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Unread 08-29-2018, 03:14 AM
Danielm55t Danielm55t is offline
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pic: 3d printable swerve

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Unread 08-29-2018, 03:34 AM
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Re: pic: 3d printable swerve

I understand the 1:1 absolute encoder for steering, but the Mini CIM also appears to have a 1:1 absolute encoder. I'm pretty sure you're going to want to change that.

First of all, absolute encoders tell you what angle they're at, not how fast they're turning. You don't ever care about what angle your Mini CIM shaft is pointing at, you only care about how fast it's spinning. For that reason, you really want to use an incremental encoder.

Second, that Mini CIM shaft will be spinning very fast (max 5840 rpm). If you choose an encoder with a low CPR, it can be okay to measure the speed 1:1 with the motor. However, it may make more sense to use a higher-CPR encoder and place it after some reduction so that you don't have to worry about your ABS gears meshing at 6 ft/sec.


All-in-all, I'm not sure how well the ABS gears will hold up in testing, but that's what testing is for after all. I'm assuming you're using this with a very underweight chassis, so it might be able to hold it. I certainly wouldn't trust ABS gears with a competition robot, but I expect you know that already. I'm most concerned about the spur gear reduction, which appears to be between a metal pinion and a plastic gear. If this is the case, I would expect that plastic gear to degrade pretty quickly due to the difference in the hardnesses between the materials, but I guess you will find out how big of a problem that is during testing.

Good luck!
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Unread 08-29-2018, 10:27 AM
Danielm55t Danielm55t is offline
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Re: pic: 3d printable swerve

Do you have an example of an incremental encoder that would work? I don’t have a lot of experience with using encoders and the various types and what to look for when choosing one.

For gearing the encoder slower I should be able to just swap out the dark grey gears for something that gives me a 3:1 or 2:1.

Based of the testing I have done with an older version the gears hold up fine for testing but I wouldn’t trust them for competition use. All of the gears are plastic so there shouldn’t be any metal on plastic rubbing.
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Unread 08-29-2018, 11:16 AM
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Re: pic: 3d printable swerve

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Originally Posted by Danielm55t View Post
Do you have an example of an incremental encoder that would work? I don’t have a lot of experience with using encoders and the various types and what to look for when choosing one.

For gearing the encoder slower I should be able to just swap out the dark grey gears for something that gives me a 3:1 or 2:1.

Based of the testing I have done with an older version the gears hold up fine for testing but I wouldn’t trust them for competition use. All of the gears are plastic so there shouldn’t be any metal on plastic rubbing.
Really any incremental encoder will work. The best I can recommend in general are the SRX magnetic encoders from CTRE. They can be either incremental or absolute encoders depending on how you configure them, and I've only heard good reviews. We use them pretty much whenever we need an encoder. These were also in FIRST Choice the past few years, and AndyMark sells these and these.

That said, based on your design it seems like you would want an encoder with a built-in shaft instead of one that has a thru-hole for a shaft or reads a magnet that attaches to a separate shaft. You're best bet will probably be looking at a website like DigiKey or Mouser for a incremental encoder that suits your needs.
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Unread 08-29-2018, 04:16 PM
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Re: pic: 3d printable swerve

Quote:
Originally Posted by Danielm55t View Post
Do you have an example of an incremental encoder that would work? I don’t have a lot of experience with using encoders and the various types and what to look for when choosing one.
I don't know how much adaptation, if any, would be needed to make these work, but this season my team used these encoders (or some similar incarnation) from USDigital without much *headache. As configured it would run you about $130 USD for 4 of them (the cables aren't included)

*The encoders we had on the robot were old, sitting in a drawer, and had had a long life. One was dead at our first competition, the other had a disc that slipped off the output shaft and was mangled inside the robot in the offseason. Your mileage may vary.
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Unread 09-06-2018, 06:35 AM
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Re: pic: 3d printable swerve

the only thing I can see resulting from this is a broken swerve drive in the middle of a match

reason why is that there is no way those gears will hold up under the high loads that a dirvetrain is put under
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Unread 09-06-2018, 09:15 AM
GeeTwo GeeTwo is offline
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Re: pic: 3d printable swerve

Quote:
Originally Posted by baconbot View Post
the only thing I can see resulting from this is a broken swerve drive in the middle of a match
Not if used as designed (emphasis mine):

Quote:
Originally Posted by Danielm55t View Post
designed to be printed out of ABS or PETG on a cheap printer as a prototype
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