Arm control

Arm is too heavy for the 2 motors to bring up the cone and stack it on the mobile cone in the back. It comes up with great difficulty and then bangs down when going back down due to weight. What are the possible solutions ? Rubber bands is one way, but we are yet to device a good way of handling. Can you share how you overcame this problem with rubber bands and Any other ideas ?

Post a picture of your arm, please, so people can help.

First of all a picture would be great and for a simple fix if it isn’t aluminum, switch be cause that saves a lot of weight. Another thing is take off extra pieces that aren’t really needed. Also if you can, add more motors because two motors can be done, but it’s more efficient with four.

Here are the pics of the arm and robot. We are using aluminium parts. Thanks in advance.

Make sure the motors aren’t fighting eachother. Try switching the polarities of one and see if it works after. Another thing, make sure you have bearing flats on everything. It does seem like it should be able to raise the lift correctly but I would recommend some form of elastics to aid the lift.

Hopefully this helps :slight_smile:

  • [TVA] Delta III

I don’t know if you did this just for the pictures, but the motor on the right isn’t driving anything. There is no shaft in it. Your arm is being driven by only one motor. If you put a shaft into the right and left motors and add gears to connect them to the gears on the arm, then it will work much better.

Additionally, the gear ratio does not provide a lot of torque, or rotational force, because you are using a medium sized (36 tooth) gear on the motor shaft and a large (84 tooth) gear on the arm. For the most torque, you want a small gear (12 tooth) on the motor shaft and a large gear (84 tooth) on the arm. I would recommend changing the gear on the motor shaft to a 12 tooth gear, which means you have to take off the motors and move them up a few holes so the gears mesh.

And, just so you are aware, all of the metal looks like steel to me.

I’m going to assume that you just hadn’t finished putting the gears on the motor on the left when you took the picture (if not you should do that). The gear ratio is definitely too aggressive for only 2 motors and a steel arm. I would switch to a 1:7 with the 12 tooth pinion gears as @Bryan R suggested. Ask if you don’t understand how to do that.

After doing the above, if it still doesn’t work, add two more motors (so 4 total) and then add rubber bands.

Thank you for your suggestions. It seems the kids had taken off the right gear to work on something.
But we will switch to a better gear ratio.

As I said, it was getting up with difficulty, but while coming back it comes with a BANG. Hopefully the drop will get better with a better gear ratio ?

hi bye

A better gear ratio will help, as will using latex or rubber bands to take some weight off the motors. The last trick is to limit motor power in the down direction. The robot we built here last week uses 100% power upwards, but only 25% down.

Absolutely add bearing blocks to everywhere a shaft passes through structure. It will help a lot.