Need help raising arm.

We have built a robot with the trax system to gather up the cylinders and balls for gateway competition. It seems like with those items we can not raise the arm. I attatch a picture of the setup we have. Is there a way to get the arms raised by a different method? I went with the sprockets and heavy duty chain b/c it seem more reliable than just the two little gears driving another gear that raised and lowered the arm. Can someone please help us by giving us tips or advice.

Thank you,

The usual solutions are

  • Elastic to lift the deadweight of the arm, so all the motor needs to lift is the carg
  • higher gear ratio
    – use a smaller sprocket on the bottom
    – or change the top sprocket to a large gear,
    powered by a small gear on the same shaft as a large sprocket, powered by your existing chain.
    – or use a linear slider rack gear to push your arm up, rather than rotate it from the joint.
  • more motors

Its hard to separate intrinsic reliability from craftsmanship tradeoffs.
With lots of experience, you can build up your intuition about the build culture you are in,
but it may not apply to another culture.
Around here, lots of people are able to build reliable gear powered arms, and this is the second forum report of low performance with chain driven arms.

Elastic lift: Are you talking about like a rubber band or bungee type cord that ties on to the arms and to the bottom to help it raise and prevent from just falling?

The sprocket on bottom is my smallets I have ;( What do you mean by higher gear ratio? I am new to this.

What is a linear slider rack? Sorr I am asking so many questions to your solution.

Thank you in advance.

My team uses a similar design. Attached is a picture of our design. All of the gears are high strength.

You could also add another motor.

tutman 96… We had a similiar design before I changed to chain driven… Kept having the gears slip… But also b/c I had small gears on the bottom not big gears… That might help!!! I might have to go to the orginal idea… Where would you put your motors? Did you have one powering all that?I mean one for each arm, or did you have 2-3 on each side?

Your arm is geared much too fast. Here’s a pic of “classic” VEX arm gearing – a 12-tooth gear driving an 84-tooth gear bolted to an arm. The robot in this picture uses latex as a “counterweight” and lifts the arm with a single 3-wire motor.

This was built before the 12-tooth steel pinion gears were available (you can just see a red 12-tooth VEXplorer gear in the pic) and the 84-tooth gears were doubled-up.

Well I ditched the chain and went back to the good ol gear system like you showed me… Success!

I have 2 per side on the 12 tooth gear