Here are some rough pictures of the first brackets for the arm. They are just rough examples and haven’t been finished yet. I’m just testing the torque and geometry of the pieces.
The arm gives 6.4 lb (102.4 oz) of vertical push at the tip of the elbow. So in theory, any 3 arms, in a tripod gait, can lift a 19.2 lb(307.2oz) payload. And all 6 could lift 38.4 pounds but that would be pointless since only 3 lift in a gait. Unless I used a different gait but I’m not.
Each arm weights 1.5 pounds so that’s a total of 9 pounds in arms. That leaves and absolute maximum weight of 10 pounds for the chassis, tracks and drive train . Not alot but I think I can do it. I plan to lighten the arm brackets by cutting lightening holes into them so that will reduce weight considerably per arm. And I’ll be running a large lipo pack to save weight.
Thanks guys. I did some more work on the Models. Included the pan and tilt with standard servos and lights as well as the 2 airsoft guns pulled from toy tanks with laser pointers. The 2 guns, camera and servos/brackets only add 1.2 pounds.
And a scale pic next to a human for size reference.
These conceptual drawings are awesome but there are some limitations to the Atom28/SSC-32 control. The main thing is there is a 255mm limit to the length of any of the leg properties. Not sure if it’s too big from looking at the images, but the length of the tibia looks to be the longest part. If it’s shorter than 255mm then you’re in. It would be a shame not to be able to use the 3DOF programming that is tried, tested, and well just totally awesome.
The other design concern is, the tip of the foot needs to be directly below the knee axis. With the servos centered the foot to knee points should be aligned vertically, and the knee to hip should be aligned horizontally.
The PowerPod (free) PC program can create the Basic Atom 28 program for an inline 3DOF hexapod too. It’s not just limited to the round ones. It’s basically a plug and play hexapod operating system. lynxmotion.com/Category.aspx?CategoryID=15
im just rhowing it out there, but 1) coolabitlity 2) mobilaty
now the tracks are great for cruising around and conserving enrgy, and then the legs can fols out and get him over, lets say, some gravel that the tracks cant handle, or with the right foot, sand maybe jk, sand would break everything, but it could get him through 2-3 inches of water by the size of those legs, maybe even more
The Tibia can be 250mm, that should work fine. Maybe less. I haven’t made the tibias yet because i’m waiting on some idlers and sprockets before I start the chassis. My main concern was the legs themselves. I wanted to be sure the servos would provide enough power to operate as a hexapod with a moderate payload. And so far, they seem more than up to the task.
I plan to use the powerpod software. But can it create Atom Pro 28 code?
The centered positions will have the leg segments vertical and horizontal at center. It is kind of crouching in the model.
EDIT: ohh, I see what you’re saying now. If my servos are centered at the vertical and horizontal positions, the elbow and hip won’t be able to rotate far enough to retract on top. And I was thinking that I could offset the center position to use all of the 180deg to allow the tibia and fibula to rotate on top. hmmmmmm… Is there no way to offset the program to readjust the Signal for center?
Form over function?? What can I say…yup.
In reality, hydraulic arms on a real tank is not only beyond the current hydraulic technology but also impractical. A tank can go just about anywhere, and the only reason it would need arms, would be to cross very deep water crossings or to transverse large boulders.
At this scale. Well, have you seen a 2 foot long tank with 6 arms?..Didn’t think so.
I’m not a programming whiz like alot of you guys, but I love to build stuff. And I tend to build only uncommon and custom things. All my planes, helis, trucks hovercraft, are all huge and different from anything I’ve come across. I don’t see much point in building something that 100 other people have, unless it’s for educating yourself or cause you really want it. Most of my projects are for fun. For the wow factor and to sit back afterwards, look at the finished project and say, now that’s something I’ve never seen before. My hobbies keep me sane. My job keeps me crazy. So I get bored with the same things all the time. I like to mix it up.
im the same way evolution, not very good at programming, but i like to think out of the box when it comes to mechanical designs
btw, were u planning on putting a special type of foot onto the hex? instead of just a rod? cause i, without any thought, was able to come up with some ideas that would work well, you could probably too, and make to too with some…stuff