A lot had been gained from the initial prototype, and it was now time to apply this knowledge to a new iteration . You may notice that i had skipped prototype iteration MK2 and MK3 as these were transitional prototypes and never got fully 3D printed. These transitional prototypes were generally small updates to main plates and gearing where only a few components would be 3D printed and tested. MK4 was the next full iteration where every single part had been updated and was time for a new 3D printed prototype so lets dive in to some of the changes.
First thing you may notice is the case shape and size. As i had mentioned before the first prototypes are never a thing of beauty as they are more of a proof of mechanical concepts. I wanted to begin sculpting the case into a spaceship and slowly improve upon the design over each iteration. The front lugs extend out similar to the forward mandibles and missile tubes of the Millennium Falcon. the rear lugs taper inwards and are actually tucked into the case as seen below.
This reduces the lug distance to only 44mm making it comfortable for wrists of all sizes. To put this into perspective a 44mm watch usually has a lug distance close to 50mm as the lugs extend out of the case. You'll also notice the rear rocket thruster assembly was added to house a new crown serving as the "afterburner" of the thruster. The crown was modeled after the wheels of a mars rover to continue playing with the spaceship theme of the piece.
Although aesthetically the piece was starting to take shape, the mechanics of the project were still my main focus as prototype MK1 lacked any functionality. The Geneva gear was too loose causing the jump hour display to buckle in certain orientations and not stay properly locked. The same calculations were made to double check my work only to to end up with the same results. I then knew that the 3D printer precision was more likely to blame for such small discrepancies. I widened the slots to the gear to create a "tolerance zone" so that once printed it would be within my desired range. Sure enough when i had finally finished printing Prototype MK4 the Geneva gear issue had been resolved and ran much smoother than the initial prototype. There was still some fine tuning to be done but it was a step in the right direction.
The next issue to tackle was the linear cam path minute system. Prototype MK4 still had many issues with this linear system as the guide would buckle whenever pushed by the camplate. This is all part of the research and development process though as you learn a vast amount from simple prototypes and can apply that knowledge to the next round. I knew that it would take further improvements to develop a new time display mechanism. There were no textbooks to reference, thus the calculations and equations had to be derived by myself. problem solving is one of the most exciting aspects of watchmaking in my opinion. When something has never been done before you are creating a challenge to see whether or not it can be done. As we will soon find out this mechanism was indeed possible, however it required a lot of tuning to get just right.
Above is an image of the linear cam path system for MK1 and below is the system for MK4. The groove drives a small pin under the guide which slides across to steel shafts. The guide (highlighted orange) saw the most change in the overall system as the main issue was its contact with the steel rails. to remedy this i strengthened the component to reduce flexing. Secondly the sleeves which make contact with the rail were also extended. although this may seem counter intuitive in reducing friction, it allows for a more stable glide. What was happening with MK1 was those 4 thin flanges that hold the rail would buckle as soon as the guide was at a slight angle. lengthening the contact surface on the rails allowed the guide to stay parallel with the rails and reduce the angle at which it could deviate.
Another issue that was corrected was the distance between the 2 rails was shortened. the theory behind this is to keep the guide parallel with the rails. For example, imagine doubling the distance between the 2 rails; each time you try to move the guide up, one end can move slightly more than the other deviating from parallel thus causing the part to buckle.
All these changes did improve the mobility of the system to some degree however it was still no where near as smooth as it needed to be. As soon as the Prototype MK4 was printed and assembled i took notes on functionality, issues and how they could potentially be improved. Then it is back to the CAD files on Solidworks and creating the next iterative prototype.