Dog Gear?

[Dan-o]

We are designing a similar system since we don't have room in our budget for 1 or 2 Super-Shifters. Unfortunately, I am having trouble understanding just one concept about this method of power transmission.

My understanding is that the power source (crankshaft) is connected to the output rod (driveshaft) by a pair of gears. The input gear is rigidly coupled to the crankshaft. The output gear is connected by a bearing to the driveshaft so it can rotate freely if the dog collar is not engaged. The dog collar is coupled to the driveshaft so that it rotates with the shaft, but can move axially to engage or disengage the output gear.

First, is my understanding of this system correct? Second, how can a piston push or pull the dog collar as it rotates on the shaft? In other words, I need to undestand the linkage from the piston to the dog collar.

Thank you very much in advance for any help you can provide.

[MrForbes]

This is about as far as we got on our Inventor design yesterday.



The black shaft is driven by the motor/gearbox. The pink spool has bushings which allow it to rotate and slide on the shaft. The light gray pin is pressed into the black shaft, it turns with it.

Not shown is the "fork" and it's actuating pneumatic cylinder. The fork fits into the groove at the left end of the spool, and slides the spool along the black shaft to allow the two pins on the end of the spool to engage or disengage the other pin.

To wind the winch, the spool is slid by the cylinder/fork to the right to engage the pins, then the motor runs, then stops. The cylinder is energized the other way to disengage the pins, pulling the spool to the left, and allowing the winch to unwind suddenly.

This still in the design/fabrication stage, if you see any problems, please let us know!

[Andrew Y.]

i cant believe i didnt think of that one! haha

looks good. Only concern that i have is if your going to move the shaft, how to keep the spool in place?

and im curious, anywhere that sells doggears that we could use?

[Madison]

Originally Posted by squirrel

This is about as far as we got on our Inventor design yesterday.



The black shaft is driven by the motor/gearbox. The pink spool has bushings which allow it to rotate and slide on the shaft. The light gray pin is pressed into the black shaft, it turns with it.

Not shown is the "fork" and it's actuating pneumatic cylinder. The fork fits into the groove at the left end of the spool, and slides the spool along the black shaft to allow the two pins on the end of the spool to engage or disengage the other pin.

To wind the winch, the spool is slid by the cylinder/fork to the right to engage the pins, then the motor runs, then stops. The cylinder is energized the other way to disengage the pins, pulling the spool to the left, and allowing the winch to unwind suddenly.

This still in the design/fabrication stage, if you see any problems, please let us know!

Is the motor or gear train that drives the winch backdrivable?

[MrForbes]

This one is. We need to get it built and see how it works. If the backdriving is too much to deal with, we'll probably put a ratchet on it.

[thefro526]

Originally Posted by Andrew Y.

i cant believe i didnt think of that one! haha

looks good. Only concern that i have is if your going to move the shaft, how to keep the spool in place?

and im curious, anywhere that sells doggears that we could use?

Specifically, here's Andymark's dog gear : http://store.andymark.biz/am-0020.html.

You could probably buy the gears from one of their shifting transmissions and make your own housing if you wanted to make a cheap and easy dog gear release system. http://store.andymark.biz/gearssprockets.html

[Collin Fultz]

Originally Posted by Dan-o

First, is my understanding of this system correct? Second, how can a piston push or pull the dog collar as it rotates on the shaft? In other words, I need to undestand the linkage from the piston to the dog collar.

1. Yes.

2. Take a look at this shaft and this linkage. Basically, the shaft that the dog powers is hollow and slotted. The slot allows the pin on the dog to move axially along the shaft. The hollowed out portion of the shaft is where that shifting shaft rides.

It's tough to explain but once you see one for yourself it makes perfect sense. If this didn't help, let me know and I can take some photos of our Super Shifters for you to help explain.

Good luck!

[Dan-o]

Collin,

Thank you very much for your explanation. I feel like a huge lightbulb went off and all of the pieces simultaneously came together. I am trying to develop a design to use all of our drive train motors cooperatively to power our tower-hanging winch design at the end of the match and I think I now know just enough to make it work.

[Tom Line]

Originally Posted by Dan-o

Collin,

Thank you very much for your explanation. I feel like a huge lightbulb went off and all of the pieces simultaneously came together. I am trying to develop a design to use all of our drive train motors cooperatively to power our tower-hanging winch design at the end of the match and I think I now know just enough to make it work.

Dan - you might be overkilling that a bit. A single fisherprice geared down will EASILY raise your robot in 4 or 5 seconds. It might make your life a lot simpler to just dedicate a single fisherprice + AM planetary to that task. If you end up going the way you explained though, I can't wait to see how fast that thing picks you up!

[Akash Rastogi]

Originally Posted by Dan-o

We are designing a similar system since we don't have room in our budget for 1 or 2 Super-Shifters. Unfortunately, I am having trouble understanding just one concept about this method of power transmission.

My understanding is that the power source (crankshaft) is connected to the output rod (driveshaft) by a pair of gears. The input gear is rigidly coupled to the crankshaft. The output gear is connected by a bearing to the driveshaft so it can rotate freely if the dog collar is not engaged. The dog collar is coupled to the driveshaft so that it rotates with the shaft, but can move axially to engage or disengage the output gear.

First, is my understanding of this system correct? Second, how can a piston push or pull the dog collar as it rotates on the shaft? In other words, I need to undestand the linkage from the piston to the dog collar.

Thank you very much in advance for any help you can provide.

Here's a post of some finished CAD for a kicker 1323 and 11 are using.

http://www.chiefdelphi.com/forums/sh...85&postcount=8

There's a custom hub attached to the sprocket.

[RRLedford]

How can this winder scheme pause for storing energy as tension/torque while waiting to take a shot?
After full wind point is reached, can motor just be de-energized? Does the high gear down ratio prevent wind back under the reverse pulling torque/tension of the cable/bungee wrap?
Can motor driver program allow motor to hold a fixed wind up position against full torque of winder at full tension position without it burning out?

Or, is there a freewheel integrated with the dog scheme to first let gearbox shaft disengage from torque load while freewheel still carries this torque, then further dog travel also releases freewheel to spin back at opposite rotation to the windup, delivering stored energy to kicker? In other words, is it a two stage dog release - 1st gearbox is disengaged to take load off motor, and then a freewheel is disengaged to fire off shot (when ready)?

-Dick Ledford

[Dan-o]

Originally Posted by Tom Line

Dan - you might be overkilling that a bit. A single fisherprice geared down will EASILY raise your robot in 4 or 5 seconds. It might make your life a lot simpler to just dedicate a single fisherprice + AM planetary to that task. If you end up going the way you explained though, I can't wait to see how fast that thing picks you up!

Tom,

Thanks for the advice. We understand that it would probably be acceptable for us to develop a winch that could pick up our robot in 4-5 seconds, but our goal is to be able to quickly hoist 3 robots (if necessary) in a few second panic scenario at the end of the match, so long as other teams are equipped to grab us and hold on for the ride. In a perfect world, we would grapple the bar in 3 seconds, hang within 4-5 seconds and our partners would be able to grab ahold of us and elevate themselves with the remaining 12-13 seconds. However, I think we're all going to figure out in the first week of competitions that it actually can take quite a bit longer to achieve this.

Additionally, I often see teams skimp on power for their arms, manipulators, winches, shooters, etc... for the sake of having a really beefy drive train. We're set out to prove that this sacrifice might not always be necessary.

[Dan-o]

Originally Posted by Akash Rastogi

Here's a post of some finished CAD for a kicker 1323 and 11 are using.

http://www.chiefdelphi.com/forums/sh...85&postcount=8

There's a custom hub attached to the sprocket.

Great job Akash. That looks like a very simple (this is a compliment) way to clutch a motor. I wish you guys luck in the competition.

[Andrew Y.]

Originally Posted by thefro526

Specifically, here's Andymark's dog gear : http://store.andymark.biz/am-0020.html.

You could probably buy the gears from one of their shifting transmissions and make your own housing if you wanted to make a cheap and easy dog gear release system. http://store.andymark.biz/gearssprockets.html

thanks for the links, but we purchased a few shifters from Andy Mark this year...and im not impressed at all...maybe my standards are a bit high(who knows)...we are looking to design our own next year but having trouble finding someone who sells dog gears

[MrForbes]

Make your own.

or get some that were made for a motorcycle transmission? might take quite a bit of adapting