Update For My Robot

I posted another video updating you guys on my robot. Definitely check it out!


This robot is really coming along, and are you able or planning to de score from the middle tower.

Yeah so thats kind of taken a back seat for a while because I had no idea how I was going to do that, but I really like what people are doing with the tower takeover like intakes, so I’ll probably find a way to expand the intakes laterally for the middle tower.

Well, we’ve all had that problem where we measure from the center of our sprocket instead of the edge. So far, you seem to be learning a lot though, keep up the good work. A tip: You don’t need to support a screw joint(which is what I’m assuming is on your flip down) on both sides so what you may be able to do is scoot your intakes over a bit so they’re closer to the wheels.

Edit: It also seems that you added a chain or 2 extra on your right side intake.

Just a heads up for the screw joints (because there are various ways to do it):


The video below is the best way to do it for almost all cases. However, instead of the “jam” nut (aka nylock), you should use a keps nut. It is lower profile and you don’t need a washer to keep it locked in. Nice job either way.

Edit: For clarification sake, an ideal screw joint should go in this order:

  • Screw head
  • Bearing
  • C-channel or piece that will hold screw in place
  • Keps nut (fully tightened)
  • Nylon washer
  • Piece that will be rotating about the screw
  • (optional) Bearing
  • Washer
  • Nylock
    (in that order)

Looks like you’re making some good progress!

It seems like most of the friction problems on your bot are because bearings don’t fit under the lip of a c-channel normally. However, if you file down one side a little, you can make it small enough to fit under the lip. You could save yourself the complete redesign if you have a tool to do that.


On the subject of joints, here’s a good article you can check out:


Nice. For the roller, ill suggest adding standoffs to the sprockets , so there is more support across the 2 sides and make the assembly more robust

Here is an example of what i’m talking about
Good luck for the rest of your season!


Nobody has mentioned this so I will. You can get a pillow bearing in CAD. What I do for any parts that the library I am using doesn’t have is go to vexrobotics.com and find the part, there they have the CAD files for everything.

Here’s the download link:

Also great work on the robot keep at it!


Would a metal washer work in place of a nylon because I don’t believe I have nylon washers that thin.

I tried using standoffs but they get in the way of the ball because I have everything so close together. My system has the ball basically almost hitting the metal axel while it is being rolled up so if I had the standoffs it would be in the way.

lol thanks! I was looking for it on the website but I couldn’t find it

yeah true, but I’d have to take apart my robot anyway to sand them down. I’ll definitely be keeping that in mind in the future though!


honestly taking it apart and putting it back together with some improvements is a really good way to make rapid progress.


Yes, I prefer nylon because the material is smoother and lighter. Not noticeable enough for one given place, but collectively it adds up throughout the robot. So yes, steel washers work fine. [BTW] all Vex washers are ideally the same thickness, about 1mm.

I 100% agree with this, and I’d be doing that if I had access to parts


Yes rebuilding while you have time will also make you a lot faster at the task, it should be beneficial once the season kicks off. The steel washers are .032" thick and the teflon ones are .040" thick. Remember that the teflon ones crush though.

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The Teflon washers are significantly better than the steel ones for applications that deal with shaft rotation. Teflon has a CoF of about 0.05, while steel has a CoF between 0.4 and 0.6 (depending on a large number of factors; an easy way to calculate CoF is to let the material sit on a flat surface and then angle the surface upwards to see what angle it starts to slide down. The tan(theta) value of that is the CoF of the two material’s interaction).
Even compared to a typical nylon washers’ coefficient of friction, the Teflon washers still have quite the lead in how low their CoF is. For this reason, I use Teflon anywhere that an object spinning on a shaft makes contact with a stationary object, because the interaction will always have less friction per newton of normal force with Teflon than with any other vex legal material. Interestingly, Teflon was invented by DuPont and is made of polytetrafluoroethylene (PTFE)- a synthetic fluoropolymer of tetrafluoroethylene, and, according to http://www.appstate.edu/~clementsjs/polymerproperties/$p$lastics_$f$riction$5f$w$ear.pdf
“ PTFE has the lowest recorded m value for any material with a dynamic coefficient of friction of between 0.05 and 0.15 and a static coefficient of friction of approximately 0.05.”
Unfortunately, all these awesome properties of Teflon have a drawback: they are more pricy than other materials of washers. Because of these factors, the best build practice when dealing with washers in my opinion is to always use Teflon when dealing with parts that need to have low friction, and use steel washers for structure and metal spacing.


You’re thinking of the Vex Teflon washers. Nylon has different properties than Teflon

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Even so, nylon washers from McMaster-Carr are a cheap alternative to the vex-sold Teflon washers. Here’s an article that talks about some of the differences between the two materials: https://www.newprocess.com/nylon-vs-teflon-washers/


takes ratchet advice from me