Quadruped Joint

Hi, I am planning to make a quadruped similar to the one in the link: Quadruped robot 4DOF - YouTube

I am interested in the screws this person has used to fix the joints together with them remaining in their place when the quadruped moves. I have included a picture to indicate the screws I am talking about.

Thank you.

Quadruped screws.png

Look up "shoulder screws" or "shoulder bolts" - one of those is probably what you want.

Here’s the image attached to the top post so others don’t have to download it.

ef4dda7510e43bf0ce604577c11b14efdf7558ce.png

How to insert uploaded images.

The screw itself isn’t what’s allowing the joint to move as it does. A lot depends on the object with which the screw connects.

There are “robot servos” which offer an additional pivot point.

Depending on the construction of the robot, there could be a bearing in the joint.

I’ve seen people drill holes into the bottom of a servo and used the reinforced hole as a pivot.

I used Lego turntables in one of my earlier hexapods. You can kind of see the square shape of the Polymorph used to hold the turntable to the popsicle stick at about 1:12 of this video (the contraption kind of walks in this video).

Depending on the size of the robot, you might not need a second pivot point. There are lots of walking robots which rely on the servo mechanism as the only pivot point of the joint.

Below is the same robot which has the bearings in the joints. Only 6 of the 18 joints have bearings. The other 12 joints rely solely on the servo as a pivot mechanism.

There’s not single system for making these sorts of joints. You’d probably have to find the source of the kit used in the quadruped example to find out what parts were used.

BTW, while quadrupeds have fewer servos, it’s actually easier to program a hexapod than a quadruped. It’s hard to beat the “creapiness” of a quadruped so the extra effort is likely worth it.

Thank you so much! I was searching for other servos like the one in the link but I couldn't find any cheaper ones. Do you have an idea where I can find cheaper servos like the one in the link?

Zbyszek:
Thank you so much! I was searching for other servos like the one in the link but I couldn't find any cheaper ones. Do you have an idea where I can find cheaper servos like the one in the link?

You want one like the HobbyKing servo but for a lower price? I'm not aware of a lower priced robot servo.

I purchase most of my servos from HobbyKing. I've had bad luck purchasing servos from ebay.

I link to a couple of my favorite servos in this post. This thread includes discussion about servos.