Pump

[RobDeCotiis]

Anyone know how long it takes for the pump to fill the 2 canisters with air? and what psi are we allowed to fill the containers to? i know we're only allowed to work with 60 psi but are we allowed to store 120 or something? but the most important thing is how long does it take to fill the 2 containers to 60 psi?
Thanks
Rob - anxiously awaiting the pump he's taking home from school to start figuring out next year's stuff

[mtaman02]

you mean the 2 cylinders, the compressor supplied by first. if your just talk ing about the pump going to the cyclinders it should not take to long. but if you have like cylinders and canistors and pum (neva mind a full pneumatic system) give or take depending on a leak about 2 minutes pending what the length of the tubing is it could be more or less time. if u can explain in detail how the system will be hooked up i might be able to give you a better estimate. i think 2 minutes or less though. if the tube is long then it will take longer sry dude w/o more info can't be too much help.

[Ashley Weed]

If I am at all following you in your inquiry.... we always store air before entering the field. However after two attempts at the goals with each arm, you have to wait about 15 sec. before the tanks are refilled. evulish may be able to verify this more, and make sure I am talking about the same thing as you.

[RobDeCotiis]

ok sorry for confusing you guys.. how long do you estimate it would take the compressor to charge the air tanks with say 10 cubic inches of air at 60 psi.. what i'm saying is if i have a piston using 10 cubic inches per stroke @ 60 psi, how long is it gonna take the air tank to recharge to max capacity?(ie so i can do the next stroke with the same amount of air in the tanks)

[Lloyd Burns]

The most accurate, practical and direct way to find out would be to use a stopwatch on the actual system. I found that we could go from about 60 psi to 110 psi in about 10-15 s (a timing loop in PBASIC was used), using a single small reservoir, 2 yrs ago, but longer with both reservoirs last year, using the high- and low- pressure switch pair.

Sometimes it took lomger - especially with a leaky actuator we had, that would pass air around the piston if it were not fully open or fully closed.

[Warren Boudreau]

Originally posted by RobDeCotiis
ok sorry for confusing you guys.. how long do you estimate it would take the compressor to charge the air tanks with say 10 cubic inches of air at 60 psi.. what i'm saying is if i have a piston using 10 cubic inches per stroke @ 60 psi, how long is it gonna take the air tank to recharge to max capacity?(ie so i can do the next stroke with the same amount of air in the tanks)

Let's back up a bit. The compressor will pressurize the air in the accumulators to about 120 psi. That air is then regulated down to 60 psi, the working pressure for the systems. So you don't lose 10 cubic inches of air in the acccumulators, you lose 5 cubic inches.

We found that it doesn't take long to replace the air used in one stroke of a cylinder. What takes most of the time going from 0 to 120 psi. 0 psi being ambient pressure, not a vacuum.

I recommend using the limit switches and the control system to control the pump. That way you can turn the pump off at 120 psi and turn it on again around 80 psi. That way, you will always have 60 psi air to work with.

I hope this helps.

[RobDeCotiis]

ok, you're making it much clearer to me, but i still have a few questions. first of all, if i'm using 10 cubic inches of air per stroke @ 60 psi(5 cubic inches at 120), how long will it take the pump to restore that air pressure? also, does anyone know if we're allowed to splice control wires? like if we want to run 2 actuators at the EXACT same time, could we just splice the wires and do it that way? the code would have very slight differences in timing, and we want exact. are we allowed to do that, and would it work?

[Warren Boudreau]

No need to splice wires. Just out a T in the air line coming out of the valve and drive both acuators with one valve.

Unless you are using the big actuators, the valves should handle it.

You can adjust the flow rates to each actuator by fiddling with the little knobs on the fittings on the cylinders.

As far as the time it takes to restore the air in the accumulators, you will have to run some tests. But my recommendation is to just set the pump up on the limit switches and let it cut on and off as needed. As long as the pressure in the accumulators stays above 60 psi, then your actuators will work at 60 psi. Did you know that you can reduce that 60 psi? If you don't need a lot of force (pressure*actuator area), you can run a lower pressure and use less air per stroke.

Can you give some specs on the actuators that you are using? Number of acuators, diameter, stroke, and actuation frequency (strokes per minute)?

[RobDeCotiis]

No need to splice wires. Just out a T in the air line coming out of the valve and drive both acuators with one valve.

Unless you are using the big actuators, the valves should handle it.

You can adjust the flow rates to each actuator by fiddling with the little knobs on the fittings on the cylinders.

As far as the time it takes to restore the air in the accumulators, you will have to run some tests. But my recommendation is to just set the pump up on the limit switches and let it cut on and off as needed. As long as the pressure in the accumulators stays above 60 psi, then your actuators will work at 60 psi. Did you know that you can reduce that 60 psi? If you don't need a lot of force (pressure*actuator area), you can run a lower pressure and use less air per stroke.

Can you give some specs on the actuators that you are using? Number of acuators, diameter, stroke, and actuation frequency (strokes per minute)?


__________________
Warren B

[RobDeCotiis]

oops lol sorry bout that i was reading it in the reply window, trying to figure out what i'm saying back, and i accidentally hit enter.. heh anyway, the system i'm thinking of right now is 2 pistons .75" diameter, 2" stroke, 60 psi. as for the strokes per minute, i'm not quite sure. i'd like to figure out the maximum number of strokes per minute, which is what i'm trying to do.. that's what the whole compressor question is about.. as for the t line, i never thought of that.. heh shows how dumb i am.. lol.. if i was doing that, i'd run the two air tanks in line, right? that way the pressure would always be the same for each piston(one thing i need), and they would both go off at the same time(another thing i need). so basically, how many times do you think i'd be able to use these pistons a minute(if i use both at the same time, i'm using 1.76 cubic inches of air @ 60 psi per stroke.
Depending on that number, i'll either use larger or smaller pistons, based on the number of strokes per minute we can get out of this compressor..

Rob

[Warren Boudreau]

OK Rob,
I did a little research for you. The pump in the kit is a Thomas Industries model 405ADC38-12. It's flow capacity is as follows:
Pressure (PSI)..........Flow(CFM)
40............................0.50
60............................0.38
80............................0.33
100............................0.24

CFM is cubic feet per minute. I would use 80 psi as your nominal operating pressure.
I'll leave the math up to you. Or, in the words or your favorite teachers, "The exercise is left to the student."

Enjoy.

[RobDeCotiis]

thank you so much.. this really helps a lot with my project

[kmcclary]

Originally posted by Warren Boudreau
OK Rob,
I did a little research for you. The pump in the kit is a Thomas Industries model 405ADC38-12. It's flow capacity is as follows:
Pressure (PSI)..........Flow(CFM)
40............................0.50
60............................0.38
80............................0.33
100............................0.24

Wait a sec... Something is not right here. Are you SURE that's the one we're using? (I don't have one here to check...) According to the specs at:
- http://www.thomaspumps.com/products/...log/select.pdf
and
- http://www.thomaspumps.com/pdf/standard_catalog.pdf
although many WOB-L (R) pumps CAN go to 150 PSI, the 405 series is limited to a maximum rating of 100 PSI!

We're running our systems at a max of 120 PSI. Are we really running them over spec?

BTW... Where'd you find the flow rates you're quoting? They aren't in either of the above files. Can you please post the URL for the doc?

Thanks!

- Keith