easily climb the bumps. In this configuration there is no bottoming out issues, and the CG can be kept quite low.

However, we discovered a critical flaw when we tested this.

When a 6 WD robot climbs a ramp*, the center wheel acts as a pivot as the robot climbs over the crest. This results in half the robot being lifted into the air Highly unstable!

Take a look at the demo bots in the game vid (The non-animated ones of course!). They all have FOUR wheels. This is a much more stable configuration b/c all four wheels remain in contact as the robot climbs. There are no sudden rocking movements forwards or back.

Of course, as Dean himself pointed out, 4 WD robots don't turn very well...

*or a tracked drive

False. There is indeed a 6 wheeled robot.

[Creator Mat]

can someone explain to me how the serve/crab drive will not be an effective climber? I don't understand how the fact that a swerve is complected would matter when climbing. Climbing is all about traction and a swerve with the right wheels would have the same traction as other systems.

[BrendanB]

Originally Posted by Creator Mat

can someone explain to me how the serve/crab drive will not be an effective climber? I don't understand how the fact that a swerve is complected would matter when climbing. Climbing is all about traction and a swerve with the right wheels would have the same traction as other systems.

It depends on how you build it. If you make a typical swerve with small wheels, then have fun going through the tunnel. But if you use larger wheels and put them directly in the corner of your robot without any frame to inhibit contact between the wheels and bumps, then I would say that you have a very good chance of getting over the bumps.

Mecanum would seem like a very poor choice this year, especially with such a small area to get through the tunnel. But some will do it and someone will do a great job with it. There always is at least one good team with mecanum!

[dustinjeremy2k]

Originally Posted by =Martin=Taylor=

When I first started analyzing the game I figured that a basic 6 WD robot with 8" wheels could easily climb the bumps. In this configuration there is no bottoming out issues, and the CG can be kept quite low.

However, we discovered a critical flaw when we tested this.

When a 6 WD robot climbs a ramp*, the center wheel acts as a pivot as the robot climbs over the crest. This results in half the robot being lifted into the air Highly unstable!

Take a look at the demo bots in the game vid (The non-animated ones of course!). They all have FOUR wheels. This is a much more stable configuration b/c all four wheels remain in contact as the robot climbs. There are no sudden rocking movements forwards or back.

Of course, as Dean himself pointed out, 4 WD robots don't turn very well...

*or a tracked drive

Nicely put... I guess I was not as clear. And with all due respect to those that posted earlier, I've been doing this a while too, and played the games you referenced... and climbed with ease each time without a tread and less than 5 wheels! Very stable! Just trying to simplify a problem that’s easy to make unnecessarily complex.

[yoshibrock]

Currently, as a team, we're trying to decide between using mechs or a swerve system. I happen to be privy towards a swerve system, but it would be our first year using it, so a lot of people are nervous. I think that swerve would give better traction than mechs as well as the ability to have a multi-direction robot, but there are arguments against swerve as well (mainly how complicated it is). I guess I'm just a teensy bit biased

[DiehardCybercard]

that is a concern my team will have when we have the drive base argument. we built our first mechanum base this year in off season. so we are fairly new to exotic drive systems.

a big factor with a swerve drive though is that is a lot of weight added to your robot. the more weight you have on the robot the riskier it will be to drive over the bumps.

im really interested to see how teams approach this challenge.

[Madison]

For the sake of discussion, I'm attaching a picture that shows an 8WD system going over the bump.

[Akash Rastogi]

Originally Posted by Madison

For the sake of discussion, I'm attaching a picture that shows an 8WD system going over the bump.

Thanks.

We're debating between a 6wd with 8" wheels or an 8wd with 6" wheels. I'm personally leaning towards the 8wd.

Originally Posted by DiehardCybercard

that is a concern my team will have when we have the drive base argument. we built our first mechanum base this year in off season. so we are fairly new to exotic drive systems.

a big factor with a swerve drive though is that is a lot of weight added to your robot. the more weight you have on the robot the riskier it will be to drive over the bumps.

im really interested to see how teams approach this challenge.

False.

This weight is at the bottom of your robot, low to the floor. This amounts to a low center of gravity as long as your arm or hanger is also lowered while driving over a bump. Low CG= easier movement over the bump.

[Kevin Sevcik]

Originally Posted by Madison

For the sake of discussion, I'm attaching a picture that shows an 8WD system going over the bump.

Madison,

You should put a CG marker on your sims, things get more interesting when you start looking at where your robot starts tipping, and where you end up after you tip.

[Madison]

Originally Posted by Kevin Sevcik

Madison,

You should put a CG marker on your sims, things get more interesting when you start looking at where your robot starts tipping, and where you end up after you tip.

Given that my model is symmetrical in two planes, the CG is right in the middle. The robot will obviously behave differently going over the bump if the CG is very far forward or aft, but my model isn't complete enough to capture that yet.

8WD may send the robot "higher" on its way up the bump, but the same behavior that causes that also prevents the end of the robot from falling quite as far as it might on a 6WD system. I am under no illusion that the robot will ever stop successfully on the flat top of the bump and understand that it's going to dive hard into the ground on its way down in all cases, though.

It's also possible to implement 6 or 8WD systems wherein the wheels are not equidistant from one another and see some altered behavior from that. In 8WD, moving the center wheels closer makes the system begin to approximate a 6WD frame -- so it won't ride up as high while climbing, but falls correspondingly further on the trip down. It's all about trade offs, obviously, but I am more concerned with minimizing the force of the giant thud that'll happen on the way down than I am with tipping to 45* on the way up.

[M. Mellott]

Half-tracks, anyone? Short tank treads in the back, powered omnis up front. Power to push & climb with the addition of maneuverability...

[RoboMentorY]

Originally Posted by Madison

For the sake of discussion, I'm attaching a picture that shows an 8WD system going over the bump.

We just put these set of screen shots together with a 6WD, 6" wheeled system with a 0.25" drop center. As a powerpoint slideshow it shows the angle changes as the wheels change contact the bump. One can envision the crash at the tipping point on the down slope. Enjoy.

[JohnFogarty]

Going with tank treads we have a good way to make em

The team I'm working with is sponsored by Outback Manufacturing, and they'll be going with tracks built with the sponsor. If people have heard of these or have questions, I'd be glad to answer anything about them.