So, with my X-Drive, the left side has the brain, battery, radio, and a motor. The right side has little to nothing. When it drives backward, the robot tries to pull a mini wheelie (Because the weight is in the front ), and only the very light right side does this causing the X-Drive to slip to the right a little. What are good Counterweights (With as little steel possible) to combat this? At a competition, a team had a mesh pouch with nylocks and nuts in it. They called it the “nutsack” and I’m not so sure that’s a good idea.
TL;DR: One side of the robot has a lot of weight, the other doesn’t, whats a good counterweight? “With as little steel possible”
This is a great post, when anyone in VIQ or VRC is looking for counterweights, the answer is “Nope, move stuff around”. Thanks @Ethan5956F for the reminder that Moar weight is seldom the answer. Fatter is never better
While I agree that the best solution would be to design so that the weight is evenly balanced, I understand that sometimes you need a short term solution. Last year I had 2 teams build bots that were kind of like souped up claw bots that would pick up the stack of 4 cubes and be able to place them in autonomous (one of those teams even qualified for worlds with his skills score!) But when they picked up the stack of 4 their robots would tip over, so counterweight was necessary (like a forklift has a huge counterweight).
One team zip tied about 20 angles on the back of their robot and attached it, they nest perfectly. The profile was pretty slim so it didn’t add too much size. The other team took all the old black screws that we had (We just upgraded to all star drive screws) and built a box with plates and filled it up with screws. If you do the box, make sure it doesn’t leak!
This statement is kinda overgeneralizing the capabilities of an x drive tbh. it depends on the wheel angle, wheel radius, internal motor gearing, external gearing, any other contributor to MA, and which directions we’re considering given those previous data points. There’s lots of ways to make an x drive have a higher MA than a tank drive (because that’s what we’re really comparing; you can increase torque simply by adding more motors, but that isn’t the point of my argument). In fact, even if the wheel radius, external and internal gearing, are exactly the same on an x drive as on a tank drive, it’s possible for the x drive to have a higher MA because the MA is also determined by the angle the wheels are at.
Traditionally, x drives are considered to have their wheels facing 45° apart from the center, giving the traditional x drive an MA of 1/sqrt2 in the orthogonal directions (this is considering its from the “X” perspective, not the “+” perspective). Wheels at different angles from the origin net different MA’s. Because of this, in addition to the fact that all you have to do to change MA other than that is just change the wheel size and/or internal gearing or the motors (or add external gears, but that’s a bad idea for an x drive cuz of slop lol), x drives aren’t really lacking torque. You have a set amount of power per motor, and it’s up to you to find the optimal MA to reach your goal; same as with a tank drive (sorry for the long post on such a small statement I just enjoy x drive mechanics lol)
Changing the size of the tires is like gearing it different. Energy needed is a relation with distance and time, so if you use a 3inch diamiter wheel,and tell your moter to rotate one time, you will travel the 3Pi ; ~9.4in. If you have 4 inch diameter wheels and you tell the moter to rotate once in the same time frame, then you would be traveling 4Pi ; ~12.5 inches. Therefore you would be traveling ~3.1inches more in the same ammount of time, which would be like gearing the 3 inch tires up 33% ,make sence? You could also think of a fan, the closer you are to the center of the fan the slower the blades are spinning, which also means the fan has more torque the closer you are to the center. The same principle applies to gears and sprockets. The closer you are to the center the higher the torque and the slower the speed (assuming the same input speed) it is not based on number of teeth, but based on diamiter. You can use the number of teeth because it is proportional to the size with the other gears. If that didn’t make sense, think of it like this: if you take a 30 tooth sprocket , and and 84 tooth gear __they are almost the same size , and wrapped a chain around them (and pretend the chain wont slip on the gear, ) then spin the gear- the sprocket is not going to spin 2.8times faster because is has 2.8 less teeth, they will spin almost the same speed , because they are almost the same diameter… Hopefully that makes sence, if not you can ask , or just ignore what I said ; ) ; ) : )
Check out 1115B tower takeover, instead of anti tips they have a block of steel plates screwed together making their robot weigh 24 pounds. like jesus so you probably don’t need that extreme of a solution, still, steel plates work because you can control the size and shape of plates super easily. I think the only thing that is more dense than that is a clump of high strength axles but it looks kinda bad.