# Spring 2017 Mini Pathfinder Size Calculations Update

By: Johnathan Chan (Manufacturing-Chassis)

Intro

The size of the Mini Pathfinder will be determined by the size of the 3DoT board. The chassis should the the minimum size needed to encompass the 3DoT. Since the 3DoT has dimensions of 70mm in length and 35mm in width, we used this as part of the basis of our calculations. The other part of the calculations that we used are from the measurements from the patent drawings.

Calculations

The Sojourner rover patent files were found online and printed out. The drawings were measured and compared to the dimensions of the Sojourner rover found online. The measurements taken from the drawings were very close in proportion to the given dimensions of the Sojourner rover. The length and height of the Sojourner rover is 65cm x 30cm (650mm x 300mm) which gives a ratio of 2.167. The measurements of the drawing gave a length of 139mm and a height of 63mm which gives a ratio of about 2.21. This gives an error of about %2 ( [(2.21-2.167)/2.167] * 100% ≅ %2). Since only the overall dimensions of the Sojourner rover could be found, we used these patent drawings for the basis of our scaling of the electronics box (chassis). Comparing the given length of 650mm to the measured length of 139mm gives a scale of 4.68 for the patent drawings. The electronics box length is measured at 68mm and height at 29mm, this gives a ratio of 2.34. If we apply the ratio above for length to height (2.34), then we get a height of 30mm. So for the total scale factor for our Mini Pathfinder chassis for the length and height will be 4.57. We use the measurements taken from the patent drawings and get a scale factor of 6.87 for the width of the Mini pathfinder from the calculated dimensions.

Figure 1. Patent Image Measured

Using these scale factors, we can determine the size of solar panel we need as well with 560mm/4.57 ≅ 122.5mm for the length and 360mm/6.87 ≅ 52mm for the width. The dimensions for the wheels of the sojourner are 130mm in diameter. Using the scale factor the diameter of the Mini Pathfinder is 130mm/4.57 ≅ 28mm.

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