PTC Authentication

Rule <R15a> states that motors, including their internal PTC, may not be altered from their original state in any way. Some VRC events may choose to conduct PTC Verification Testing using a PTC Authenticator to ensure compliance with Rule <R15> and help establish a fair playing field for all teams. This is the same testing that was done at the 2014 VEX Robotics World Championship. For full details on the testing process and the PTC Authenticator, please visit:

Not all VRC events will be doing this testing; it is up to the Event Partner to determine if they will be doing testing at their event. Failed tests will lead to an event disqualification as per <R22> of the VEX Skyrise Game Manual.

We know that the overwhelming majority of our teams would never even consider partaking in the illegal modification of motors. However we are aware that a small number of teams have been doing this to gain an unfair advantage. Ethical and fair play are central to the ethos of the VEX Robotics Competition, as such we have taken the steps of creating this testing process to help ensure teams are all competing on the same level.

“These motors are loaded (manually stalled by hand)”
on mechanisms with a low gear ratio it seems hard to

last year at wolds they tested our arm motor in the wrong direction causing an axle to twist between two gears which we didnt notice at first

Would it be possible to release a complied binary file of the code that could be loaded with something like this This way event partners with limited programming experience could just load the file with out having to use robotc/easyc.

The link on for the PDF is broken.

Edit: Seems to be working now.

It works for me (using Chrome)

Thanks so much for allowing this system of verification to spread beyond just high level competition. I know modding motors like this has been a problem for a long time and I know I am not the only competitor who is very happy to see this end.

It’s absolutely possible, use a tool like that to read back a flash image from the cortex that can then be downloaded onto another system.

An axle twisting is usually the result a design flaw, not an inspector’s mistake. To prevent this you should design the robot or use sensors to make it nearly impossible to twist an axle.

Although, it would be interesting to see a robot with such a ridiculous gear ratio (125:1 lift anyone?) that it simply couldn’t be stalled by hand.

I had a 196:1 gear ratio for sack attack. I could not stall the motors, however, I could only lift up 2 or 3 times in a match.

Another robot from my school had 98:1.

Last year for a robotics class I also made a 343:1 robot that could pull 300 pounds, until the 84 tooth gears exploded :wink:

Using sensors to prevent an axle from twisting wouldn’t help in this situation as the inspectors plug your motor into a different Cortex. Therefore, you don’t have any of your sensors & code that normally protect the motors (if they didn’t do this then the PTC test wouldn’t be able to tell if your PTCs work or if your code just shuts off the motors).

If you have a high enough compound gear ratio, and something physically prevents your lift from going up, then no amount of design quality will be able to save your axles. Support can prevent them from bending but not from twisting. With the high strength axles this is now less of a problem, but subjecting your lift to that much torque still doesn’t seem like a good idea.

Usually, good design quality (except for in extreme cases) prevents the need for a compound ratio, and on a lift you can prevent twisting on some of the shafts by bolting the final gear directly to the arm. Although we’ve had stalls happen in matches, and been through PTC testing, we’ve never had an axle twist on our robots and I don’t think it should be a concern for GDC or for inspectors when they administer these tests.

I agree that teams should avoid compound gearing because it’s a hassle, slow, large, etc, but that doesn’t mean that teams should be prevented from using high compound gear ratios by PTC tests that would twist their axles.

I just wish there were a better way of testing for modified PTCs or that it wasn’t necessary (sigh).

Can teams expect to get 15-20 minutes of rest time after the test (assuming they pass)? I can imagine a scenario where a team is given a random PTC check and has to compete in a important match soon thereafter. What is the recommended procedure? Should the team be allowed 15-20 minutes of “guaranteed” cool-down time? Perhaps the inspection be deferred until after the match under the provision that an inspector can witness that the motors weren’t modified back to factory configuration?

I realize this is a bit of stickler question, but in the heat of the moment (no pun intended), I find having a definitive official answer helpful.

I suspect most inspectors know what its like and would be very helpful in this situation, at worlds one of our (many) inspections was right before another game, we had a chat to the inspector and he was happy for us to leave the robots by the field where he could see them until after the next game. I’m not sure if there should be a ruling on this however because it could slow down competition quite a bit.

Going back to the original topic, I am really happy that these checks are being done now. As someone who has been on the receiving side of accusations from other competitors around this (yet never even considered doing it) its a great thing - even if it is done right before a match. I hope it becomes a regular thing at all competitions.

In regards to the axle twisting issue, would it be possible to put a hex key in a collar on the drive shaft to try and stop it moving before it gets to the gears? Or even grabbing any excess shaft with some pliers to stop it moving.

At worlds, we were checked many times, but the way the inspector did it in our division is that he pulled us over right after a match and checked then. I think this better for two reasons, first it won’t affect the next match’s performance, and it also tests the exact condition the robot was in during the match. The issue with doing it 15 minutes or more before the next match is that you are essentially then giving someone a 15 minute window to switch out motors for tampered ones.