My group for a Robotics class ordered a turntable and attached it to my robot… but the turntable arm is too heavy and makes our robot fall over! Is there any way that we could counterweight it???
Sounds like you are on the right track with the need for a counterweight. I’m sure you can think of a number of things to use. Often, students will use plate steel stock from Vex for competitions. You will probably want to mount the counterweight on the turntable opposite to your load.
Here is a link that might help you: Calculate Counterbalance Weights
I am not sure if this answers your question. You may want to provide more information if not
We tried to use fishing wire but that kinda defeats the purpose of a turntable… What we currently have is a small steel plate bolted to the turntable and then basically the clawbot arm (picture to show)
Here is a crude drawing based on what I think your are saying. The blue disc is the turntable. My suggestion is to extend the length of the arm c-channel and mount your weight on the back so it balances the load on the claw.
You are mostly correct besides that the two bars that are on the turntable are about as long or longer than the bar the the claw is on… Also what kinds weight should I put on the extended bar?
You can use whatever you want if this is outside of the bounds of formal competition - some sort of dense metal. In competition we typically use the steel plates as mentioned above and stack them as needed.
@AllisonRobot, the more preferable way would be to avoid any additional counterweights and, instead, move the turntable such that the weight of the back and the front of the arm assembly naturally balance above the turntable center:
This way you minimize amount of torque passing through the turntable, which will make it easier to turn.
You may also want to add some rubber bands to your four bar (shown as squiggly line). This will reduce the load on the lift motor as well.
Turntables are used in heavy industrial machinery like cranes and excavators because it is not easy for those to turn precisely on the spot with their treads, traction wheels or outriggers.
However, with omni wheels available for the vex robots, turntables are generally not necessary, because omni wheel based holonomic drive could turn on the spot easily and precisely.
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@technik3k Ya that seems like a better way. I will try that with my robot and update you both.