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Originally Posted by marshall
Your turn encoder is not 1:1 output with your turning so you're going to end up with some funny math and/or alignment issues over time. Just something to consider.
It looks good though. The shifting mechanism is clever.
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With some simple gear ratio math I think we should be able to get the right angle.
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Originally Posted by Ari423
I see the thrust bearings, but I don't see any radial bearing/bushing to keep "Pivot Module Bottom" from rubbing against the frame. Is there something I'm missing or are you ok with metal-on-metal contact there?
Also I'm a little skeptical about the on-the-fly gear meshing. It definitely could work, but without a synchronizer like in a car transmission I could imagine a fast-moving gear crashing into a slow-moving gear and shattering. Just something to keep in mind.
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I felt that with the small amount of rotation happening within that part (no more than 180 degrees at a time) I felt that just using a bit of lubricant would suffice.
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Originally Posted by Peyton Yeung
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I found my inspiration for both this transmission and swerve from this very video.
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Originally Posted by asid61
Interesting take on a swerve drive. Using drive units separate from the main modules used to be a norm, but now people like to place the two closer together to save space. I would recommend that in your case, as your swerve is currently quite large and has a lot of unnecessary shafting.
I really don't like crash shifting.  Your gear mesh is highly dependent on how accurately your cylinder/linkage move, not to mention the huge gear tooth stresses from having two different-speed gears mesh. What's wrong with just using a ballshifter/dogshifter, or no shifter at all? Any of those will reduce weight and footprint, not to mention complexity.
That being said, I like the way you've set up the gearbox. All the positive shaft retention everywhere is nice too.
Your caster box/module looks really solid, except for the washer on the horizontal bevel gear. Washers are not accurate in thickness, and in your case it also looks like it might rub the outer race of the bearing.
Why are you cutting away so much of the large turning gear?
I think your encoder stage should be fine, as long as you do the right math to convert it to true angle.
LOVE the wires and chains in CAD. looks very nifty. 
And lastly: what made you choose this design over a bevel-beside-wheel swerve? For the amount of machining you're doing, that might end up a lot more compact and lighter for you. |
I decided to make the two separate as I wanted a simple swerve pod that would be able to be replaced in a short amount of time, and be easy to manufacture. I feel that making them separate will give more flexibility at times of failure. I also wanted a dual speed transmission on the bot, and I came up with few good ways to do such within each pod.
My team used dogshifters this year and I felt like the mesh speed was not optimal. I (as the competition driver) had to back off the throttle to shift between gears, and I would lose a lot of momentum. I am hoping this will provide on-the-fly shifting, possibly even with a choice between manual and auto shifting. As for using a shifter, this was more of a personal preference. I have been the driver for 3 years for my team, and I am one of the more aggressive drivers (I pushed a robot up on its back wheels and all the way across the width of the field a few weeks ago), so torque is a necessity. However, my team typically picks a position that requires high speed and maneuverability on the field. A shifter seems to be the best choice.
Any suggestions to replace the washer?
I think the gear you are referring to (the big gear on top of the 1" x 2" tube) is a versa gear from Vex. So it comes with the versa key slots in the center.
Thanks! I have been working a lot on using chains and wires in assemblies this off season. I still am learning a lot about using these and this was one of my better uses of it.
I am not quite sure of what you are referring too about bevel-beside-wheel swerve. I think I have an idea of it, but could you explain further or link a picture?
Thanks for the help!