pic: Coaxial Swerve Drive Module with 2-speed Ball Drive and Nitrile Tread

[Kevin Ainsworth]

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[fb39ca4]

Fancy. How much does each module weigh?

[Tyler2517]

Originally Posted by fb39ca4

Fancy. How much does each module weigh?

7lb 3" it says it in the post.

[nathannfm]

Are you planning on building a drive with these before the season?
I really like the bevel gear embedded in the drive wheel eliminating an extra stage.
What kind of module rotation speeds are you looking at (rps)?
Did you design your own ball shifter? From the cutaway it looks different then the VexPro one.

I think we would all appreciate you posting the CAD or a few more views, you can hardly see the rotation motor.
Very nice work!

[Oblarg]

Great-looking design. With just 1 CIM per wheel, though, isn't that top speed a bit high, unless you're planning to use autoshift code?

[Tyler2517]

What is the benefits in running this one over the last design? 2 speed shifting is nice but you have decreed mechanical efficacy and a higher center of gravity.

Still like the design though really smart roundabout thinking.

[Jared Russell]

Originally Posted by Tyler2517

2 speed shifting is nice but you have decreed mechanical efficacy and a higher center of gravity.

If 2451 truly gets about 82% of the theoretical free speed out of these transmissions, that's in the efficiency ballpark of most FRC skid-steer drive trains. Some teams can hit the low 90s, but that is the exception rather than the rule.

Also, the intuition of "what's too fast for high gear" is somewhat different for an independently steered/driven swerve than for a skid-steer drive train. Your wheels never need to fight each other, so you are asking less of your drive motors than in a 6/8WD where you need to force wheels to slip sideways in order to turn.

[mplanchard]

Beautiful model. Thank you for sharing. Marie

[Bryce2471]

I really love this design overall. I've wanted to design a swerve with a single reduction ball-shifter for quite some time. I do have some questions and concerns though.

1. It looks like there is no thrust bearing above the vertical miter gear. This is not a big deal by its self, (We used thrust washers last year) but it will increase the speed of deterioration on the gears, and decrease efficiency in that gear-set. It also looks like you're planning on using the VEX Pro aluminum Miter gears. This is also not a big deal, lots of team use them, but I suspect the fact that they are aluminum will increase wear speed. With those two things combined, your drive performance may not suffer, but you will probably find yourselves replacing the miter gears pretty often. What is the process for replacing a miter gear? How long will it take?
2. How many man-hours will you spend to machine all the parts? How about to assemble the modules? I feel like you could have designed a module with the same performance, that would have been much less resource demanding to build.
3. What kind of bearing are you using to move the robot's weight from the red base plate to the top of the castor? In the cross section, it looks very thin.
4. Not sure if it is a problem or not, but I couldn't help but notice that your pneumatic cylinder is mounted to a plate, that has standoffs to a plate, that has standoffs to a plate, that is stood off from a plate, that has standoffs to a plate, that is mounted to your frame. Not sure why, but that makes me cringe a little.
5. What gears are you using on the ball-shifter shaft, and as the CIM pinions?

[Aren_Hill]

Originally Posted by Bryce2471

1. It looks like there is no thrust bearing above the vertical miter gear. This is not a big deal by its self, (We used thrust washers last year) but it will increase the speed of deterioration on the gears, and decrease efficiency in that gear-set. It also looks like you're planning on using the VEX Pro aluminum Miter gears. This is also not a big deal, lots of team use them, but I suspect the fact that they are aluminum will increase wear speed. With those two things combined, your drive performance may not suffer, but you will probably find yourselves replacing the miter gears pretty often. What is the process for replacing a miter gear? How long will it take?

VEXpro Bevel gears are 4140 hardened steel not aluminum.

-Aren

[magnets]

This is a fantastic design. There have been many designs of two speed swerves posted over the years, but nothing has come close to what you've put together.
I know from looking at your swerve design from last year that you guys shouldn't have trouble machining the parts in this design, but I've got to ask, how do you guys even have time to make these parts and finish the robot on time? What sort of tools do you have, and how many people do you have working?

[Bryce2471]

Originally Posted by Aren_Hill

VEXpro Bevel gears are 4140 hardened steel not aluminum.

-Aren

Thanks Aren, that makes a lot more sense. I was actually amazed that the gears seemed to be holding up.

I'm still curious how the miter gears would be replaced, and how long it would take.

[Jared]

Originally Posted by Bryce2471

I really love this design overall. I've wanted to design a swerve with a single reduction ball-shifter for quite some time. I do have some questions and concerns though.

1. It looks like there is no thrust bearing above the vertical miter gear. This is not a big deal by its self, (We used thrust washers last year) but it will increase the speed of deterioration on the gears, and decrease efficiency in that gear-set. It also looks like you're planning on using the VEX Pro aluminum Miter gears. This is also not a big deal, lots of team use them, but I suspect the fact that they are aluminum will increase wear speed. With those two things combined, your drive performance may not suffer, but you will probably find yourselves replacing the miter gears pretty often. What is the process for replacing a miter gear? How long will it take?
2. How many man-hours will you spend to machine all the parts? How about to assemble the modules? I feel like you could have designed a module with the same performance, that would have been much less resource demanding to build.
?

I don't see how not having a thrust bearing reduces the life of the gears. It may affect the life and efficiency of the 0.375" bearing sitting above it though.

We've done something similar with our climber (3 CIMs on a 10:1 worm reduction) with the worm resting against the inner race of a normal radial bearing, and we saw no issues.

[Tyler2517]

Originally Posted by Jared

I don't see how not having a thrust bearing reduces the life of the gears. It may affect the life and efficiency of the 0.375" bearing sitting above it though.

We've done something similar with our climber (3 CIMs on a 10:1 worm reduction) with the worm resting against the inner race of a normal radial bearing, and we saw no issues.

I can confirm what Bryce2471 is saying we saw reduced life and over time reduced efficiency due to us not having the thrust bearings between the mitter gear and the radial bearing.

[Jared]

Originally Posted by Tyler2517

I can confirm what Bryce2471 is saying we saw reduced life and over time reduced efficiency due to us not having the thrust bearings between the mitter gear and the radial bearing.

Of the gears or of the bearings? Also, did you do a comparison with thrust bearings to see if life improved? I don't see how the gears would have any additional loads on them due to a lack of thrust bearing.