Slowing Rotation/ Components That Use Oil Legality

Hi all,

We’re hoping to slow down the rate of rotation for an un-powered, pivoting part of our robot (mounted on hex). One thought was to use something like this (with some slight modifications to the shaft to make it fit :slight_smile: ) but I’m told that they are probably illegal because they use oil. If true, any other suggestions?


I see a problem only if the oil comes out.

I recommend reading the rules carefully, particularly R10 & R8. In this case, Oil is not a lubricant, but I’d still want to avoid contaminating things.

How you interpret R8, particularly blue box item G, is important. One might ask Q&A of this item (link to it) is considered a Hydraulic Item. I would say it is not, but MY OPINION HAS NO VALUE AT COMPETITION.

Possible alternatives? How about a very high gear ratio connected to a lightly-braked disk? I am thinking of a wide-rim metal disk with a leather strap over it (located as a tire might be). You can vary the braking force by loosening or tightening the strap. This]( shows a strap used to grip oil filters using the same principle.

If you can explain to us what the mechanism is and how it is being moved, maybe we can suggest an easier way to accomplish the same goal.

I agree with Don, R08 (G) is the rule and I believe, this part would be interpreted as “hydraulic fluids”. Sorry.

Those same speed limiters are used on the scale this year, I believe. I’d Q&A it, since the device isn’t listed as a hydraulic device and the Q&A very much likes to use how devices are listed as reasons for their inclusion in the rules (look at all the Q&As about Air bags, linear actuators this year).

Thank you all, I’ll check out the Q&A and then maybe ask the question.

Q&A 286 has been asked.

I love it when the Qand A gives us non answers.

They kicked it over to the LRIs.

I’d call this a no-go.

If an item is not identified by the manufacturer/VENDOR as a hydraulic item, then it’s not a hydraulic item for the purposes of the FIRST Robotics Competition.

That seems pretty clear to me that this part is legal, no where on the part description is the word hydraulic(s).

Even regular gas springs say that the force mechanism is oil(partially) and they are legal.

I’m with Allen, this part is really no different from a gas spring.

The subject part uses oil ONLY to produce damping torque, while a gas spring uses a combination of gas (often compressed Nitrogen) and a relatively small amount of oil.

This device is rated for a maximum of 12 cycles (rotations) per minute. I would be concerned that its operation during an FRC match might exceed that rating and cause it overheat, and that overheating could cause either oil leaking or unexpected loss of function. Either of those might make it unsafe. I am with Al, R08-G governs here.

Of course my engineering guesswork above could be wrong. I think this question is a good example of the difference between robot inspection and design review; the folks who wear the black vests, and their deputies, have very limited time for the former, and none at all for the latter, while they work to make sure every robot at their event is ready to play.

I could see making a case for R08, but I don’t see how you can make a case for R08-G after the Q&A specifically said that if the manufacturer doesn’t call it hydraulic then it’s not hydraulic. I would also be open to changing R08-G to include parts that use oil as an exclusive force mechanism but that’s not what the rule says nor is that what the Q&A just explicitly stated.

By the above argument, I think that most gas springs including this one would also be illegal, because they have a limited cycle rate that could be exceeded during a match. There is no rule about the amount of oil that can be used, just that it must not contaminate the field or other robots.

I think that gas springs and the component in question are both legal, but your team should be smart in its use of them, and make sure they don’t leak.

I stand corrected on the usage of the term “hydraulic”. As the GDC said (Q286) if the manufacturer doesn’t say it is hydraulic, then it isn’t hydraulic.

As a matter of common engineering usage, I think a device that develops damping torque by means of internal oil pressure ought be considered a (passive) hydraulic component. But as The Rock says, it doesn’t matter what I think.

How about using eddy current braking?

Great video!

A passive eddy current brake, that works like the ones that Prof. Melloch demonstrated in the video, will not develop a holding force at standstill. That is because eddy currents are induced by a changing magnetic field, and the permanent magnet’s field in the aluminum sheet does not change unless the sheet is moving relative to the magnet.

An active eddy current brake that would develop a holding force at standstill can be constructed using electromagnets that are fed with alternating current. This is the same principle as that of an AC induction motor. However, such a device would not be FRC legal, per R33.

Sorry for the diversion away from this thread’s topic. I’m an electric motor geek.