One of the conclusions from the last prototype was that we need a gearing in order to lift more weight than just the arms.

As per TA-recommendation, Tuesday we got our hands on some LEGO Technic. With the LEGO-parts we built a few different “gear boxes” to try out. They had different gearing and different placement of the motor axle, vertical or horizontal.

Prototype Planner LEGO Gearing‍

During the testing, we spent a lot of time constantly improving the earlier 3D-printed prototype with arms and string. We added LEGO-adaptors, a splint and glued some of the parts in place. Before we made these improvements the force from the motor was not adequately transferred to lifting the arms.

When the necessary improvements were in place, we could evaluate if the gearing brought value to the product, and if so which one. One of the gear boxes stood out. It was smaller than the rest, and had a larger gearing, approximately 40:1. It simply consisted of a spindle and large gear. This one was able to lift the greatest weight attached to the arms. It still did not entirely meet our final goal for lifting weight, but nearly. We believe that in order to reach the final goal (how heavy we think the petals will be) we need to make other changes to the prototype than increasing the gearing.

We think one of these other changes could be to attach the string further out on the arms. This will decrease the load on the rotating axle. Also, if the string is longer the disc will need to rotate further. We hope this will give a smoother movement of the arms. Right now, the movement is a bit jacky because the string sometimes gets a bit stuck.

Another improvement could be to change the power supply from 5V to 12V, the maximum the motor can be supplied with.

Next up: Overnight print of new and longer arms and a new base plate for the longer arms. We will also need to print a new rotating disc as we managed to break the old one during testing. We can also implement some minor improvements in these new printed parts.

Tomorrow we will also work on implementing some micro switches that constrain the disc from rotating too far in case the motor jams since the motor is not self indexing on its own.