28" Hexapod-Hybrid Tank with 1/4 Scale Servos

I haven’t put much thought into the foot design but probably something with a small pad so the legs don’t dig into sand and soft dirt. I’m not much concerned about water. I already waterproofed the HS-805’s ad the electronics will be waterproofed as well.

If you have some ideas, I’d love to hear them. :smiley:

You Water profed evrything!!! that’s awsome! I’m like you guys too, I don’t like to build things that has already been build many times exept like I will build the scout just to learn how to make it walk and all and then I will construck another biped, but special… :smiley:

Sam

This version of PowerPod only makes code for the Atom 28. The Pro version will be available later. It will also allow multiple gaits in addition to the alt tripod. Laurent is taking a break from PowerPod to update SEQ, then RIOS, so it may be a little while before the PowerPod Pro will be available. So anyway the main concern I had was that the tibia was longer than 255mm, which would be a show stopper.

The thing about the tip of the foot being aligned vertically with the knee joint. You should build the leg so the tube is inline with the knee servo. As the leg is currently constructed, it would (in my opinion) look silly. There is an option to increase the tibia angle, which sets the foot tip farther out from the knee joint, but it would only make the tibia vertical in the current design. This is ok, but if the leg were redesigned with the tubing placed below the servo, this added tibia angle could be used to make the foot tips farther out at the bottom, making it more aesthetically pleasing to the eye. Man that’s hard to explain. :frowning:

ahhhh, now I understand. You didn’t mean the angle you meant the actual tibia itself had to e mounted directly in line with the knee servo. I get it now. That I can do. I haven’t started on the tibia yet. Tomorrow I will mock one up.

The 805’s are already water-“resistant” with o ring seals on the screw heads and case joints. All I had to do was spear some 100% silicone on the o- rings and replaced the ball bearing assembly on the output shaft with a sealed bearing and added a dab of heavyweight grease to the output shaft and case.

Here is the tibia attached to the elbow. It is 233 mm from elbow pivot to tip of foot. The tibia is attached very rigidly to the servo case itself. How?..It’s a secret. :wink:

Here are some more pictures of the finished leg. Now I just need to round the edges of the brackets and polish/oil them. Then make 5 more legs. There’s a couple pics next to my 209 Scout.

[size=150]Full down:[/size]
http://i138.photobucket.com/albums/q253/gfisher2002/Prototypehexarmwithtibia002.jpg

[size=150]Centered:[/size]
http://i138.photobucket.com/albums/q253/gfisher2002/Prototypehexarmwithtibia001.jpg

[size=150]Full up:[/size]
http://i138.photobucket.com/albums/q253/gfisher2002/Prototypehexarmwithtibia003.jpg

[size=150]Retracted:[/size]
http://i138.photobucket.com/albums/q253/gfisher2002/Prototypehexarmwithtibia004.jpg

[size=150]Next to 209 Scout:[/size]
http://i138.photobucket.com/albums/q253/gfisher2002/Prototypehexarmwithtibia005.jpg
http://i138.photobucket.com/albums/q253/gfisher2002/Prototypehexarmwithtibia006.jpg

That baby is honestly a beast! Keep it away from your 209 Scout, its making it look puny :smiley:

Even W.A.L.T.E.R. isn’t setup like your average rover or other diff drive bot. He does corridors and hall ways pretty well now.

I agree totally! :smiley: That’s why I decided to work towards creating octapods of various types and hybrid bots. I don’t know which aspect of Walk 'N Roll I am looking forward to more - the hardware or software. Both are certainly going to be unique.

8-Dale

yeah, when I have a traked vehicle kit from LM I will try to modifi it later on by adding an arm, then 6 legs drules 8) it’s gonna be awesome but I need moneyy :laughing:

Well, here it is. An almost complete 1/4 Scale Giant Hexapod kit. I have my SSC-32, Botboard and Atom Pro, 14 Cell 8.4V 8000mAh NiMh pack, stand-offs, Carbon Fiber Spacers, Aluminum brackets, Servo Hinge Mounts, 18 X HS-805BB’s, Aluminum tube legs, Servo Power Distribution Panels, 50 ft of HD Servo wire, complete Hardware set, etc.

I’m cutting the first set of templates out for the chassis right now and moulding a few more Servo Hinges.

I can’t wait to get started on it. Making the original sets is so much work, it was nice to just whip up copies of them.

Here are some pics:
http://i138.photobucket.com/albums/q253/gfisher2002/robots/hexhybrid001.jpg

http://i138.photobucket.com/albums/q253/gfisher2002/robots/hexhybrid003.jpg

http://i138.photobucket.com/albums/q253/gfisher2002/robots/hexhybrid002.jpg

And of course, the 30" tank that will be ripped apart to salvage the tracks, idlers, suspension and sprockets. Here is my 209 Scout sitting on it for size reference.

http://i138.photobucket.com/albums/q253/gfisher2002/robots/hexhybrid004.jpg

http://i138.photobucket.com/albums/q253/gfisher2002/robots/hexhybrid006.jpg

http://i138.photobucket.com/albums/q253/gfisher2002/robots/hexhybrid005.jpg

wow… that’s… beatiful good job!!! :laughing:

I’ve been playing with the idea of putting a regular biped foot at the end of each leg for Walk N Roll. However, to do it right I would probably have to add another DOF to each leg for the ankle. With eight legs and four wheels already, that will require a total of exactly 32 servos (excluding the grippers on the front legs for now), I don’t think this would be very workable.

It might work for a hexapod though. :slight_smile: It would make each leg 4DOF instead of 3DOF, but this would still be in the realm of reasonable control, requiring 24 servos for movement if the ankle is made movable.

8-Dale

I think you should do that. :slight_smile: I’m not much of a programmer, remember.

I understand exactly what you’re saying and I can envision what it would look like. It would be helpful for leaning positions. And you could take it one step further and add 4 pressure sensors to the front/back and sides of each fot so that it levels the foot itself on every step to match the angle of the terrain. And add 2 DOF to the ankle. LOL Now we’re talking.

Tell you what, I’ll build the clunky big one that runs on Powerpod and you build the fancy one that actually does cool stuff. :slight_smile: LOL

:laughing:

Well, experience is the best teacher in many ways. Just figure out what you want to do, and what you need to do it and go for it. :smiley: That usually works for me. Keep at it until you get the results you want.

Hmmmm, a 2DOF ankle would give rotation in both directions. Now, that would be an interesting foot. We’d have a 5DOF leg for a hexapod/octapod. Yes, 30 servos to control for a hexapod and 40 servos for an octapod just for the legs. I think this would be better left for a hexapod. :smiley::smiley:

With all this talk, I am starting to want to move right on and start building Walk 'N Roll. I have a good start on the brackets if I take my BRAT apart and I could always fiddle with a hexapod along the way. Hmmmmm, decisions decisions… It would be easy enough to add 2DOF more to each leg.

I think this is what most would call research… :slight_smile:

Uh huh, OK, yeah, that’s what we can do alright. :smiley:

I don’t even know if I am going to be able to power my Walk 'N Roll yet and have it be able to move itself. It might work if I use a single U channel for the body with tubing coming out from that.

8-Dale

Well, I can hook you up with a good deal on a large lipo pack to save weight.
And I can spare some HS-475 servos. What servos were you going to use on the legs?

I’m back to work on another project for a few days so I’ll come back to the Hex later this week, and hopefully get the legs and chassis assembled.

Keep me posted on your progress.

Just as an outside observer, I think you will find that projects like this probably don’t do well when the size and weight are ever increasing. The tank part is pretty straight foward. I think you will encounter serious issues with the hexapod part. With the hexapod, all the component motion is rotational, which may result in the servos eventually fighting each other unless some very advanced programming is done. I don’t have a hexapod, but I bet the small ones operate reasonably well due to some leg slippage with the surface on which they operate. A large scale hexapod on a surface that doesn’t allow the leg to slip some probably will have some issues.

I don’t think the HS-475 servos are going to work for Walk 'N Roll, so I am planning to use at minium HS-645s. Walk 'N Roll is going to be pretty heavy even with a lighter chassis. It’s one of those things where I won’t really know if it will work until I build it and try it out. Right now I am planning to use a 6V or 7.2V 1600 mAH battery pack for each side of an SSC-32 and probably just a 9V for the electronics. I’ll have an SSC-32 for the legs and one for the wheel assemblies.

Right now, I can’t really do much with robotics since my Windows PC died. :frowning: It will probably be a month or two before I can get that fixed if I can find a new socket A motherboard for it - they are getting harder and harder to find. I am exploring options for doing all my robotics stuff under Linux now.

8-Dale

:open_mouth: thats awsome , id calll 911 if i seen that coming thru the yard ,whats the cost so far

I have been thinking about this some more… I think I could use 475’s for the hip horizontal servo, since it would not have to do more than move the leg from side to side - no lifting at all. This would reduce the cost of building the legs a bit.

Then I could use 645’s for the hip vertical and knees which are the only places where lifting is done.

While I am collecting more parts for the legs and SES chassis of Walk 'N Roll I could fiddle with the BRAT. Then I could disassemble the BRAT (do I hear any Johnny 5 fans out there?) when I need the parts for Walk 'N Roll.

How much would you want for some of those 475’s?

8-Dale

If this were true none of the hexapod robots would be able to walk properly. How do you figure the servos would fight each other? Do you mean the servos in the same leg or in different legs fighting each other?

If there is slippage in the legs, there would probably be some jerkiness evident in its movement too. Too much slippage and the hex wouldn’t be able to make good (or any) forward progress. I just don’t see this being true in the hex videos I have watched.

I don’t have and have never built a hexapod either, but I have watched how they walk since I am going to build an octapod, and do understand the basic mechanics of how they work. I just don’t see any evidence of what you are saying.

8-Dale