MorpHex part 3
Posted on 21 February, 2012
MorpHex, finalizing the upper section
When I posted the MorpHex part II video I cheated a little to make the upper sphere sections to operate as intended. The “cheat” was to use some kitchen rubber bands. As you can see from the pictures below the 5990 servo push the upper section out/upward. The rubber-band work like a spring and simply make the sphere section move inward.
As you probably can imagine, this isn’t a very stable solution. Since my goal is to make MorpHex able to roll, the upper sphere sections need some additional support. I’m solving this by making six special brackets.
Some details behind the process of making the brackets:
The brackets are made of PC (Poly Carbonate). They are all handmade and I’m using a band-saw to cut them out. I’m using a simple technique by cutting six at ones:
Using two long 3mm screws for clamping the parts together. By making six in one cut you save time and it’s easier to make several duplicates.
I do wish I had a CNC machine though! It would be so much easier to make even more complex parts. The next step is to mill out a track/slot. I’m using a manual XYZ milling/drilling machine:
A simple table made of rubber coated aluminium holds the parts in place:
I’m using a guidance template of aluminium to hold the PC part in place:
Milling out the guidance track:
So far so good, only 11 more to go..
I didn’t take any photos of the next process. But I had to repeat it one more time to make an additional slot and also make a little part that hold a pair of the main parts together. The final result of the brackets look like this:
The parts are glued together. Mounting the brackets to each sphere section was relative easy. I’m using only one nylon 4mm inset screw for mounting the bracket. As you can see the brackets makes the upper sphere section much more stable and no need for rubber bands:
So far I’m very satisfied with the result. Without even doing any changes to the code I’ve managed to make MorpHex roll! So far the rolling motion is not very controllable, more like a proof of concept. When I’m finished writing the “roll code” I’m sure it will perform much better and hopefully be easier to control in “roll mode” too.
I did spend some time to figure out a good solution for operating the servo power switch. It’s operated using a simple tool for turning it ON. As you also could see in the video turning it OFF was pretty easy.
Close-up of the switch:
I’m using a simple custom tool to operate the switch:
The small hole work as a hook for turning the switch ON:
That’s it for now. I’ll post some pictures of Morphex when its complete.
Then the most exciting part of this project begins..
After my last post I found it necessary to some additional improvements, like strengthen the ribs on the lower sphere sections:
The solution was pretty simple; just a little piece of PC glued to the rib and a 3mm nylon screw for extra strength:
I’ve also done some small changes to the battery holder, relocated the main switch and mounted a plastic band to keep the battery wire as close to the body as possible:
Also pay attention to the main fuse. When dealing with LiPo’s directly connected to the main board its always a good idea to use fuse for limiting the max current in case of an accidental shortcut. In this case we don’t want a great ball of fire..
For replacing a battery I need to remove a 3mm hex screw. Then just slide out the battery and replace it:
The battery is fixed in place by a 3mm hex screw mounted on each end of the bottom plate. I don’t want a loose battery in “rolling mode”..
These two pictures demonstrate the effect of having an expanding body.
Some more pictures of MorpHex in different poses:
Some standing poses:
One of my favorite pose:
Standard pose with closed body:
Standard pose with fully expanded body and upper sphere sections:
In the future I plan to mount about 36 RGB Starlite LED’s as background lighting. The Starlites are made by Basic Micro:
MorpHex video part 3
I’ve just made a new video of MorpHex for demonstrating the rolling feature. One thing you may notice is that MorpHex rolls more or less in a curved direction instead of a straight forward direction. This is caused by the asymmetric design; the upper sphere section vs. the lower section. I’m about to get my hands on some more of those high torque servos and I’m thinking of making MorpHex more symmetrical again. Actually, that was my original plan:
I’ve found a way around the wiring issue but I might want to go for a totally different leg design too. At this moment I’m not sure.
Anyway, here is the new video:
I hope you enjoyed it! I’m also using this video to promote my April contest entry at the Boca Bearings 2012 Innovation Competition. The video with the most votes will be announced winner at the beginning of the following month. Out of all monthly winners the jury of Boca Bearings will select a grant prize winner who will receive $10000 in cash. The two follow up winners will receive their own Makerbot 3D printer.
To be the monthly winner I need your vote.
If you want to see more advanced robots coming out of my hands leave your vote here. Thanks a lot, its highly appreciated!
End of page 3. Go to the MorpHex MKII page to read more about MorpHex.