View Full Version : Push/Pull rods

02-16-2011, 11:40 PM
I have been thinking a lot about robot design's lately and was wondering why I haven't seen more push/pull rods. My first thought is that it makes the design more complicated, but I wanted to post and see if anyone else has any thoughts.


02-17-2011, 05:35 PM
By push/pull rods do you mean linear actuators? Like these http://www.trossenrobotics.com/linear-actuators.aspx

Sorry if I'm way off I'v just never heard that term before.

02-18-2011, 01:19 AM

Look for this text: "Focus Shot10(RCE-BL100G 100A Brushless ESC(Governer Mode))"

Its in the third row left side image. This is a shot of a push pull setup for servo's on a RC Helicopter.

The idea, in general is that the servo is not located at the point of rotation but off-set and uses rods to push and pull, creating a lever like machine.

This would allow for more torque to be applied from the same servo then the servo can produce otherwise, but makes for a more complicated mechanism.

I want to make a CAD model to show what I mean, but I'm not quite there with solid works yet :*)

Does that help explain what I mean?


02-18-2011, 09:36 AM
I believe those are called ball links. I am working on a project that uses them but I haven't determined if they will work for my application.

02-18-2011, 09:39 AM
It has ball links on it, but I believe the name for the mechanism itself is a bellcrank.

02-19-2011, 06:24 AM
sthmck - looking forward to hearing from you if they worked.

Anyone else use them or try to use them?


02-20-2011, 04:28 PM
I believe Gdubb uses them on his turrets tilt mechanism. I wanted to use them on mine but it didn't fit well into my current design.

02-20-2011, 04:47 PM
I use a lever with a single connecting rod for my turret elevate. It was done that way to make the mechanism lower. I tried a lever lash up on Bhekas legs, but it proved to be a bad idea. The mechanical advantage was nice, but my design for the levers was very weak and didn't hold up. So went with stronger servos. There are some pictures in my gallery.