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.:eek:

[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 :p

[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

[kevin.li.rit]

I suggest Pin in

[Al Skierkiewicz]

Charlie,
I am going to put this question to our mechanical guy and check over the transmission tonight. Hope you don't need an immediate answer.

[Davidka]

Where is the pin? Does anyone have any pictures on where it's located on the drill motor?:yikes:

[rbayer]

Originally posted by Davidka
Where is the pin? Does anyone have any pictures on where it's located on the drill motor?:yikes:

They are deep, deep inside the gearbox. Here's the steps we took to get them out:

1. Pop off plastic cage that surrounds motor.
2. Twist off black assembly from the front part (clutch, etc).
3. Pick up gear assembly that you just revealed
4. Pick out pins.
5. Carefully replace gear assembly, making sure it is seated properly.
6. Replace black assembly, making sure to seat fully and twist until it is in the proper orientation.
7. Replace cage.

Does anybody have any good pictures of doing this, as it's very hard to explain with just words?

Also, if you are planning on using the left-handed screw provided in the kit, I would recommend you attach your coupling BEFORE you take out the backdrive pins. Otherwise, it becomes very difficult to keep the motor from turning while you screw in the left-handed screw. Anybody have any ideas on other ways of doing this?

[DougHogg]

DLO¬i]Originally posted by caffel [/i]
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.:eek: [/QUOTE]

Hi,

We took out the pins last year, and we didn't notice any "lash situation". Could you expand on that? Also what is "red RTV"?

Thanks in advance,

[Cory]

See the Whitepaper for the Bosch 3360 Gearbox Dissassembly (http://www.chiefdelphi.com/forums/papers.php?s=&categoryid=2&perpage=10&direction=DESC&sort=date)


We had a problem with the pins. We had the gearbox assembled correctly, and we disassembled it again and put it back together using the whitepaper I linked to, and they still would not run. They sounded as if they were running in neutral, although there is no visible neutral position. When we disassembled them again, and removed the steel pins that were directly under the output shaft, the motors run perfectly. Also, If you remove the clutch, there are two metal tabs with small springs on the end that will fall out of the top of the motor. Without these in, in our testing, the motor runs very poorly. As of now, we have a very makeshift system keeping them in, but something permanent will be done soon. I will post some pics of the motors with this retainer, and the base as soon as I can get some

Cory

[caffel]

To Don H.
Think about what happens within in the clutch.
The pins keep the drive half of the clutch separated from the output half. (the bowtie shaped piece with the splined hole in it).
In the standard set-up, there is little freeplay (sloppiness) when the motor runs and when it reverses.
Take out the pins and there's a gap left where they used to be.
Gaps cause what is called 'lash' by gear heads.
So, now picture the situation when the motor starts up. The motor turns about 10 degrees or more before the gap is closed, then the two parts hit hard.
If the robot is up against a load, all of that load resolves itself into that very small point of contact, (high pressure per square inch)
These are hardened metal parts. They wear well when used properly, but banging them together like that is not recomended.
They are likely to break.

[Al Skierkiewicz]

Charlie et. al.,
I disassembled the transmission last night, and this is what I found.
If you just want to remove the locking feature from the trans, it is an easy two minute job and there should be no change to trans operation.
1. Pull the shifting collar away from the the clutch end (while turning the output shaft.) You will see that it engages the torque clutch assy.
2. Holding the trans in one hand and the torque assy in the other, twist the trans and the two parts will fall apart. (This is a simple bayonet mount about 1/12 of a turn locks the parts together.)
3. If the two locking pins (approx 1/8" dia x 3/16" long) have not already fallen out on the table, remove them from the assembly. They are located next to the bowtie shaped output coupler immediately behind the output shaft.
4. Install the torque ring into the torque/end assy. (It only goes in one way.
5. Here is the tricky part...Reassemble the trans to the torque assy while turning the output shaft until the parts engage inside the transmission.
6. Twist the trans and torque assy. until they are locked in their original position and test operation.
Again the design of the locking pins, although superior to previous designs, still have the potential for catastrophic failure if used to brake a rapidly moving 130 lb robot. The assy was designed to lock the output shaft of a power screwdriver to tighten screws, not stop a robot.
Hope this helps.

[ROB at RAGE]

Out as usual! Have you ever tried to drive with the pins in or had a large force aplied aganst the pin and then powered the motor, if you do you will not like the sounds you hear. the pins were designed to retrain the hand force you you put on a chuck to tighten or losen it, not the forces that get aplied by robot mechanisms.

Some tank tred drives might need them to be stearable though.

[DougHogg]

I was thinking of posting some pictures of the transmission in various stages of disassembly. However when I tried to put the pins back in so I could show them in place, the drive shaft wouldn't turn at all.

Can anyone describe the original location of the pins, since I don't have a transmission available now that has them?

[ROB at RAGE]

I am going to look tomarrow, but i thought there were four dogs tha engage the splined dog, and the spacing is diferent on the two 90 degree oposing sides. One gap for where the pin is and one where the dog is, and put it togerer the wrong way makes the dog slopy and the pin to lock up.

I know this was true for the old ones and will lok at the next opertunity.

In the past some teams made there own dog and welded it in place. If that work that works this year who knows.

On a side note last year we ran two regionals and the nationals all the way to the final rounds with out damaging a drill motor or transmission all the while shifting the transmition also. I new it was to good to last for this years stuff.

[Al Skierkiewicz]

The four bosses that engage the drive dog are integral to the operation of the locking pins. When the motor is driving the output shaft, two of the bosses push the pins away from the lock position while the other two drive the output shaft. When you reverse the motor, the bosses change purpose and the the other pair pushes on the locking pins. As such there is always a little slop between forward and reverse due to this design. Certainly not enough to be worried about.

[caffel]

To: Al S.
So are you saying that you should leave the pins in there to avoid increasing the slop?

[Al Skierkiewicz]

There is no additional "slop" with the pins removed. If you examine the front of the drill (that part to which the output shaft is attached) and visualize the force produced by a robot back feeding the output shaft, you will see that the pins will transfer that force to the ring that surrounds the output shaft. Since there is only plastic holding that ring in place, (the same plastic that holds the output shaft in place) leaving the locking pins in place is a risky thing to do if you use the Bosch transmission.