The standard form-factor Hitec HS-422 servos are approximately 1.50(l) x 0.75(w) x 1.50(h) inches, are easily modified for full-rotation use, and have loads of torque - far more than you would need for something that size. Placing two of them back-to-back gives you an easily-controllable gearmotor pair that measures a little less than 3.50 inches wide, with 1.50- and 0.75-inch dimensions in length and height, depending on how you orient the pair of servos.
If you’re set on building a base with treads, you can get tracks that mesh with drive sprockets made specifically to mount on servo horns, or the output shafts themselves.
You’re telling us little bits and pieces about what you’re trying to accomplish, but we can only help so much without details. Measurements and an accurate description of the treads you are planning to use would be good. Photos would be better yet. Photos and measurements would be great.
In the interest of pictures being worth 1024 words , I’ve got a set of photos of the dissection of one of those little B-8 micro servos. I can send the photo links to anyone who would like to check them out, or if there is interest, I can post them to a new thread in the General Electronics forum.
I just thought of something. Buy two of the 14.00$$ motors from LM (the one’s chunga suggested) and solder them into pairs to give your ROver bot some more Humph to move all of the onboard components. If you really want it to be sophisticated 4WD is a must
Looking at the same gearbox from different sources, they list it as being 75 x 24 x 34mm (2.95 x 0.95 x 1.33 inches). That 3-inch measurement may bust the form-factor that he’s trying to stay within (stated: “at least 2/4” hight X 4" in length"), if he tries to use two of them. Still, with treads, you only really need to drive one end, and the power is transmitted over the entire track’s length. Depending on how he assembles them, he can probably get enough torque to drive the thing using just one gearbox. After all, the way it’s being described, it just sounds like a tracked base, camera, pan-tilt platform, receiver, and a battery to supply the electrons for it all. It probably shouldn’t require all that much power to move it around.
Still, without more information on the treads and/or construction he’s planning to use, it’s hard to really know what will suffice, what won’t, and what would be overkill.
id have to agree with you there, im pretty sure that one gear box would suffice as lone as he made the tracks meash fine and they line up right so that the tracks are straight
Good luck on converting those B-8 servos to full rotation - I get the feeling that you’re going to need it. As I said before, it may be possible to do it, but I wouldn’t advise trying to do it.
You stated before that you wanted the total length to be maybe 4 inches.
Two Hitec HS-422 servos laid end-to-end come to around 4.2 inches, including the mounting tabs - maybe 3.2 if you were to cut them off and mount the servos some other way. HS-422s would give you a lot more torque, a much more robust drivetrain, and are FAR easier to convert to full-rotation than the B-8 servos will be.
Then again, it’s your project.
You asked us for advice, and a number of us have given it to you, in the interest of helping you to achieve your goals and minimize your frustrations.
What you choose to do with it is your decision.
You’ll be sadly disappointed. Aside from the fact that you’ve been informed they are difficult to convert, they will be lacking in power to drive your tracks. The guys here are right. Listen to their advice. Just because you don’t have a part, doesn’t mean you can substitute it with anything you have on hand.
LOL. You are asking me if I read the last post. I doubt I’m the only one that sees the irony in that. I commented on using the 8gram servos because you gave the impression you didn’t want to remove the 422’s from your other project (unless I misunderstood the devil smiley and !!!'s). You’ve proven that regardless of what you say you are doing, you may do something totally different from one minute to the next. Even if it is something you were advised not to do. I was assuming you would try to use the 8 gram servos anyways. If I was wrong, I apologize.
well its a simple project just like the EH-1
it only uses three servos
the reason why im doing this project is to
get better at working with aluminum
thats right he hexpodis going to be made out of aluminum
its going to have a small pan and tilt on it
its going to be controlled by a ps2 controller
and the hexpod is not going to be micro
just a reguler old sized hexpod
, I’ve got a set of photos of the dissection of one of those little B-8 micro servos. I can send the photo links to anyone who would like to check them out, or if there is interest, I can post them to a new thread in the General Electronics forum.
Im affraid I lost count 
