Dog Gear?

[de_]

Isn't there 2 inherent weaknesses in a AM shifter used as a release mechanism given the forces the kicker could be putting on the dog. There is a small 3/32 pin through the dog to connect it to the internal pull shaft. If you use the air cylinder connector, it has a tiny bearing with an smaller roll pin running against it. Last I heard both pins have occasionally broken using 26lbs of pull force with a 3/4 air cylinder. Now I hear people have to use 1.5" air cylinders to trigger a release. Surely those pins are going to break.

[jgannon]

Originally Posted by de_

Isn't there 2 inherent weaknesses in a AM shifter used as a release mechanism given the forces the kicker could be putting on the dog. There is a small 3/32 pin through the dog to connect it to the internal pull shaft. If you use the air cylinder connector, it has a tiny bearing with an smaller roll pin running against it. Last I heard both pins have occasionally broken using 26lbs of pull force with a 3/4 air cylinder. Now I hear people have to use 1.5" air cylinders to trigger a release. Surely those pins are going to break.

In 2007, we naively ran the 3/4" bore cylinders in our AM shifters at 60psi. The spring pins sheared before ship date. I'd estimate that we didn't shift them nearly as many times as a typical kicking system would be expected to fire, so I'm surprised to hear that people are doing this successfully. Has the design changed?

[AdamHeard]

Originally Posted by jgannon

In 2007, we naively ran the 3/4" bore cylinders in our AM shifters at 60psi. The spring pins sheared before ship date. I'd estimate that we didn't shift them nearly as many times as a typical kicking system would be expected to fire, so I'm surprised to hear that people are doing this successfully. Has the design changed?

You're supposed to shim the shaft so the dog can't actually touch the face of each gear. Not sure if you did this.

We've never sheared a pin after a few seasons of use; We later switched to bolts (which were actually weaker), and still haven't sheared any.

[ttldomination]

My team ordered an AM Shifter, Gen1, and we realized that there is no output shaft, but instead, there is an output sprocket. Now, the sprocket faces a lot of resistance to turning. Is there something that we can do to modify that? Should we try and order the supershifter? Or did you guys just use it like it came?

[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?

[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

[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

[Andrew Y.]

Originally Posted by squirrel

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

we have been exploring this possibility. I think itll be our big project for this off season.

Another solution would be to adapt the 2 speed from a 1/5 or 1/8 RC 2 speed transmission.

[Cory]

Originally Posted by Andrew Y.

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

I'm curious what you're not impressed about? We never buy shifters from AndyMark, but our robots always use a boatload of their products and pretty much everything they sell is a good value compared to us making it ourselves.

[Chris is me]

Originally Posted by Andrew Y.

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

What troubles you with them?

If you're servo shifting, "well there's your problem". Pneumatic shifting is the way to go. Most complaints I've heard about the gearbox are that they don't shift well enough without pneumatics.

[AdamHeard]

Originally Posted by Andrew Y.

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

I'm curious too, AndyMark is our first stop for just about any sort of gearing, and we've ran their shifters (pneumatic) on many of our robots with no complaints about reliability.

[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?