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Prototype transmission for potential use this year
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Re: Prototype transmission for potential use this year
Looks great. Do you think you could eliminate a lot of this play with a hex hub? You could try to broach the bronze gear to the same shape.
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Re: Prototype transmission for potential use this year
well the play isn't on the bronze gear, that mating is actually pretty good. it's specifically between the andymark hub, keystock, and axle. Also we don't have the tools for hex shafts and it would be a major pain to deal with the bearings considering how it has to be assembled. but even then there would be some inherent play anyway. One option would be to setscrew the key in place. or get the 3/8 hubs and then bore and broach it ourselves for a tighter fit. The axle was sanded down though so maybe whoever did that went too far. may not be worth messing with though
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Re: Prototype transmission for potential use this year
Are you able to turn the wheel by hand on the new version?
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Re: Prototype transmission for potential use this year
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Re: Prototype transmission for potential use this year
Nice work aligning the worm and minimizing lash in the gearmesh. :]
Have you measured the free current? |
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Re: Prototype transmission for potential use this year
This looks great guys. I think that this version will help you in many of the pushing battles that you all faced last year. Your omni-directional drivetrain was very fun advantage to pair up with last year during the elimination rounds and I wish we would have provided you all with some more firepower. Thanks again for selecting our team last year and I hope that we get to work together in Saint Louis again in 2014.
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not just a full stop, it also prevents any unwanted changes in speed. so if something is trying to accelerate or decelerate us that force is going to be put into the chasis instead of the motor. So as I stated if we want to go a set speed, any changes in speed will be met with extreme resistance other than what we tell it to be. Also I tested a PID loop earlier today that seems to work extremely well, so much so that the only issue was that when loaded down too much it would draw 80-100A and shut the jaguars down. I have a video of my PID loop with the old transmission, and the only difference a load makes is higher current draw, the tracking is just as good. |
Re: Prototype transmission for potential use this year
Regardless of gearing method, the motor will shift up and down it's curve as the applied load changes (being pushed is an applied load).
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indeed it will. I never said it wouldn't however with this system is such that it makes the job much easier on the cim. For example if we were moving forward at a certain speed. A robot behind us is attempting to push us forward faster. It's not going to happen. All him trying to do so would REDUCE the load on our drive motors and the extra force would be directed into our chasis. If we wanted to remain stationary, and someone tries to push us, provided we have enough traction our robot will move absolutely nowhere regardless of how hard they push. or we can advance forward at the rate we want to advance at and not any faster than we want, due to this type of setup. Now granted if we faced head on against another robot, if we don't have more force than they do we won't be able to push them back, but at the same time they wouldn't be able to push us back either and all the cims simply have to do is not move and all the force is transferred into the transmission structure |
Re: Prototype transmission for potential use this year
Neat idea. However, I am fairly certain that your worm wheel will loose teeth when you have the weight of the robot behind it. If your robot is going fast, and suddenly you stop applying power, the worm wheel won't be to turn the worm gear, so you'll just snap a tooth off. It will be different than just testing it on a table.
In the video you talked about having to use a smaller worm wheel in order to get the same reduction. These are pretty fragile, so you could switch to a bigger worm wheel with a two-start worm. A few other recommendations. Be sure to lubricate your gears! Make sure there isn't any play sliding the worm or worm wheel up and down on their shafts and that the unsupported drive axle doesn't wiggle around, but a little play in rotating the gears (like you showed in the video) is really important. That backlash makes the transmission operate more smoothly, and helps with lubrication, especially when you're using gear like this, than "slide" instead of "roll" on each other. |
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