During this time, I have watched some beneficial videos such as 

AT自动变速箱是怎么工作的？传动原理讲解 How Automatic Transmission works?

详解AT自动变速箱控制工作原理，理论结合实战  How automatic transmission hydraulic control system works

自动变速器第7课，教你如何看懂动力传递图！_哔哩哔哩_bilibili

6AT行星齿轮组变速箱模型，换挡逻辑一目了然，可能得两目_哔哩哔哩_bilibili

On the last video on the list, the creator designed and made a 6-speed planetary gearset that ran smoothly and was selling it on Taobao, and I wanted to buy and take some inspiration from it; however, they don’t ship it to the UK. Fortunately, he had a video showing an assembly drawing, so I could ‘sneak peek’ at the mechanisms after some screenshots and adjustments.

Due to the poor quality of the picture, I did not understand how every component was connected, and the semester has started then, I left this project for a while 

Nearly a month later, I started thinking about it again and rewatched this video https://youtu.be/d6aRw_FuxYM   and looked at that sneak peek again; I suddenly realised how they connected the first carrier to the second sun or ring gear and clutched them at the same time. I then tried to draw a cross-section of the gearset and finalised this design. 

I thought it was finally the success time, but I was so wrong, here was the problem, 

1. I did not consider enough tolerances in my design and set the gear backlashes to 0

2. Due to the small scale, the pink tube and the blue tube connecting the drive were not strong enough, which resulted in breaking when I tried to take the support structure out.

3. I printed every component in one piece; therefore, I could not assemble the planetary gears to the carrier.

It was a colossal fail, but I have learned a lot from it. 

The IForge was running low on filaments at the time, so I started to familiarise myself with the laser cutting machine. I had an idea of only using a laser cutting machine and stacking them together layer by layer since it is much more precise and quicker than the 3d printers, and it would be easier to assemble them.

Video blogger (核桃车间) has made his own 3d printed 6 speed planetary gearset model and was sold online, therefore I purchased his components and assemled myself. During the assembly, I have gotten so many inspirations from him, such as modular components, use of bearings, carbon fibre tube, clutch and connection designs. 

so finally my second and third iteration was manufacturable and able to be put together and testing