Strange Swerve 4.0 Triple Strange 1533

[SenorZ]

Fantastic. We've been toying with swerve all summer (mostly in design) and it didn't turn out this slick.

I think elegant is the term to use (as in an elegant solution).

[Type]

One question for you, why did you decide not to use the VersaPlanetary encoder for the turning motor?

[marshall]

Originally Posted by Type

One question for you, why did you decide not to use the VersaPlanetary encoder for the turning motor?

I'm not on the team but it's a 1:1 ratio the way they have it setup now. Using the encoder block would result in a ratio that is not 1:1 and would then make for some complex math and silliness to figure out the angle of the module.

[Cothron Theiss]

Originally Posted by Noudvanbrunscho

Ooh oops, missed that part, went directly for the photo's. Thanks!

Haha, those are some great pictures to look at. The last bit of text was easy to miss.

Originally Posted by iyportne

Grooves in all plates made the same way. Mount plates on fixture in lathe and use a 1/4" Dia parting tool to cut out groove.

https://youtu.be/vE3397650W4

Oh wow, that's exactly what I was wondering. That looks great! What's the actual diameter on the ball bearings? I know in commercial bearings, the inner and outer races are cut into a concave path so that the balls automatically center in the path. What made you choose to do use parting cutter? It'd be easy to hold tight tolerances on the depth with, but it'd leave a flat bottom in the groove. Are you guys seeing any issues with the balls catching or jamming since they can move side to side relative to each other and since you don't have an inner cage?

[nuclearnerd]

Originally Posted by Cothron Theiss

Are you guys seeing any issues with the balls catching or jamming since they can move side to side relative to each other and since you don't have an inner cage?

I'd be more worried about the balls brinelling such a soft race. I'd love to hear how this design fares over a large amount of use.

The cage problem (if it is a problem) would be easy to solve. Just make sure every second ball is smaller. The smaller balls will act as spacers, and since they won't contact both races, they can turn in the opposite direction as the larger balls, eliminating rubbing. Bearing balls are available in increments as small as 1 thousandth of an inch. You can even use plastic balls, since they won't be load bearing.

[iyportne]

Originally Posted by marshall

I'm not on the team but it's a 1:1 ratio the way they have it setup now. Using the encoder block would result in a ratio that is not 1:1 and would then make for some complex math and silliness to figure out the angle of the module.

Right...the code library is based on absolute position. The encoder is a TT Electronics/BI 6127V1A360L.5FS from Digikey, a linear angle position sensor, makes the code robust and the bot powers up knowing the wheel angles. Of course, the mechanical challenge has always been to get the encoder to match the rotation of the swerve module, but they got that down now after a couple of design interations.

[iyportne]

Originally Posted by Cothron Theiss

...What's the actual diameter on the ball bearings? I know in commercial bearings, the inner and outer races are cut into a concave path so that the balls automatically center in the path. What made you choose to do use parting cutter?...Are you guys seeing any issues with the balls catching or jamming since they can move side to side relative to each other and since you don't have an inner cage?...

The balls are 0.250" DELRIN bearings. The channel depths are 3/32" leaving a 1/16" float gap between plates. The parting tool is actually 0.250 circular arc so the channel is a concave path with nearly full contact with bearing circumference. Running dry there is no apparent bearing-to-bearing interference. The first prototype was cut with CNC Mill using a ball end mill, but that was very slow and produced too much cutter advance ridging perpendicular to ball path.

[CalTran]

That swerve looks dope. ~22lbs for a swerve is insane.

[Type]

Originally Posted by marshall

I'm not on the team but it's a 1:1 ratio the way they have it setup now. Using the encoder block would result in a ratio that is not 1:1 and would then make for some complex math and silliness to figure out the angle of the module.

Thank you, I must have missed that.

[Cothron Theiss]

Originally Posted by iyportne

The balls are 0.250" DELRIN bearings. The channel depths are 3/32" leaving a 1/16" float gap between plates. The parting tool is actually 0.250 circular arc so the channel is a concave path with nearly full contact with bearing circumference. Running dry there is no apparent bearing-to-bearing interference. The first prototype was cut with CNC Mill using a ball end mill, but that was very slow and produced too much cutter advance ridging perpendicular to ball path.

Ahh, ok. All of that sounds good. I've never used a parting tool with a convex face.

Also, this may just be the angle, but the teeth on your watercut gear look more shallow than the teeth on the VexPro gear. Is this just a trick of the light, a mistake in the manufacturing, or did you use a slightly different profile from what's on the VexPro gears?

[dmpage318]

Originally Posted by Cothron Theiss

Also, this may just be the angle, but the teeth on your watercut gear look more shallow than the teeth on the VexPro gear. Is this just a trick of the light, a mistake in the manufacturing, or did you use a slightly different profile from what's on the VexPro gears?

The teeth are in fact more shallow. They were designed to match the profile of VexPro gears but this is how they turned out from the waterjet. We're not too concerned about it because it won't be under a big load and won't be turning very quickly.

[Brainiac33]

Here is the link for the Strange Swerve CAD MODELS!!!
https://grabcad.com/library/strange-swerve-4-0-1

[frcguy]

Originally Posted by Brainiac33

Here is the link for the Strange Swerve CAD MODELS!!!
https://grabcad.com/library/strange-swerve-4-0-1

Awesome! Excited to take an in-depth look.

[Lil' Lavery]

And the VersaPlanetaries v2 arrived just in time to swap out all the burned out 775 Pros!

Kidding aside, I'll be intrigued to see how the 775s hold up should this make it to the competition field. Pushing matches aren't the only time a drivetrain could experience high current situations, nor are they always entirely avoidable (especially in games with designated scoring areas and/or chokepoints).

I'll also be interested with regards to how the modules hold up to side loads on the wheels. This is a very aggressively packaged module, and it has custom bearings to boot. I'm wondering how well those bearings will deal with scrub forces on the wheels, and what potential there is for those forces to get passed even further up the module.

Certainly a very ambitious and advantageous take on a swerve module.

[Cothron Theiss]

Just now noticed that it's a 1/4" bolt serving as the axle. That seems a little thin to me, but if it works, that'll be great.