FRC T-bone-ing and Hexagonal drive
 

Is T-bone-ing just when two robot clash head to head? Also what are the benefits of a hexagonal drive train?

Re: FRC T-bone-ing and Hexagonal drive
 

T boning is when the front of one robot hits the side of another robot.

Hexagon drive train lets you build a robot without as severe of "corners", might be easier to get around other robots or obstructions.

Re: FRC T-bone-ing and Hexagonal drive
 

T-Boning is when one robot "crashes" into the side of another robot. It's one of the most popular and easy ways to play defense because when you ram into the side of another robot and they try to drive forward, they're going to go in circles because the side of their robot that you are driving against can't move. This is furthermore effective because it technically does not count as pinning a robot. The advantage of a hexagonal drive train is that you cannot T-bone them because they don't really have a flat side to push against.

Re: FRC T-bone-ing and Hexagonal drive
 

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?

Re: FRC T-bone-ing and Hexagonal drive
 

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

Re: FRC T-bone-ing and Hexagonal drive
 

Are there any technical advantages of a hexagonal drive?

Re: FRC T-bone-ing and Hexagonal drive
 

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.

P.S. If you are going to make a odd-sided drive, make a nonagon. 100% of nonagonal robots have won Einstein.

EDIT - I didn't know CD automatically sensors "curse words"

Re: FRC T-bone-ing and Hexagonal drive
 

One solution to the T-boning problem that is much simpler to implement is to make your bumpers out of different types of fabric. 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.

EDIT: Emery cloth is way too abrasive to be used on bumpers

Re: FRC T-bone-ing and Hexagonal drive
 

What are the consequences of a hexagonal drive then? Can you send me a picture of the nonogonal robot?

Re: FRC T-bone-ing and Hexagonal drive
 

That sounds like such a dirty way to play and I love it. Kinda like pine-tarring in baseball, but for robots.

Re: FRC T-bone-ing and Hexagonal drive
 

Wait is the nonogonal robot 148's tumbleweed?

Re: FRC T-bone-ing and Hexagonal drive
 

Are hexagonal drive train any better at turning?

Re: FRC T-bone-ing and Hexagonal drive
 

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.

Re: FRC T-bone-ing and Hexagonal drive
 

Yes it was.

Re: FRC T-bone-ing and Hexagonal drive
 

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.

Re: FRC T-bone-ing and Hexagonal drive
 

Citation Needed

Re: FRC T-bone-ing and Hexagonal drive
 

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

Re: FRC T-bone-ing and Hexagonal drive
 

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.

Re: FRC T-bone-ing and Hexagonal drive
 

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

Re: FRC T-bone-ing and Hexagonal drive
 

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.

Re: FRC T-bone-ing and Hexagonal drive
 

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

Re: FRC T-bone-ing and Hexagonal drive
 

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.

Re: FRC T-bone-ing and Hexagonal drive
 

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.

Re: FRC T-bone-ing and Hexagonal drive
 

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.

Re: FRC T-bone-ing and Hexagonal drive
 

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.

Re: FRC T-bone-ing and Hexagonal drive
 

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.

Re: FRC T-bone-ing and Hexagonal drive
 

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:

Re: FRC T-bone-ing and Hexagonal drive
 

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.

Re: FRC T-bone-ing and Hexagonal drive
 

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?

Re: FRC T-bone-ing and Hexagonal drive
 

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.

Re: FRC T-bone-ing and Hexagonal drive
 

I totally agree that rectangular frame perimeters are easier to do. For some teams, it might be relatively easy to build a hexagonal frame perimeter. For some teams, it may be hard. Some teams will value the extra stability highly, and others will not.

As with everything in FRC, each team needs to make their own analysis to decide what choices will give them the greatest utility.

Re: FRC T-bone-ing and Hexagonal drive
 

I don't think you understand my point. 1678 is a team that has the organization and resources to devote effort into properly testing and designing a hexagonal drivetrain.

I don't want this post to leave teams thinking that if they build a hexagonal drivetrain they'll miraculously be better robots when they still can't handle the game object efficiently.

A drivetrain won't win you an event, what you mount on top will.

Re: FRC T-bone-ing and Hexagonal drive
 

In general I agree 100%, but there are examples...



Especially in weaker regions, a drivetrain alone can get a team into the playoffs for most games.

Re: FRC T-bone-ing and Hexagonal drive
 

Ty, would you consider PVC, speed drive, or filecards to be more important for the Beatty BEAST of '02? And I'm sure Element '06 and Element '07 would disagree--winning a regional from the last pick with nothing but a drivetrain (and good partners/defense ability) kind of puts a hole there...


That being said, a drivetrain by itself won't win an event, but a bad drivetrain will lose you that event. The three most important elements of a robot are drivetrain, drivetrain, and drivetrain (Mr. Bill Beatty, in paraphrase). However, I would consider rapid acquisition of game objects to be a close fourth--and if you can acquire them, you can presumably remove them from your robot.

tl;dr: A good robot--which is a combination of a good drivetrain, a good manipulator system ("on top of" the drivetrain), a good drive team, and a good strategy--is essential to winning an event, but different teams' mixtures of those four elements can all win.

Re: FRC T-bone-ing and Hexagonal drive
 

Game breaking strategies like 2002 are not an accurate example in this era of FRC. 3rd robots aren't going to get picked for their hexagonal drivetrains. They're going to get picked for having solid, well driven drivetrains. If a team has to sacrifice either of those two in the least then they are not a team that should build a hexagonal drivetrain. My team, 319, is one of those teams.

Re: FRC T-bone-ing and Hexagonal drive
 

Sure, there are exceptions, but I don't think Ty's assertion is incorrect. You're generally not going to win an event because you have a stellar drive train alone. A bad drivetrain can certainly lose you an event, but a good one isn't going to win without a functioning manipulator, drive team, and strategy.

Bumper profiles and bumper fabrics are things that are important for the 90th percentile teams trying to become the 95th or 99th percentile teams. They are far less important for the 50th percentile team. Rather than spending time, money, and manpower into researching bumper shape/material, it's probably better to invest that into, say, intake shape/material.

Re: FRC T-bone-ing and Hexagonal drive
 

I don't understand what all the fuss is about when it comes to their complexity. Instead of going all-out like 971 in 2014, many teams can easily make something like the kleinbots' offseason CAD or 148's x009 prototype.. Both of these accomplish the same goal as a hex-chassis but with much less complexity and required knowledge.

Re: FRC T-bone-ing and Hexagonal drive
 

Not sure I'd qualify x009 as something "easy" for many or most teams to make. Good sheet metal fabrication is hard to find in a good deal of places around the country, and the design knowledge necessary is a whole other animal.

Bottom line is hex adds complexity. In some cases it might not add much, but if you're going to get tripped up on that you should probably be doing KOP or a transition drivetrain like VersaChassis anyways.

Re: FRC T-bone-ing and Hexagonal drive
 

You're not wrong but I don't think it would be too hard to adapt a standard WCD or kit bot chassis to give the sides a slight hex shape but exactly how hard depends on, as you said, the machining resources of the team and how much the side sticks out. The other main problem is it makes bumpers that much more complicated...

Re: FRC T-bone-ing and Hexagonal drive
 

If you're already doing a custom built chain-in-tube WCD (or any other 6WD+ design with all live axles), is it really that much harder to do a hexagon? It looks to me like it's just moving the corner wheels to the inside of the tube/channel and adding some blocks to mount the angled bumpers. Making the bumpers with the odd angles shouldn't be that much more difficult than a rectangle; the hardest part would be cutting and sewing the cloth to give a tight fit.

This is probably not a 50th percentile team issue, but I suspect it's a good bit below 90th.

Re: FRC T-bone-ing and Hexagonal drive
 

+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.

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. :P

Re: FRC T-bone-ing and Hexagonal drive
 

I have to agree that a good drivetrain won't win you an event, but a bad drivetrain will make you lose.

In 2014, our drivetrain was a sheet metal beauty. A marvel of engineering, to quote our chassis mentor. It only weighed 25 lbs IIRC, and it was sturdy to a fault. However, we spent nowhere near enough time making a manipulator, and we ended up with a robot that couldn't control the ball. At competition, we played lights-out defense, to the point where our opponents scores were consistently 40 puts below their average. We even started keeping a tally of how many robots we disabled throughout the season (we got to 9 in 2 events IIRC). But since we couldn't do anything with the ball, we never got picked for elims and we didn't make it to DCMP.

In 2015, we only spent a few days making a quick VersaFrame and Nanotube gearbox mecanum drive chassis, and we spent a lot more time working on our manipulator. By competition, we had a 100% success rate for stacking (we didn't drop a single stack), which got us picked for elims at all of our events and advanced us to DCMP (almost CMP). However, our drivetrain didn't drive straight or fast, so we wasted a lot of time lining up with the scoring platform. Also, the unnecessary weight in the drivetrain kept us from adding the air storage tanks we needed to speed up our pneumatic elevator. If we spent a little more time on the drivetrain, we might have made it to CMP.

Tl;dr - As a medium-to-low resource team, we did pretty well when we spent more time on the manipulator, but we could have done even better if we improved our drivetrain.

Re: FRC T-bone-ing and Hexagonal drive
 

The best way I have seen so far is making a seperate, hexagonal, gusseted bumper frame out of 1x1 tubing. If you have the ability to make gussets it is just like making any other mechanism frame out of versaframe.

Re: FRC T-bone-ing and Hexagonal drive
 

I was shocked with how similar our bots ended up looking in 2014, great minds or something I guess... :rolleyes:

We pretty much made our bumpers the same way as you guys, except replace the 2x4 with a funky looking sheet metal piece. Sheet metal was bent in-house with a vise and hammer (we were still working out of a shipping container in 2014...)

Agreed with everyone on this bumper shape not being a priority for most teams. We worked with 971 on the science behind it, mostly because we were tired of being immobilized mid-match when we just want to score points. The research we did before build definitely paid off in a game like 2014.

-Mike

Re: FRC T-bone-ing and Hexagonal drive
 

Great minds think alike, weak minds seldom differ.

The bumper sides were in three pieces of plywood, connected by a sheet metal piece. The piece was bent at the workplace of one of our mentors. At first, we maintained frame-to-bumper legality by extending little metal tabs from the drivetrain to the plywood. Turns out, those tabs were pretty weak to side-on high-speed ramming. We replaced them with C-shaped sheet metal brackets extending from the drivetrain to support the bumpers, which I made by clamping the machined piece in a vise and whacking it with a mallet.

Re: FRC T-bone-ing and Hexagonal drive
 

I agree with these two, but also want to add something. Making your drivetrain shaped like a hexagon isn't even the best way (in terms of effort to reward) to beat T-Bone pins! Drop down casters, smooth bumper fabric + solid core noodles, etc. all seem to produce a higher reward without having to change how you design drivetrains in the first place. Don't reinvent the wheel when you could just add one that drops down if you really need it.

Plus, how many times have you been a great scoring robot with a fast drivetrain that performs well, only to be beaten by T-bone pins? The teams that need to beat T-bones to become competitive already know this, and the teams who are reading this thread who hadn't really considered the problem before probably have bigger things to worry about than this defensive edge case.

Re: FRC T-bone-ing and Hexagonal drive
 

Can any teams that have used sailcloth for their bumpers give recommendations? There are a lot of options for materials. Which materials are best? Is there one that's clearly optimal for use on bumpers?

Re: FRC T-bone-ing and Hexagonal drive
 

Not to mention that if a hexagonal drive base proves to have a huge advantage (I haven't worked the numbers, but I'm not convinced), teams will develop "anti-anti-t-boning" features. A gap in the front bumper for instance would allow any defensive robot to T-bone a hexagonal robot nearly as well as a square robot.

Re: FRC T-bone-ing and Hexagonal drive
 

Only if they hit it right on.

Re: FRC T-bone-ing and Hexagonal drive
 

Putting these two together and reaching a bit farther, I'm imagining a defensive robot with an enormous crescent wrench head.

Re: FRC T-bone-ing and Hexagonal drive
 

If I understand it correctly, one of the effective things about T-Bone pins is that they are "self-engaging". Check out the attached sketch (in stunning powerpoint CAD!) When the defensive robot on the left (yellow) hits the offensive robot on the side (blue), the contact force is angled to the right of the Blue robot's turning center. This creates a torque (green arrow) that turns the blue robot into the front bumper of the yellow robot. Since the other corner of the yellow robot is on the left side of the turning center, contact there will try to turn the blue robot back the other way. The result is as long as the yellow bot pushes, the blue robot can't exert a turning torque greater than the one caused by the contact, so the two robots become locked together at a 90 degree T (not shown).

A hexagonal robot (shown in blue on the right) changes the contact location and angle in an attempt to move that contact force closer towards (or completely across) the blue robot's turning center, reducing the leverage and producing less "T-Bone torque". But this can be subverted by notching the front bumper of the defensive robot (shown in yellow on the right). The notched bumper contacts the blue robot at almost exactly the same place, and with as much T-Bone torque as the scenario on the left. (although it might be a little reduced if the hex angle is sharp enough).

An easier way to reduce the chance of getting T-boned is to move the turning center closer to the front or back of the offensive robot. If you moved the turning center on the blue robot all the way to the right of the diagram for instance, the yellow robot would produce almost no T-Bone torque (or even reverse or helpful) T-Bone torque. The turning center can be repositioned using permanent or drop-down omni wheels (as suggested earlier), or with swerve drives. Those features allow an offensive robot to "pick and roll" off a T-Bone pin.

That's my understanding of things anyway. I'd be interested to hear if other people of different theories or data.

Re: FRC T-bone-ing and Hexagonal drive
 

Using permanent omni wheels to allow you to roll off of a T-bone pin may be jumping out of the frying pan into the fire. If you move your center of rotation very far towards one end of the robot, you are making yourself more susceptible to being steered from the other end by an opposing robot.

Re: FRC T-bone-ing and Hexagonal drive
 

This is entirely game dependent. Several teams were successful in 2014 using a 2+2 setup. Similarly safe zones in 2011, 2012, 2013 would have lent themselves well to this setup.

"Beat the defender, get into position and score."

In 2014, the secret was to score quick enough that a safe zone wasn't needed.

Re: FRC T-bone-ing and Hexagonal drive
 

Exactly what I meant by "may be". If a defender can steer you away from where you want to be, that might be as effective as stopping you where you are. Note also that you may be opening yourself up to being effectively defended via steering by robots which cannot generate enough force and drivers who do not have quite enough skill to effect a T-bone against you.

Re: FRC T-bone-ing and Hexagonal drive
 

Too many people in this thread are speculating. That puts a lot of noise out there for teams looking for good information.

Re: FRC T-bone-ing and Hexagonal drive
 

Question (somewhat rhetorical): As it relates to being the victim of a T-bone pin, does swerve (or mecanum, or other omnidirectional drives) help you get out, or make the problem worse? What about if you're trying to place the T-bone?

Re: FRC T-bone-ing and Hexagonal drive
 

Wheels with rollers (mecanum, omni) don't get T-boned, they just get pushed. This could be a positive or a negative depending on your team's strategy. Swerve also can't get T-boned because you can turn the wheels 90* and drive away from the T-boner.

Wheels with rollers also can't cause a T-bone, since they can't push with any substantial force. Swerve drive can place a T-bone.

Re: FRC T-bone-ing and Hexagonal drive
 

In regards to swerve, we didn't do enough testing with this in mind to make scientific statements. That being said based on the three we've run, I would think it would make it easier to get out of T-bones in a perfect world. I'd highly recommend not investigating swerve as a t-bone solution. There are so many points in a swerve drive where the increased load from being t-boned could cause your gearing to experience increased friction and make the situation worse.

Our experience running butterfly in 2013 offseason made it seem well suited for that style of safe zone to safe zone sprinting, but we also ran a normal 6wd that year and had similar performance.

It's hard to say for sure, there are many variables involved with the implementation (and how its' driven) that matter a great deal, so it's not as simple as X drive versus Y drive.



The best thing to do is to proto and test what you want to run if this is a performance advantage you are going for. Designing your setup to be a modification of the AndyMark or Vex kit drives would make this iteration easier for most teams.

Re: FRC T-bone-ing and Hexagonal drive
 

Source? You're operating under the assumption that the wheels can under the extra pinning load (which for some swerves isn't true) and that the wheels all retain normal loading making driving it sane. And that the driver thinks of that.

I've seen swerves get TBoned.


I've also seen mecanum wheeled robots shove 6wd robots sideways.. Physics is weird sometimes, this is why we prototype.

Re: FRC T-bone-ing and Hexagonal drive
 

Curious. What kind of butterfly did you run? This style? How did you have the controls set up? Were the front and rear wheels able to actuate independently?

Re: FRC T-bone-ing and Hexagonal drive
 

They ran the neutrino style with slightly faster gearing. Each module had it's own actuator and motor.

Re: FRC T-bone-ing and Hexagonal drive
 

Hexagonal and round robots have trouble fitting through doors in some venues. Williams Arena, I'm lookin' at you!

Re: FRC T-bone-ing and Hexagonal drive
 

Not true - I'm not sure about mecanum, but you can definitely friction pin other robots with omnis, we did it all the time in 2014.

Personally I'm a fan of active mechanisms to get out of T-bones. Using our offseason edition of our H-drive in 2014 we never got stuck in a pin unless it was against the wall. However, a hexagon is another way to achieve the same goal. If your team feels it's worth pursuing, go ahead and do it - speaking from experience, it really is an awful feeling to not even be able to control the movement of your robot just because someone's pushing you around.

Re: FRC T-bone-ing and Hexagonal drive
 

1058 did it with mecanum against teams with weaker tank drives or other non-tank drives pretty consistently in 2014. However once we met teams with more powerful drive trains we were less effective.

Re: FRC T-bone-ing and Hexagonal drive
 

We retrofitted our 2014 bot for a hex frame (Octoframe, actually) last fall and used it at an off-season event. There is a brief thread on CD about the experience:

http://www.chiefdelphi.com/forums/sh...30#post1406830

We weren't on the receiving end of a lot of T-Bone attempts at the event, but our driver did get a bit of experience with it. It helped a bit with T-Bones, but didn't appear to be a magic bullet. The biggest problem with bulged side bumpers came when we tried driving parallel to the wall. Once the tip of the bulge hit the wall, it turned the robot slightly toward the wall, which started an instant vicious cycle that sucked the bot tight into the wall. I don't expect we will try them again soon.