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GBX-162, Realistic Swerve

asid61

By: asid61
New: 04-15-2018 03:19 AM
Updated: 04-15-2018 02:59 PM
Views: 1187 times


GBX-162, Realistic Swerve

GBX-162 is a realistic swerve drive. In the past, many of my designs have fallen short in one way or another or had failure points, but this is pretty much how I would make a swerve drive if I had to do one in-season. It weighs 6.4lbs with a CIM or 5.8lbs with a MiniCIM (without the versaframe shown in the photo).
Geared for 17.4fps free speed, it's fairly fast without sacrificing acceleration. To change the ratio to something slower I would need to switch to a larger bearing to suit a larger gear, but it wouldn't be a terrible change to make.
Of course 1072 will never use this design unless the students come up with something on their own! But I figured it would be a good idea to make a swerve drive that I'd feel confident in fielding in CADathons at least.

CAD files are located here:
https://workbench.grabcad.com/workbe...IQSQ0z1UVX5D8O
Look in GBX-162 -> Release for Pack&Go and STEP files.

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04-15-2018 09:54 AM

Billfred


Unread Re: pic: GBX-162, Realistic Swerve

You always have the most gorgeous renders.

One thing I noticed about your mounting: Have you considered 1533-style slots instead of the holes? It nerfs some of the pocketing, but it does give you the ability to locate it along any length of VersaFrame without having to poke new holes in the tubing.



04-15-2018 10:13 AM

C4


Unread Re: pic: GBX-162, Realistic Swerve

Do you have the parts list/CAD for this?



04-15-2018 10:20 AM

Oblarg


Unread Re: pic: GBX-162, Realistic Swerve

It's a small thing, but thank you for listing free speed rather than "top speed" with some unknown/arbitrary "speed loss constant" applied to it.



04-15-2018 10:28 AM

s_forbes


Unread Re: pic: GBX-162, Realistic Swerve

Nice and compact! Is that a ball bearing on the end of the CIM shaft and in the center of the large rotational gear? I would omit that part for fear of overconstraining the motor shaft. The shaft is strong enough to support the pinion without that bearing.

What is being used for the large bearing for the module rotation?



04-15-2018 11:27 AM

caleb7hayes


Unread Re: pic: GBX-162, Realistic Swerve

I'm asking this because I can't clearly see it, but how are you planning on mounting encoders to track distance and rotation of your module? Beyond that it looks great, good work!



04-15-2018 01:14 PM

NerdRage


Unread Re: pic: GBX-162, Realistic Swerve

I love the packaging and small form factor of this swerve! Having attempted to design swerve on my own multiple times, I understand how difficult it is to get something nicely packaged. I was wondering if those screws on the bottom were all the support that the fork gets in terms of radial loads? Do you have another bearing, or is all the load through the bolts on the bottom? Also, what do you have in terms of taking the thrust load?



04-15-2018 02:03 PM

asid61


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by Billfred View Post
You always have the most gorgeous renders.

One thing I noticed about your mounting: Have you considered 1533-style slots instead of the holes? It nerfs some of the pocketing, but it does give you the ability to locate it along any length of VersaFrame without having to poke new holes in the tubing.
You know, my renders used to look only decent until I saw Nick Coussen do a render on a dark background, so now I use the same background for all my renders.
I like the idea of the slots, but I don't particularly see the need honestly. I don't like using Versaframe over just making my own tubing, after spending hours this year getting VF just right. Given that we have a CNC and a manual mill, it's actually faster for us just to cut tubes to length on the manual rather than use VF.

Quote:
Originally Posted by C4 View Post
Do you have the parts list/CAD for this?
I'm just generating the STEP and Pack&Go files now, and will update the description with the link as soon as that's done.

Quote:
Originally Posted by Oblarg View Post
It's a small thing, but thank you for listing free speed rather than "top speed" with some unknown/arbitrary "speed loss constant" applied to it.
I always get mildly peeved when I see "adjusted" speed listed. Adjusted for what?

Quote:
Originally Posted by s_forbes View Post
Nice and compact! Is that a ball bearing on the end of the CIM shaft and in the center of the large rotational gear? I would omit that part for fear of overconstraining the motor shaft. The shaft is strong enough to support the pinion without that bearing.

What is being used for the large bearing for the module rotation?
There's a balance to be struck here with the overconstraining. On one hand I agree with you and don't want to risk the shaft binding. But on the other hand, if I don't have it, tolerances could totally throw the spacing of the CIM pinion off relative to its meshing gear. Tricky, tricky stuff. I'll probably remove to make room for an AMT CIMcoder on the CIM shaft.
I'm using a 6814 bearing, 70mm inner by 90mm outer, 10mm thick. Very cheap alternatives to the Silverthin bearings a lot of designs use.

Quote:
Originally Posted by caleb7hayes View Post
I'm asking this because I can't clearly see it, but how are you planning on mounting encoders to track distance and rotation of your module? Beyond that it looks great, good work!
Whoops, I knew I forgot something! The plan was to use Muchskull's AMT CIMcoder for the drive, I'll add that in before releasing the CAD. Rotation is settled with a Versaplanetary Integrated Encoder.

Quote:
Originally Posted by NerdRage View Post
I love the packaging and small form factor of this swerve! Having attempted to design swerve on my own multiple times, I understand how difficult it is to get something nicely packaged. I was wondering if those screws on the bottom were all the support that the fork gets in terms of radial loads? Do you have another bearing, or is all the load through the bolts on the bottom? Also, what do you have in terms of taking the thrust load?
The setup here is similar to the one 1323 runs, so I'm not too worried about most of the lower module specifics. The screw is a dead axle for the wheel, and the forks are attached to the turning gear by means of 4 10-32 screws tapped into the forks with a couple of tiny pins on one fork for locating the bevel gear. Because of the small wheel it's quite easy to make it compact and strong.
If you mean the thrust loads from the bevel gear, those are taken just on regular ball bearings. Other swerves have run the same setup without issues. There is space for a roller thrust bearing, but I wouldn't add it unless I needed it.



04-15-2018 02:10 PM

Andrew_L


Unread Re: pic: GBX-162, Realistic Swerve

Is it realistic because you're never gonna use it?



04-15-2018 02:37 PM

AdamHeard


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by Andrew_L View Post
Is it realistic because you're never gonna use it?



04-15-2018 02:53 PM

leafy1072


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by Andrew_L View Post
Is it realistic because you're never gonna use it?
Is it realistic if you make it and it doesn’t work?



04-15-2018 02:57 PM

Andrew_L


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by leafy1072 View Post
Is it realistic if you make it and it doesn’t work?
You know Anand just as well as I do - no way he'd make a swerve in season.



04-15-2018 02:57 PM

asid61


Unread Re: pic: GBX-162, Realistic Swerve

Link to CAD models (also in description): https://workbench.grabcad.com/workbe...IQSQ0z1UVX5D8O

I added Munchskull's CIMcoder and removed the bearing in the middle gear.

Quote:
Originally Posted by Andrew_L View Post
You know Anand just as well as I do - no way he'd make a swerve in season.
Bingo. Not worth the time it takes IMO. COTS swerves, however, are on the table. The Swerve&Steer still has numerous issues, but here's to hoping for improvements!



04-15-2018 03:10 PM

leafy1072


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by asid61 View Post

Bingo. Not worth the time it takes IMO. COTS swerves, however, are on the table. The Swerve&Steer still has numerous issues, but here's to hoping for improvements!
#SomeoneElsePleaseMakeSwerve



04-15-2018 04:35 PM

ollien


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by asid61 View Post
Link to CAD models (also in description): https://workbench.grabcad.com/workbe...IQSQ0z1UVX5D8O

I added Munchskull's CIMcoder and removed the bearing in the middle gear.



Bingo. Not worth the time it takes IMO. COTS swerves, however, are on the table. The Swerve&Steer still has numerous issues, but here's to hoping for improvements!
Care to detail what's wrong with Swerve&Steer?



04-15-2018 07:43 PM

asid61


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by ollien View Post
Care to detail what's wrong with Swerve&Steer?
Apart from tolerance/machining issues in 2015 when they came out, there's no way to add a drive encoder, it's heavy, and it's super tall. They require you to use an MA3 for rotation, the top speed is fairly low, and the use of a PG71 for steering means that it's slow to rotate. A copy of 1323's swerve, or even a Team221 module, would perform better. Of course the latter is not available anymore.



04-15-2018 08:54 PM

R.C.


Unread Re: pic: GBX-162, Realistic Swerve

We will def have some form of a swerve module for sale. After 3 iterations we think it's ready for sale!



04-15-2018 08:55 PM

frcguy


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by R.C. View Post
We will def have some form of a swerve module for sale. After 3 iterations we think it's ready for sale!
Yay!



04-15-2018 09:05 PM

Andrew Duerner


Unread Re: pic: GBX-162, Realistic Swerve

Having more robots moving around the field like 1323 would be a game changer. Awesome news R.C.



04-15-2018 09:09 PM

Mike Marandola


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by R.C. View Post
We will def have some form of a swerve module for sale. After 3 iterations we think it's ready for sale!
Your season has been a very good advertisement so far



04-15-2018 09:34 PM

NerdRage


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by R.C. View Post
We will def have some form of a swerve module for sale. After 3 iterations we think it's ready for sale!
Holy cow, this is amazing news! We're definitely very interested, having done swerve back in 2009 (as 2272), and the past offseason.



04-15-2018 09:59 PM

pkrishna3082


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by asid61 View Post
Apart from tolerance/machining issues in 2015 when they came out, there's no way to add a drive encoder, it's heavy, and it's super tall. They require you to use an MA3 for rotation, the top speed is fairly low, and the use of a PG71 for steering means that it's slow to rotate. A copy of 1323's swerve, or even a Team221 module, would perform better. Of course the latter is not available anymore.
I agree that the AM swerve is not ideal for most of those reasons, and I am looking forward to seeing the 1323/WCP swerve module! However we were able to get decent drive speed control by adding a CIMcoder to the drive motors. Yes, it isn't perfect since it's on the input to the gear reduction and not the output, but it is an option.



04-15-2018 10:22 PM

asid61


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by R.C. View Post
We will def have some form of a swerve module for sale. After 3 iterations years we think it's ready for sale!
FTFY



04-16-2018 03:36 PM

s-neff


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by asid61 View Post
I added Munchskull's CIMcoder
Is this this significantly different from the stock AM CIMCoder?
We used the stock version for the first time this year in a 3-mini-CIM drive (WCP SS), and had our motor bolts back off and the motors loosen up. No issues on the mini-CIMs without the CIMcoder.

I have to wonder if the layer of plastic is reducing the preload available from the bolts, same way the versaplanetary encoder stage weakens those gearboxes. Before I use them again, I want to add a metal stand-off around each of the mounting bolt holes...



04-16-2018 04:15 PM

asid61


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by s-neff View Post
Is this this significantly different from the stock AM CIMCoder?
We used the stock version for the first time this year in a 3-mini-CIM drive (WCP SS), and had our motor bolts back off and the motors loosen up. No issues on the mini-CIMs without the CIMcoder.

I have to wonder if the layer of plastic is reducing the preload available from the bolts, same way the versaplanetary encoder stage weakens those gearboxes. Before I use them again, I want to add a metal stand-off around each of the mounting bolt holes...
Munchskull's design uses the robust AMT-102 encoders, while I've had nothing but issues with the AM Cimcoder. Tightening the CIM with the CIMcoder breaks them permanently. We wasted a lot of time last year with them, but no longer.
Plus, the AMTS have latching headers. I'm a big fan of that. AMTs have a lot more precision than the CIMcoders too, with an index pulse, and at about half the price.
The VP encoder stages actually do come with metal standoffs, but they're easy to lose.



04-17-2018 09:09 AM

kingbrandon14


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by pkrishna3082 View Post
I agree that the AM swerve is not ideal for most of those reasons, and I am looking forward to seeing the 1323/WCP swerve module! However we were able to get decent drive speed control by adding a CIMcoder to the drive motors. Yes, it isn't perfect since it's on the input to the gear reduction and not the output, but it is an option.
Why is it not ideal to have the encoder on the input side? Wouldn't it be better to have encoders on the input side so that you get more increments per rotation, therefore higher precision?



04-17-2018 09:16 AM

pkrishna3082


Unread Re: pic: GBX-162, Realistic Swerve

Quote:
Originally Posted by kingbrandon14 View Post
Why is it not ideal to have the encoder on the input side? Wouldn't it be better to have encoders on the input side so that you get more increments per rotation, therefore higher precision?
Yes and no. You also have backlash through however many gear reductions you happen to have, so those extra sig figs may not be worth it after all. With the AM swerve modules I was able to turn the wheels a decent amount (1/16 turn maybe) without changing encoder values. Will it actually matter? Probably not. Such things are more important on something like an elevator or arm where encoder precision is a lot more important. Usually, if you are off by an inch, especially in Power Up, it's not too bad.



04-17-2018 09:38 AM

RobotNerd1


Unread Re: pic: GBX-162, Realistic Swerve

Emphasis mine

Quote:
Originally Posted by pkrishna3082 View Post
Yes and no. You also have backlash through however many gear reductions you happen to have, so those extra sig figs may not be worth it after all. With the AM swerve modules I was able to turn the wheels a decent amount (1/16 turn maybe) without changing encoder values. Will it actually matter? Probably not. Such things are more important on something like an elevator or arm where encoder precision is a lot more important. Usually, if you are off by an inch, especially in Power Up, it's not too bad.
I beg to differ. As the programmer for our team, encoder precision for the rotation of swerve modules can make or break your autonomous. If one module is off by a little bit it can cause the whole robot to rotate and/or drift during robot operation.



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