Building VRC Legal Chassis without giving money to VEX

[Illyana]

If you are one of the teams looking to build VRC legal chassis, but hate sending money to vex, then we’ve got you covered!

Tetrahedral Tensegrity chassis will solve you moral dilemma!

It may not get you TC, but it will make you immensely proud of your build!

Steps:

1. Get a pack of 1000 VRC legal Nylon Spacers from Amazon.
2. Get 1/8" square steel rod and shaft collars from a local hardware store.
3. Get 100 ft. of VRC legal 1/4" rope or paracord from your rock-climbing uncle.
4. Find three old 4" omni wheels in the engineering room behind the bookshelf, where the freshmen team hid them last year when they lost the fourth one.
5. Build the tetrahedral base, ensuring the rope is well taut and secured with zip-ties on the ends to prevent slipping.
6. Go to a local VEX competition and enjoy seeing everyone jaws drop, while inquiring you what the heck they’ve just seen rolling onto the practice field.

[Stanford_Orfila]

I’ll make sure to show this to my teams, you can expect a Tetrahedral Armada coming from us in the near future.

[ZPoweredNathan]

This is quite possibly the greatest thing I have ever seen of all time

[cad321]

Can we take a minute to appreciate the fact that you’ve actually drawn the rope/knots in your CAD model

[djavaisadog]

This is a beautiful post. Top quality work

[Sylvie]

i can’t beleive you would cantilever omni wheels like that smh

[9MotorGang]

Instant judges award.

[djavaisadog]

hm… sensing pilons-type behavior.

[Sylvie]

i think you may be right …

[Illyana]

The trick to building this in real life is the custom ground corner and “pacman” pieces:

After you get all the right angles on the corners and pretighten the rope, assorted “pacman” spacers will let you to taut it for extra rigidity and balance the length of the edges:

Up next: custom sprockets and chain from cut up pneumatic tubing and unbraided rope.

[djavaisadog]

clip-on spacer made real. Incredible

[CuteRedpandas]

what’s wrong with buying stuff from vex, is there a problem with them that i don’t know about?

[rich.varone]

TLDR: Yes.

A few of the recent links:

[cw: SI/SH, substance abuse, sexual harassment] - How I was Abused by 148, IFI, and Grant Cox

Many of you in this community may not know me, but because of the circumstances it’s time for me to share my story. It’s a long one, but I hope you’ll see it through to the end. Innovation First Inc, FRC 148, and Grant Cox exploited my innocence and pushed me out when I was no longer useful. I went into high school bright eyed and bushy tailed, ready to take the next big step in growing up. My best friend was trying out for the robotics team, so naturally she convinced me to join her, and we b…

[cw: sexual harassment] An Open Letter to VEX

I am writing this post to our forum out of a sincere request to all FRC suppliers, namely VEX Robotics. There are many quality control failures from other product lines from VEX and other suppliers, however, I believe Falcon 500 to be the most egregious and widespread by far. Falcon 500s were announced over three years ago – October 31st, 2019. Featured in that announcement was Field Oriented Control (FOC): a technology that was advertised as a game changer, and was unavailable on any motors in…

Breaking: Tony Norman has Resigned as President and CEO of IFI

FUN was forwarded this email from a credible source and upon follow up was confirmed and was provided permission to post: From: Tony Norman Date: Wed, Nov 23, 2022 at 1:49 PM I want to provide an update to everyone. As you may have seen online, there are rumors and allegations surrounding my character, and the perceived impacts it may have had on the culture here at IFI. As an engineer, entrepreneur, son, and father, I am so sorry if any of my actions were hurtful. So out of respect to…

[CuteRedpandas]

ah, yeah that is definitely a problem

[QwertyChouskie]

In FTC you could:

• Buy from a different vendor
• Cut and drill holes in standard aluminum sheetmetal/plexiglass/polycarbonate/etc.
• CNC the aforementioned materials
• 3D print parts
• And more!

FTC gang for life!

[ibrue]

At one point I guy I know on discord made a drive using only high strength shafts. Might have to bring that back out. I think you could buy some quarter inch square shafts like this:

Amazon.com: Stanley National N180-174 Stanley Square Key Stock, 1/4 in W X 12 in...

And make that drive. I might try and build it just for funsies lol

[Illyana]

I am replying here, because the answer on my vexforum topic got stack waiting for approval in their moderation queue.

Correction: after 16+ hours in the queue it was finally approved this morning. Must have required an executive level review or meeting of an entire moderators team. And all that for the post that only mentioned Chief Delphi by name without even a link!

---

@SaltyCB

How are you planning to achieve optimal rope tension? The rope will likely require retensioning after a while as it will stretch out.

Just like @OrangeMan said, I’ll use “pacman” spacers.

@seenSeal

With the “requirement” to custom machine a few spacers to pull off this design

My “custom machining” was done with utility knife and hammer and then a bit of drilling and grinding with a dremel.

@seenSeal

I was wondering how polycarbonate might be able to be used to push this innovating solution to the next level.

Maybe polycarbonate sprokets or gears could be a good soultion.

That’s a great idea! @Sylvie?

@9MotorGang

Do you think it would be possible to build something like this in a traditional tank format?

Yes, I think it is possible, but I find the aesthetic beauty of the tetrahedral design irresistible for the first prototype.

Actually, the idea was to make this type of build possible for teams with very constrained set of tools and budget, so they could get cheaper parts from variety of alternative sources.

@ibrue

At one point I guy I know on discord made a drive using only high strength shafts.

Drilling and tapping 1/4" metal shafts, which are made from the hard steel, would be off limits for most vex teams.

Using 1/8" rods as the long screws is also problematic, because once you bend it, you could hardly make it straight again.

I think the choice of nylon spacers on the rope is optimal for competitive robots, because it will just spring back into original shape after each bump or fall.

There were attempts before to build something less triangular, like the Stevonator chassis:

But just looking at it, you can sense all the screw connections loosening after the first test drive, unless you douse it daily with threadlock.

If you think about all the torsion forces that chassis got to experience, you will start appreciating the beauty of the triangular symmetry of tetrahedral design.