Robots Tipping Over

[Cory]

Originally Posted by squirrel

I've never understood putting all that effort into making the drive base as light as possible, when the effort would be more effective if applied to the mechanism. If that means rethinking the mechanism design to make it simpler but still effective, all the better.

I don't see why a team wouldn't do both.

I can't speak for anyone but 254, but every year it's our goal to make all systems as light as possible without expending what we judge to be an unreasonable amount of effort, or sacrificing functionality/robustness.

At best this nets us more weight for added functionality, or wiggle room for when we get to the events and decide there's something we really want to add to the robot (Or allows us to slap 10-20 lbs of dead weight onto the base of the robot). At worst it means we don't go overweight.

It's a no brainer for us. Any weight we save from the base is weight we can use somewhere else. Just because it's no longer in the base does not mean it will negatively effect our center of mass. Smart design dictates no matter how heavy or light your robot is, you don't put the weight up high.

[FRC4ME]

Originally Posted by Rick TYler

Start an FTC team. The small chassis sizes combined with high-friction wheels and tons of torque motors results in robots that go down more often than submarines with screen doors. On the other hand, a really large number of them this year were self-righting. 575 must have flipped over backwards an average of three times per match, and was not unusual. The faster the robot, the more likely they were to go over. With 575 it was accelerate too hard, flip over, whack bucket over the top while accelerating hard and the robot was back up and running.

I believe 339 (FTC) tipped almost every match at the Championship. One of which included smoke as a bonus.

[sdcantrell56]

After subscribing to the train of thought of building the drivebase without any real regard to weight for a couple years, and each year worrying about overall robot weight, I am now a firm believer in saving as much weight as possible every where that is possible including the drivetrain. Any weight saved means adding a new device or function or improving on another. At the bare minimum it means adding weights in exactly the right spots to maintain the best center of gravity. This year the weight savings extended to the point of using extremely fancy and rare plywood in our drivetrain. Next year and this offseason, we are looking into experimenting with timing belt instead of #25 chain as well for even more savings.

In short, every system should be as weight-reduced as is reasonably possible.

[Eugene Fang]

Originally Posted by Cory

If you can optimize the weight of your drive base, you should. This does not mean you should have a 50 lb base and the remaining 70 lbs 4' off the floor...that's just not smart engineering. What it does mean is that when your scoring mechanism weighs 60 lbs you aren't thinking "Oh ****, how many 1" holes through 0.125" aluminum does it take to remove 20 lbs of weight?", because your robot is 10 lbs underweight. Or it allows you to add more functionality.

Last year, we had weight issues, as we were a couple of pounds overweight and eventually passed inspection at 119.8 pounds.

We kept that in mind this year, and designed everything, from the chassis to the scoring mechanism, as lightly but as robust as possible. We ended up at about 105 pounds at ship.

This allowed us to add more functionality, adding fans, encoders for traction control, and even another gearbox to slow down our shooter slightly. Eventually, we were still under 120 lbs, and we ended up strapping rebar to the bottom of our chassis.

[Rick TYler]

Originally Posted by XaulZan11

We are going back to regolith?

You can't fool me, young man. It's corn all the way down.

[MrForbes]

Originally Posted by Cory

I don't see why a team wouldn't do both.

Lack of resources, mainly. It's tough out there. Given the choice between having a nicely engineered and fabricated lightweight chassis/drivetrain vs. a light manipulator, I'll take the manipulator.

I know we're not the only team that can't have both.

[Eugene Fang]

Originally Posted by squirrel

Lack of resources, mainly. It's tough out there. Given the choice between having a nicely engineered and fabricated lightweight chassis/drivetrain vs. a light manipulator, I'll take the manipulator.

I know we're not the only team that can't have both.

Just wondering, what do you consider "light?"

This year our entire drive train (chassis+wheels+transmissions+motors+chain) ended up at just over 30 pounds, and we didn't do anything special such as 7075 aluminum axles/gears or any machining for lightning holes. We even had a couple of solid aluminum blocks for modularity purposes, so if we had welded it, we could have dropped the weight about 3-4 pounds.

We usually aim for under 45 pounds drive train + electronics board, maybe a bit more if we have pneumatics.

[engunneer]

Bumper stacking seemed to be more common than tipping, but still rare. It did happen to us in Galileo in QF3_1 TBA video

we didn't move the whole match.

I do recommend looking at the other videos, it's much more interesting than us not moving

[MrForbes]

We do pretty much the same thing, I think this year our bare chassis ended up right around 22 lbs, with the supports for the lower mechanisms in place (those 2x4s added a couple pounds). I don't consider this "light", but I also don't consider it to be "unnecessarily heavy", even though it could be lightened considerably if needed. We did a bit of work to lighten the upper stuff instead, and the final robot weight was 119.

I'm all for good lightweight robust design, with efficient material use, etc. I just don't see any need for lightweight wheels, lighweight transmissions, small chain or drive belts, or going to the trouble to cut lightening holes in the chassis, when the effort could be applied to the rest of the robot, with the result that the CG is lower and the mechanism performs better.