Use of discontinued parts in VRC

#1

Why are discontinued parts permitted for use in vrc? I believe they disadvantage newer teams which won’t have access to parts that would improve their robots.

To give an example, I want to create tracking wheels for odometry. Because of the low amount of space, I have to use single roller Omni wheels, the problem being that vex no longer sells them. Robotshop and robosource do not sell them either. I can’t technically make a post on the forum asking to buy them off someone because of R6 (whose merit I won’t discuss here).

Currently, I’m trying to dremmel a poor 2.75" Omni in half to fulfill the requirements. I’ll edit the post later with pics.

Vex plz fix

#2

Most parts are discontinued because there is something wrong with it. Correct me if I’m wrong but I don’t think any of the discontinued parts provide an advantage.

#3

The example in my post was one, but there are others. Low strength chain would be very helpful in situations, and I saw it used in more than one reveal video last season.

#4

But why should teams that have parts that are discontinued not be able to use them? The rule as it stands seems to make perfect sense although I understand the frustration of not being able to get the part you would like anymore.

#5

you’d probably have better luck with a hacksaw tbh.
but about discontinued parts, I don’t think they should be banned, mostly because if you really want those parts, you CAN get them (although it might involve pestering nearby teams to sell you some) and lots of them are very useful.

#6

also, low strength chain isn’t discontinued.
lookie here
you just have to buy the chain with some sprockets, you can’t buy the chain by itself

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#7

Are you referring to the really thin 2.75" omnis? Because there’s quite a big problem with them.

#8

What’s the problem? (I’m just worried cause I’m using them on my drive right now due to a lack of normal 2.75” omnis)

#9

In between the rollers, there are parts of rubber that dig into the field and prevent smooth motion in the direction perpendicular to your movement.

#10

Ok, I’ll have to get normal omnis then

#11

Yeah, the discontinued ones aren’t that great and had problems, hence why they were discontinued and don’t really provide any advantage.

#12

Hmm, I’m not sure I agree here.

For reference, here’s the text of <R6>:

As I read it (and feel free to correct me if I’m wrong), that rule doesn’t prohibit use of parts bought second-hand on robots. Instead, it establishes a test for determining whether something is an “official part”: If it is or was sold by VEX as part of the EDR product line (as described in other rules), then it’s an official part and you can use it on your robot. That status doesn’t change if a part is sold second hand, and such a rule would be basically impossible to enforce anyway.

12 Likes
#13

FYI, This is the correct interpretation.

14 Likes
#14

Thanks drow, glad to hear it

#15

Isn’t the wheel going to be too thin to support that weight? And what about the bearings. In that case you would only be able to fit one bearing per wheel not two. Unless you also cut the bearings in half.

#16

A position tracking wheel doesn’t have to support the weight of the robot, it’s simply a free spinning wheel with a potentiometer on the other end of the shaft. The wheel is also on a joint so it just hits the ground without having to support any weight.

4 Likes
#17

Sorry I didn’t read the entire post. I thought it was for weight-bearing. But you could find used wheels on Craiglist or eBay, there are people selling older sets there.

#18

To be clear for anyone reading this: tracking wheels, and anything else that you would expect to spin over a range more than about 250°, should use an encoder, not a potentiometer.

9 Likes
#19

I think that’s what he meant. Other wise it used a potentiometer, it would lock up and either lock the wheel up, or destroy the potentiometer.

#20

Huh I didn’t think there was a difference, but nice to know there is now