Mechanical Maniacs #7750 Robot
Our robot is designed and built by this team alone. Every member gets a say in how it's done, and gets to help in building.
Mecanum Drive
The most important part of the robot is the drive. We like mecanum wheel drives because of the high mobility. The design allows us to have the ability to move fluently to the left and right without turning, which maximizes our time efficiency. We have used mecanum drives in the past and were pleased with the mobility on the ground. To further optimize our advantage on the field, we use a 20:1 gearmotor, which gives us a robot that is twice as fast as a standard 40:1. The speed is a huge advantage.
Both designs had their pros and cons (as all designs do). Neither of them are fully developed in these pictures. We knew both of them were equal in the way the drive would function because they both have mecanum wheels, even though one does not look like it, and both were capable of being geared. So the decision was more on strength, compactness, compatibility, and overall what design was the one the team liked best.The terix beam one was easier to mount other things to, though the beams also took more space than they needed to. We also considered weight, we wanted to be able to move fast so we needed to be light. We decided to go with the one built from last year’s field mainly because its compactness and the plan of putting all the electronics on the first layer, and having the mechanisms on the top layer. It also helped to cut back on some of our expenses to reuse pieces of last year’s field. The drive was made of last year’s mountain aluminum churros and lexan plates that we made. We used the sides of the mountain as our side walls. We threaded the churros and used them like support rods and drilled holes through the churros to connect lexan to them. We also made the top plate come off with four big bolts so we can maintenance it easier.
Intake
We decided to go with the integrated particle intake because of the simplicity of it and the team vote it as the best idea.
We discussed how the intake would work, and designed an intake that would have a wide mouth that would then have a shoot that went to the launcher that had flywheels attached. Going from the mouth to the shoot it would be slightly tapered so the ball would go to the center and then up the shoot. At the fount of the mouth there would be a big flapper intake that would span the whole intake width. And then all the way up the shoot would be a track that would feed the ball into the launcher. The frame is built out of lexan and churros. The lexan was formed by heating it up on a woodstove and bending it to make a solid piece. The churros have aluminum piping over it to create a idler. With that same aluminum piping we made the big axle that spanned the mouth of our intake and held the latex tubing. Now the latex tubing is what grabbed the ball at the very beginning and centers it for the track to take it to the launcher.
Launcher
We planned to use flywheels because we thought it would give us the ability to shoot from anywhere on the field. And we thought it was the most consistent and fastest system.
We had many issues, first we had problems making the wheels. Second we had problems with the frame holding them.Then we had axle problems where the they would pivot off center causing vibration. We then worked on a flicker design that would allow us to shoot the ball with more accuracy without having to dump the mouth and track system. The system is made out of a lexan piece that is mounted to a motor axle. As it spins, it hits a “primer bar” which aligns it for launch. If you continue to spin it it will whack into the ball, sending it into the air. The whole system can also be moved a servo, which allows us to adjust the angle.
Difficulties
- When you build something in PTC CREO it is extruding and shaping, no cutting was needed. In real life we had to manually cut the aluminum side walls.
- This might seem easy, however it brought us to our second problem.
- We don’t have a lot of tools.
- We used a saw to cut down to the flat part of the side wall, then we bent the aluminum in a clamp so it would break off. And then we took a big aggressive file and filed it down. Granted, there are better ways to do all that, but we have a very limited tool selection.
- Precision
- The most complex tool that we have is a hand drill. It is very difficult to drill precisely with a hand drill.
- We thought that the center vortex base wasn’t flush with the ground.
- We drilled the holes assuming that it was flush, only to find when we assembled our field, that it wasn’t. This is because that part of the mats are cut out on official fields.
- Strength
- Because we were only using one sheet of lexan our base would flex in and out too much.
- Beacons aren’t totally stable
- When you hit the beacon with a flat surface, the beacons rock back and forth with the walls.
- Fitting in the 18” box
- We put bolts on the outside of our robot that stuck out too far, so we had to cut holes in our lexan so we could fit.
- Flexible Walls
- Walls would flex when we tried to capture beacons causing us not get the beacon. We solved this problem by adding aluminum supports.
- Chain comes off
- We don’t have the motor far enough from the sprockets so the chain is slack. We fixed this by moving the motor.
- Bearings warp
- We ordered ball bearings to help our axles to run more smoothly. The problem is that they warp under the pressure, making them run weird. They act “clumpy.”
- Axles don’t fit previous hubs
- The new axles don’t fit, so we have to either drill the hubs, or borrow some new ones.