Swerve Drive Modules

[JVN]

Originally Posted by Tubatroopa

What would you say is a comparable drive train in power and maneuverability like the swerve?

Power is a silly comparison, since it is based purely on motors. a 4-motor 2WD has the same "power" as a 4-motor swerve.

As far as maneuverability -- I don't think sideways motion makes a swerve drive robot more maneuverable in application than any other drivetrain.

Most teams don't get the software right.
Most drivers can't control it.
Most swerves tend to fall apart at bad times.

Build a reliable skid-steer drive and you'll be just as good as a swerve in most games -- I bet you'll spend less effort to make it work, and I bet it is less likely to bite you in the butt at the wrong time.

-John

[msimon785]

Thanks everyone. Especially John. I'm going to fix that in the design.
And as to not building swerve, I too have seen it work and fail. Of course, 1717 has an exceptional design that we will not be able to match for at least a year or two.
However, We feel that this is a good way to open our team up to the sheet-metal world. If the swerve works well, we may build our 2012 chassis with SM. If we can form a solid relationship with a SM manufacturing shop, its worth a try.

@AdamHeard, yes we did. I'm going to do my best to get our team away from Mecanum drive.

[Aren_Hill]

If you do decide you really love swerve and want to make one, spend an entire offseason just mechanically making it, then set it aside and ignore it for a season. Then spend the entire next offseason making it drivable.

The biggest reason I'll tell people to not go after swerve, is the control is never quite good enough, it lacks the direct mental connection most tank drives achieve and from that loses effectiveness.

[Hawiian Cadder]

I dont know the efficiency on the bevel gears, but i bet a 4 wheel omni drive with an rs775 and a cim on each wheel would be more maneuverable, and probably push better too. I thought disco-bots did something like this year.

[msimon785]

I updated the design a bit to fit everyone's suggestions. (I did not fix the drive shaft yet, though. I am a little worried that it'll be difficult to assemble like this, so I may make the dual-triangles on the side into large rectangles with filleted corners.
You may notice that I removed the riveted sprocket from the top due to the fact that it is very obviously ineffective. I am going to eventually replace it with timing-belt pulleys from McMaster. Does anyone have an idea as to how I might attach these to the frame?

[msimon785]

Also, I know 1717 uses the main bent SM piece with open sides, in additional to two side plates which rivet on. This makes assembly way easier, but makes repair quite difficult. Of the two designs (one piece, three pieces), which is preferable? Also, would it be a terrible idea to weld the timing-belt pulley to the SM? I know it would warp considerably.

[Chris is me]

There is no way that you would be able to bend that module in one piece.

[42!]

What method are you using to hold The output shaft to keep the module standing straight? This tends to be one of the more important things to get right in swerve drive. As it is i don't see any method in place to hold the module against side force.

[msimon785]

Originally Posted by 42!

What method are you using to hold The output shaft to keep the module standing straight? This tends to be one of the more important things to get right in swerve drive. As it is i don't see any method in place to hold the module against side force.

I'm not sure what you mean. The output shaft infers the bolt holding the wheel/sprocket, correct? What do you suggest I add to prevent unwanted sheet-metal bending?

[42!]

I was actually referring to the shaft that the whole module pivots on, as it it i see it being held by one bearing at the top of the module, normally teams will have a second shaft around the drive shaft that the module turns on. Then this shaft can be held by some sort of bearing system that attaches to the robot.

[msimon785]

Originally Posted by 42!

I was actually referring to the shaft that the whole module pivots on, as it it i see it being held by one bearing at the top of the module, normally teams will have a second shaft around the drive shaft that the module turns on. Then this shaft can be held by some sort of bearing system that attaches to the robot.

Okay. Well, yes, in this design it is effectively held by one bearing. Where exactly do they place that second shaft? I can also, of course, just change it to a roller bearing, which are longer.

[42!]

The drive shaft is placed in the center of the shaft the module rotates on. In most systems there are two bearings hold the drive shaft. There should also be a system to hold the shaft the module pivots on. if your confused about this you should look at 221's Swerve system Revolution swerve http://www.andymark.com/ProductDetai...ctCode=am-0760
They have one of the more reliable swerve systems around

[akeisic]

Guess what team choose NOT to use a swerve drive this year? Wildstang! And it's practically been there signature for years.

It's typically about what goes on top of the drive train that makes the difference. Glad to see you're working the details BEFORE the season starts.

[Clem1640]

We've used Martin Gears' HM1616 (16 teeth, 16 Diametrical Pitch) miter gears for the last 2 years, but will probably switch to M1616 (not hardened) if we do this again. Gears have 3/8" unfinished bores. We cut our own keyways (finished bore gears are too expensive). We've had good experience with these.

Here's a view of our 2011 Pivot Module. Our Module includes the motors and angle sensor:

http://wiki.team1640.com/index.php?t..._annotated.jpg

Mass is 9.1 lb including motors, gearbox & sensor.

[Taylor]

Originally Posted by msimon785

@AdamHeard, yes we did. I'm going to do my best to get our team away from Mecanum drive.

What trouble did you have with Mecanum drive? We did direct-drive mecs from AM nanotubes and had our most reliable, successful drivetrain in 7 years.