What is wrong? [HELP]

Our final, final robot weighs around 85 pounds, WITH the electronics. For years, 256 has had to swiss cheese our robots to make the legal and under the weight limit, however this year is different, and we didn’t do it on purpose.

I don’t think we forgot anything:

-Sturdy drivetrain
-sturdy frame
-articulating ball shooter
-accurate bridge actuator mechanism
-very well working ball intake
-very well working ball elevator

What I don’t get is how we have managed to come under weight. It is our first time making a custom chassis and superstructure, but I didn’t think that could loose us so much. I’m afraid something on our robot is under-built, and too weak, but everything is stronger than me in some cases.

What should I do? :confused:

Our scale works perfectly, and since we were also unsure, we used another one we never used before and got the same weight

I would invest in a new scale.

Strap on 33 lbs. An underweight robot makes it difficult to balance with other teams on the coopertition bridge.

Stop bragging about being under weight. :rolleyes:

Seriously though not knowing the details of what your robot looks/performs like it’s hard to answer that question. I can list possible places you could have missed but I need more info.

Is your frame too thin/weak?

Do you have normally have pnumatics but not this year?

Are there fewer sensors?

Did you use a different drive system than normal?

Is your robot really short?

did you use just the smallest motors in the lkit?

Are you lacking protection/shielding around your electronics to prevent balls from sticking in your robot?

Is your robot not the full 28"x38" that you’re used to?

Just some stuff I though of quick.

ASAP, weigh it on a scale that you’ve never seen before, just to cover your bases.

Beyond that, add weight as others have said. That or make yourself the robot that aids the balancing while popping the last shot off.

And nothing wrong with being that far under.

Thanks for the help! I’m thinking it’s the lack of pneumatics and lighter frame, though I never thought the combination of the two would loose us 30 pounds…

Nor my new problem: What to do with those 30 pounds? The bottom of our robot is mostly hollow to allow our intake to pick up from both sides, so it’s hard to put things places.

Have your programmer add more 1’s into the program an remove as much of the 0’s as possible :rolleyes:

At our pre-bag scrimmage, without our shooter on, but WITH our bumpers, our robot was 81lbs! It was VERY hard to control.
With the shooter (and no bumpers), it should be around 90, 95. Still light. I think not using pneumatics is a big deal for us.

We managed to avoid that problem by welding up a nice 27 pound steel frame for the bottom of the robot. And we have about 10 lbs of pneumatics, too.

One rookie Tucson team we’ve been following has a really light robot like that, they came up with a neat design for their sheet metal sponsor to make, and their robot is somewhere around 85 lbs.

Since the bridge causes short wide robots some issues, especially when there are balls under the end of the bridge, you might see if there is some heavy thing you could add to the bottom that would make bridge climbing easier, and flipping less likely. We’re looking into this for our robot.

There was a team at kc that put a steel plate into their robot chassis which helped them not become so tipsy during comp it worked very well for them. Bridge balancing does become harder without some “good weight”

This sounds like a great opportunity to try to lower and center your CG. We did something very similar weighed in at 93lbs at bag, so during un-bag we added steel plate to beef up our frame in the 4 corners as low as possible. Moving weight out the the edge of the frame helps improve your stability much like a tightrope walker with a long weighted pole.

I’d agree it’s beneficial to be closer to 120-lbs to ease balancing multiple robots.

I put a picture of this steel plate on flickr, and it is linked in the robot showcase thread I just created:

http://www.chiefdelphi.com/forums/showthread.php?threadid=104366

Thanks all for your help! I really appreciate it. :smiley: An underweight robot is just as bad as an over weight one, so I’m glad we’ll be able to beef up our machine.

We decided to use the extra weight to lower and center our CG, and well as make our robot look really cool. :cool:

We’ve tested it on a total of 3 different scales as of today. All 3 gave us the exact same measurement, +/- a .5 lb.

Not sure if I told you already, but we are about 15 under. We are definitely gonna bring some thick steel to attach on Thursday.

As for where, you could attach it to the very bottom of your robot, sort of like a baseplate. This should not change much, as it would be low enough to allow balls to pass over without any problem.

You could always just put on one of those half-freshmen that lay around after accidents… :ahh:

Yeah, I think you told me; About 105 pounds. The problem with sticking the weight low for us is there isn’t much room “low” on our robot for stuff to go.

We have 108 square inches of space down at the bottom of our robot. Our robot is 27*37 inches (999 square inches) for a base, and 108/999 is about 10% of our robot’s base area. The other 90% is used for ball pickup.

You’ve seen our design (new pictures should be on CD media sometime soon). There’s no room on the bottom. :stuck_out_tongue:

I would add a 148 style pneumatic for some 3 robot balancing if we had the weight. I recommend an attempt at implementing that. Any other weight is what steel plate is for.

Thats a good idea.

Especially since you (256) are going to two regionals, you do have some extra time to perfect your mechanism. Also 30 lbs of steel might be a bit much to squeeze into 108 sq in.
You are not using pnuematics, but instead you could use a motor to have a stinger come down by means of a 4-bar linkage or something of the sort…

Are you guys counting chain and fasteners? Those can hike up the weight quickly enough.

You could have added additional drive power.

Alternatively, if you use a launcher you could increase the weight of the flywheel to maintain angular momentum which helps with consistency.

In San Diego we added a few 2.5-lb weights on the chassis to lower the CG and help balance with other robots.

One team in San Diego installed a custom motherboard to run Linux, so they could independently process Kinect data (which was installed on the robot as a webcam). they were way overweight, but for some reason decided to drop motors and structure rather than getting rid of the extraneous sensor equipment.

Chain and fasteners included.

I’ve been looking into the 148-like stinger, but unfortunately the place where we’d put it isn’t low enough to the ground for it to reach, so IDK about that one.