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 We need to grow smart not grow fast. - Andrew Schreiber [more] |
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This is a render of a swerve drive that the Bit Buckets have been working on for design practice during the off-season. We're not planning on building it, either before or during build season, but we did manufacture most of the parts for one of the modules as machining practice.
The drivetrain is designed to be light, durable, and largely built out of parts we already own or can easily and inexpensively procure.
It's driven by four CIMs through AndyMark CIMple Box gearboxes, for a top speed of about 10.5 ft/s and each module is steered by a BaneBots 550 motor in a Vex Pro VersaPlanetary gearbox. The tubes that goes up from the modules are machined from the top part of a bicycle fork. As a result we can use bicycle headset bearings (not shown) to support the modules.
Questions or constructive criticism are welcome.
Discussion
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24-12-2013 23:18
Chris is me
Re: pic: Swerve Design
Awesome design. Using a bike fork for the module top is very clever - I've been looking for an excuse to use one in FRC for years but we never build anything dealing with that kind of loading. I do have to ask, how are you handing the headset compression?
25-12-2013 10:27
MrBasse
Re: pic: Swerve Design
Can we get a view of one of the modules that would show the interior components and how they interface with each other? We've never done swerve before and I would just like to get mind head around the design process a little.
25-12-2013 11:22
yash101
Re: pic: Swerve Design
Great job, 4183! Is this your 3rd or 4th year in FRC?!?! Keep up the great work!
25-12-2013 16:36
Bryce2471
Re: pic: Swerve Design
Cool design, I like how you chose to use stand-offs instead of front and back plates on your lower wheel modules. Although, this may just be how I'm looking at the render. It seems like you could cut down on the foot print size taken up by the drive system.
The first time I designed a swerve module, it took up a 7" by 7" area in the corner of the robot. Upon redesign, I got it down to a 6" by 6" foot print. Then I redesigned again and got the size down to a 3" by 9" box.
I've noticed that each time I make my design smaller, it seams gets stronger and lighter as well. so there's multiple benefits of optimizing for size.
Also, make sure you have accurate and robust encoders on the steering of each module, they are important.
28-12-2013 18:37
z_beeblebrox
Re: pic: Swerve Design
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Originally Posted by cmrnpizzo14
That looks light, how much should it weigh?
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The top and bottom plates and the module sides are .25" aluminum. Would any pocketing on those be useful?
28-12-2013 18:52
theCADguy
Re: pic: Swerve Design
Awesome design! Nice work. 
Here is a similar design by 221 Robotic Systems. It's a customizable research platform, and has an interesting setup. Steering is accomplished using one motor to rotate two swerve modules. Another motor rotates the rear swerve modules. It seems as if the modules can be turned more than 360°, as the CIMs driving the wheels are located on the center of the drive train, and connect to the modules using a sprocket and chain.
http://www.team221.com/viewproduct.php?id=128
It seem very similar to your design.
28-12-2013 19:00
z_beeblebrox
Re: pic: Swerve Design
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Originally Posted by theCADguy
Awesome design! Nice work.
Here is a similar design by 221 Robotic Systems. It's a customizable research platform, and has an interesting setup. Steering is accomplished using one motor to rotate two swerve modules. Another motor rotates the rear swerve modules. It seems as if the modules can be turned more than 360°, as the CIMs driving the wheels are located on the center of the drive train, and connect to the modules using a sprocket and chain. http://www.team221.com/viewproduct.php?id=128 It seem very similar to your design. |
28-12-2013 19:05
magnets
Re: pic: Swerve Design
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Originally Posted by z_beeblebrox
Solidworks estimates 36lbs, which seems pretty reasonable.
The top and bottom plates and the module sides are .25" aluminum. Would any pocketing on those be useful? |
A few ideas for weight savings
You can shrink the module plate by making the whole thing a big triangle and pocketing the center, like this. Your current design looks like you're making them wider so you can add the little support thing. You shouldn't need one because the lower axle with the wheel on it will make the thing stiff enough.
The big green plates mounted to the frame could also get smaller by making them curved, and you could probably mount the steering motor directly to the frame, with no need to make the green plates go out that far.
The idea for using the bike parts for the bearing is really neat.
28-12-2013 21:58
z_beeblebrox
Re: pic: Swerve Design
Based on the suggestions given, I've made some changes to the design. I've removed the spacers from the module and added pockets. I also mounted the steering motor to the frame rails and reduced the size of the gearbox plates to what was actually needed. It's now about 38.5lbs. (For comparison, the 2013 KOP chassis with 4 CIMs weighs about 32.)
I also noticed that the first iteration was several pounds too light; I hadn't counted the correct mass for the the motors and gearboxes.
Edit: I added some pocketing to the gearbox plates and took off another .5lbs.
29-12-2013 16:57
yash101
Re: pic: Swerve Design
That is quite lightweight! If you want to get even lighter, I notice that there is some material that won't necessarily add any structural value, so there are many places to drill holes at to reduce weight! Hopefully you use this in 2014 so I get to check it out at the competitions!
29-12-2013 17:18
z_beeblebrox
Re: pic: Swerve Design
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Originally Posted by yash101
Hopefully you use this in 2014 so I get to check it out at the competitions!
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29-12-2013 18:23
s_forbes
Re: pic: Swerve Design
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Originally Posted by z_beeblebrox
The top and bottom plates and the module sides are .25" aluminum. Would any pocketing on those be useful?
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Weight down low is a good thing. Weight up high is not.
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