TOP HEAVY!!!!

[MrForbes]

Originally Posted by Shaun Coon

ANY SUGGESTIONS?

I suggest you post some pictures of your robot, so we can see what you might be able to change to help fix the problem.

[Cal578]

Do you have your battery mounted as low as possible? That's the heaviest single component of your robot (almost 14 pounds, about 10% of your complete robot), so it has a big contribution to CoG. We mount ours flat on a board that is mounted to the bottom of the frame. Although, we may change ours to vertical this year, to improve accessibility, since it's all the way at the back and next to the bumper.

Another option is to train your drivers not to hit the throttle too hard. This can be enforced in your software. But this is not an ideal solution; it still leaves your robot susceptible to sudden stops, impact by other robots, tilting while going over the bump or bridge, etc.

Good luck!

[DonRotolo]

Shaun,

This is a rookie year for you guys, right?

OK, this kind kind of thing is what someone needs to write down so that next year's team knows it. One lesson is that the electronics guys need some space, the mechanical guys need to understand that (because high-up electronics have a tendency to get hurt, and high-up weight is always bad).

Please see if you can take a photo and post it so we can offer reasonable suggestions that will work in the time we have left.

One last thing: Congratulations! Not many rookie teams have a working robot already.

[tsaksa]

Originally Posted by DonRotolo

Shaun,

This is a rookie year for you guys, right?

OK, this kind kind of thing is what someone needs to write down so that next year's team knows it. One lesson is that the electronics guys need some space, the mechanical guys need to understand that (because high-up electronics have a tendency to get hurt, and high-up weight is always bad).

Please see if you can take a photo and post it so we can offer reasonable suggestions that will work in the time we have left.

One last thing: Congratulations! Not many rookie teams have a working robot already.

Absolutely agree here. Just look up the equations for angular momentum and kinetic energy of rotation and you will see why a tall robot may not behave well. Reducing the height (if you can) will pay back large dividends in stability. It is really difficult to increase the weight of your base by 25% late in the build and not go over weight. But decreasing the height the same amount is often quite possible, and may not even be that difficult.

[MrForbes]

I guess I should have posted a link about 5 weeks ago...sorry!

http://www.chiefdelphi.com/media/papers/1974

[Jon Stratis]

Now that I have some more time...

We saw in testing our robot a two nights ago that we have a similar (although not as extreme) issue - we can pop a wheelie transitioning from fill reverse to full forward. Essentially, we have too much weight in the back of the robot, and not enough in the front. We did a pretty good job of managing the height of our CG, though, so we don't actually tip over!

We weighed the robot by putting on end on blocks, and the other on a scale (may not be 100% accurate, but close enough) - we found the back weighed about 65lbs, and the front about 30lbs. We have a little more weight to add still (light weight panels, some small modifications as we see things aren't working correctly, and our bridge manipulator), but we should be able to add some nice steel plates to the front somewhere to help balance out the CG.

[wilsonmw04]

I would also added the bumpers for the simple fact that you are adding mass to the base of the bot, therefore, lowering the CG.

[JamesCH95]

Get some 775s or 550s and CIM-U-LATOR gearboxes and drop several pounds per motor up top. Add the CIMs back to the drive train down low.

[Cal578]

Originally Posted by JamesCH95

Get some 775s or 550s and CIM-U-LATOR gearboxes and drop several pounds per motor up top...

(emphasis added)
CIM == 2.8 lb each
775 == 0.75 lb each
CIM-U-LATOR == 0.5 lb each

Total weight savings == 3.1 lb (top only)

If you add the CIM's to the bottom, it's a net gain of 2.5 lb. Is that in your weight budget?

If you can (I know it's late in build season), shortening the robot as others have suggested can be a big improvement. CoG goes down, angular momentum goes down, stability goes up. Our team did this, and we believe the advantages outweigh the disadvantages.

[Matt C]

Get rid of your 80/20 "camera mount" up top including the uprights, leave the shooter support.

Replace with some of that wonderful lexan you got accidentally.

Look to relocate the battery in the center behind your lift mechanism, instead of at the back of the robot.

Also, consider moving the transmissions and motors forward, in between the front two wheels (instead of the back).

I'm currently looking at small pictures on my phone . . have you guys actually gotten the scale to weigh it yet?

The bumpers will help your top bottom a bit, but you NEED to fix the fore/aft problem.

[David Brinza]

I posted about Team 4's "Tip-proof" robot in CD a few years ago.

It has an educational and entertaining YouTube clip showing what you can do with a very low CG.

[JamesCH95]

Originally Posted by Cal578

(emphasis added)
CIM == 2.8 lb each
775 == 0.75 lb each
CIM-U-LATOR == 0.5 lb each

Total weight savings == 3.1 lb (top only)

If you add the CIM's to the bottom, it's a net gain of 2.5 lb. Is that in your weight budget?

If you can (I know it's late in build season), shortening the robot as others have suggested can be a big improvement. CoG goes down, angular momentum goes down, stability goes up. Our team did this, and we believe the advantages outweigh the disadvantages.

You're right, it's just a few pounds for both motors, clearly.

[Bob Steele]

Has it occurred to you to not go over the bump?
Use the ramps... or do you have a problem there too..??

Having those big CIMS up high is where to start... see if you can bring them down or use a lighter alternative motor...

But first put your bumpers on and see if you still have the problem

You don't have to go over the bump...
You can play the game by going over the ramps...

There is danger going over the bump... you can be defended and knocked over..(not as strategy...but defense being played....)

On your own ramp you cannot be defended...

just a thought...

[thefro526]

You could always add some sort of passive appendage that acts as a wheelie bar of sorts. It'd essentially act as a pendulum when your robot tips any noticeable amount. It should help keep you from tipping.

[Andy A.]

In addition to fixing the core problem, which is a high CG, you can do some software controls to prevent the driver from accelerating too quickly. Ramping up speed changes over a second or two can really help, although make sure your drivers are aware of the impact that might have on balancing. I'm not generally a fan of putting dampeners and filters between the driver and robot, but this is sort of 'free' and can quickly tuned or turned off as needed.

If you have a gyro, you could also use that. If the gyro saw the bot tipping too much, it could either limit any further acceleration or even go in the other direction momentarily. Traversing the bridge or bump would obviously cause some issues with that, so that may just not be practical this year.

Get your CG as low as you can and consider software dampeners to control any remaining issues.