FRC T-bone-ing and Hexagonal drive

[Joe Ross]

Originally Posted by jijiglobe

Many teams use a high friction cloth (such as emery cloth) for their front and back bumpers so that they can T-bone other teams, while using low friction cloth (such as sail cloth) for their side bumpers. so that other teams have difficulty T-boning them.

Citation Needed

[mrnoble]

Originally Posted by Joe Ross

Citation Needed

Agreed. Emery cloth? That would be... surprising if that passed inspection.

[Darkseer54]

Originally Posted by mrnoble

Agreed. Emery cloth? That would be... surprising if that passed inspection.

I remember discussion about using polyurethane coated cordura, like what is listed here, but I don't know if anyone has actually used it in competition yet.

[mrnoble]

Originally Posted by Darkseer54

I remember discussion about using polyurethane coated cordura, like what is listed here, but I don't know if anyone has actually used it in competition yet.

I could see that happening, but emery cloth is an abrasive, not just tacky. Some enterprising student out there is reading this thread and thinking that sticking sandpaper on their bumpers will be a good idea.

Dear Enterprising Student,

It's not a good idea.

Sincerely,

Every Other Team

[Ty Tremblay]

The important thing to remember here is that a hexagonal frame perimeter is an ENHANCEMENT and not a necessity. Don't sacrifice build time to design a hexagonal drivetrain unless you think that t-bones are what's holding you back.

In my opinion, only the top ~5% of FRC teams can both benefit from a hexagonal drivetrain and have the resources to build one without sacrificing elsewhere on the robot.

[Knufire]

Originally Posted by Ty Tremblay

The important thing to remember here is that a hexagonal frame perimeter is an ENHANCEMENT and not a necessity. Don't sacrifice build time to design a hexagonal drivetrain unless you think that t-bones are what's holding you back.

In my opinion, only the top ~5% of FRC teams can both benefit from a hexagonal drivetrain and have the resources to build one without sacrificing elsewhere on the robot.

I'll also add that slick bumpers gets you a lot of the benefit of hexagonal bumpers without nearly as much effort.

[MichaelBick]

Originally Posted by Ty Tremblay

The important thing to remember here is that a hexagonal frame perimeter is an ENHANCEMENT and not a necessity. Don't sacrifice build time to design a hexagonal drivetrain unless you think that t-bones are what's holding you back.

In my opinion, only the top ~5% of FRC teams can both benefit from a hexagonal drivetrain and have the resources to build one without sacrificing elsewhere on the robot.

A big advantage of hexagonal frame perimeters imo is that they have a higher area to perimeter ratio. In years that the frame perimeter is limited (2013, 2014) this allows you to build a longer robot, which makes for a more stable robot. If you look at the math, you don't even have to hex your perimeter significantly to see nice length gains.

[jijiglobe]

The emery cloth thing was a mistake on my part. I heard the word tossed around a couple years back when I was a freshman. In retrospect, what I heard was probably a joke because I just did a little research and making emery cloth bumpers would be insane.

[EricH]

Originally Posted by mrnoble

I could see that happening, but emery cloth is an abrasive, not just tacky. Some enterprising student out there is reading this thread and thinking that sticking sandpaper on their bumpers will be a good idea.

Dear Enterprising Student,

It's not a good idea.

Sincerely,

Every Other The Inspection Team & Your Team

Fixed that for you. That would be a pretty quick "you guys need to rework this" from the inspectors, followed by "Hey, Enterprising Student, this was YOUR idea, YOU fix it" from your team.

[Ty Tremblay]

Originally Posted by MichaelBick

A big advantage of hexagonal frame perimeters imo is that they have a higher area to perimeter ratio. In years that the frame perimeter is limited (2013, 2014) this allows you to build a longer robot, which makes for a more stable robot. If you look at the math, you don't even have to hex your perimeter significantly to see nice length gains.

While true, it can still be a red herring for most teams. Most teams struggle to build solid drivetrains, they don't need to be distracted by building complicated ones too.

[pmangels17]

Originally Posted by first_newbie

Are hexagonal drive train any better at turning?

It's...a lot more complicated than that. A drivetrain's ability to turn (assuming a skid steer AKA tank drive) is based upon the geometry of the wheels and how they contact the floor.

See this guide for a good summary of how different drivetrains behave in different scenarios: http://www.simbotics.org/files/pdf/drivetraindesign.pdf
You might look under the Applying Principles section for bits about wheelbase and track width and stuff like that to answer your question, but the presentation as a whole is fairly comprehensive and very useful to someone just getting into drivetrain design (which I presume you are interested in) and exploring beyond the buy-a-kitbot-and-put-it-together level of mechanical and physical analysis.

[MichaelBick]

Originally Posted by Ty Tremblay

While true, it can still be a red herring for most teams. Most teams struggle to build solid drivetrains, they don't need to be distracted by building complicated ones too.

It doesn't need to be complicated. Here is a picture of 1678's slightly bowed out frame perimeter in 2014, utilizing a WCD with thin outside wheels:

[Ty Tremblay]

Originally Posted by MichaelBick

It doesn't need to be complicated. Here is a picture of 1678's slightly bowed out frame perimeter in 2014, utilizing a WCD with thin outside wheels:

1678 went to Einstein with that drivetrain and pioneered the math and testing with 971. I'd hardly say they're an example of a typical FRC team.

Most teams shouldn't make this a priority. Putting, say, a week into a hexagonal drivetrain won't make your robot better than putting that same amount of time into the things you mount to your drivetrain.

You've gotta walk before you can run. If you're already running, build a hexagonal drivetrain.

[sanddrag]

Can anyone elaborate on what exactly is happening with the plywood in the bumper in a robot like 1678 pictured above? Is it separate pieces cut and joined somehow?

[asid61]

Originally Posted by Ty Tremblay

1678 went to Einstein with that drivetrain and pioneered the math and testing with 971. I'd hardly say they're an example of a typical FRC team.

Most teams shouldn't make this a priority. Putting, say, a week into a hexagonal drivetrain won't make your robot better than putting that same amount of time into the things you mount to your drivetrain.

You've gotta walk before you can run. If you're already running, build a hexagonal drivetrain.

Having seen 1678's robot itself up close the last couple years, I have to say that it's not their robots' build quality that makes them what they are, but rather a fantastic driver and fantastic strategy. This year, their robot seemed to be made mostly out of versatubing-like material and other COTS parts, excepting the can grabbers.
Their 2014 robot was even simpler than this year's robot IMO. Surgical tubing catapult, Vex ballshifters IIRC, dual intakes, and ball stabilizer. If somebody could get a closeup of the way they made the hex chassis, that would be interesting to see.