Forward Tipping

Hello, I’m back with another question. We are having issues with our claw bot that we are building. Most claws that have tipping issues tip backwards and this is easily solved because the robot typically does not need to be moving when it is throwing the stars over. Usually the robot tips over when the lift is high up and is about 1/2 a second from dumping the stars, so anti-tip pegs keep the robot from falling and that is the solution. Our robot is constantly tipping forwards, and we are unsure of how to solve this. We have added anti-tip pegs in the front which prevent us from falling forwards, but when the lift is up with 5-6 stars, it begins to tip forward. This is a problem because the wheels usually have very little to no contact with the ground which prevents us from being able to move. Other bots that we have seen do not tip forwards at all no matter how much weight they are picking up. Just as a basic description, the towers are in the very back of the robot, it is a 2 bar, and has a traditional claw similar to Big Meaty Claw mk3.
Thank you

Pictures (and maybe even a video of the robot tipping) would be great to see.

I will post those as soon as I can, hopefully tomorrow afternoon. Thanks.

maybe try moving a bit of your weight forward like your batteries and cortex. also pics would be helpful to provide a much better solution.

Wouldn’t moving the weight forwards cause it to tip forwards more, or is my logic backwards? Anyhow, I will post pictures as soon as I get a chance, latest by tomorrow afternoon.

@The Electrobotz SORRY yes i meant move it backwards, i think i zoned out when replying. Lol.

What about moving to a 4 or 6 bar? The motion of a 2 bar is circular, leading to weight being put farther forward when the lift goes up. A 4 bar would help to solve this by offering a higher gear ratio in a non-parallel format… maybe. Not sure how that would help. With 6 bars however, the motion of the lift more represents an inverted parabola. When using this system, all sorts of geometry can be tweaked, lending to almost linear motion upwards for the first half, then backwards motion in the later half of the lift cycle.
It’s really involved, and likely not what you’re looking for. I’m posting here for other teams that may have this problem.

I have attached a picture of the robot to this post. Sorry about the delay getting the pictures up.

That’s ok, but most of the main weight is in the back of the robot anyway.

I see where you are coming from, but the hanging system that we recently attached to the robot requires it to be able to move around very far backwards. This is why we need a 2 bar. Thanks for the advice though.

BTW, don’t mind the trash wiring job. We really struggle with that part. :slight_smile:
IMG_0253 (1).JPG

Just wondering, but why did you make the base so small?
If your base is longer, you could make the wheels wider apart or add anti-tip wheels.

The base is 25 holes x 35 holes. We did this because we wanted to be able to have the claw be in front of the robot so that is lower. Originally, we had a standoff intake so we really needed the standoffs to be able to drop low enough and be relatively parallel to the ground.

By looking at your claw, it seems that the c-channel part of your claw is raised higher than the rest of your base. Therefore, you could still change the 25hole to a 35 hole and simply move the standoffs to the middle where it doesn’t touch the two sides. You would have to redesign the standoff part a little but that shouldn’t be a problem.

Thank you, that is something we will look into. However, is there some other way you can think of solving the problem before we go changing our drive base again.

Since you already said that you have tried antitips pegs, the only other thing I can think of is moving the back drive motors back a little more but I don’t think you can do that because of the C-channels for the lift.
Maybe you could change the placements of the c-channels connected to the standoffs to be a bit lower. This may help a bit, but may become slightly bent in the long run.
If you have any questions, you can always pm me.

it seems to me that you have plenty of space in the front of your robot to put small channels similar to this team

@The Electrobotz it looks like your wheels are a bit close together and it might be a good idea to spread them far apart as this would increase the stability of your robot. If you put in the time to change the drive base it would benefit you in the future and you wouldn’t need any anti tips,

My students found they could solve the tipping by adding a 2nd battery as a counter weight

I had the same problem but moving the front wheels forward solved it for me.

LOL. That team will end up getting DQ a lot unless they change the anti-tipping on it. They keep touching their near zone when putting stars and cubes over the fence. It should be an easy fix for them, though.

You may not need to go with a full 35 long (17.5 inches) to achieve your goal. Split the difference and see what happens. Go 15" long on the base (30 holes) and that will likely do it. Like others have suggested, adding weight to the back will also help.

Keep in mind that you can only add a 2nd battery if you are using a power expander. Without that, having the 2nd battery on the robot is not legal.

An argument that I am very much not looking forward to having with a referee is that while a wheel may go past the tape, it is only touching the field tiles at the very bottom, so I can extend (with a 4 inch wheel) 2 inches past the far edge of the tape (which is not considered to be near zone as per Definition of Near Zone Note 2) and still be completely legal. I very obviously don’t have that robot, but it looks like that is what’s happening.