VIAIR 250C-IG Compressor

[jbsmithtx]

Originally Posted by kmusa

When we asked the question, we were hoping that we would be allowed to use the braided hose (yes, it weighs more, but it's the piping right after the compressor that gets the most thermal abuse). Required was a surprise, but the net result was the same.

I think FIRST needs to more rigorosly check these pneumatic systems. I know that our team ran the standard 90C compressor this year, and in fact the thing got so hot that it literally BLEW the tubing apart. We would hear a hissing noise and then a pop. It wasn't until later that we realized the benefits of adding a steel X joint right after it. Bigger surface area to cool = less blown tubing which wan't fun when you were standing next to it.

So my $.02, we should be required to use x - amount of metal tubing after the compressor so that we can better circumvent problems for teams like us that never got around to adding a fan until later...

[ArtemusMaximus]

Originally Posted by jbsmithtx

I think FIRST needs to more rigorosly check these pneumatic systems. I know that our team ran the standard 90C compressor this year, and in fact the thing got so hot that it literally BLEW the tubing apart. We would hear a hissing noise and then a pop. It wasn't until later that we realized the benefits of adding a steel X joint right after it. Bigger surface area to cool = less blown tubing which wan't fun when you were standing next to it.

So my $.02, we should be required to use x - amount of metal tubing after the compressor so that we can better circumvent problems for teams like us that never got around to adding a fan until later...

They were rigorous with our bot and found a minor mistake in pneumatic system. However, they were way more rigorous with the bumper sizing and the number on the bumper and thats after passing inspection. For us being rooky team that was extremely frustrating. ...
Oh look at me, digressing to a rabbit trail

[AllenGregoryIV]

Originally Posted by jbsmithtx

So my $.02, we should be required to use x - amount of metal tubing after the compressor so that we can better circumvent problems for teams like us that never got around to adding a fan until later...

This assumes two things. That one blowing up a hose is a problem, which though startling I don't believe it's a safety issue. Second that if you use the compressor as it's properly supposed to be used a <10% duty cycle then I highly doubt you will have that problem. We only have that problem during long practice sessions never during a match.

[cbale2000]

Originally Posted by jbsmithtx

... So my $.02, we should be required to use x - amount of metal tubing after the compressor so that we can better circumvent problems for teams like us that never got around to adding a fan until later...

I don't think that adding a requirement like this is needed since the problem does not necessarily affect all legal compressors, or for that matter, even all usages of the compressor in question (since a compressor on a robot with minimal pneumatic usage is unlikely to get very hot. It might certainly be a good thing to add to a recommended practices section of the manual or elsewhere though.

Originally Posted by AllenGregoryIV

... Second that if you use the compressor as it's properly supposed to be used a <10% duty cycle then I highly doubt you will have that problem. We only have that problem during long practice sessions never during a match.

This depends heavily on how frequently pneumatic actuators are used on any given robot.

For example, last year we could dump our entire system down to about 70PSI from a full charge with a single volley of Frisbees (a fairly large pneumatic actuator inserted disks into our shooter), we also used pneumatics on our 10pt climber, meaning our compressor was basically running constantly throughout the entire match, even up to the last moments. After the match it would get so hot you could burn yourself on it.
By comparison, this year we only used pneumatics to shift drive gears and to actuate the collector (which was not used nearly as frequently and had smaller bore cylinders). We probably didn't even need a fan, but we added one nonetheless to be safe and because the weight cost and mounting difficulty was minimal.

Now granted one could argue these issues are a byproduct of designing a robot that relies too heavily on pneumatic actuators, and that's certainly a fair argument, but I doubt you will see the problem going away anytime soon regardless. IMO the Viar 90C compressors are rated far under the needs of the average FRC team and running it at the recommended duty cycle is simply impractical for robots that have a pneumatic systems that use a lot of air.

[Al Skierkiewicz]

Everyone,
The heat comes primarily from the compression of gases. With the smaller compressors, there is less thermal mass to sink the heat produced. Even the old Thomas compressor would get hot after a while. In the case of the newest Viair compressor being discussed, the manufacturer requires the use of the supplied stainless steel reinforced hose and supplies it with the compressor. That part is what the Q&A supports. Some teams did try using metal tubing on their robot this year. Until further notice and/or change of rules, copper tubing remains an illegal pneumatic part. There is no way for teams or inspectors to know that the copper is rated for 125 psi or that it is even rated for gas pressures above 10 psi.

[ArtemusMaximus]

Well, this thread turned out to be a lot more helpful than I thought it would be.
I appreciate everyones input.

[AllenGregoryIV]

Originally Posted by cbale2000

This depends heavily on how frequently pneumatic actuators are used on any given robot.

My statement was to show that it shouldn't be a requirement not that it's not possible to do that on a robot. You could the run compressor for 2.5 mins straight and after a few times blow the hose. What I was saying is there shouldn't be a requirement since many teams will never run into that problem.

[cbale2000]

Originally Posted by AllenGregoryIV

My statement was to show that it shouldn't be a requirement not that it's not possible to do that on a robot. You could the run compressor for 2.5 mins straight and after a few times blow the hose. What I was saying is there shouldn't be a requirement since many teams will never run into that problem.

I see, I must have misread your comment.

[yash101]

Originally Posted by ArtemusMaximus

And here is heat sink design I was working on.

It is not the motor of the compressor that gets way too hot. The pump portion of the compressor is where the heat actually is generated, because you are concentrating the kinetic energy of air into a much smaller volume when you compress it. This causes a ton of heat to be expelled. To make the heat sink design more efficient, it would be wise to focus it's efforts on the small appendage that sticks out the end of the motor.

The reason why it seems as the motor gets quite hot is because the entire body is metal, so it conducts heat well. A ton of heat is generated at the actual compressor, making it extremely concentrated. Entropy finds conduction as one of the easiest way to spread out the heat, so it heats up the motor, which runs quite cool at that load.

If you were to build that heat sink, it would add more weight than benefit. The compressors shouldn't create so much heat within the two minutes of the game, that you would need to cool them with more than a small fan, even under a ~100% duty cycle!

[ArtemusMaximus]

Originally Posted by yash101

It is not the motor of the compressor that gets way too hot. The pump portion of the compressor is where the heat actually is generated, because you are concentrating the kinetic energy of air into a much smaller volume when you compress it. This causes a ton of heat to be expelled. To make the heat sink design more efficient, it would be wise to focus it's efforts on the small appendage that sticks out the end of the motor.

The reason why it seems as the motor gets quite hot is because the entire body is metal, so it conducts heat well. A ton of heat is generated at the actual compressor, making it extremely concentrated. Entropy finds conduction as one of the easiest way to spread out the heat, so it heats up the motor, which runs quite cool at that load.

If you were to build that heat sink, it would add more weight than benefit. The compressors shouldn't create so much heat within the two minutes of the game, that you would need to cool them with more than a small fan, even under a ~100% duty cycle!

As I noted previously, we mounted small fan on top of the cylinder heatsink and that seem kept it decently cool. However, during testing we had motor heat up so much that it was too hot to touch. Hence my original approach was start with motor. I also wanted to keep it as simple as possible that includes simplicity to manufacture it.
Looking again at the pictures I posted, I just realized that big fan over the Cylinder will not be efficient as it creates a dead-zone right where airflow is most important. I will try to think of something better.

[Al Skierkiewicz]

Originally Posted by yash101

The compressors shouldn't create so much heat within the two minutes of the game, that you would need to cool them with more than a small fan, even under a ~100% duty cycle!

Ah, but it does. Hence the exercise to keep it cool.

[ArtemusMaximus]

Originally Posted by Al Skierkiewicz

Ah, but it does. Hence the exercise to keep it cool.

and so does say the manufacturer sticker

[ArtemusMaximus]

Do you guys think it would be legal to:

- unscrew 3 bolts holding the top part of the compressor's heatsink head
- slide custom heatsink around smooth part of the cylinder
- put top of the compressor head back where it was?

In a sense it is not a modification, but on other hand it's open for interpretation.

[Al Skierkiewicz]

As of right now, this is a modification and therefore violates the do not modify rules. Please watch the 2015 rules for any changes that might apply.

[ArtemusMaximus]

Originally Posted by Al Skierkiewicz

As of right now, this is a modification and therefore violates the do not modify rules. Please watch the 2015 rules for any changes that might apply.

I kinda knew you are going to say that and suspect rules won't change much in regards of pneumatic system.

I just need to think harder