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Sector Gear Animation
weston_thompson499
Member Posts: 9 ✭
I'm working on an assembly that has a sector gear that acts as a pinion for 2 racks, which allows for some timing of events to take place. The sector gear sits on top of a spur gear that is driven by another spur gear. The sector gear is really just and extrude-remove of a section of teeth of the gear below it. Is there any way to relate the the movement of the racks to the sector portion of the gear, and not the whole gear below it, so it will accurately depict the timing and movement of the racks? I can't seem to find anyway to make it happen. I'm not necessarily a newbie, but I'm definitely a novice. Hopefully the picture below will help explain what I'm trying to do. As this is a work in progress, I don't have the teeth on the other rack yet, but hopefully you get the idea.
Comments
You could set limits for the revolute mate of on of the spur gears.
If I understand you correctly I think that will just stop the whole assembly from moving once it's through the first rack. Let's say it takes 60 degrees to get through the first rack…I think that does stop the rack, but the gears just stop turning all together so the sector never makes it to the second one. I tried to limit the travel of the rack, but it has the same effect. Once the rack is through with it's travel, the gear assembly stops (or the animation won't play at all), because it's getting the relationship from the bottom "drive" gear, and not the sector. If any of that makes sense?
I am a bit confused by your description. Are you trying to get the linear gear to engage both pinion gears at the same time? That sounds like a lock up condition since the spur gears are different sizes for one thing.
I missed the sector gear stack. Which engages one gear in the stack then switches to the other. Looks like the left gear will still crash with rack and wants to move down. If the sector gears are fastened then I'm thinking a normal rack & pinion mate should work. If they aren't fixed then all bets are off.
Can you attach a link to your document. For further study?
Sure. Please don't judge me though. I'm still learning. I'm sure there are some better ways of doing this.
https://cad.onshape.com/documents/0fac01fba31b572a929300e9/w/e09a1874c6191281302ca278/e/dd6fe4cbfa714b564f22d574?renderMode=0&uiState=66dfbfa6c61abf06b0f24ea2Error
The smaller spur gear is driving the larger spur gear. The top portion of this larger spur gear is a sector. Just an extrude remove of the gear below. The bottom gear will rotate counterclockwise, and the sector 4 teeth on the top will engage the linear gear (rack), moving it approx .75" to the left. The gear will then continue it's travel counter clockwise, but the top rack will stop movement due to lack of engagement. As the sector continues it will then engage the lower rack and move it approx .75" to the right. It will then continue its rotation until the teeth disengage the lower rack. I can't seem to make this animate correctly. Any animation I do is tied to the larger spur gear below the racks, and not the sector gear. Either the racks just keep moving through the entire rotation of the spur gear, or if I limit the travel of the slider racks, then it locks up the whole mechanism once the limit is reached on the first rack gear.
Are the racks spring loaded to a closed position?
Hi Weston. No Judgement just questions. There is some folks on this forum that like the challenge. There's no stupid questions for this group.
Having looked at your model I don't think the rack and pinion gear 'mate' can't be made to work for an animation. The mate would need to be disengaged when when the section gear no longer makes contact and a new rack and pinion mate would have to engage as the pinion continues around to move the rack back and forth 3/4". That doesn't mean the arrangement won't work just the OS mating.
There are some other methods I can think of besides rack and pinion that may work better and cheaper if you're interested. Does the back and forth need to be constant speed or could it be allowed the accelerate during the cycle?
The back and forth does not need to be constant speed. It's really all about timing between the 2 racks. It doesn't move back and forth constantly. It will move one direction, sit idle for an indefinite period of time, then move the other way when certain parameters are met and set idle again. Ideally the mechanism will be ran off one micro linear actuator (driving the incomplete rack on the LH side. Working on that now). Connecting the two racks as you have above will not work, as they have to move independently to accomplish similar, yet opposite tasks.
Also, I can't seem to get the teeth to mesh on my drive rack (purple). I think I need to apply an offset to the mates, but it won't let me do an offset in the Z axis. What am I missing? Thank you!
Negative. I don't think that will be necessary.