VIAIR 250C-IG Compressor

[ArtemusMaximus]

Originally Posted by cbale2000

I used a multimeter with a temperature probe on it to get the reading. Don't know if its the most accurate but it seemed to work well for comparison at least. As far as where the probe was placed, I used the top of the heat sink since that's where the compressor seemed to get the hottest (and thus would show the greatest variation in the tests).



Unfortunately in my test the fan direction was dictated by the mounting solution required for it on the robot. That said, however, on this years robot we were using an identical compressor and a slightly smaller fan (80mm or 100mm, not sure) with the fan mounted above the compressor and the compressor was cool to the touch immediately after coming off the field, so top mounting seems to be effective as well (Though the compressor on our robot this year may also not have been working as hard).

I do agree though that it might be worth another test to see what, if any, difference direction makes to the mounting position of the fan.

Thanks again.
I wanted to add another thought. When I was looking to use bigger fan I realized that too big of a fan has a dead zone right under the center of the fan assembly. In my opinion it would be a good idea to place fan in such way that whatever needs to be cooled would be directly under the blades and not the center. I hope that make sense to everyone.

[ArtemusMaximus]

Originally Posted by Mark Sheridan

Do note the Viar 90C performance is at 13.8 volts. The Thomas 215ADC38/12 is quoted at 12 volts. Thus the 90C has better performance due to the higher supply voltage in its testing. It would be nice to get data points at 12 volts.

Anyone have a flowmeter handy? Maybe just time the two compressors to fill a known volume would be enough.

http://www.viaircorp.com/90C.html#tabs-2
http://www.cfpwarehouse.com/thomas/c...215adc3824.pdf

I found that chart somewhat confusing. I thought that 13.8V referring to last PSI value. If what you are saying is true and 13.8V applies to the whole table than evaluation need to be done for the VIAIR 250C-IG Compressor as well as it has same issue - 13.8V is also stated at the end of the table.

[ArtemusMaximus]

Originally Posted by Mark Sheridan

Do note the Viar 90C performance is at 13.8 volts. The Thomas 215ADC38/12 is quoted at 12 volts. Thus the 90C has better performance due to the higher supply voltage in its testing. It would be nice to get data points at 12 volts.

Anyone have a flowmeter handy? Maybe just time the two compressors to fill a known volume would be enough.

http://www.viaircorp.com/90C.html#tabs-2
http://www.cfpwarehouse.com/thomas/c...215adc3824.pdf

Mark,
I tried to look for air flow meters but they are expensive. Our team doesn't have enough funding to justify such a purchase. I wasn't able to find rental locally for the meter either.

I also contacted VIAIR and asked for CFM performance table @ 12V. here is their reply:

... we do it that way since most people use our compressors in vehicles which supply 13.8v from a 12v battery source ...

Hello again,

All of our test machines here strictly run on 13.8v so that everything tests out the same so I can’t provide the CFM at 12 volts.

Sorry about that.

Let me know if you have any other questions.

[Mark Sheridan]

Originally Posted by ArtemusMaximus

Mark,
I tried to look for air flow meters but they are expensive. Our team doesn't have enough funding to justify such a purchase. I wasn't able to find rental locally for the meter either.

I also contacted VIAIR and asked for CFM performance table @ 12V. here is their reply:

Well I hope no team wants to buy ones for such a singular use. I use a mass flow meter (~$800) at work but i am using it for important stuff. I don't want to undo the fixture to test just a compressor.

I bet most teams would just care about how fast a compressor tanks to filll 4 air tanks. I might get around to this if I can buy a thomas 215 this summer. The volumes won't be totally the same, thus the test won't be totally repeatable but I think if the data is that subtle and the compressors are roughly the same, i personally would not care to be more accurate and go with the cheaper compressor.

[adciv]

You could probably use a pressure transducer and a known volume of airtanks to come up with a good estimation of flow rates for a compressor.

[ArtemusMaximus]

Originally Posted by adciv

You could probably use a pressure transducer and a known volume of airtanks to come up with a good estimation of flow rates for a compressor.

I think this method would be of somewhat limited usefulness.

[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.

[skottmorris]

If anyone needs the CAD file for this compressor, I have taken the time to clean up the terrible STEP file VIAIR provides. Everything looks good except for the top component. The source STEP file is missing so many surfaces. I tried to get them to create a new STEP file, but did not have any luck. See attached.