So far I’ve not connected them to any sensors yet, thats more for a future project, I just didn’t want to do much extra wiring work later. I’ve some ideas for sensor solution but have to try out some prototypes first.
I didn’t plan to do that, it is possible by using larger cover though. But I wanted easy access to both serial connectors for SSC and BB2 board, and the three switches.
A-pod walked for his first time yesterday, so far with no control of the abdomen and head, more just for testing the calibrations. But to be honest I’m not 100% satisfied of how A-pod performed. Since I started this project I’ve been thinking if this leg construction is stable enough? I’m thinking of the single femur joint where only the servo axis are supporting the weight combined with the more flexible (than aluminium) ABS plastic. This worked fine for my original Phoenix, but A-pod has about 1 kg greater mass.
So I’ve been thinking of reinforcing the legs by using an additional femur part combined with the injection molded servo hinge. The two femur parts also have to be fixed together using some spacers. I think this will make the construction much stronger and most of all more stable. At this point A-pod tends to wobble a bit while walking (not much, but enough to irritate me ). Body translation and rotation works fine though.
At this moment I’m a bit unsure what to do, but some reinforcements are necessary…
i too had thoughts about if the legs were stable enough but i have every bit of faith in your work so you will fix this problem, or set back.
i to am working on Femur parts for my stalker project and they come in two parts. its a nightmare trying to get it to look right, especially as i am adding a vacuum formed shell. just cant get the internal structure right.
I’m pretty sure we are going to solve this. Instead of using the molded hinges I might go for the ASB-04 too, I thought they wouldn’t fit but I’m trying to find a way around it. Another hybrid?
The main problem is the rather flexible ABS plastic material combined with the slack from the servo axis/joint.
if you prep the surface right using a base/primer then use an undercoat (spray) then use a rubberised paint (usually used in industrial application) this will keep it from scratching, or pealing.
the idea of hiding the A inside the plastics not bad. try it!
I’ve decided what to do about A-pod.
I’m going to use an additional femur part on the opposite side.
I’ve already made one prototype and it didn’t look to bad either. But the best part is that the leg became much more stable. I was really surprised for how much stable it became. I did made some femur part of aluminium but the additional femur part made of ABS was more than enough to make it stable. And by double the tibia’s in the future will make it even more stable. For the prototype I used ASB-04 brackets on the femur and tibia servo, but finaly I’m going to use the molded hinges.
Now I’ve to order some parts before I can finish it.
You might want to look at some of the airplane building techniques for making strong and light components. To keep the plastic from flexing, you might consider bracing each outside of the leg part with something that doesn’t stretch easily. You might bond a thin piece of aluminum (like from the side of a drink can) to each side of the leg part. When the bending force is being controlled on the outside of the leg part, the inside of the leg part can then be lightned.
Thanks for your tip zoomkat! The other major advantage of using an additional femur part on the other side is that the slack from the servo joint/axis are almost completely removed too.
Below is a simple experiment I did to add a support on a servo opposite to the servo horn. It would add stability to long heavy sections operated by the servo and limit stress on the servo horn. The bearing setup is the best for low friction and the “pro” look on a bot. That being said, a certain amount of flexing can help reduce stress on critical parts.
Finaly, today I managed to make a little video of A-pod. The original sound had some glitches so I needed to replace the soundtrack in youtube. I’m not done with all the mechanical improvements for the legs yet, but the body movement and head control work fine (therefore very little walking). I’m still playing with the code. I’ve also rebuilt the abdomen joint, the low profile servo didn’t manage the panning function so its replaced with a 645.
I’ll post more pictures when I’m done with the legs.
Thanks to you all for your comments about the video!
Highly appreciated!
I forgot to mention that I also moved the two LiPo regulators from the Abdomen to the center of body. I did that mainly for moving the COG just a little bit and for making the abdomen a little smaller.
I really hate to clutter up your awesome topic, but I’m a definite fan of this project (yet another one). That vid is very very cool. Thanks for sharing. I’m looking forward to whatever else you do with it.
That is a truly awesome robot!
this may sound kind of stupid, but i think you should stage an epic battle between Phoenix and A-Pod (It would be close, but i think A-Pod should win)