FRC T-bone-ing and Hexagonal drive

[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.

[BrendanB]

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.

+1

In 2014 3467 had some extra edges up our sides which were a necessity for our shooter packaging and not added for t-bones which ended up being a benefit in a heavily defensive game.

We poured a lot of time and effort into the frame extensions, bumpers, mounting, & maintenance that didn't need to be spent there. I wouldn't advocate building another frame like that in the future and fully agree with Ty that unless you have an higher level of manpower, experience, & resources you should probably avoid trying this during build season.

To help with t-bones I would prefer a drop down omni wheel or ball caster that teams can easily remove or add depending on their needs without locking our drivebase into a specific design/layout early in the year.

Personally the bumper construction & mounting is what makes this frame style very hard to pull off easily.

Originally Posted by 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?

Can't speak for how 1678 achieved theirs, but on 3467 we had five individual pieces of plywood with the three side pieces held together by a patiently cut down/sanded 2x4 since we didn't have access to sheet metal. It was as unpleasant as it sounded and very weak. IIRC a versa gusset or two was thrown in at some point after the plywood started to crack.

[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.

[jkelleyrtp]

Originally Posted by Ari423

A hexagonal robot (if done correctly) is less susceptible to T-bone-ing in most cases. Other than that, not really. I usually find that the benefits don't outweigh the consequences. They are more complicated to design and build than a traditional rectangular bot, so you may want to choose to stick with a more basic drivetrain and work on making a kick @$$ manipulator. That's up to your team based on your team's resources and how your team wants to play the game.

A common thing on CD recently is just building outskirts out of sheet or tube in a pointed fashion to mimic hexagonal bases on top of a basic drive. All it really boils down to is bumper placement. See 148's x009 chassis.

[Mark Sheridan]

Originally Posted by Ari423

A hexagonal robot (if done correctly) is less susceptible to T-bone-ing in most cases. Other than that, not really. I usually find that the benefits don't outweigh the consequences. They are more complicated to design and build than a traditional rectangular bot, so you may want to choose to stick with a more basic drivetrain and work on making a kick @$$ manipulator. That's up to your team based on your team's resources and how your team wants to play the game.

Yep, the bumper material is the most important material in the first place. A hexagon with cordura will have a lot more trouble then a square frame with nylon or sail cloth. Changing bumper material the first option a team should consider before changing their frame.

Right now on 3476, we are practicing sowing with these new materials, that's more important to us then working with a new hex frame.

[EricDrost]

T-boning is when one team is pushing against the side of another robot, creating a T shape if both robots are long or both robots are wide.

Sometimes hexagonal bumpers help so that a team can only push their bumpers against a component angle of your side bumpers, allowing you to get out of a T-bone. Depending on how the team T-boning you orients themselves, hexagonal bumpers may not work.

Watch defense played on 971 in this match. Occasionally when a robot makes contact to the side of their robot, they can roll out quickly. Occasionally they can't. https://youtu.be/G07Ci0VcUjs?t=40s

It certainly can't hurt to make your bumpers hexagonal, but you should ask yourself two questions before you decide to do so.

Is my team a major target of defense?
Is this the most effective use of my resources in handling defenders?

[Ari423]

T-bone-ing is when one robot's front pushes another robot's side. If the robot being pushed has traction wheels, this increases the friction on the pushed robot's wheels to the point where it cannot move. It is debated whether or not this should count as a pin, but as of 2014 it did not.

By hexagonal drive do you mean a normal robot with a hexagonal perimeter or a drive system where each side has an omni wheel?


EDIT: sniped x3