Anybody know if the spur gear on the Keyang motor can be pulled so we can put something else on the shaft?
Bruce
I believe the Keyang gearbox is considered an integral part of the motor and can’t be modified. The actual rule is in <R61>.
Here is the rule you mentioned.
<R61> So that the maximum power level of every ROBOT is the same, motors used on the
ROBOT shall not be modified in any way, except as follows:
The mounting brackets and/or output shaft/interface of the motors may be modified to
facilitate the physical connection of the motor to the ROBOT and actuated part.
The gearboxes for the Fisher-Price and Globe motors are not considered “integral” and may
be separated from the motors.
The electrical input leads on the motors may be trimmed to length as necessary.
The intent is to allow teams to modify mounting tabs and the like, not to gain a weight reduction
by potentially compromising the structural integrity of any motor. The integral mechanical and
electrical system of the motor is not to be modified. Note that FIRST will not provide
replacements for modified parts.
I think it is stating that we can modify the output shaft.
Am I reading it wrong?
Bruce
Is the spur gear actually part of the gearbox though?
EDIT: R61 says it is not. So you should be fine. Looking forward to seeing you at the Wisconsin Regional.
Now that I think about it, I remember that there is something unusual about the way that the spur gear is attached to the motor shaft on the Keyang. There is actually another spur gear inside the gearbox that’s inserted inside the wormgear. If you remove the stock spur gear, you will probably need to machine a custom insert to fit in the worm gear, so I’m not sure that removing the stock gear would help you. You should probably take a look at the Keyang for yourself so you know what I’m talking about (because it sounds confusing to me).
I think you are confused.
The spur gear he is referring to is on the outside of the gearbox, on the output shaft. It couples with one of the half dozen black hubs you received in the kit of parts.
The outside spur gear has a smaller spur gear attached to it that couples directly with the worm gear on the inside. This isn’t at all obvious from just looking at it. I took one of these apart last year and was surprised to see how it was attached.
That makes sense to me…it’s the easiest way to attach the inner gear to the outer one-- the outer gear is long enough to fit into a gear shaped hole in the large diameter inner gear.
So the shaft itself is not really what is transferring torque.
You got it exactly. 
Hmm, was hoping not to have to use the plastic coupler. Wanted to put a timming pulley on the shaft instead of the gear.
Bruce
You could always try using a pulley large enough to machine a coupler out of the center. It’s not the easiest thing to do, but you could make a hole the same size and shape as the output gear, and just press the pulley on to the gear.
Were you able to take it apart without damaging the gearbox? We stripped the plastic spur gear on the inside last year after wear and tear from 2 competitions and a lot of demos, and I was trying to take it apart and confirm it actually was stripped. I didn’t want to completely destroy the motor/gearbox assembly though, and it looked like you had to dremel off the metal tabs to get it open. Is this correct or did you do it a different way?
I think that I just had to remove the retaining clip on the end of the shaft.
This works really well; last year 228 machined a custom aluminum coupler for the window motor (as seen in the photo below). It took a long time to machine it manually, but I wouldn’t hesitate doing it with access to CNC milling (which I have here at WPI :D).
http://www.team228.org/gallery/58/slideshow/bds-01.jpg](http://www.team228.org/media/pictures/view/2627)
Wow, how in the world would you do that manually? Even with a digital readout and a nice mill, don’t you need a CNC machine to move in x and y directions at the same time? I guess if you had a rotary table, that would help a lot, but would you still be able to get everything to the correct dimension?
If you are making a custom hub, keep in mind that the small, ~.25" shaft doesn’t rotate. Only the gear on the outside rotates. So, don’t rely on using the small shaft to hold your hub on the gear.
228 has a rotary table and my dad, who made the part, is a machinist.
I second that. We’ve occasionally had to make some strange parts that are best done on a rotary table or indexer. Rotate the part so many degrees, then move it so far in the x direction, reset, rotate so many degrees, and repeat
If you have DRO you can machine it without a rotary table or index head. Just calculate the center x,y locations of each location. If you have an index head, it can be done with a drill bit in a Bridgport. We have done that in the early years when adapting motor/transmission combos. you can even do it with a drill press with careful layout, but you are apt to generate a loose fit using that method. Just make a good sliding fit to the same outer diameter as the gear on the Keyang motor.