I am gay for Molemann 

 by Robin Baessler

ME 250 was a very interesting experience for me.  I transferred to U of M this semester from the ME program at Wayne State.  This is a unique approach of blending design principles to physical machines that I did not see at Wayne State.  Many times you will hear the comment “Well, it looked good on paper”.  In this class we got to experience this on a smaller scale, and learn from smaller failures before we begin to design larger machines out in the industry.  

The design Heuristics was the most fascinating lecture because it forced you to stretch your original ideas and find a way to think outside of the box.  I believe this is an absolutely necessary skill for design engineers to have, and those cards seemed to be an excellent way to strengthen that.  I do think that these design principles should have been covered in more than just one lecture.

Machine shop time was difficult to manage as it got later into the semester.  It is apparent that space is limited and there can only be so many machines in one room.  This said I think it would be beneficial to allow students to start manufacturing their projects sooner, and to keep the extended hours.  Near the end we had to sacrifice precision and use hand tools to get the job done, rather than do things right.

The one complaint that I do have about being the team leader is the lack of information the other team members have regarding the machine shop times.  Although we compiled a group class schedule, so we could easily tell when others were unavailable, it was still clumsy reserving machines.  Since they were unable to see what times were available, it created unnecessary delays and extra communication to figure out who could get on a machine and when.  If the list of reserved times could be public, and only reserving a machine left to the leader that would make the process much smoother.

This class was a very positive experience.  I was able to work with a great group of people, and Joe, and learn from some a group of professors/instructors who are passionate about what they are doing here.  Only kidding Joe, you are in that group as well.  I have felt that the concepts learned in other classes are interesting, but they do not really become exciting until you can find ways to apply them to an actual project and see them in action.  The Ball Tower Game was a great way to combine the theoretical and physical aspects of the ME program.  

The competition I am sure taught all of us a lesson in what parts of the course and our designs we thought were insignificant.  For our group, it was our castors.  Our original ones were smaller and pointed, which caused our vehicle to get stuck in the holes for the balls.  The next revision was made with a larger contact face to prevent us from getting stuck in the holes, but also had a large chamfer to help get over obstructions.  One was also made shorter than the other so the vehicle would be able to rock when driving over the hinge, and still keep the wheels in contact.  Unfortunately for us we did not learn until the semifinals that we did not evaluate every possible way to drive over the hinge as our vehicle got stuck resulting in 3^rd place.  The major lesson that I took from this course is to take extra care in designing and evaluating the smaller things in your design, because they might be the ones to leave you stranded.  

In conclusion I learned that through the power of suggestion, begging, and a little candy, a single GSI successfully got his name as a part of nearly half of the classes projects.  Now I am not really gay for Molemann, but I would definitely not disagree if someone if they said Connor likes the sound of his own name : )

Final Team Documentation!

Final Strategy

For MS10, our machine followed our strategy previously described in the blog post "Revised Strategy and Design". The machine moved from the starting box and then drove to the front of the arena. Our machine used the ball collection  mechanism on the front to collect the black squash balls and yellow ping pong balls by driving along the front edge of the arena. It then dropped the balls into the other team's goal. Finally, the machine either prevented the other team from scoring in their goal or collected ping pong balls from the tower and dropped them into our goal.

Final Machine

Our final machine has three modules. I will go through each module from least important to most important.

Tower Pushing Module

 This module consists of a pushing bar (1/2" square stock aluminum and 1/4" plate aluminum) centered on the backside of the machine and two guides (1/16" plate aluminum) on either side of the machine. These were attached to the chassis with bolts and screws. Our original re-design did not have the pushing bar, but our team soon realized that we needed an extension to reach over the tower's bottom platform and make contact with the tower's side. The guides on either side a bent out slightly to make it easier to position the machine around the tower. During the competition we ended up not using this module because using the ball collecting mechanism was much faster.

Ball Collecting Module

This module consists of the 1/16" plate aluminum which has been bent into the shape shown in the image below. This was attached to the chassis with bolts and screws. Our team selected the shape because it was simple and the box-like shape on the left side of the module would be able to hold the balls and prevent them from rolling out as more balls were collected. The bottom edge of the module is angled downward to keep the black squash balls from getting stuck under the module and keep the balls rolling smoothly. Our team used this module to collect balls when we executed our strategy. During the competition, it was pretty effective in keeping all of the balls as long as the driver did not suddenly stop.

Chassis

Our most critical module was the chassis. The frame of the chassis consisted of the 1/4" plate aluminum.  Each of the four side pieces plus the bottom piece was fastened together with square brackets (made from angle bracket) and screws. The motor (double gear box motor at a gear ratio of 344:1) and two pillow blocks (made from the angle bracket and bearings) were mounted on PVC spacers to align the wheels with the motor correctly. These are fastened onto the bottom plate with screws and washers. We decided to use the double gearbox motor since it was the best choice in terms of making it easier to align the wheels and in getting the right amount of speed and torque. We also added two extra points of contact to the ground at the front and back of the machine to make the chassis more stable and less prone to tipping. These were lathed on the mill from the 3/8" diameter aluminum stock and then fastened with screws and washers. The coupler that connected the motor to the wheels was lathed and milled from the 1/4" diameter steel shaft. Steel was used since steel is very strong and was less likely to bend and cause alignment problems. Finally, we used the laser cutter and the 1/4" acrylic plate to create a top piece for the entire chassis. This acrylic plate is held in place with four dowel pins.

Initially when we were testing the finished machine we had no problems with the chassis. The day before the competition we had a problem with the set screws and the motor axles. We found that the set screw was cutting into the axle. As a result of this, the wheel and the motor axle were not rotating in unison. We replaced the axles with allen wrenches that we cut to the length of the original axles. The allen wrenches were made of a stronger material than the original axles, which prevented any problems with the set screw. After this, our chassis as well as the entire machine, were ready to go for the competition.

Here is a final picture of our machine at the competition:

Team Video

Team Video 

We painted our machine before the competition. The final machine complete with paint job is featured in our team video below:

Machine Completed!

We have finished our machine! Here is a video of Holy Moly! in action:

We plan to paint our machine and then we will be ready for the competition!

To-Do List & Chassis (MCM) Completed!

We have completed out Chassis as well as the motor/coupler/wheel assembly today. We are currently working on making some minor adjustments to align the coupler assembly better. We have also completed the ball collecting module as well as the tower pushing module.

Holy Moly! machine on the ball tower area

Almost completed machine

Right now, we have a few more things to take care of. Below is our To-Do list for the rest of the time before the competition:

• Drill and tap attachment holes for ball collecting module in front of vehicle
• Attach ball collecting module to chassis
• Drill and tap attachment holes for tower pushing module to both sides of vehicle
• Attach tower pushing module to chassis
• Make minor adjustments to motor/coupler/wheel assembly
• Wire motor, battery box, and controls
• Test drive and practice driving vehicle
• Make final adjustments

Finally, our schedule for the rest of the class is below:

Machine Progress

We have completed all of our solid works models and 2D drawings for todays MS assignment, and we are now in the process of manufacturing our MCM, the chassis. Here are some photos of our work so far:

Tapping holes in the side piece

In-Progress assembly of chassis frame

Assembled chassis frame

We have also completed the coupler and the motor spacer, which are not shown in the photos above. We are nearly done with the chassis, and we are preparing to start manufacturing our last two modules. One will be a ball collection attachment on the front, and the second will be a tower pushing attachment on the back. Our machine will have a big advantage in the ball tower game since our machine is very adaptable to different strategies. 

Revised Strategy and Design

          The revised strategy involves very minimal movement.  First, we drive past the wave field after there is enough clearance for the machine to drive past.  We may have to delay up to 8 seconds to allow for this clearance.  Then we will drive straight along the edge and gather all possible balls on the front of the table.  Then we will deposit the balls into the opponent's goal and sit there and block it.  The maximum points we can earn from this move is 96 points, while giving the opponent 10 points.  Still, the point differential will be great enough to win.  As a back up plan, the machine will also be able to push the tower by going in reverse. 

 



          The revised design uses only the dual motor/gearbox as far as the motors go.  Having only one motor reduces the risk of failure.  The front arm will collect balls on the front edge of the table without being very close to the edge of the table.  This reduces the risk of falling off of the table.  The front of the machine will hold the balls using a passive approach, but with minimal movement, the balls will not ever have a chance to leave the containment.  We also are going to have a ball caster at each corner for stability and wide tires to increase traction.  The rear will consist of a U-shaped device to push the tower in case of failure or if a similar strategy is being used by the opponent.