Quote:
Originally Posted by ekapalka
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?
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.
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.
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.
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...
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! |
That's a good encoder. To align the wheels, you can use a hall effect sensor and magnet aligned such that the wheel are all pointing the same way when the hall effect sensor is activated. Alternatively, putting a hole directly above each wheel axle and stretching surgical tubing between the wheel axles will make a pair wheels face the same direction. Then you just set constants in the program to get them aligned properly.
Belts are fine. They offer greater efficiency at the cost of width/ space. I just think that you could use a large reduction to the wheel axle instead of using so many gears. Then you could just use a belt or just a pair of gears to go to the coaxial axle from the cim.
0.25in is pretty hefty. Keep in mind the WCP gearboxes are heavily pocketed. When you pocket your swerve modules, which you should, make sure to get the pocket design checked out by a mentor/ engineer to maximize strength and minimize bending. Get the wheel very close to the edge to stop bending issues.
Vex bevel gears are fine. The low pitch gives them resistance to bending issues. What do you mean by a set screw? Avoid set screws on shafts whenever possible. A machine shop, or even a basic benchtop mill will be able to cut a 3/8" hex on the end of a 1/2" hex shaft without problems.
10lbs? I'm a huge weight freak when it comes to drivebases. Especially when it comes to swerve drives, the main setback that I see with them is size and weight. Size you are good on. 10lbs is very heavy though. Even if this will not be used in competition, I strongly advise you remove unnessesary weight. Like I mentioned with removing gears, there are ways to reduce weight.
Quote:
Originally Posted by Tyler2517
What is the use of all the extra material below the wheels axial?
The module looks supper tall. This will give you a higher center of gravity decreasing performance.
The co-axil looks complex.
I don't see the need for the gears. Most teams that i have seen that don't use shifting go directly from the cim to the co-axie with a timing belt and the majority of reduction in the yoke. Removing the gears will give you a higher mechanical efficiency and less moving parts in the high speed parts of the transmission.
The top of the modules bearing can definitely be using a bushing saving weight and cost. I personal like the thrust bearings riding on the bearing like 1640.
The plates look complex with a lot of milling operations on places that are not holding weight. Mainly where the bearings are why is this? It would be lighter and cheaper not to have to get plates that thick and mill them down even if the beaing plate are not smooth.
Over all a great start
|
I have noticed that designing a tall module with a cim facing up actually produces a similar COG when compared to a very short module with the cim facing down. Unless you can get the cim facing sideways, which requires more bevel gears and such, it's easier to keep a tall module.