Question over mixed ax12 ax18 use

[TooBarFoo]

I have the PhantomX platform with AX-12s. It going to start getting a high load with additions of a up running high level ROS, Lidar, Various sensors, directional mic array A head / grabber with two AX12s and 2 hobby servos plus lights camera and printed parts hanging out front and finally 4 AW-12W running a roller system to enable a form of wheeled motion for tight spaces.

With all this said budget remains a very big issue and i have the ability to only upgrade one 6 pack of ax-18s. My question is what would be some recommendations for placement of the ax-18s. My first thoughts where to replace all the Femurs to help with total weight load but I am concerned about the extra weight hanging out of the front. Recommendations on best loading the Hex would be very appreciated

Thanks

2BFoo

[jwatte]

The AX-18 are a lot faster than the AX-12, but they are not a LOT higher load capable. A little, but not a lot.
If you actually need to bear load, I'd suggest putting torsion springs around the knees, and hip joints. As long as they help the robot "stand" against gravity when un-powered, they help a lot with overload and power consumption.
I have some pictures for what this can look like (mounted on a Phantom X quad): https://photos.app.goo.gl/kE3zN8sbUrf9uw882
You'd need to make some custom fasteners for the springs -- 3D printing, or CNC aluminum (I used the latter.)
The springs themselves are something like these: https://www.mcmaster.com/#9271k621/=1bi631k

[TooBarFoo]

Thanks for that, Speed is not on my want list so this seems a much better route, Reducing load and resulting heat will help with stability all round and I could play with spring loading to counter the leverage of the weight out front. I also know I will need to tackle power consumption down the line so the wins going down this route just keep piling up. Again, super appreciate the direction. Thx

[jwatte]

Btw: I don't know if the spring I pointed at is the right tension for what you end up using. There are a whole slew available:
https://www.mcmaster.com/#torsion-springs/=1bl2djf
(There are also left-hand and right-hand versions -- useful for mirrored sides of the bot)
Maybe these are the ones I actually used? https://www.mcmaster.com/#9271k272/=1bl2e22

[m3atsauc3]

The AX-18 are a lot faster than the AX-12, but they are not a LOT higher load capable. A little, but not a lot.
If you actually need to bear load, I'd suggest putting torsion springs around the knees, and hip joints. As long as they help the robot "stand" against gravity when un-powered, they help a lot with overload and power consumption.
I have some pictures for what this can look like (mounted on a Phantom X quad): https://photos.app.goo.gl/kE3zN8sbUrf9uw882
You'd need to make some custom fasteners for the springs -- 3D printing, or CNC aluminum (I used the latter.)
The springs themselves are something like these: https://www.mcmaster.com/#9271k621/=1bi631k

That's a very elegant solution to counteracting torques. I've seen something similar with leaf springs, but your idea seems easier to implement. I might have to try it myself as well!

[TooBarFoo]

Thanks for the updated guidance. So I have been playing a bit with spring plate adding downward support to the top of same motor you added springs to. Seemed like it would be easier and while it helps its not ideal so going to follow your route. Also convinced me to take the plunge and finally order a 3d printer so I can print casings. It will be a while before I have anything to show but will be sure to share some images when done