Creating the Lightest Pneumatic System [Archive]

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Mike Schreiber

13-01-2014, 05:28

Pneumatic Systems are heavy. We all know it, but we have a lot of flexibility in components we can use and I wanted to probe the CD community to see what people do to shave ounces off of their pneumatic setups. Given the mandated components in R78 has anyone shopped around for functionally equivalent parts that are lighter? I assume most teams have used these items because they are free in the KoP or on FIRST Choice.

I'm specifically referring to the pressure relief valve, pressure switch, and the pressure vent plug. Are the 574ml Clippard tanks the most mass efficient air storage solution?

I've heard of some teams using smaller diameter fittings and 1/8" OD pneumatic tubing, can anyone confirm this and/or provide a vendor, advantages/disadvantages to this?

I like the idea of using the SMC manifold sold by VexPro for simplicity, but I can't imagine that it is lighter than individual valves, it's a large aluminum block milled from solid, fittings and tubing on each valve seem like they would be lighter. Is this true?

Also these SMC solenoids are only rated to .7 MPA or 101 psi - according to my interpretation of R77 D I need an additional pressure relief valve on the low pressure side because the operating pressure is less than 125 psi. Is this the case? Or am I okay because the 60 psi regulator acts as a relief? If this is not the case, there is certainly a weight savings reason to go with Festo over SMC in the form of an extra pressure relief valve.

Richard Wallace

13-01-2014, 05:47

Also these SMC solenoids are only rated to .7 MPA or 101 psi - ...The ratings I see on the VexPro site (http://www.vexrobotics.com/vexpro/all/solenoids-and-manifolds.html)are different. Where did you look?

Al Skierkiewicz

13-01-2014, 08:39

Mike,
There is a difference between max (failing or burst) pressure and working pressure specifications. The VexPro meets FRC specifications at this time (2014).

Mike Schreiber

13-01-2014, 09:28

Mike,
There is a difference between max (failing or burst) pressure and working pressure specifications. The VexPro meets FRC specifications at this time (2014).

Thanks for weighing in Al, I was hoping to hear from an LRI.

I got the operating pressure from http://content2.smcetech.com/pdf/SY3.5.7.9000.pdf page 9

I see VexPro has it listed as .9 MPa on their site, but if I choose to use a different SMC solenoid, other than the one they sell I cannot find a data sheet other than the one above. In competition, I know these are generally accepted as okay, but I want my bases covered in case I'm asked (I've heard horror stories).

Al Skierkiewicz

13-01-2014, 10:08

Mike,
This issue was raised last year and I was in contact with a few of the IFI people who assured me that the products they are selling meet our specifications. The 0.9 MPa is the guaranteed max pressure which converts to 130psi. The working pressure of 0.7 MPa (~100 psi) is the guaranteed working pressure (the valve will not bypass air at this pressure or below). As our working pressure is specified by robot rule at 60 psi or less, these valves are a good choice for our application. WildStang used the four port manifold last year and were very happy. I am sure it will show up on this year's robot as well (when it gets built).
In general, teams should review the operating recommendations for the valves they use. While lower working pressure is legal under the robot rules, some valves are not guaranteed at pressures below 40 psi. Some valve designs require a minimum pressure to both seal and move. Your mileage may vary.

Racer26

13-01-2014, 10:30

ebarker

13-01-2014, 10:34

This is slightly off topic from the OP but I have some questions;

1) in the past there was a max CV rating on pneumatic solenoids. The only limitation is 1/8 NPT.

2) in the past there was a max volume of stored air.

I see no limitations on those items this year. Is that everyone's interpretation ?

Many years ago the KOP had a simple Festo pneumatic valve that you connected to each end of the cylinder, and to the supply. There was ONE electric solenoid that operated the valve. We prefer to use that type of valve.

I'm interested in these valves (http://www.automationdirect.com/static/specs/nitradirectionsolenoidavs3.pdf) from Automation Direct.

There are the double and single solenoid types, very economical. Can someone explain the advantage of double versus single solenoid.

Thanks, Ed

jijiglobe

13-01-2014, 10:38

To shave pounds off of a pneumatic system you can use an offboard compressor and plastic air tanks. Then the only noticable weight comes from your pistons which is not something you can work around. Keep in mind that an offboard compressor needs to be controlled by the robot because of some odd rules.

Al Skierkiewicz

13-01-2014, 11:38

Ed,
The volume limitation was by number of storage devices and that limitation was removed long ago. The Cv specification was removed as redundant this year since the 0.160 id tubing and associated fittings limit the volume and some manufacturers are no longer printing Cv specifications.

FrankJ

13-01-2014, 13:33

Hi Ed:
Aside from being a supporter of First AutomationDirect is a next day delivery for you & they have good stock.
The AutomationDirect valves are legal this year (Cv.78) The nominal pressure rating is 20-115 PSI. The way I read the rules means a separate relief valve unless you have something that says otherwise.

R77-D. Solenoid valves that are rated for a maximum working pressure that is less than 125 psi rating mandated above are permitted, however if employed, an additional pressure relief valve must be added to the low pressure side of the main regulator. The additional relief valve must be set to a lower pressure than the maximum pressure rating for the solenoid valve,

One reason to use a double solenoid valve is for spring center. The center position can either block or connect the A & B ports. So the cylinder will stop or flop when the solenoids are not powered. Another reason would if you want the valve to stay in the position last set rather than a spring return to the "off" position.

Mark McLeod

13-01-2014, 13:40

There are the double and single solenoid types, very economical. Can someone explain the advantage of double versus single solenoid.

They both perform the same actions as far as extending/retracting a cylinder.
The difference is that a single solenoid has a home position that it always returns to when the robot is Disabled, while the double solenoid always remains in the last position it was set to.

A single solenoid is preferred when you have a mechanism that must always be stowed in a home position, or a mechanism that you want to activate at the very end of a match no matter what. It can be a little less safe, because the mechanism will activate whenever the robot is Disabled.
An example from last season might be a low bar hanger that would retract automatically when the match ended giving you 10 pts as long as the robot was in position.

A double solenoid is a good choice when you want a mechanism to remain in the last position you chose. Especially when there is no particular home position, like a gripper. It's a little safer because the mechanism doesn't suddenly move whenever the robot is disabled.

Mark Sheridan

13-01-2014, 14:09

I'm specifically referring to the pressure relief valve, pressure switch, and the pressure vent plug. Are the 574ml Clippard tanks the most mass efficient air storage solution?

I've heard of some teams using smaller diameter fittings and 1/8" OD pneumatic tubing, can anyone confirm this and/or provide a vendor, advantages/disadvantages to this?

I think these storage tanks are the most weight and cost efficient. I found some aluminum tanks that are better but there volumes were several gallons and the price was just outside the cost limits. I used the other storage tanks on Andy-mark and liked them. Not sure if I will try the 574 ml tanks this year.

I have used 1/8" OD tubing at my work. I use them a lot because I tend to restrict the flow anyways. Last year we had some small cylinder that were in a small area that forced our 1/4" OD line to be bent in a radius not recommended by the MFG. Also, we were bending the push connect too much and caused leaks. So we had to constantly checking on it and re zip tie-ing it to try to reduce the radius So this year we want to some 1/8" OD tubing on hand just in case we had a tight area.

Freelin-Wade sells a version of polyurethane tubing that is equivalent to the 1/4" on Andy-Mark, it has the same rated burst and durometer. Last I checked, Mcmaster sells only the Nylon which should be ok. I use this 5097T312. Should work fine. The plan I am using for my team is to do everything in 1/4" and use the quick disconnect fitting 5779K699 with 1/8" to see if the flow rate is ok and then swap the fitting to make it 1/8" I am only going to do this if we need the weight or the smaller bend radius.

Mike Schreiber

13-01-2014, 14:59

Hi Ed:
Aside from being a supporter of First AutomationDirect is a next day delivery for you & they have good stock.
The AutomationDirect valves are legal this year (Cv.78) The nominal pressure rating is 20-115 PSI. The way I read the rules means a separate relief valve unless you have something that says otherwise.

Al,

My question isn't whether these valves are legal, it is whether I need to add the extra relief valve because the maximum working pressure is below 125 psi (R77D). The same question goes to these AutomationDirect valves. It doesn't make sense to me to add it because they will never operate above 60psi, but according to my interpretation of the rules I need it. I understand the difference between failure pressure and operating pressure, but which does "working" refer to? Are the SMC valves only okay because IFI has said they'll operate up to that pressure, and what about the varieties of SMC valves VexPro doesn't sell?

nuttle

13-01-2014, 20:52

Norgren 16-004-003 (http://store.norgren.com/us/en/Browser.aspx?fhp=fh_location%3d%2f%2froot%2fen_US% 26fh_view%3ddetail%26fh_secondid%3d16_004_003) is a little lighter than the usual 16-004-011, but also allows you to omit a brass fitting (if you're using the new compressor). Likely not worth worrying over though. You can also get smaller pressure gauges that should be a little lighter, if you're really trying to save a little weight/space. I also like Clippard TV-2SP (http://www.clippard.com/part/TV-2SP) for the dump valve but I'm not sure if it saves any weight as I don't have one handy...

Al Skierkiewicz

14-01-2014, 07:45

Mike,
The specs are a little confusing. The way I read the sheet you linked, the pressure rating is recommended operating pressure. The sheet gives a range of 0.15 to 0.7 MPa but it does not specify a max operating pressure.

theun4gven

14-01-2014, 14:17

Last year we had some small cylinder that were in a small area that forced our 1/4" OD line to be bent in a radius not recommended by the MFG. Also, we were bending the push connect too much and caused leaks. So we had to constantly checking on it and re zip tie-ing it to try to reduce the radius So this year we want to some 1/8" OD tubing on hand just in case we had a tight area.

AutomationDirect Union Elbow (http://www.automationdirect.com/adc/Shopping/Catalog/Pneumatic_Components/Pneumatic_Fittings_-a-_Air_Couplings/Push-to-Connect_Pneumatic_Fittings_%28Thermoplastic%29/Union_Elbow/UL14)

A union elbow works very well for these tight corners. I don't like sharp bends in my airflow, but sometimes you just need to get the air around a tight corner.

Mark Sheridan

14-01-2014, 16:20

AutomationDirect Union Elbow (http://www.automationdirect.com/adc/Shopping/Catalog/Pneumatic_Components/Pneumatic_Fittings_-a-_Air_Couplings/Push-to-Connect_Pneumatic_Fittings_%28Thermoplastic%29/Union_Elbow/UL14)

A union elbow works very well for these tight corners. I don't like sharp bends in my airflow, but sometimes you just need to get the air around a tight corner.

We use those too when we can. the tight corner was even smaller than an elbow joint, not an ideal area but it was the best place to put a lock for our climber. I think the cylinder was 5/16" so the elbow joint would be the same size as the cylinder. The thing was comical, the air flow of the 1/4" hose was totally not needed for this application.