Legal compressors?

[Maine951]

My team is trying to look away from the small compressor. The am-2005 on andy mark. We have gone through 2 of them last year and 1 in the previous year. We don't want to go to the bigger compressor that has been with first due to the weight of it. Are there other legal compressors we can use? Or is it any compressor as long as it doesnt go over the cfm?

[jee7s]

Per R79:

R79
Compressed air on the ROBOT must be provided by one and only one compressor. Compressor specifications may not exceed nominal 12VDC, 1.05 cfm flow rate.

So, if it's powered by 12VDC with max flow rate of 1.05cfm, you're in business.

But, the better question is why do you have compressor failures? My team has used the same compressor for three years now. It's a Viair...I assume that's what you mean by "small compressor". Are you overheating it? I've run into a couple teams that ran the compressor well past its duty cycle (the Viair Spec says 9% -- yes, that's NINE percent) who ran into trouble. One large fan blowing on the top heatsink goes a long way to keeping that motor cool.

[sanddrag]

I'm curious which one 254 uses. It's similar in appearance and size to the standard small Viar, but distinctly different.

[Chexposito]

R79
Compressed air on the ROBOT must be provided by one and only one compressor. Compressor specifications may not exceed nominal 12VDC, 1.05 cfm flow rate.

Pretty much any compressor that fits that criteria.

Edit: NVM posted while I was posting.

[jee7s]

Originally Posted by sanddrag

I'm curious which one 254 uses. It's similar in appearance and size to the standard small Viar, but distinctly different.

Viair has a few options that comply with the rules:
http://www.viaircorp.com/c-models.html

We get the 90C as part of FIRST Choice, my team uses the 92C, and that 95C seems to have a different motor. Perhaps that's the 254 compressor?

[Nirvash]

From what I see,

4.10.4 R77
The only pneumatic system items permitted on 2014 FRC ROBOTS include the items listed below.
A. Items available in the 2014 KOP,
[...]
J. Compressors compliant with R79.

Which is

4.10.6 R79
Compressed air on the ROBOT must be provided by one and only one compressor. Compressor specifications may
not exceed nominal 12VDC, 1.05 cfm flow rate.

So yes, you can use a different compressor, assuming it meets those specs.

However, I am more curious HOW you have gone through three compressors now, while the VIAIR may not be a workhorse of a compressor, it should last a lot longer then that. Are you running your compressors for extended periods of time without active cooling on them (A fan cooling the compressor head)?

(And took too long to post, didn't I?)

[DonRotolo]

Originally Posted by jee7s

One large fan blowing on the top heatsink goes a long way to keeping that motor cool.

FWIW, it isn't the motor that gets so hot, it is the compressor cylinder (head & piston).

[Joe Ross]

The Thomas 215 compressor also meets the CFM requirements.

[yash101]

Originally Posted by DonRotolo

FWIW, it isn't the motor that gets so hot, it is the compressor cylinder (head & piston).

That makes sense because when you compress gasses (and solids/liquids), each molecule has heat. When there are a ton of molecules in one place, the heat adds up until it is unbelievably high. Entropy takes away most of the heat via the heat sink. However, active cooling is something that can just almost always aid in passive cooling! The motor will typically be a quite efficient one that shouldn't get too hot. The problems start occurring when the motor is so close to the piston that the heat is moved to the [cooler] motor because of entropy. This is similar to what happens in the air conditioner. The gas is compressed, taking away the heat. that way, in the condensor, it is decompressed, leaving you with supercooled gas to cool the air using!

[jee7s]

Originally Posted by DonRotolo

FWIW, it isn't the motor that gets so hot, it is the compressor cylinder (head & piston).

Yeah, I know its not the motor. I was typing too fast on that one.

[Nirvash]

Originally Posted by yash101

That makes sense because when you compress gasses (and solids/liquids), each molecule has heat. When there are a ton of molecules in one place, the heat adds up until it is unbelievably high. Entropy takes away most of the heat via the heat sink. However, active cooling is something that can just almost always aid in passive cooling! The motor will typically be a quite efficient one that shouldn't get too hot. The problems start occurring when the motor is so close to the piston that the heat is moved to the [cooler] motor because of entropy. This is similar to what happens in the air conditioner. The gas is compressed, taking away the heat. that way, in the condensor, it is decompressed, leaving you with supercooled gas to cool the air using!

As long the the compressor manufactures used proper high temperature bearings, any heat transfer between the head, piston rod and eccentric bearing is negligible. The failure mode for most compressors is either the cup (part that glides and seals between the piston and the piston sleeve) wearing prematurely due to heat, or the sleeve flaking due to being overheated which damages the cup.
It is worth to note, that with someone who knows what they are doing, these parts are easy to replace.

[Trent B]

If you haven't I would take advantage of positioning one of the large papst fans provided in the kit of parts at the top heatsink. It made the difference between near instantaneous burns and being uncomfortable to hold onto for a couple of seconds last year in our pneumatic intensive robot.

It definitely presents a strong case for active cooling, and our compressor was (and still is) reliable for 2 competitions, 2 off-seasons and a build-season scrimmage.

[sanddrag]

We've gotten them hot enough to melt pneumatic tubing about an inch away from the head, but we've never had one fail, even running the robot almost nonstop for several hours.

[colin340]

i want to say in 2012 the holycows????? ran a car seat one, that inflated a lumbar support.

[Cory]

We have used these two compressors:

http://www.gd-thomas.com/productlist.aspx?id=10124&tp=p (the Thomas 215 that Joe mentioned)

http://www.gd-thomas.com/productlist.aspx?id=10120&tp=p