Lynxmotion Tech Support

Thanks for your kind words Xan!



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.

_________________
[b]Kåre Halvorsen, Zenta[/b]
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Zenta's blog
http://zentasrobots.com/
Zenta's YouTube channel
http://www.youtube.com/ZentaOlbaid
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Hi,

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...

_________________
[b]Kåre Halvorsen, Zenta[/b]
-----------------------------------------
Zenta's blog
http://zentasrobots.com/
Zenta's YouTube channel
http://www.youtube.com/ZentaOlbaid
-----------------------------------------

sorry to hear it hasnt turned out as expected!

i think the idea for the Femur would be good.

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.

all the best.

_________________
Jonny Poole,
Freelance Concept Art & Animatronics, 3D Art and 3D Modelling, as well as Physical Modelling, Mechanical design, and illustration.
http://www.innerbreed.co.uk/
Create, Innovate, Inspire.

Thanks for your concern Innerbreed!

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.

Any suggestions are welcome!

_________________
[b]Kåre Halvorsen, Zenta[/b]
-----------------------------------------
Zenta's blog
http://zentasrobots.com/
Zenta's YouTube channel
http://www.youtube.com/ZentaOlbaid
-----------------------------------------

I had the same problem using ASB plastic, also found it wobbles under the weight.

whats your thoughts on CNC aluminium tibia/femur parts? would be stronger!

maybe for the femur you could add the injection molded servo hinge and another ABS femur to this, and for the tibia you could double the leg up..

eg...

http://www.lynxmotion.com/images/html/build38b.htm
fig 2/3

_________________
Jonny Poole,
Freelance Concept Art & Animatronics, 3D Art and 3D Modelling, as well as Physical Modelling, Mechanical design, and illustration.
http://www.innerbreed.co.uk/
Create, Innovate, Inspire.

Actually my plan was to double the tibia part since I've an idea for making the FSR sensor. I'll post more info when I've a protype for that.

I don't have any anodoizer kit to dye the aluminium. But I've been thinking of sorta hidding the aluminium part behind the ABS femur

Thanks for your suggestion!

_________________
[b]Kåre Halvorsen, Zenta[/b]
-----------------------------------------
Zenta's blog
http://zentasrobots.com/
Zenta's YouTube channel
http://www.youtube.com/ZentaOlbaid
-----------------------------------------

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!

good luck.

_________________
Jonny Poole,
Freelance Concept Art & Animatronics, 3D Art and 3D Modelling, as well as Physical Modelling, Mechanical design, and illustration.
http://www.innerbreed.co.uk/
Create, Innovate, Inspire.

Thanks for your tip, we do have a sandblaster at work to prep the surface too.

Thanks for your whishes!

_________________
[b]Kåre Halvorsen, Zenta[/b]
-----------------------------------------
Zenta's blog
http://zentasrobots.com/
Zenta's YouTube channel
http://www.youtube.com/ZentaOlbaid
-----------------------------------------

Hi,

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.

_________________
[b]Kåre Halvorsen, Zenta[/b]
-----------------------------------------
Zenta's blog
http://zentasrobots.com/
Zenta's YouTube channel
http://www.youtube.com/ZentaOlbaid
-----------------------------------------

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.

_________________
[b]Kåre Halvorsen, Zenta[/b]
-----------------------------------------
Zenta's blog
http://zentasrobots.com/
Zenta's YouTube channel
http://www.youtube.com/ZentaOlbaid
-----------------------------------------

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.

http://www.lynxmotion.net/phpbb/viewtop ... 2697#32697

Hi,

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.

Enjoy!

_________________
[b]Kåre Halvorsen, Zenta[/b]
-----------------------------------------
Zenta's blog
http://zentasrobots.com/
Zenta's YouTube channel
http://www.youtube.com/ZentaOlbaid
-----------------------------------------

Very impressive, as usual! Keep up the good work!

_________________
Jim Frye, the Robot Guy
http://www.lynxmotion.com
I've always tried to do my best...

THAT IS THE NUTS!
Well done.

even better than i thought.

outstanding work once again.

_________________
Jonny Poole,
Freelance Concept Art & Animatronics, 3D Art and 3D Modelling, as well as Physical Modelling, Mechanical design, and illustration.
http://www.innerbreed.co.uk/
Create, Innovate, Inspire.