WOW… :ahh: …thats really nice compared to ours, even though we are a second year team hehehe
First of all, I do want to point out that the person who designed this has put a lot of time into it. It is a very nice concept. but there are few things that caught my eyes and can be modified to make it better (this is where i need the engineers and mentors to correct me if i am wrong).
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the Drive shaft on the wheel? is that going through 3 bearings (looks like there are 3 plates). if it is, thats BAD. you want to fit everything between two plates. (I can be wrong about this one, I was taught to never put 3 bearings on the same shaft)
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looks like, the front, back and top sides itselves have 36 hex head screws. Dont you think it can be reduced down? maybe use only 16 screws? why not take a few aluminum L brackets (8 should be good) which are 1/8th thick and use them to hold all sides together (2 on each side).
The overall concept is great. A few tweaking might help you to perfect the design. If you are seeking for help, dont hesitate to ask me or any mentors. Also, if you do want to take a look at a good crab module, you might want to look at “The Navigators (team 79)” crab drive from 2003.
Good luck…
-Arefin.
Or you could check out any of them by Wildstang… I hear theyre kinda good :ahh:
Though it can be very hard to do for a compact drive train like this, in general, you want to isolate your precision parts from your main structural parts that should be bending to some degree. The only real way to do that for a crab drive is having one or two gearboxes for the whole robot chained to each module with power transferred coaxially.
Of course, this is purely a very general design rule and because a bigger concern than weight efficiency is often ease of manufacturing, you may have no choice.
My 0.2c
the design looks nice, but there are a bit too many bolts on there. The builder could consider welding three sides together and have one side connected by bolts, because holes reduce strength and bolts can be heavy.
How many of those gearboxes do you plan on including on your chassis? And what’s the gear ratio? (I’m having difficulty seeing through the holes in the side)
Odds are four, since it’s a swerve drive.
Nice design. I agree that it would be better to reduce the number of bollts. Weld anything you can if you have the resources. What rpm do you have coming out of the gearbox?
I’m curious as to why you choose such a large wheel diameter? If you went to a smaller wheel, you could make a considerably more compact, and lighter gearbox. Its not as if their are any field features that require a large wheel either.
Also, with a smaller wheel, you don’t need as much reduction in the gearbox itself, creating a more even more compact and lighter gearbox.
Actually, there are some design considerations if you are planning on driving over the aproximately 1.6" high bar that makes up the base of the goals. One of the things that I have been taught to do is to give your wheel a diameter that is at least three times the height of the object you want to climb over for best traction. You could technically do this with a diameter that is two times greater than (but not equal to) the height of the object you want to climb over, but for best results, the object you want to drive over should be 1/3 the height of your wheels. (Please correct me if I am wrong about this)
But back to your design, it looks like you have a good start, but I can’t really offer any excellent input as I am also in the learning stages myself. 
Thanks for the feed back, and as most of you have pointed out there are way too many bolts and I agree, so that problem is being addressed. The heights of the wheels are such that if it does drive over the field Goal, it will be able to get back over. The gear reduction for each module is 18:1, the output shaft RPM is around 230. There will be 4 modules, like Cory said.
If you have any ideas for improvements, just drop me a message.
It’s a really nice design, but what about weight? For 4 of these and the arm, and also size of it so that it can be able to move between the middle larger tetras? Those are just some things that might become problems, but you probably have it all planned out. But overall, that’s a really cool omni drive system.
nitpick It’s not an omni, or holonomic drive. It’s swerve/crab. The difference between the two is that while with swerve you can translate in any direction without changing the orientation of the robot, with a holonomic drive, you can not only translate, but rotate the robot around itself at the same time.
Well since weight is always an issue in the end, I did my best to keep the weight of each swerve module as light as possible. According to the weight calculator in Inventor each module will weigh around 8 pounds.