Hello, I want to know about if VPLE18-M5H-4/2-1/4 is legal for the competition?
-Steven
Anyone have an answer? We’re kind of stuck.
Thanks in advance for anything.
I really hate to ask this…
… But you have checked the spec sheet for that solenoid against R76 (or R78D), R78C, and it doesn’t violate any cost rules, right?
If it doesn’t pass those rules tests, then you can’t use it. If it does pass the tests, then you can use it.
I have checked the rule for the solenoid, it said the solenoid was legal in the last competition. But the rule didn’t say that the solenoid will be legal in the competition this year.
-Steven
Check the rules for this year. I referenced them. If the solenoid meets the requirements in those rules, then it is legal. Namely, COTS part (pass), pressure rating of 125 psi or used with a regulator down to its pressure (spec sheet should have this), Cv of 0.32 (spec sheet), and maximum 1/8 NPT port diameter (see spec sheet again). If it passes all of those requirements, then it passes R78’s “allowed” test, which allows it to be used per R75.
If it does not meet the requirements, then it is not legal. But I really don’t think those requirements changed from last year. (Be warned, my memory may or may not be faulty–I can’t remember if it is faulty or not.)
Well, the vendor of the solenoid didn’t give enough specs for us to check the solenoid to pass the inspection test. I really need to know the specs or it is legal or not.
-Steven
I’m surprised the vendor couldn’t give those specs…
Who was the vendor, and what were they doing with this valve? (It’s entirely possible Festo distributors sell these on the open market, but I’ve never seen them in the catalogue. FIRST included them in the KOP for several years.)
By the way, to convert that 14 “cfm” rating to real units, and then to C[sub]v[/sub], you’ll have to know something about the conditions under which that rating was established. Your first stop should be to search ChiefDelphi.
This thread seems to have the answer for that festo solenoid. IndySam is stating that the cV is above the .32 limit (.8) and Mark has provided a reference.
Here’s a post I made a few years ago about this valve. There, I ended up with C[sub]v[/sub] = 0.395 at 25°C and 60 lb/in2 for the Festo VPLE18-M5H-4/2-1/4 (using SI conversions). Today, re-doing the calculation, I got C[sub]v[/sub] = 0.407 (using Imperial, unconverted). Would someone care to read up on the calculation method (linked in the previous post, and in the attached spreadsheet) and verify the numbers?
All of this assumes that C[sub]v[/sub] (flow coefficient) is calculated at the as-used pressures. If the manual’s C[sub]v[/sub] limits apply at the valves’ maximum pressure ratings, or at the manufacturer’s chosen measurement conditions, they may not match what I did above. (C[sub]v[/sub] at the valve’s maximum pressure rating is most generous for the teams. If inspecting and faced with a spec sheet for an unfamiliar valve, I would instruct the team to calculate it this way, to use the most lenient interpretation given the ambiguity.)
For reference, for this valve, C[sub]v[/sub] at 25°C and 120 lb/in2 (which the valve should never see in FRC service) is 0.219. At 100 lb/in2 it is 0.265. I don’t actually know the pressure rating of this valve, but seem to recall that some Festo valves were only rated for something near 100 lb/in2, and received special dispensation from FIRST.
By the way, there was some sort of controversy about calculating the flow coefficient in Machine Design. I never really figured out the implications of that.
Finally, for completeness, here’s another version of the valve’s spec sheet: http://www2.usfirst.org/2005comp/specs/Festo1.pdf. I believe that’s the old one, describing only one of the possible wiring patterns.
Festo VPLE18-M5H Flow Calculation.xlsx (12.2 KB)
Festo VPLE18-M5H Flow Calculation.xlsx (12.2 KB)