pic: 6-sided tank drive



This is a 6-sided base inspired by 148’s 2014 drivetrain. The wheels shown are 5.75"x1.5" custom wheels (but 6x1.5 wheels also fit within the perimeter). The sides are made up of 4 identical pieces of tubing, 15" long. The front and back tubes are 26" long. Overall width is 34", overall length is 28.9". Oh, and if anyone is curious, the wider angles are 149.07deg and the smaller ones are 105.46deg.

Not sure if the 1*1 stuff supporting the bumpers is vexpro versachassis stuff, but if so I’d double layer it or use thicker material. That stuff is really thin for a bumper frame.

If it’s welded together with 1/8" walls, it shouldn’t be a problem

right; the 1*1 vexpro stock has much thinner walls. I’m not sure which it is.

If I may ask, why are your angles “149.07 degrees” and “105.46”? You will never ever need that kind of precision in a FRC situation, especially on a frame which will be bashed and smashed into every 6 seconds anyways.*

Even with a chopsaw/bandsaw/mill/cnc mill/whatever, it is certainly a better real world design if you round those off to some amount. How critically important is it that you are exactly perfect? In your robot’s frame, just about never.

Also, just a recommendation, While it is less pretty, using 1/32" (or preferably 1/16" or 1/8") increments instead of decimals is much less of a hassle for whoever will measure the parts, and just a couple clicks in CAD

Not trying to be a wet blanket on this design, it certainly is cool, but it would be beneficial for every party involved if you simply rounded to the most convenient dimensions, where there will be an immeasurable difference in performance, but a significant improvement in both engineering design quality, and manufacturing

*after all, the entire point of a 6 sided drive like this is for the very purpose of escaping trapping t-bones"

The weird angles are the result of the not-weird side lengths. The tolerance should be pretty high.
Oh, and it’s welded 1/8" aluminum tubing

Does it meet the 110" rule?

Question for you, how exactly is this useful? I love the design, it looks pretty fancy, but in the long run it will amount to more work and not be worth it if doesn’t have any specific benefits compared to a 4-sided tank drive.

This design is helpful for avoiding t-bone pins and defense in general. Also hexagons have a greater area to perimeter ratio.

If you are going to forgo the square, a hexagon is really the best option for a traditional tank drive. For things like holonomic and 3 wheeled swerve, other n-gons may be appropriate.

Circles are mathematically the optimal perimeter-to-area figures, but would be difficult to make, and a nightmare to put bumpers on.

You can more efficiently optimize the use of the perimeter sizing by moving the front/rear wheels to inside the frame, and making the center wheel wider.

Ah, good point, although T-Bone pins are rather rare. However, would the bot be able to play an effective defense? For example, if the objective was to T-Bone a bot of the other alliance, it would require rather exact precision as to hit the bot right in the middle of their side.

I saw them happen quite a bit this season. Robots waiting for the ball from a human player after a truss were prime candidates for being bulldozed back to the inbound station

Not necessarily, if they are hit square to an angled face, at least the drivetrain is not perpindular to the t-boning robot.

T-bones happen a LOT at the high level of play in certain games.

Fair enough. It is true that they happened this season a lot, but this was due to the lack of mobility some robots had as they waited for the ball from the human player. On a good driver, t-bones tend not to be effective as a good driver will stay in motion as much as possible.

There must have been some AWFUL drivers on Einstein this year… and 2011… They were getting T-boned all the time! :wink:

Someone get these teams some better drivers :confused:

It really depends on the game. It’s true, this year was difficult to avoid being T-boned as most robots were incapable of driving right by the human player station without stopping and successfully getting the ball. Mixed with that and the fact that it’s hard to move and pass the ball, it was one of the better years for t-boning, but still, t-boning is not what I would consider a very effective defensive strategy most years.

Mixed with that and the fact that it’s hard to move and pass the ball, it was one of the better years for t-boning, but still, t-boning is not what I would consider a very effective defensive strategy most years.

Since Adam is too modest to boast about his team ( :wink: ), I’ll be the one to inform you that that is a very dangerous and mostly incorrect statement to make.

That’s how I had it laid out originally. Thankfully, I kept the other design around :smiley:

A good driver should be able to avoid defense, yes, but a good defensive driver should be able to get a t-bone or two.

If tbones were rare and could be easily avoided by good drivers you would not see teams like 254,971,973,148,1114,118,1730,33 and countless other elite teams dedicating engineering hours, money and weight to mechanical aids to get out of pins.

This year we were caught in pins constantly and it slowed us down significantly while simultaneously wearing down our wheels. Often less high scoring teams don’t face the same level of defense as their higher scoring counterparts so their robots weaknesses are never exposed.