pic: Two bot side balance

It’s pictures like these that make me question Newtonian physics…the one that makes me question it even more is the Robotnauts “illegal” but ingenius bridge device.

How is this legit but 118’s machine was not? There appears to be a mechanical device under that robot that straddles the bridge angle.

It straddles the angle, but it will likely only react against one side at a time. The part on the outside of the angle appears to just act as a stabilizer since they can’t balance on a row of wheels alone. They are just resting on the bridge while occupying the smallest footprint possible as a result of a cleverly placed center of gravity; making it much more like Swampthing than 118’s robot, Endeavor.

Upon closer inspection of the other photos, I no longer believe that the part outside of the angle does anything but help with alignment. All of the force is directed through the inside alignment rail and the wheels directly to the bridges surface.

Edit: and now VB3 gives me the option to modify my previous post, how convenient :rolleyes:

This is clearly illegal. Physics does not support a scenario in which that robot can remain on the bridge without applying force to both sides of the angle, unless the CG remains over the bridge surface, which is highly improbable.

Cannot believe this was allowed to compete after 118 was denied.


Wow. 2 things:

  1. Creative design 3534. Many teams thought of devices like this to aid in balancing either with 1 or 2 other robots, but…

  2. If this device is not just a CG tweak it would be clearly illegal. 118 amongst other teams (ourselves included) would be utilizing a side hanging device that accomplishes the same effect had it not been ruled illegal before the first qualification day of the week 1 regionals.


It’s not probable, but it is possible that their CoG is indeed over the bridge surface. Just from looking at this picture, it seems like they have a relatively small superstructure, which could free up weight to use as ballast towards the bridge side. However, I have no idea if this is actually the case. If someone from this team or someone who is familiar with this robot could clear this up, that would be wonderful.

EDIT: From this image, it appears that the side over the bridge is considerably more dense than the other side, including solid aluminum (steel?) blocks being used as ballast, so the possibility of an extremely biased CoG is possible. However, it also appears that there is a metal piece under the robot touching the side of the bridge. I can’t tell if it’s just used for allignment or if it reacts against the bridge.

it still looks to be leaning to the right, if the inner edge of the monorail was removed the robot would fall (my guess). If this is the case, it’s illegal.

Over on the left side of that picture you can see stacks of weight attached to the frame. In addition the battery is also located on that side.

If that’s nothing more than a CG trick, that’s just awesome.

What I heard and observed from being at the competition is that 3534’s center of gravity is indeed over the bridge when it does its side hang.

You can clearly see from the picture that this team tried to put as much weight on one side of their robot as possible. Why would they have designed it to ALMOST have its CG above the bridge but not quite?

Agreed… This is fundamentally the exact same mechanism of “grasping” the sidewall as 118 used if the CG isn’t over the bridge surface, like you said. The only solutions physics could allow for this Free Body Diagram (that I can think of) would involve either “gluing” yourself to the surface of the bridge or “grasping” the sidewall of the bridge similar to how 118 did.

I don’t have that hard a time believing this one wasn’t ruled illegal, though… This one looks to basically be sitting on the bridge. 118 looked to be hanging off the side. So much of how the GDC ends up ruling things is based off how the solution looks. If they see something they don’t like, it seems like they then figure out how to rule it illegal… * sigh *

Wow, if that really is true about the robot being designed so it’s CG is in the 8" on the bridge-side of the robot, that is simply incredible! Congratulations!

Even if it is illegal, I’d still say congratulations on accomplishing it - I would wish it (and 118’s hanger) were legal!

Given that the robot was able to drive up the bridge (I’m assuming from the other photos that it made it up under it’s own power), there must be enough weight over the drive wheels for it to power itself up, in which case grappling the lip is not necessary to stay on the bridge. I highly doubt you would be able to drive a robot up the bridge if it relies on clamping force on the lip to keep it from falling off. I’m curious as to how the friction from the portion of the robot touching the lip did not inhibit it from driving up though.

Doesn’t look “clearly illegal” to me.

Congrats to 3534 for creating and carrying out this design! Out of the box approaches are risky but oh so cool.

I watched this team’s alliance triple balance on the practice field. If there is any more weight on the side off the bridge, the robot will fall off. It does not “grasp” the bridge. It does not apply force to two or more sides of an arena element. The notch is there for alignment.

People need to relax a bit before coming to conclusions on this and ask questions.

Hey cptopher, can you explain how this works because it’s legality might be questionable? If it is legal though that is some clever work and I commend you for pulling this off.

I was able to see this robot in action. It is steel ballast on the edge. The parts you see under the robot are alignment guides, and do not touch the sides the the rail when it is on the bridge. I believe (not being certain) that there is a surface which rides on top of the rail.

It would be no different than if a robot got bumped off the side of the bridge and they were resting on their chassis.

The head referee checked at the end of each match to make sure there was no lateral contact on the bridge.

It is just a a simple CG trick. 98 lbs on the right side wheels, 20 on the left. We sit on the rail, with a simple guide that its twice the width of the flange for alignment only. The belt drive gives us traction on the top surface only.

This was a huge design commitment for the team. All 4 Cims and gearboxes are on the right side with a driveshaft to the left wheels. The belt is driven by this shaft, geared for the same linear speed as the wheels. We have 30lbs of balast weight on the right side C rail. And a sliding battery tray. The super low CG also makes us a good stable two bot regular balancer too.

Thanks to all for the interest. We were honored to receive the Creativity Award at Livonia districts.

Team 3534 ME Mentor

Wow, cool! It’s hard to tell from the photo that there is ballast on the bridge side of the robot, thanks for clearing that up.

Are you going to champs?