pic: 3216 Swerve

[ekapalka]

Originally Posted by asid61

1. Why do you need the encoder to have a 1:1 ratio? You can still tell if the wheels are out of alignment, and realistically it would be better to just have some way of keeping them in line for calibration mechanically, with something such as surgical tubing between the axis of the wheels. I think 1640 had something on keeping modules in line on their Swerve Central site.

The encoder I'm intending to use is a USDigital MA3 absolute magnetic shaft encoder (not the incremental encoder used to measure speed). Preferably, the robot should be ready to go as soon as its turned on with little or no calibration (which I guess might be unrealistic, but I'd still like to make the code relatively straightforward). I'm not sure what you mean by a mechanical solution... something to align the wheels with human assistance, or something else?

2. Is this a shifting design? If not, you are almost certainly using way too many gears and pulleys. You can probably cull almost every gear by using a sprocket reduction to the wheel. For example, using a 10t #25 sprocket on the shaft with the bevel gear and a 42t #25 sprocket on the 4" wheel (I assume it's 4 inches) will net you around 18fps adjusted, and you can lower that via a single pulley reduction going from CIM to turning module. Less gears means cheaper and less complex.

Its not a shifting design. The max free speed is supposedly around 16.5fps. Aside from the weight difference, I'm not sure why I chose to go with belts. I chose the particular gears I'm using to take up the least space. I tried with various other ratios, but the one I chose allowed me to make the plates that hold the module together significantly smaller by having the gears be positioned close around the bearing. Like this.

4. Is the center of the turning module, looking down from the top, equidistant from both of the sides that mount the swerve module? That way you don't need to worry about module orientation when putting it on a chassis, and programming becomes a bit easier.

I'm currently re-designing the body, but the version shown in the pictures is equidistant. Unintentionally, though - I'll make sure to do it this way in the final design as well.

5. How thick are the top and bottom plates, and why?

0.25in, because its the thickness of the WCP SS and DS gearboxes. Additionally, its the thickness of most Vex/AndyMark bearings (minus the flange), to there's a lot of nice flush edges.

7. What bevel// miter gears are you running? I've never found a good place to get them cheaply at other then Vex, and the Vex bevel gears are pretty large.

Vex 15t Bevel gear. I haven't found a problem with them other than the fact that they're 3/8in hex and most everything else is .5in hex, so the shaft going to it has to be milled from one to the other and it needs to have a set screw put in it...

8. How much does this weigh? If it weighs more than 8-9lbs, you need to rethink weight distribution. It's definitely possible to get it lower than that.

With quite a bit of hardware missing, it weighs 10.25lbs, but once I add the missing hardware, cut out relief pockets, and (maybe) trade out one of the heavy bearings for a bushing, it should be around 9-10lbs. Its not for competition, so I'll be satisfied with anything under 11lbs.

Thank you for your input!