Drill Motors: Pins IN or Pins OUT

[Caleb Fulton]

IN OR OUT?!?!

[Don Wright]

Unfortunately, it's not that easy. Do you want to coast after you return the joystick to neutral, or stop right away? If you want to coast, pins out. If you you want to stop (like you have brakes), pins in... Depends on your control strategy.

[Matt Leese]

I should note that you can also control coasting/breaking ability with the Speed Controller. If you set the Speed Controller to the break setting, it will break you no matter if the pins are in or out of the gear box. If you set the Speed Controller to coast, it will coast if there are no pins in the gear box. If there are pins in the gear box, it will break.

As a word of advice, I'd say remove the pins and use the Speed Controllers if you want to break. The pins are just an extra item to break in the gear box when put under stress.

Matt

[Cory]

this was mentioned before, but I'll say it again. Keeo in mind that id you are on the top of the ramp and the match ends. If you have the pins out, and someone was pushing you at the end, you may roll backwards right into your stack of boxes.

Cory

[DougHogg]

Originally posted by Matt Leese
I should note that you can also control coasting/breaking ability with the Speed Controller. If you set the Speed Controller to the break setting, it will break you no matter if the pins are in or out of the gear box. If you set the Speed Controller to coast, it will coast if there are no pins in the gear box. If there are pins in the gear box, it will break.

As a word of advice, I'd say remove the pins and use the Speed Controllers if you want to break. The pins are just an extra item to break in the gear box when put under stress.

Matt

How do you set a Speed Controller to break or coast?

[Matt Leese]

There's a jumper that can be set on the speed controller. It's in one of the corners (the lower left hand if you look at it from where you can read the InnovationFIRST logo).

Matt

[Matt D]

I know what and where the jumper is, but what exactly does it do? What advantages does it have over leaving the pins in?

[Matt Leese]

The coast/brake jumper on the speed controller works by either closing or opening the circuit that the motor is on. When set to coast and there is no input to the motor (ie, an input to the speed controller of 127), the speed controller open circuits the motor so that it can spin freely. When set to brake and there is no input to the motor, the speed controller closes the circuit to the motor. This causes there to be resistance to the back driving of the motor. The speed controller absorbs the created force and dissipates it as heat.

The main difference between the speed controller and the pins is that the speed controller will engage immediately whereas there's still a bit of a turn (though very slight) with the pins. Also, I've seen more trouble with gear boxes breaking (ie the pins take too much stress and break) than with the speed controllers going. I'd trust the speed controllers over the pins.

Matt

[caffel]

If you just take out the pins, there will be a nasty lash situation between the two rotating parts that are still there.
Last year, we had some success with using red RTV to fill in the gap. To do that, however, we discarded the black ring which surrounds the pins and replaced it with a ring that would contain the RTV and rotate along with this new 'coupling'
This year that ring is not removeable.

Ideas appreciated.

[hi_im_sean]

if you leave the pins in, exactly how easy do they break under heavy braking. also would it be safe to punt the robot in reverse for a brief second to stop it.

remember we are talking about drill motors here.

[Matt D]

I have a few more questions about how the jumper is used. The current jumper is attached to pins B and C. Is this the coast configuration or the brake configuration? How do you configure it for the opposite, remove jumper? Attach to A and B? Attach to A and C?

[Al Skierkiewicz]

I assume you are talking about the locking pawl in the drill transmission. Many teams leave this part in thinking that the braking (locking the output shaft) is a good thing. If your travel speed is fairly high, when you remove drive from the motor and the locking mechanism clicks in, damage to the transmission is almost assured. Remember the locking mechanism was designed to lock the shaft to allow turning screws while in the screwdriver mode of the clutch. With the new motor/transmission we have this year, that may have been addressed differently by the manufacturer.
Brake mode on the speed controller causes both the low side FETs pairs to turn on producing a dead short across the motor. As the motor is being turned by the momentum of the robot, the motor acts like a generator and dumps all of it's current into the dead short of the speed controller. (In practice the load is the resistance of the FETs in "ON" plus the resistance of the wire between the motor and the controller, or roughly .1 to .3 ohms.) In coast mode, all FETs are turned off and the motor has no electrical load.

[Greg Needel]

I would agree with matt and say out (since I already took the pins out this year) and I just wanted to comment on the getting pushed off the top statement that if you are getting pushed off the top with out the pins your wheels will turn but won;t you be pushing back anyway?.....and also if someone has the power to push you off the top would you rather roll back or just sit there getting pushed on ........remeber it is usally the case that the less time that your robot has in contact with another robot the less chance something will break.

I also think that if someone can't stop their robot from rolling down the hill to hit one of therir stacks then they have more problems then the pins

[Matt Leese]

If I remember correctly, there is no A label near the jumper. Instead, set the jumper to the B side for brake and the C side for coast. In general, if it's not working the way you expect, just swap the jumper. There shouldn't be any harm done to the speed controller.

Matt

[caffel]

To Al S.
Assume that you remove the pins, what do you think about the issue of lash between the motor side of the clutch/coupling (one side of the pin) and the output side (the other side of the pin). There will be over 10 degrees of free play.
When the motor starts or reverses, there will be a hard collison betwen these two parts.
Its kind of like a misalignment coupling but with the rubber star shaped insert left out.

Charlie Affel, 487