A sit-snowboard is a weight supporting mechanism that allows people with lower extremity impairments to perform the sport of snowboarding. Comfort and control of the Twinrider (the only sit-snowboard on the market) are insufficient for advanced riders who reach higher speeds and ride more bumpy slopes. The goal of this study is to design a sit-snowboarding mechanism that provides sufficient comfort and control for advanced users.

In the new mechanism design (Snowcruiser), vertical suspension is added between the seat and the board using two mountain bike forks. Independent compression of the forks, nose/tail translation of the seat and board flex are allowed. These alterations prevent control interference, visional and vibrational discomfort due to seat tilt, vibrations or shocks on the seat. A continuous interaction of the snowboard with the surface though board flexion and less vibrations on the board also improves control.

With a quantitative test the performance of the new design is evaluated by a straight descent from a bumpy, artificial slope. The prototype carried a dummy weight and the descent is guided by a skier. Using four accelerometers of which two were placed on the board and two on the seat, accelerations were measured. To assess the severity of these vibrations and shocks the standard BS 6841 is used. Vibration Dose Values (VDVs) for the board and the seat are determined after weighting the accelerations to the frequency and direction as described in the standard. Seat tilt and contactless distance were determined using data from high speed cameras. Setting each combination of maximum and minimum height, compression and rebound speed resulted in eight Snowcruiser models. With analysis of the variables, speed dependency is checked and an insight is gained on the behavior of the different combinations of settings. Also a qualitative test is performed in which two riders actually sit in the prototype and slide over hills while turns are made.

The measurements show that the VDVs on the seat are lower for all Snowcruiser models than for the Twinrider, indicating less discomfort. The riders of the qualitative test confirmed this by experiencing a smooth run: No shock is felt when landing after a hill. The Seat Effective Amplitude Transmissibility (S.E.A.T.) is not lower for the Snowcruiser than for the Twinrider, so vibration isolation is not more efficient for the Snowcruiser. However, the Snowcruiser shows reduced accelerations on the board. The Snowcruiser is able to keep the seat horizontal for small inclines. The qualitative test shows that more board flexion is possible. The variable of contactless distance is strongly depending on riding speed, and therefore not a useful variable in this study.

Both tests show that comfort and control are improved for the Snowcruiser and that the goal is achieved. A height of 500mm, maximum compression and fast rebound form the most promising combination of settings. The measurement method presented in this study is a valid method for performance evaluation of comfort and control for a sit-snowboard, using the variables VDV and seat tilt.

Large multi-object spectroscopy telescopes measure the light from millions of stars and galaxies for the use in astronomical studies. One part of these telescopes is the fiber positioner, where a few thousand of optical fibers need to be individually positioned very accurately. The problem with current fiber positioners is the small patrol area, the long production times and the light loss due to the incorrect movement of the tip. The goal of this research is to design a new type of positioner which solves the mentioned problems; large patrol area, fast production and reduction of light loss. The final design is an r-theta design with one rotating motor and a displacement mechanism to move the fiber horizontally over the focal plane. The design is based on the best suitable straight line mechanism from the Reuleaux collection: the Scott-Russell linkage. Flexures are used in the final design. This eliminates backlash and slip-stick effects in therefore improves the accuracy. An experiment with a scale model has been done to show that an exact horizontal positioning with the fiber exactly orthogonal is possible with this design. By adjusting two parameters in the design, the movement and the angle between the horizontal and the fiber can be adjusted. This means an exact movement can be finetuned in order to reduce light loss. The flexure based displacement system is monolithic and can be made by laser cutting. This reduces the production and assembly time of the system drastically. The design meets the patrol area requirement and shows large potential to increase this area up to an estimated 4 times the pitch. In order to validate the remaining requirements of this very promising design, additional experiments with a real scale fully functional prototype is needed.

Prosthetic devices remain inaccessible for many amputees in low-income countries. The lack of trained professionals and resources to fit a prosthetic (interface) are principle reasons. The low cost at which additive manufacturing technology (AM) is able to produce a custom made part could change this. As such, the aim of this study was to design an AM transradial interface specifically for low-income countries. It was decided to adopt the WILMER Open Socket design for AM. The interface was not manufactured in its final form. Instead it was decided to print the interface perfectly flat and reassemble it post-manufacturing for increased print reliability and optimal material properties. Flexible yet durable TPU 95A filament was chosen for this purpose. Reassembling the separate pieces occurred with two different locking mechanisms, which were designed specifically for this purpose. These locks were validates using tensile strength tests. The fully assembled interface was tested as well in two different orientations to validate its strength. In contrast to traditional interface fitting, the new design requires merely anthropomorphic measurements, as the actual surface of the residual limb remains mostly uncovered. This study proposes a different approach to AM prosthetic interface design. The fabrication method has been embraced fully, resulting in a comfortable, visually appealing, and durable design for low-income and challenging settings.