So being a rookie team we have came across a lot of new experiences since the start of the season.
The main thing that we want to focus on in our offseason is our drivetrain.
We have the money for a practice bot during next season but we are looking into different drive systems that could possibly grant us an advantage.
I know the typical thing is “get a working drive train and get practice” but that’s what the off season is for. Our team wants to experiment and push our limits and hopefully open boundaries.
So as far as drive trains go, we have almost no clue where to get them in a “kit-like style”. We were looking into two stage shifting ones but we don’t know how they work or how to manipulate them. We also came across mecanum options but don’t know what they do vs. a normal West Coast Drive. Finally, we looked into swerve drives but we have absolutely no clue where get them, how they work or how to drive them.
Any insight and possible direction is greatly appreciated!
I’d recommend looking further into West Coast Drive style drivetrains, with or without shifters. They are pretty much applicable to every year and are relatively simple to build and maintain.
I think you need to first narrow down your problem statement. A drivetrain that could “possibly grant you an advantage” is a bit vague. If you can come up with goals that are a bit more specific and measurable, I think it would greatly help with narrowing down the scope of the project.
Additionally, it seems like part of what you’re searching for is just the knowledge of what different types of drivetrains exist in FRC and what off-the-shelf components exist for these drivetrains. You don’t necessarily need to build one to gain his knowledge; there are plenty of online presentations and seminars explaining some of the basics. I can link a few when I get off mobile, but I’m sure others here will beat me to the punch.
Mecanum drive has greater agility than West Coast Drive. It allows you to move from sideways (strafe) when the wheels are put on in the correct orientation. West Coast Drive, as jamesmcip said, can pretty much used in every game (except for water games of course :P). It is usually a 6 wheel drive drop center which is directly driven. We haven’t used swerve yet but we are hoping to prototype one this summer. Swerve allows you to spin each wheel independently. If made right, swerves allow for high agility as well as high defense resistance. However, they take more effort to assemble and program.
You can get COTS two stage gear boxes from here. They should all have a CAD file in the Downloads tab of each gear box so you can see how they work without buying or physically assembling one.
I would suggest looking at this presentation from 1114.
Fancy drive trains don’t win matches effective mechanisms, strategies and well trained drivers do. To put it another way the best drive train in the world won’t win if there isn’t an effective game piece manipulator attached to it. Even if you attach an effective mechanism to that fancy drive train you won’t get far if your driver can’t drive it well or you miss matches because it is broken or you are struggling to maintain it.
So your best bet is to focus on making your existing robot more effective or experiment with manipulating other items. If you really really need to build your own chassis stick with a basic west coast style, ie a 6wd drop center design.
IIRC there was a regional winner in 2014 which was a drive base with a lawn chair on top of it.
Defense is important, good drives allow you to play defense.
This is somewhat echoing my post in your other thread about “wishlist suggestions” but again I’m going to suggest for your team to learn how to build a decent west coast drive before anything else.
In your post you say your team mostly has no clue on how to get them in a “kit-like style”. There’s always the Kit of Parts drivetrain, which is a robust design, but has some drawbacks in terms of customization and the like. There is a guide on the VexPro site for implementing different products with the KoP chassis, if you like that route.
IMO, the easiest west coast drive system that comes to closest to a “kit-like style” would be one that mirrors the 6 wheel drive system guide that also uses VexPro parts. There’s even this comprehensive step by step whitepaper guide that’s hosted on this site itself. Not a lot of precision machining required for both, either.
Read up on presentations on drivetrain designs and styles online. Talk to area teams. Search up old posts from these forums. There’s a wealth of information that can be found online, only if you put the effort in looking for it!
And was that lawn chair bot the captain of the alliance or the 2nd pick of the 1 alliance, ie the best of the worst?
Based on what I’ve seen living on the West Coast, the drivetrain is not what makes a good robot. Some of the best teams in the world (1678 and 254 come to mind) opt for the same basic west coast style every single year. (With minor differences). Everything above the drivetrain is what really counts. Focusing too much resources into your drivetrain is how you end up being a defense bot that can’t manipulate any of the game pieces.
A dead-simple drivetrain helps ensure you meet more important goals. There’s plenty of amazing teams who are able to have both a crazy drivetrain and amazing mechanisms (1986, 987, 1114). But for any normal team I’d reccomend sticking to the basics for the essentials.
What team was that???
You would have to ask Oblarg as he is the one that said a team won with like that.
This product is the exact drive given out in the Kit Of Parts for the last 2 years and is a great platform to experiment with both basic 6 wheel drive and the other types of drives that you mention.
AndyMark sells many kinds of shifting gearboxes, but our most advanced one is the new EVO Shifter which lets you independently choose which high and low gear you want. You can customize all the options and we will build it for you and ship it out in just a few days. Feel free to disassemble and reassemble it to get a more hands on experience of how it works. The basic principle is that it uses a pneumatic cylinder to push and pull a “dog gear” between 2 sets of gears, one that spins faster but has less torque, and one that spins slower but has more torque. This will require you have at least a basic pneumatic controll system on your robot.
If you get the AM14U3 base kit this shifter is a drop in replacement for the gearbox that that kit comes with. Just 4 bolts.
As others have said mecanum wheels let you drive sideways if spun in the correct direction. There are lots of resources on this forum that can explain in depth how the work.
Again, if you get the AM14U3 base kit you can buy this upgrade kit to convert the chassis to a mecanum drive.
Here is the AndyMark Swerve and Steer. It is an all in one swerve drive package designed to be mounted one per corner of a rectangular robot.
I would also direct you to 1640s exhaustive swerve drive website to learn more about how they work and how to program them.
There are literally hundreds of drivetrains, ik andymark sells two speeds, our team lead mentor realesed his own two speed that uses pneumatics to shift. fairly easy to build with no real machining and it can be found in the whitepages we like the vex Frame, and if we decide on one speed we use the tough box and if we decide on two speed we use our teams design. Then you have wheels which make a big difference I will always recommend andymark high grips, depending on the game though you may need inserts within the spokes to prevent them from breaking.
I’m also from a rookie team looking to do some drivetrain experimentation in the offseason. It seems to me that almost everything suggests that for a new team (and for experienced teams), tank drivetrains are the way to go. One video that really helped me think about the basics of a WCD was this video by the mentor of 1678: https://www.youtube.com/watch?v=GCjBx3TXB6Y. It’s a CAD tutorial, but he shares some of the considerations for a drop-center WCD. 1678 also has some great videos on their channel.
As a question to other CD members, is there any white paper or other resource that could serve as a comprehensive overview on WCD, discussing the various considerations that go into a drivetrain (speeds, wheel size, wheel types, advantages of chains vs. belts, ideal drop on the center wheel, 6 vs 8 wheels, and the list goes on). There are a lot of factors that people on CD talk about, but it’s hard to find any definitive answers on the advantage/disadvantages of different setup.
While true that mechanisms can make or break a robot (See: 469 2010), a bad drivetrain can incapacitate a robot entirely. If you can’t move on the field, you can’t really do a whole lot.
That being said, one thing that 1073 focused on for this season was a solid 8 wheel sheet metal drive train with a center drop. Obviously ymmv especially when manufacturing resources are a constraint. We decided to go for 8WD as opposed to 6 with a center drop simply to deter a lot of the rocking. With 4 always guaranteed to be on the ground, your robot becomes a lot more sturdy. So far it’s worked like a dream especially paired with 6 cims
This isn’t actually true, in my experience. The amount of rocking in a typical center-drop 6WD is pretty close to negligible.
On a 28" long robot, 6" wheel using the Versablocks drop (~.125"?), the rocking was fairly noticeable. IMO, choosing 8w (or 4w) for a more stable shooting platform is a valid design choice.
With which wheels, and on carpet or on a hard surface?
With colsons on carpet, I’ve never found the rocking to be non-negligible.
4" x 2" Colsons on carpet.