4194B Drivetrain (Differential, Planetary, Pneumatics)

[anthonyl14107096]

Originally Posted by Godzilla

How easy is it to change out a motor?

Well, it depends on which motor. For the dedicated drive motor, it takes only around 30 minutes to switch it out. For the motors that drive the differentials. It would take like an hour to 2 hours to change. Thank god that there is time in between matches during the world championships.

[Godzilla]

Originally Posted by anthonyl14107096

Well, it depends on which motor. For the dedicated drive motor, it takes only around 30 minutes to switch it out. For the motors that drive the differentials. It would take like an hour to 2 hours to change. Thank god that there is time in between matches during the world championships.

Do you have to take out each individual shaft collar or can you just take off the entire unit as one piece?

We did that with our drive train. We just sandwiched the spacers and gears together with shaft collars.

[anthonyl14107096]

Originally Posted by Godzilla

Do you have to take out each individual shaft collar or can you just take off the entire unit as one piece?

We did that with our drive train. We just sandwiched the spacers and gears together with shaft collars.

We never move the planetary, they stay where they are. Its easy to access the dedicated drive motors. To replace the differential driving motors, we can remove the arm of our robot, then remove the "back plate" which contains all four of the motors driving the differentials. So essentially, we just take off the motor housing unit, the back plate.

[michael_lararia]

aight i just wanna clear some things up here

our planetaries are a little bit more complicated than your average gear box. you cannot calculate the gear ratios with simple 1:1 and 2:1 ratios, as it is not based on a linear plot. There are two inputs and one output, changing it from a linear 2d plot to a parabolic 3d plot. Hence the difference between our torque and speed modes are a little bit more complicated.

Heres my way of explaining it. When it is run in torque mode, the chain and the planets are moving in the same direction. As long as they are running at the exact same speed, it is the equivalent of gearing 2 motors in series. Therefore it is the addition of their torque.

Then when we switch to speed mode, the chain and planets are moving in opposite directions. This results in the addition of the speeds of the two inputs

4194B ^_^

[AndrewRemmers1902]

Can you make a STEP file of the assembly?

-Andrew

[anthonyl14107096]

Originally Posted by AndrewRemmers1902

Can you make a STEP file of the assembly?

-Andrew

Here you go
http://www.mediafire.com/?3izo0tdxh6fubk8

[Fido488]

I didn't see this posted yet so I figured I'd share it to help people understand planetary gears better (it did for me).

Another old movie on gearing:

http://youtu.be/rQhzruw2Qh8

I found it confusing at the beginning but at the end it made it all much more clear to me.

Hope this helps,

Fido488

[dontworryaboutit]

Originally Posted by jpearman

Guess I have to build one as well, I thought high speed (1:1) was the beginning of the animation with the motors turning in the opposite directions, and high torque was when the planet holder was stationary and the ring gear turning giving a 1:3 ratio. I'm also having a hard time seeing the benefit of this mode as using the second motor to hold the planet holder would seem to waste the power available from this motor, if it were held instead by a pneumatic clutch then it makes more sense to me. I also updated the animation to remove the wagon wheel aliasing issue.

Here's the link again

linky

If the ring gear is powered in the same direction as the planet carrier, you're in high-torque mode (motors in opposite directions).
If the ring gear is powered in the opposite direction of the planet carrier, you're in high-speed mode (motors in same direction).

Instead of trying to list the rest of this, here's a table of inputs/outputs:


*When you backdrive it, it will force the motors into the neutral setting (Ring moves twice as fast as Planet Carrier).

[banditofernando]

Originally Posted by dontworryaboutit

If the ring gear is powered in the same direction as the planet carrier, you're in high-torque mode (motors in opposite directions).

This is the one thing I don't understand. How can you run one motor in the other way. Wouldn't that try to turn the sun gear the opposite way, which can't happen since the sun gear and the other gear are on the same axles????

[dontworryaboutit]

Originally Posted by banditofernando

This is the one thing I don't understand. How can you run one motor in the other way. Wouldn't that try to turn the sun gear the opposite way, which can't happen since the sun gear and the other gear are on the same axles????

The Planet Carrier (the blue gears in the animation) are on the same axle, but they have the green inserts which allow the Sun Gear to move separately from the Ring Carrier.