pic: Closeup of top joint and FP motor

[NK2007]

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[Arkorobotics]

How does that little motor take on that torque?

[Cyberguy34000]

How does that little motor take on that torque?

A: Gas shock is mounted near the bottom, and we are talking about mounting a spring on the back. Essentially the arm torque forces are balanced enough that that little motor will just give it small pushes to where we need it.

-Chris

[NK2007]

After doing numerous calculations, theres about 10ft-lbs of torque. This is after the gas shock. In theory, the fisher-price can handle at least 20 ft-lbs, so we shouldn't have a problem.

F.Y.I. The entire manipulator only weighs 13 lbs.

~neill

[eugenebrooks]

Originally Posted by Arkorobotics

How does that little motor take on that torque?

Take a look at the springs...

[NK2007]

Originally Posted by eugenebrooks

Take a look at the springs...

Actually the rear spring isn't connected yet, and with it, the arm is pretty much in equilibrium.

[sonofdad123]

your driver must be pretty skilled or your code's gonna be really good; to use that thing to give small pushes to the arm might prove difficult... especially if its at equilibrium. nice design though!

[=Martin=Taylor=]

What happens if the arm gets hit from the side? Isn't that gonna put a lot of force on that little joint? You might bend the bearbox's output shaft.

[Cyberguy34000]

your driver must be pretty skilled or your code's gonna be really good; to use that thing to give small pushes to the arm might prove difficult... especially if its at equilibrium. nice design though!

It's actually got a potentiometer mounted on the far side of the shaft. The programmers are going to have 3-4 different height positions for us to use. We actually were able to give them the robot for a few days a full 2 weeks before we ship, a fairly amazing feat for us, and they've been able to do quite a bit with that time.

What happens if the arm gets hit from the side? Isn't that gonna put a lot of force on that little joint? You might bend the bearbox's output shaft.

Yeah we're a little concerned about that, more concerned about damaging the potentiometer on the other side though. We're talking about putting some protection on it, but nothing's been quite decided yet.

[vic burg]

You know, jsut a precaution, if your arm is a bit heavy, you might need to make sure that the motor has enough torque to keep the arm from oscillating because of the weight.

Just trying to help out! Since I don't know what the rest of the arm looks like.

[NK2007]

Originally Posted by vic burg

You know, jsut a precaution, if your arm is a bit heavy, you might need to make sure that the motor has enough torque to keep the arm from oscillating because of the weight.

Just trying to help out! Since I don't know what the rest of the arm looks like.

Heres the picture of the entire robot.
http://www.chiefdelphi.com/media/photos/26775?

The overall arm weighs 13 lbs, and as stated above, with the spring and gas shock, the motor requires little torque to move.

Also, to clarify the idea of bending the motor shaft, Im pretty sure it will be really hard to do, as the shaft is 1/2 inch. Notice this is not the small Banebots motor and 36mm gearbox that came with the kit. This is a Fisher price motor paired with a 42mm Banebots gearbox.