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4587 Swerve 1.0

Cash4587

By: Cash4587
New: 05-17-2018 10:48 PM
Updated: 05-17-2018 10:48 PM
Views: 1218 times


4587 Swerve 1.0

Here is a swerve drive I have come up with that would be very achievable with a CNC router, manual lathe, and a manual mill. The goal was to design it so it could be manufactured entirely in house. We may or may not build something very similar, if not this exact module with some tweaks for our off-season project. Updates, more pictures, and a GrabCAD link will come soon. As always feel free to leave suggestions as well as ask any questions you might have.

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05-17-2018 11:15 PM

gorrilla


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by Cash4587 View Post
Can you post a bottom right iso?
What does the connection between the module and mounting plate look like(what are you using for the rotation surface)?



05-17-2018 11:19 PM

gorrilla


Unread Re: pic: 4587 Swerve 1.0

Also why this versus a coaxial design? You guys always make beautiful robots so im wondering why you'd go for taking up more vertical space instead of lateral space in the frame with a coax design.



05-17-2018 11:39 PM

Cash4587


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by gorrilla View Post
Can you post a bottom right iso?
What does the connection between the module and mounting plate look like(what are you using for the rotation surface)?
I plan to use a Chinese Silverthin bearing. As far as I can tell it is basically the same bearing but way cheaper. It is a 3.5"ID x 4.0"OD x 0.25"Thick bearing. The triangle shaped pieces are bolted to the 84t steering gear.

https://imgur.com/IiJ6pGi

Quote:
Originally Posted by gorrilla View Post
Also why this versus a coaxial design? You guys always make beautiful robots so im wondering why you'd go for taking up more vertical space instead of lateral space in the frame with a coax design.
It makes the module plates Identical when machining them as far as I have thought through it. With a lateral design I would have to mirror some plates and then also machine them differently. I just wanted our first module, which will end up being used for this years game to be simple. With there being plenty of height in this years rules it's not that big of a deal. Also lateral makes your frame taller unless you use a 775pro or miniCIM, which I also don't want to do.



05-18-2018 12:02 AM

asid61


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by Cash4587 View Post
I plan to use a Chinese Silverthin bearing. As far as I can tell it is basically the same bearing but way cheaper. It is a 3.5"ID x 4.0"OD x 0.25"Thick bearing. The triangle shaped pieces are bolted to the 84t steering gear.

https://imgur.com/IiJ6pGi



It makes the module plates Identical when machining them as far as I have thought through it. With a lateral design I would have to mirror some plates and then also machine them differently. I just wanted our first module, which will end up being used for this years game to be simple. With there being plenty of height in this years rules it's not that big of a deal. Also lateral makes your frame taller unless you use a 775pro or miniCIM, which I also don't want to do.
Where are you planning on sourcing this Chinese Silverthin? I might have need of one for an offseason project.
Swerve looks solid, although I wouldn't volunteer to machine that bevel gear.



05-18-2018 12:25 AM

PatrickW


Unread Re: pic: 4587 Swerve 1.0

Very nice looking design. It appears to take a lot of inspiration from my design, which took a lot of inspiration from one of Aren Hill's designs. Please post updates when you get it put together over the off season.
#teamswerve



05-18-2018 12:25 AM

NerdRage


Unread Re: pic: 4587 Swerve 1.0

Good stuff. I like how you're doing the bevel on the wheel, instead of relying on a press fit. Is the shaft of the VP being supported by a bearing on the plate? I'd put one on just to be safe. [Edit: Whoops! Ignore that, I didn't see the picture you posted earlier]

Also, do you have a means of zeroing your modules? With the VP encoder, you're not going to measuring wheel rotation but rather output shaft rotation, meaning that you'll find "zero" falsely multiple times over a single rotation of the wheel.



05-18-2018 12:34 AM

PatrickW


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by NerdRage View Post
Also, do you have a means of zeroing your modules? With the VP encoder, you're not going to measuring wheel rotation but rather output shaft rotation, meaning that you'll find "zero" falsely multiple times over a single rotation of the wheel.
This was the main reason we didn't use the VP integrated encoder on our module this past year. We instead went with a encoder geared 1:1 with the steering of the module. It was very nice to be able to place the robot on the field and not need to make sure the wheels were pointed in the correct general direction or have an addition sensor and need to run a homing routine.



05-18-2018 01:03 AM

deltafief


Unread Re: pic: 4587 Swerve 1.0

would a cim coder be good for a swerve like this? It would directly mount on the CIM, I haven't used one before so not quite sure about the accuracy but it seems like that would be a pretty good option because it wouldn't take up space and wouldn't have the problems of the VP integrated one



05-18-2018 01:44 AM

Cash4587


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by asid61 View Post
Where are you planning on sourcing this Chinese Silverthin?
I'll PM you.



05-18-2018 01:46 AM

Cash4587


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by PatrickW View Post
Very nice looking design. It appears to take a lot of inspiration from my design, which took a lot of inspiration from one of Aren Hill's designs. Please post updates when you get it put together over the off season.
#teamswerve
Yeah, I took a lot of inspiration from Aren's design, and yours, but also many other designs as well.



05-18-2018 01:50 AM

Cash4587


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by NerdRage View Post
Good stuff. I like how you're doing the bevel on the wheel, instead of relying on a press fit. Is the shaft of the VP being supported by a bearing on the plate? I'd put one on just to be safe. [Edit: Whoops! Ignore that, I didn't see the picture you posted earlier]

Also, do you have a means of zeroing your modules? With the VP encoder, you're not going to measuring wheel rotation but rather output shaft rotation, meaning that you'll find "zero" falsely multiple times over a single rotation of the wheel.
I plan to use the WCP Hall Effect sensor. Shown here: https://imgur.com/a/fVxFl8y

The only thing I am uncertain about is how this sensor should be mounted/used. I gave it my best guess on what I thought was right.



05-18-2018 07:41 AM

samthesnake


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by Cash4587 View Post
I plan to use the WCP Hall Effect sensor. Shown here: https://imgur.com/a/fVxFl8y

The only thing I am uncertain about is how this sensor should be mounted/used. I gave it my best guess on what I thought was right.
If you do this, you will have to zero the motors before every match. You should look into a 1:1 absolute encoder.



05-18-2018 08:20 AM

Ryan Dognaux


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by Cash4587 View Post
I'll PM you.
If you can send me the source of these cheaper silverthin bearings that would be awesome

Also where are you planning to purchase your bevel gears from?



05-18-2018 09:22 AM

Bryce2471


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by Ryan Dognaux View Post
If you can send me the source of these cheaper silverthin bearings that would be awesome
+1



05-18-2018 09:27 AM

AdamHeard


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by Bryce2471 View Post
+1
Can you post in here please?



05-18-2018 09:39 AM

Nick_Coussens


Unread Re: pic: 4587 Swerve 1.0

Enough with the bearing secrets people.

We used these last off-season and during the 2018 season. Took about 5 minutes of searching on Amazon. Also it's a generic bearing aprt number so you can find a ton of different suppliers that have the same bearing. Also go to the similar items to find varying sizes similar to this one.

https://www.amazon.com/gp/aw/d/B007H...IeL&ref=plSrch



05-18-2018 11:17 AM

Cash4587


Unread Re: pic: 4587 Swerve 1.0

No bearing secrets here. The bearings I am looking at getting are not genuine silverthin bearings thatís just the only way I could think to describe them. When I find a reliable supplier on Alibaba I will post a link with a part number of what I plan to order. Sorry for it coming off like itís a secret, I just have not found a place or price for what I am looking at getting.



05-18-2018 11:48 AM

NerdRage


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by Nick_Coussens View Post
Enough with the bearing secrets people.

We used these last off-season and during the 2018 season. Took about 5 minutes of searching on Amazon. Also it's a generic bearing aprt number so you can find a ton of different suppliers that have the same bearing. Also go to the similar items to find varying sizes similar to this one.

https://www.amazon.com/gp/aw/d/B007H...IeL&ref=plSrch
Amazon's nice and all, but you can get the same bearings for $6 on eBay. I don't have any links, but if you search up "6816 bearing" on eBay you'll find dozens come up. The only problem is that shipping takes about a week to two weeks, but if you order before the season it's probably worth it.

Edit: I'm a liar. It's $8 here. I swear I've seen some cheaper though.



05-18-2018 12:39 PM

Cash4587


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by NerdRage View Post
Amazon's nice and all, but you can get the same bearings for $6 on eBay. I don't have any links, but if you search up "6816 bearing" on eBay you'll find dozens come up. The only problem is that shipping takes about a week to two weeks, but if you order before the season it's probably worth it.

Edit: I'm a liar. It's $8 here. I swear I've seen some cheaper though.
If I donít end up finding the thin section bearings I will probably get those. Hopefully I can find the thin section ones.



05-19-2018 04:19 AM

asid61


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by Nick_Coussens View Post
Enough with the bearing secrets people.

We used these last off-season and during the 2018 season. Took about 5 minutes of searching on Amazon. Also it's a generic bearing aprt number so you can find a ton of different suppliers that have the same bearing. Also go to the similar items to find varying sizes similar to this one.

https://www.amazon.com/gp/aw/d/B007H...IeL&ref=plSrch
The issue is that 6800's tend to be larger than silverthins, espiecally the thickness, and that makes it weaker once you stick it into a 1/4" plate. I would like silverthin-esque bearings for very large IDs actually for an offseason project I'm working on (either a turret or some large swervey thing) because 68xx bearings can only get so large, around 6" max.



05-20-2018 11:30 AM

Cash4587


Unread Re: pic: 4587 Swerve 1.0

I found 3.5ĒID x 4.0ĒOD x 0.25Ē bearings for about 25$ a piece not including shipping. Search for KA035CP0 on alibaba and you should find it. Let me know if you guys have any more questions. Iíve emailed other suppliers from alibaba as well to shop around for prices more results will come in the next few days.



05-20-2018 12:26 PM

PatrickW


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by Cash4587 View Post
I found 3.5ĒID x 4.0ĒOD x 0.25Ē bearings for about 25$ a piece not including shipping. Search for KA035CP0 on alibaba and you should find it. Let me know if you guys have any more questions. Iíve emailed other suppliers from alibaba as well to shop around for prices more results will come in the next few days.
You way want to look into the X contact versions of bearings. They are rated for thrust loads and momentum loads as well as radial loads.



05-20-2018 09:44 PM

Nick_Coussens


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by NerdRage View Post
Amazon's nice and all, but you can get the same bearings for $6 on eBay. I don't have any links, but if you search up "6816 bearing" on eBay you'll find dozens come up. The only problem is that shipping takes about a week to two weeks, but if you order before the season it's probably worth it.

Edit: I'm a liar. It's $8 here. I swear I've seen some cheaper though.
I'll spend an extra $80 for a robot's worth of parts if it means I get them in 2 days instead of 2 weeks, especially during a build season.

Sure, you can order things ahead of time, but I like knowing if I need more of something during the season I can get it quick.

Quote:
Originally Posted by asid61
The issue is that 6800's tend to be larger than silverthins, espiecally the thickness, and that makes it weaker once you stick it into a 1/4" plate. I would like silverthin-esque bearings for very large IDs actually for an offseason project I'm working on (either a turret or some large swervey thing) because 68xx bearings can only get so large, around 6" max.
How does a thicker bearing result in it being weaker? Just counterbore the 1/4" thick plate you're recessing the bearing into and then just clamp the outer race of the bearing to the plate? I really don't see an issue here.

If you want a larger overall diameter then I can understand going to a different series of bearing, but while we're talking about swerve modules, the 68xx series is just fine.



05-20-2018 10:08 PM

asid61


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by Nick_Coussens View Post
How does a thicker bearing result in it being weaker? Just counterbore the 1/4" thick plate you're recessing the bearing into and then just clamp the outer race of the bearing to the plate? I really don't see an issue here.

If you want a larger overall diameter then I can understand going to a different series of bearing, but while we're talking about swerve modules, the 68xx series is just fine.
If I apply a sideways torque to a bearing that's sticking way out of a plate compared to one that's completely captured by the plate, it seems like the force would be more likely to crush the plate where it sticks out, but maybe my intuition is mistaken.



05-21-2018 12:08 AM

Nick_Coussens


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by asid61 View Post
If I apply a sideways torque to a bearing that's sticking way out of a plate compared to one that's completely captured by the plate, it seems like the force would be more likely to crush the plate where it sticks out, but maybe my intuition is mistaken.
We ran like this for our entire 2018 season and the offseason before with no issues. No wear at all on the bearing or the plate. We had 3 small blocks equidistant around the bearing that clamped the bearing to the plate.



05-21-2018 06:31 AM

marshall


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by Nick_Coussens View Post
We ran like this for our entire 2018 season and the offseason before with no issues. No wear at all on the bearing or the plate. We had 3 small blocks equidistant around the bearing that clamped the bearing to the plate.
Do you have pics of this?



05-21-2018 02:09 PM

Wayne TenBrink


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by PatrickW View Post
You way want to look into the X contact versions of bearings. They are rated for thrust loads and momentum loads as well as radial loads.
+1

A true "X contact" bearing has a "gothic arch" path geometry, compared to a simple radius profile used in a traditional radial contact bearing. The gothic arch path geometry allows each ball to contact both the inner and outer races in 2 places. If you draw lines thru these contact points and the center of the ball, the lines form an "X", which is where the bearing gets its name. They are also referred to as "4-point contact" or "X-type" bearings.

A 4-pt contact bearing behaves like a simplified version of a duplex pair of angular contact bearings. Compared to a comparably sized radial contact bearing, they will have considerably higher capacity and much less axial and moment/tilt "play", making them much more appropriate for the azimuth position on a swerve drive. This would also be beneficial in cases where you have mating gears that mesh via the bearing. Tight internal clearances are also important in this regard. I don't know what you get with a "low cost" bearing, but you can hide a lot of imperfections in a bearing by making it looser.

(full disclosure) I am a Product Design Engineer for Kaydon Bearings/SKF. Kaydon invented thin section bearings about 60 years ago, and I chuckle and cringe when I see people refer to a "genuine Silverthin" bearing as compared to a Chinese copy (they are all copies, IMHO). Kaydon may not be the "low price leader", but our quality standards and engineering support allow us to participate in some extremely cool projects.

What sort of loading do you all expect the azimuth (steering) bearing on an FRC swerve module to experience? "Normal" loading seems rather mild, but the shock loads could be incredibly high for some scenarios (like dropping the robot or getting hit from the side when your wheel was up against something, etc.). I would like to do a load analysis to see what sort of stresses are generated.



05-23-2018 10:45 AM

Nick_Coussens


Unread Re: pic: 4587 Swerve 1.0

Quote:
Originally Posted by marshall View Post
Do you have pics of this?
I'll try to grab some within the next week.



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