Quote:
Originally Posted by Kevin Ainsworth
Nice design. You even have the weight of the robot pinning the steering bearing into the wheel module and the mounting plate. Others have hung the weight of the robot off the screws on the edge of the bearing which is a no-no. I don't like relying on screws that aren't seated fully like the ones you have on the main steering bearing but since you aren't holding the weight of the robot off them it should be fine. I would use stripper bolts or machined tabs but with a little loc-tite the screws shouldn't be an issue. Plus they are very close to the main plate and if one came loose it could lockup your steering for a match or burn out a steering motor.
The answer to your problem of mounting the CIM to the main plate is easy.
Flange the motor/bearing adapter (plate between the CIM and steering bearing), and make that flange larger than the hole in the main plate, assemble the whole steering module and slide the whole thing up into the plate until the flange contacts the main plate. Then you can clamp on the minor OD of the adapter instead of the CIM or bolt the flange to the main plate (my preference). If I am seeing everything correctly you should be fine. It will add a 1/4" to the overall height but that shouldn't be an issue.
One thing we've found is when the steering gear is smaller in diameter like this, the backlash in the steering gear to steering gearbox and within the Versa Gearbox, you get a decent amount of steering backlash. We are going to belt steering over gears due to this. Modifying a steering gear is simpler and easier, but for autonomous routines a low backlash steering helps a lot.
Awesome new evolution of the type of co-axial setup Aren started a couple of years back where the bevel gear is on the wheel axle. Though it looks like you're using a tiny 1/2" x 2" wheel, that could also be part of the compact look. Our 2015 1"x3.25" wheels looked laughably small.
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Thank you! I've never really liked using the screws partially to capture things, but other solutions require so much more machining or cost I don't like to use them. Fortunately most of the time they don't support any load anyway.
I actually came up with the idea for using a bevel-beside-wheel before it came up on CD, but my execution was nowhere near the finesse that Aren's (or 1323's) had.
I see what you mean about mounting the CIM; I realized that after I already did the render. The method you're describing is a little different from what I had in mind, however. I was just going to replace the clamp with a plate that goes beneath the CIM to mount to.
I really dislike using things like large timing pulleys for this (I've done it a couple times), but I completely see your point about why to do it. Usually for autonomous I've had experience just using a NavX for guidance, and I don't think you need complicated swerve maneuvers for auton anyway, but I can think of several autonomous problems that are harder to solve here.
Now I'm getting paranoid about the small wheel.
I remember that nitrile tread not wearing out for around 25 matches + practice + offseason back in 2014, but the AM treads wears out a lot faster iirc. I wouldn't think that tread wear increases exponentially over a lower width + diameter (in this case 4x faster assuming it's a linear relationship), but please correct me if I'm wrong. ATM I can live with 4x faster tread wear.