Base Sizes

Our team has been discussing if a base that 10 inches long, would work for sack attack. The problem that we are coming into is that we believe that when lifting a load of sacks (3-5 sacks), and having a base that is short, assuming using a bar linkage (4,6,8), it would cause the robot to tip forward. I know teams have created short bases before, but how did they execute it, did they add a lot of weight on the back of the base. Basically what i want to know is, is it possible to make a 10 in long base, and still not tip over.

What my team has done in the past is either have a really low to the ground chassis, or add a wheelie bar to the back of our robot. This past year for Gateway, we did not have a low chassis. When we were practicing we were tipping over, not a lot, but we still were tipping. Once we added an Angle Bar to the back of our bot, we did not tip at all the rest of the season. How high will you “tower” be for Sack Attack? If you plan on traveling under the trough, you will have to have a “tower” that is below 15". If you have a wheelie bar, and your tower does not go that high, I don’t really think you will have a problem with tipping.

Shortest CAMS Robot that I know of is the Elevation bot built by 687J (World Finalists/Science Division Champs that year). Both the base and tower look to be ~12", and the four bar linkage is a asymmetrical, which causes the intake to move closer to the back of the robot.

We used that as an advantage for our robot last year haha.

Most unfortunately I do not have pictures (and not enough time to write one thousand words), but I can explain what I’ve done. For the past three years all of the robots I’ve built have had bases about 10" long and all I’ve done is place stand-offs so that the tip is just a few millimetres from the ground. Of course, this year that might cause snagging problems. The other thing is to make a really well balanced chassis, or else add a hefty amount of counterweight to the front.

To answer your question, yes is the answer.

But I need confirmation on what exactly your planning to do though. What i think your doing is creating a very wide intake so so your base is only 10"x18"

As you know, the reason why a robot tips is because the center of balance passes the polygon of support. So as long as that doesnt occur, you will not tip over.
So, to prevent this, you ether need a larger polygon of support or more weight back. What you can do is have wheels flip out of your drivetrain(similar to a flip out holonomic, apply dead weight, or have your lift expand(to act as a counter balance), use a pulley tower, or more elegantly, make your intake go through your drivetrain, balancing out the weight automatically. I would also keep your lift’s mount steel, while making your actual lifting system/intake aluminum. Another thing you can do is have a driver raise the lift while driving forwards, or even apply sensors which automatically prevent you from flipping.

If i had more details, i might be able to give you a better answer.

My experience
In round up, we had a robot that used a drive train that was 8 inches long. The main reason why it never tipped forwards was because we used an arm system, which forces your center of gravity back. However, we did have issues tipping backwards. We tipped backwards because we couldn’t survive the rough game play. The way we fixed this issue was by lowering the drive train(we used a plus drive).

so i think this can work just as long as we have weight in the back, and have a steel tower. We are also planning on have a steel chassis to keep the robots cg closer to the ground. Also we are going to mount the pneumatics tanks were ever the weight needs to be balanced to stop it from tipping over.

Oh i almost forgot. You can try mixing the sizes of the wheels. It worked well in bowled over

I was going to mention that in my post but I forgot. If you do plan on using pneumatics, then placing the tanks at the front of your robot will help with your tipping. I have seen lots of teams place their pneumatic tanks at the front of their chassis to help with tipping.

Good luck this year!

Well, I suppose the first question is why do you need a 10" long chassis?

IMO, if it’s purely for the sake of shaving weight or materials, it’s certainly not worth it.

However, if it’s for the purpose of being able to reach a goal, then I suggest you increase the length of your chassis and straddle the goal. So your chassis is pretty much like a big U.

  • Sunny G.

oh, no. its the reason why we need our chassis to be so short is so that our “intake” can fit in the front 8in of our robot. Basically our collection has to be 8in

Will it be 8" long and 18" wide? If not, then I think you’re much better off with a U shaped chassis.

  • Sunny G.