VIAIR 250C-IG Compressor
 

We found this compressor that by the looks of it meets requirement of FRC rule book for 2014 season.
http://www.viaircorp.com/250C-IG.html
I wanted to hear your guys input especially if I missed something in the rules.
Because it looks like far superior compressor comparing to VIAIR 90C while still under FRC's 1.05 CFM limitation.

Re: VIAIR 250C-IG Compressor
 

Yep it's legal (the 12v version), we used it and loved it! It is heavyyyy so we can it off board.

Re: VIAIR 250C-IG Compressor
 

Thanks Mk.32 for quick reply. It's good to have a confirmation.
Before we found it, I started to work on a heat sink design for 90C cause it was getting very hot even with small fan. I probably better finish design, share it and may be someone would benefit from it.

Re: VIAIR 250C-IG Compressor
 

It is a fantastic piece of hardware. Never even got too hot to touch. It's hefty, but if you need the air, it's worth it. We were asked by probably 10 teams about it and many seem very interested. If you can afford the weight costs, by all means get it. We won't be using the others ever again unless we are too close on weight or don't have many pneumatics. We were a little worried about current draw, but it's no worse than the 90c. Be aware that Q&A said that it is required to use the stainless steel braid leader line and you need to design for that since it is heavy and cumbersome.

Re: VIAIR 250C-IG Compressor
 

Thanks, good to know.
Q&A you are referring to, is it Q325?

Re: VIAIR 250C-IG Compressor
 

Yes, that's the one, bit of a bummer since it weighs so much and is hard to deal with

Re: VIAIR 250C-IG Compressor
 

I compiled comparison table of compressors I found meet the FRC requirements. I hope it may help someone

Re: VIAIR 250C-IG Compressor
 

And here is heat sink design I was working on.

Re: VIAIR 250C-IG Compressor
 

I believe his is another FIRST approved compressor which I was told 254 used this year and with 17 pistons it probably got a good workout (someone may want to check me on both of those). It is only a little heavier than the KOP compressor too http://www.gd-thomas.com/product.aspx?id=12622&tp=p

Re: VIAIR 250C-IG Compressor
 

we used this to good use.

Re: VIAIR 250C-IG Compressor
 

Oh yes, thank you.
I saw that one but was too lazy to add it to the list. It seemed not much better, yet quite a bit more money.
On the other hand it still viable option and will add to the list.

Re: VIAIR 250C-IG Compressor
 

Does anyone know how this compressor compares with the old KOP compressors as far as weight and fill rates?

Re: VIAIR 250C-IG Compressor
 

Yes, see the comparison table I compiled
http://www.chiefdelphi.com/forums/at...6&d=1399254659

Re: VIAIR 250C-IG Compressor
 

WildStang also used the new (Viair look alike) Thomas compressor. We liked it but it does not have a mounting flange or hardware. We considered that using any of the hardware on the compressor to mount it likely violated the "do not modify" rules so we made a custom bent aluminum tray for it. (Look for a change in the future.)
As pointed out, the Viair compressor comes with a stainless steel hose that is required by the manufacturer and so is required by the Q&A.

Re: VIAIR 250C-IG Compressor
 

This compressor? We used it this year. Great for weight savings and cfm is alright, but it really, really likes to heat up. We thought we'd give it a try after 254 used it last year.

Re: VIAIR 250C-IG Compressor
 

When we purchased our 215 Thomas compressor, it came with a large U-shaped bracket and a rubber mounting gasket. We replaced the bracket with large hose clamp. We placed the clamp around a frame member and tightened it enough to where a student couldn't rotate it in the rubber gasket. It never moved after mounting.

Link to mounting hardware pic:
https://drive.google.com/file/d/0Bwb...DNlVzZUWUNDdjQ

Re: VIAIR 250C-IG Compressor
 

We had used the attached for comparisons earlier. (405 is the old Thomas KOP compressor, 415 was a similar model.)

Some comments:

1) The notable difference between the Viair 250C-IG and the Thomas 215 is duty cycle - 10% for the Thomas, 100% for the Viair. The weight is unfortunate, but it's a nice compressor.

2) In using the 90C, we used one of the KOP muffin fans blowing down over the cylinder - it helped a lot.

3) The 330C-IG on the chart is the bigger brother of the 250C-IG, but isn't within the FIRST limit.

4) 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. :)

Re: VIAIR 250C-IG Compressor
 

Mounting fins to the motor case may work, but most of the heat is being generated in the cylinder, and not in the motor (Viair, for instance, specifically mentions not mounting the compressor upside down, because they find that more heat transfers from the cylinder to the motor.)

What we found is that just having a fan blow on the cylinder head kept the compressor temperature reasonable.

-Karlis

Re: VIAIR 250C-IG Compressor
 

Here is Updated Comparison Table. Thrown CFM graph for better visuals.
Also added table with just Viair 90C & Thomas 215ADC38/12. Sort of to compare compressors that very close in weight and size category.
Judging from the spec sheets, it seems to me that the only reason to chose 215 over 90C is for slightly better endurance and better initial CFM performance up to 20 PSI.
I am pleased that Viair 250C-IG is legal and I think it's worth looking elsewhere on the bot to win those extra 4lbs that this compressor adds

Re: VIAIR 250C-IG Compressor
 

We also had fan blowing at the cylinder head. However we also found that our compressor was so overworked that motor was very hot as well. May be not hot enough to cause 1st degree burns, but I wasn't dumb enough to test that :).
One of the reason for extra working time probably due to a minor pressure loss that we were unable to locate. I soped the heck out of it and didn't see any bubbles :(

As I looked at the design I posted it occurred to me that it is perhaps an overkill. I will put more thought to it and if I can make it simpler while still effective.

Re: VIAIR 250C-IG Compressor
 

While we're on the topic of compressor cooling, here's a chart I made a few years back detailing the temperature difference a cooling fan makes on a VIAIR 90C air compressor...

https://docs.google.com/spreadsheet/ccc?key=0AqQx991m_YKGdEc3OV9NbG10YmluNjM2UFRhYV9Gb lE&usp=sharing

Hopefully someone finds this useful. :rolleyes:

Re: VIAIR 250C-IG Compressor
 

Thanks cbale2000,
It was useful. It makes me want to do similar experiments.
What did you use to measure temperature and which part of the compressor you were checking for the temperature?

Re: VIAIR 250C-IG Compressor
 

Good info. Has anyone done a trial to compare fan direction? I wonder if drawing air up from the heat sink provides less or more cooling than blowing down.

Re: VIAIR 250C-IG Compressor
 

fans are far more efficient at cooling on the "pushing" side as compared to the "pulling" side when it comes to open air applications. You would need a way to focus the air through the back end of the fan to make pulling air efficient (baffles or a closed in space).

Re: VIAIR 250C-IG Compressor
 

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

Re: VIAIR 250C-IG Compressor
 

This difference in the data sheets is critical - people should be sure to note that difference as the tables and spreadsheets that some have shared are significantly misleading without noting that. We use the 215 Thomas compressor because it edges out the Viair compressor when using comparable nominal voltage ratings, and is built to what we feel is a higher quality standard by a more widely known and reputable company.

Re: VIAIR 250C-IG Compressor
 

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.

Re: VIAIR 250C-IG Compressor
 

I started this thread because I found very little information on VIAIR 250C-IG Compressor on FRC related sites beside the Q325 on FRC Q&A page.
I think by the way of this thread we are trying to clarify these details.

The only definitive way to be sure of the performance differences is to buy all of them and test. However, I don't think many teams have that luxury. I know our team doesn't - we have extremely low budget.

Re: VIAIR 250C-IG Compressor
 

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.

Re: VIAIR 250C-IG Compressor
 

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.

Re: VIAIR 250C-IG Compressor
 

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...

Re: VIAIR 250C-IG Compressor
 

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

Re: VIAIR 250C-IG Compressor
 

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.

Re: VIAIR 250C-IG Compressor
 

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.

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.

Re: VIAIR 250C-IG Compressor
 

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.

Re: VIAIR 250C-IG Compressor
 

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

Re: VIAIR 250C-IG Compressor
 

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.

Re: VIAIR 250C-IG Compressor
 

I see, I must have misread your comment. :o

Re: VIAIR 250C-IG Compressor
 

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!

Re: VIAIR 250C-IG Compressor
 

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.

Re: VIAIR 250C-IG Compressor
 

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

Re: VIAIR 250C-IG Compressor
 

and so does say the manufacturer sticker

Re: VIAIR 250C-IG Compressor
 

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.

Re: VIAIR 250C-IG Compressor
 

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.

Re: VIAIR 250C-IG Compressor
 

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 :D

Re: VIAIR 250C-IG Compressor
 

Be sure to read the 2015 rules before you build next season.

Re: VIAIR 250C-IG Compressor
 

That's a long wait :)

On another note, I am getting discouraged by the prices of aluminum here. To make 3"x3"x0.75" aluminum plate with 1" hole I was quoted $91.04 :ahh:

Re: VIAIR 250C-IG Compressor
 

Honestly, I'm still of the opinion there is no need to use a heat sink on the compressor if you're blowing fans over it. Unless you're running the compressor constantly and want to keep it at room temperature, a single 120mm fan (or several smaller ones) blowing across it can keep the compressor reasonably cool under most uses.

Re: VIAIR 250C-IG Compressor
 

Needless or not, my brain is on a roll and I want to finish my design.
Here is idea for the cylinder's heat sink:

Heatsink is made of these

It will require just basic tools to make it.

Also, compressor 3D model I found is not exact measurements and it has 3 bolts not 4 that holding cylinder's heatsink with manifold. So I may have to make model myself.

If I get to the point of making it, I will also do the comparison graphs with temperature readings.

Re: VIAIR 250C-IG Compressor
 

So I did my own the compressor 3D model (Creo 2.0) taking measurement from actual compressor. There still some tweaks left to do but here it is for you assessment:

Re: VIAIR 250C-IG Compressor
 

Art,
I think if you do an evaluation of the compressor, there will be significantly more heat generated in the head than in the cylinder walls. I am expecting to see more heatsink connected to the head next season.

Re: VIAIR 250C-IG Compressor
 

Al,
What in your opinion would be a good test setup? Do you think (compressor--> pressure release valve --> 2 air tanks) would suffice?

In our experience existing heat sink (a.k.a. compressor head) with small fan (40mm zip tied directly on it) was doing decent job cooling it. However, rest of the compressor still heated up a lot. Idea is to have this new heat sink + heat sink for the motor body would + 2 80mm fans dissipate a lot of heat and thus increasing duty cycle. As I stated before, another my objective was to design heat sink in such a way that would require only basic tools to make (hole cutter drill attachment, metal saw, and may be dremmel) as we dot have access to CNC nor to even basic milling machine. Considering that objective I knew that it may cause less efficient heat sink design because it would be harder to make more elaborate shapes of pieces. However, if it will be efficient enough, than ANY other team would be able to produce it.
At the moment best idea I came up with is to use 1/8" x 1.5" x 8' aluminum flat bar easily available here for $20. for this heat sink I need 14 pieces 3" length, that makes 42 inches. lets say 48" with some waste - that only $10 worth of materials.
Motor body heat sink would need a bit more. But it still falls under $40.

Re: VIAIR 250C-IG Compressor
 

Art,
Not being a mech eng (I play one on TV) I am guessing a lot of what we see is do to the minimal thermal mass in the structure of the compressor. If we add to the thermal mass, then we also add to the weight. The new compressor is coming with a stainless steel, woven hose that is required for operation. I was wondering if a metal tube that had fins on the outside could remove sufficient heat to protect the tubing. We had a rather large shop compressor where I work that had such a pipe. It was a two stage compressor where one piston fed a second piston to get the pressure up. The cooling pipe kept the second piston from heat damage and the flywheel doubled as a fan. The finned tube sat in the draft from the flywheel for forced cooling.

Re: VIAIR 250C-IG Compressor
 

Al,
I am not mech eng either. I have brains for it, but don't have the required education :).
VIAIR 250C-IG Compressor is a good option, but at extra 4 lbs weight and extra cost it may not work for all teams.
I haven't done the math, but I am positive that heat sink I am designing would weigh less than 4 lbs.
I haven't learned enough CAD to properly heat stress test , which leaves making it and testing as the only option.

Re: VIAIR 250C-IG Compressor
 

(Computer engineer here) Looking at your design, there's two things that come to mind.
1) Could you design it in two parts that are then screwed together? This would allow you to add it to a compressor without removing the head. (This appears to be required under the design)

2) I think your fins are thicker than they need to be for cooling. Are they there for mechanical support or manufacturability? I'm trying to compare them to higher end computer CPU coolers which use thin copper plate.

Re: VIAIR 250C-IG Compressor
 

There are several tradeoffs involved in designing heatsink fins, but the main one is providing enough conduction to supply the fin with heat, and enough convection to remove the heat from the fin. (Radiation is often negligible, unless you're in a non-convective environment, like space.)

Convection is affected by fin spacing and airflow. In general, active cooling with a fan can use more closely spaced fins. Passive cooling using natural convection tends to employ widely spaced fins. The most efficient fins in natural convection are often cylindrical or conical, but those are fairly difficult to make, and so straight fins are substituted instead.

Additionally, conduction is affected by the thermal resistance over the material interfaces. If the heat has to cross a lot of material boundaries to get to where it's convected away, the heatsink will tend to be less efficient.

You'll also find that some areas of a heatsink are less efficient than others, relative to the mass of the material used. The squarish blocks on the corner of your design come immediately to mind: they're going to be relatively cold (because they're far from the heat source and exposed to the air), and thus have a small temperature difference with the surroundings, which means less heat flow.

Re: VIAIR 250C-IG Compressor
 

Yes, that was the plan all along, so there no tinkering with compressor itself. There are 2 parts for Compressor head heatsink and another 2 parts for motor body heatsink.

Fins are thicker for manufacturability reasons (material: 0.125" x 1.5" x 8' aluminum flat bar) and also so they can absorb the heat. With CPU heatsink there is always thicker part that absorbs the heat and thin fins to disipate the heat. I haven't yet figured out a way to manufacture such heatsink with basic tools.

Re: VIAIR 250C-IG Compressor
 

Thank you Tristan for your input and good overall summary of the physics involved.
I started working on it over 3 weeks ago and it hasn't been easy process.
I challenged myself with few parameters and as anything else in life few of them competing with each other:

• Cheap. So that even "poor" teams can afford it.
• Easy to manufacture with basic tools. So that even poor teams can afford it. (drill, wood hole cutting attachment, metal saw or grinder with cut wheel etc.)
• Hopefully increase Duty Cycle from 9% to at least 50%
• Easily mounted, so that compressor is untinkered ( to comply with FRC Rules)

Challenge will be making round cuts so they stick tight to the compressor, so that heat can be absorbed more efficiently.

So if any of you have any suggestions to improve the design, I am all ears :)

Re: VIAIR 250C-IG Compressor
 

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:

Re: VIAIR 250C-IG Compressor
 

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.

Re: VIAIR 250C-IG Compressor
 

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.

Re: VIAIR 250C-IG Compressor
 

I think this method would be of somewhat limited usefulness.

Re: VIAIR 250C-IG Compressor
 

The leader line actually looks quite useful. This year we had a few pneumatics leaks and didn't realize until someone pointed out the compressor has been running like nonstop. Eventually the hose off the compression had melted down a little and make the leak much bigger.

Re: VIAIR 250C-IG Compressor
 

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.