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#61
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Re: Baxter Bomb Squad 2014 ~ Nighthawk
The maximum speed with this gearing configuration should be about 14 fps right? Is that Nighthawks's speed?
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#62
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How do you get alignment of the "tower" to the wheel support structure? How do you assure center to center alignment? and then how do you assure perpendicularity of the tower to its mating piece at the bottom. Is it just a matter of being very careful with conventional tooling, do you somehow machine it as one assembly or is there some other hidden trick you can reveal? I would think this would be particularly important, doubly so because of your integral, custom bearing assembly. |
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#63
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Re: Baxter Bomb Squad 2014 ~ Nighthawk
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![]() (I circled the two channels for the ball bearings. Also, that sprocket is NOT floating, it is being held up by a piece of delrin that cannot be seen in the part section view.) The two black plates sandwich the BBs between them and act as the thrust bearing. I felt the need to add pictures of the plates themselves. The smaller round one is hidden just above the blue 3D printed part that is an unmentioned experiment for this year. ![]() ![]() Quote:
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![]() If you have any other questions just let me know! -John Taylor Novak Last edited by JTN : 24-03-2014 at 17:25. Reason: Picture was too big and I didn't like it. |
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#64
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Re: Baxter Bomb Squad 2014 ~ Nighthawk
Thank you for such a complete response regarding information on your swerve module design and manufacture.
We tried swerve a few years ago and while we eventually got it to mostly work, it co-opted some of the time that perhaps we should of spent on other subsystems. We haven't completely given up on it, but it certainly isn't a favored approach right now. As implied in the thread above, the software and control part of this takes work as well. There is a kind of elegance to pieces of your design that I admire. |
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#65
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Re: Baxter Bomb Squad 2014 ~ Nighthawk
I'm curious about the slip ring. Can you share the manufacturer and part number?
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#66
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Re: Baxter Bomb Squad 2014 ~ Nighthawk
I can send (and have sent) a private message to anyone wondering what the slip ring model is.
-John Taylor Novak |
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#67
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Re: Baxter Bomb Squad 2014 ~ Nighthawk
Hello JTN. i am Tristan Shepard (aka Skippy), I am a student and am part of our pit crew with (kyEOT) or (Engineers of Tomorrow team 2783). we had talked to your pit crew and some of your mentors ate the Queen City Regional, we talked to you all about how you made your swerve. They said if we wanted the CAD we just had to contacted you all. we used the wild swerve from andymark but saw a lot that could be improved on it. I was wondering if our team could get the CAD for your swerve module that your team used. Thanks. Skippy
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#68
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Re: Baxter Bomb Squad 2014 ~ Nighthawk
Why did you use 6 inch wheels over 4 inch ones? As far as I can tell, I think that 4 inch wheels would make the entire assembly smaller and lighter while needing less gear reduction. Any reason why I'm wrong?
How are the grooves for the thrust bearing cut? |
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#69
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Re: Baxter Bomb Squad 2014 ~ Nighthawk
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I have couple more questions too: 1. What's that pneumatic cylinder doing in your CAD render!? It really caught me off guard. 2. What is the experimental 3D printed part below your thrust bearing? |
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#70
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Re: Baxter Bomb Squad 2014 ~ Nighthawk
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After playing around with some math and CAD, I realized that smaller wheels mean smaller reductions, which either means that the intermediary shaft has to get closer to the CIM, or the sprocket on the wheel has to get bigger and closer to the ground. I think that a 24/60 gear reduction with a 16/40 chain run will fit, but just barely. (EDIT: 24/64 and 16/38 fits better). The smaller wheel also reduces the space for the thrust bearing, but I think I can get it, or a thinner solution, to fit. These issues might be fixable by a first stage belt like 192 has recently used, but I have no experience with these. Last edited by Bryce Paputa : 21-07-2014 at 15:44. Reason: found a better gearing |
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#71
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Re: Baxter Bomb Squad 2014 ~ Nighthawk
Could you clarify where this cylinder is? I can't seem to find it in any of the CAD screenshots that have been posted.
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#72
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Re: Baxter Bomb Squad 2014 ~ Nighthawk
I had the chance this past weekend to see their swerve pods in-person, including the experimental one with the 3D printed blue plate. I'd like to thank the members of Team 16 for answering all my questions with patience.
In the picture posted, the piston is located under the black mounting plate, and adjacent to the blue one (its the grey cylindrical object in the cad). From what they told me, it was designed to test out and eliminate the twitching that the modules may have when trying to drive in a straight line. Because the control system tries to compensate the drift, and then over-corrects the action, the piston would lock in to the appropriate groove when needed and make sure the robot drives in a straight line. They did mention that they would have to do some more testing with the current design since the motor was able to overcome the piston lock fairly easily. |
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#73
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Re: Baxter Bomb Squad 2014 ~ Nighthawk
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Regardless of my mixed feelings about this. I'd be very interested to hear if it helped or not. |
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#74
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Re: Baxter Bomb Squad 2014 ~ Nighthawk
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-John Taylor Novak P.S. As of now the CAD models have not yet been released to the public but I can supply images of the model instead. Last edited by JTN : 21-07-2014 at 16:11. |
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#75
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Re: Baxter Bomb Squad 2014 ~ Nighthawk
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The cylinder was intended to improve two issues. 1. We currently calibrate the wheel positions by rotating them all straight and running a task to save the voltage from the encoders as the reference values. These are saved to a file and used as the offset from then on. The cylinders would allow more precise mechanical positioning for that. 2. We would use them to ensure home position at the start of the match. notches around the perimeter of the bearing plate could allow accurate re-positioning at 45 deg or 90 deg or other intervals. The cylinders are not intended to force the module to a position. when extended, the module software would oscillate at low energy around the setpoint until the cylinder is seated in the detent. This would be detected by a cylinder mounted limit switch on each wheel. Obviously this was not required for autonomous success this year. We are always trying to mop up limitations of the hardware and software for the next time precision is needed. |
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