This is a project I've been thinking on for a very long time. Shortly explained this is a sphere shaped hexapod that I plan to give the following features:
- Roll freely like a ball
- Have different sort of locomotion for moving in any direction
- Variable inner-body dimensions
- Transform from a sphere shape into a hexapod and vice versa
- Walk like a hexapod
Before I started to make any exact sketches or started building anything, I shared my ideas with my friend Jeroen Janssen (Xan). We talked about this project when I visited him in Netherlands this summer. At first I was thinking of using a fixed sized inner body with 6 x 4 DOF legs, similar to what I used for the T-Hex hexapod. Another problem was finding a sphere shaped material that I could use. Jeroen and I went to a local toy-shop and I just asked him to look for ball-shaped object. After a little while Jeroen had found a globe! At that moment I got the feeling that using a globe could actually work. After a few months and some searching in different book and toy-shop’s I found a 28cm in diameter globe from Toysrus. It was also cheap and the plastic material seemed to be relative solid (about 3mm thick).
I’m cutting out 12 identical sphere parts. Using a simple handsaw and cutting along the lines of the Longitude every 60 deg. The line of equator was made of 1mm thick dark blue plastic band and was very easy to remove, that resulted in a perfect clean edge too! Here are some pictures of the sphere parts:
The map coating was very easy to peel of. The trick was to preheat the surface carefully and then start in one corner and just peel off the whole layer. To the left is the original part. The middle part has the globe/map layer peeled off and the right part is sanded by hand:
As you can see the material is very transparent, I do have some future ideas of mounting several LED’s for some cool lighting effects.
The principle is very simple. I’m using one digital 5645 servo in the centre of the body, the servo holds two delrin gears.
I’m using 7x of the LPA gear sets from Lynxmotion. One gear with SES holes is mounted to each of the 6 outer body sections.
This construction makes it possible to adjust the body dimension by about x2 using only one servo.
The main reason for making the body like this is to hopefully make some more free space for each leg when the robot are in the walking mode. Even with the increased body size the legs are still going to be highly restricted in free motion caused by the large sphere parts, but I think it will work I've already done some changes to the body section, like replaced the 1,5 mm aluminium parts used on the 6 outer sections to 2mm for more strength and stability. And also some more stuff like an holder for electronics.
There is still a lot of work left and I'm currently working with assembling all the legs. In total there will be 31 servos, 12* 5990 + 19*5645.
I'll post more info when I'm finished with all the legs and have some more and better photos.