Wednesday, January 11, 2017

Sketch Model Challenge

MMAE 432 

Our team
Team Name
Group members:
Wojciech Lukaszczyk
Matthew Leahu
Alex Buffo
Wallace Muhammed
Gregory Enriquez
Andrea Agomoh Zimchim

Purpose of this
This exercise was to help everyone get back into the habit of prototyping, building, brainstorming, and overall creating. During this challenge, we were to make vehicles from foam and paper products that were to be used in a dodge ball tournament. The only restriction was that anything not within the category of foam and paper would weigh 30 times more in the overall weight measurement. This affected the outcome because the lighter teams started off closer to the dodge balls placed on the ground. The budget for the entire class was $650, and it was recommended that we do not spend more than $100 on this portion of the class.
We began by first listing some functional requirements that the vehicles should have, which are listed below.

1.  Vehicle must cost under $100
2. Must have a turn radius of at least 10 feet.
3. Must be able to travel at least 3 mph.
4. Needs to be able to support at least 250 pounds.
5. Rider must be able to pick up ball from at least 1 feet away.

Many concepts were created, along with simple ideas that could improve the overall vehicle.

 From this stage, we learned that we can create some very crazy ideas, if the time permits. We also learned that even though you look really cool writing on glass, it is a pain to read off of. We decided to go with the light but effective Chariot Design, similar to that of the Romans.

We started applying our concepts towards making some features. We created a base from cardboard, that was bend into triangular sections. This geometry change affected the moment of inertia, which increased that amount of bending stress required for failure. This small piece was strong enough such that our heaviest member (about 220 lbs) could stand on this without a problem. When applying concentrated loads with his hands, some of the walls began to buckle and bend. From these experiments, we found that stress distribution has to be as equal as possible so that we do not get concentrated stresses. We decided to use this idea as the platform onto which we would sit on, but simply a little larger.

We then decided to use 22 inch diameter wheels made from the pink rigid insulation foam found at home depot. We used 2 inch thick sheets, with two wheels on each side. This meant that our overall wheel thickness was 4 inches. We also added wear rings onto the inner diameter (4 inch paper tube) to give that part the properties of a bearing. The inspiration came from old bronze sleeve bearings that did not have spheres to glide over.

A 3 inch paper tube was then placed in between the two wheels to act as an axle. This axle strength was tested by simply standing on it with increasing load. The tube did not break, but creaks were heard. Because of this, we decided to add another 4 inch tube around the preexisting tube. This would offer more support for the axle. A small interface between the two tubes was placed so that one tube does not roll within the other. The smaller 3 inch tube would extend past the inner surface of the wheel for the rest of the axle. Essentially, this meant that the 4 inch tube was simply reinforcement.

Once the wheel base was set, the rest of the frame had to be put together. At this point the shape of the chariot started to become more apparent. More of the 4 inch paper tubing was used as beams. The geometry was not ideal compared to , let say, an I beam, but it was all that was available. A 4 inch hole saw as used to carve away some of the tube such that the curvature of the perpendicular tube could be fit. The interface was held together with left over silicon caulk. They were further reinforced with band of duct tape to make sure pressure remained while the caulk cured.

A small pink foam rib was added in between the two beams so that a better distribution of stress to the base can be achieved.

Everything was glued and duct taped together. The basic reasoning behind this was that time was short, and we only had to make sure this vehicle lasted for 3 rounds of dodge ball.

We tried riding the chariot to see how fast it can move, and to see if it can handle the muddy, grassy terrain outside.

Finally, we added a crossbar at the front for reinforcement, added washers around the wheels for less friction and less wiggling, and painted paper parts black.

We tested our vehicle during the game. It held but some parts broke with excessive force (there was a race at the end). However, we enjoyed this activity highly.

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