Spring 2016 3DoT Goliath, Body Redesign

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By: Jerry Lui (Manufacturing Engineer)

 

This blog post is to address the redesign of the body to meet the following specific requirements:

  • Print time under 6 hours
  • Scaled model of the Goliath tank
  • Phone and components must fit within the body
  • Sensors must be at a height of 3 inches

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To meet the requirement of printing under 6 hours, a major redesign of the body had to be done.

 

To cut down on the print time, prefabricated Tamiya wheels and tracks were used.

 

https://www.pololu.com/product/106

 

Parts of the body were removed and replaced with thin trusses to help with the stability of the body.

 

The printer supplied by Professor Hill was lacking around 0.5’’ to properly print the base and top in one go so I had to split the parts within Solidworks to 2 parts.

 

The height of the sensors and emitters was set to that it was exactly at 3 inches (+/- 0.01inches due to the PLA shrinking and expanding from the print)

 

The body was printed with a 25% fill density, x1.2 wall thickness (typically x0.8 and x1.2 and always a factor of 0.4), and at a speed of 40mm/s. The print time was barely affected when changed to 0.8 so I opted to add slightly more rigidity to the body this way.

 

The body’s dimensions are essentially scaled down to the width of my Galaxy S4 phone (also held on by a ledge within the body) but it couldn’t have been an exact replica of the Goliath tank due to the print time requirement. There just wasn’t enough time to print all of the side panels and bolts while fitting the phone within the body of the rover.

 

The total print time came out to around 5hr 57minutes.

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Conclusion

The redesign has met all but one requirement partially (scaled model). The model has the general shape of the tank but is lacking the panels and bolts.

 

Sources

 

https://www.pololu.com/product/106