Blog - August 2010
Today, we were able to bring all of the parts of the design together into one completed robot design.
We will be taking a short break from the build of the robot as school starts up again and will resume again during the first week of September.
Today, we went through and designed the superstructure frame that would hold the robot together. We started by looking at our objectives for the superstructure:
- The superstructure needs to support the revolver and the valve block.
- The superstructure needs to support the SCUBA tanks.
- The superstructure should hold the battery.
We took our design objectives and decided that building a frame out of 1/2″ aluminum plate would allow us to build a very strong and light frame. We designed several interlocking 1/2″ aluminum plates which will be welded to form the superstructure chassis. The frame will contain cradles to contain the SCUBA tanks as well as bars that will close down on top of the tanks to lock them in place.
Today, we focused on the design of the electronics board, trying to get the board finalized. We spent some time physically laying out the electronics, trying to find the best configuration to optimize our wire paths. Also, we worked extensively on the design of the baseplate to which the electronics mount, finishing its design.
All of the electronics for this robot are made by VEX Robotics, taken from both the VEX Design System and the VEXPro line.
The design for the T-Shirt Cannon is coming along great. Today, one group of students started working on a preliminary version of the baseplate that will be used to mount the robot’s electronics.
Another group of students continued to work on the robot’s superstructure, starting to design a block that will serve as the mounting point for the revolver as well as the interface between the air hose and the revolver. Part of this endeavor was to design an indexing mechanism. The mechanism envisioned will have a lever with a bearing on the end that will roll into a slot on the revolver to lock it in place.
The design for the drivebase is coming along great. The frame members are mostly modeled and we have started to create the baseplate to which the electronics will mount.
Today, a separate team broke away from the drivetrain team and started to model the superstructure. We started with the revolver, modeling a ten-barreled revolver with ten aluminum tube barrels connected with two aluminum plates. The assembly will be welded.
Today, we continued to work on the conceptual design of the robot. Some ideas we had:
- It is necessary for the robot to be relatively narrow (<30″) so that it can fit through a standard doorway. We do not have any real restrictions on the length and height of the robot, but to keep it relatively manageable, we intend to keep it under 42″ long.
- If we moved the drive gearboxes from the center wheels to the back wheels, we could potentially move the scuba tanks lower to the ground and make the whole robot more compact.
Today, we started to wrap up the research phase of our project. Some stuff we have learned:
- We found a valve that seems to meet our needs and is in our price range. We plan to move forward with the purchase of this valve. The valve is manufactured by MAC Valves.
- Finding a regulator to regulate the 3000psi air from the scuba tank to working pressure could be expensive.
- We decided that indexing the barrels to line up with the hose will be difficult. We are not sure if a seal will be needed at this connection and we think that it will be important that the revolver is locked in place before the robot shoots. To accomplish this, we will need some sort of indexing mechanism. It seems that indexing will be easier with the revolver than with the linear magazine, so we will start looking more seriously at the revolver.
- We could manufacture a block to interface between the hose (coming from the scuba tank) and the barrels.
- If we place the two SCUBA tanks flat directly above the drivebase, we will be able to keep the robot compact and low to the ground.
Today, we discussed some of the results of our research and started to talk about general design. Some of the things we have learned through our research are as follows:
- To shoot multiple T-Shirts, the best solution seems to be having multiple barrels rather than trying to build a mechanism to reload a single barrel.
- High speed solenoid valves are expensive and it will be difficult to find one that will fit our requirements while staying in our price range.
- Every robot we’ve seen that launches T-Shirts from multiple barrels has one valve on each barrel. We’d like to try to avoid this to cut down on cost.
- Many T-Shirt shooting robots we’ve seen in the past have used PVC piping and/or PVC sprinkler valves. PVC is not rated for pressurized gas and is extremely dangerous when used for gas storage.
- SCUBA tanks seem to be a relatively easy method of air storage. They can safely hold extremely high pressure air and can be filled inexpensively at many SCUBA stores.
- If we can re-use some of the drivetrain parts from past robots, we can save money and reduce the cost of the project.
- The two choices for barrel design seem to be either a rotating revolver or a linear magazine.
- If the robot has large wheels, it may be easier to traverse large obstacles.