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#1
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Amount of tanks
if your operating 3 pistons how many tanks of air should you use?
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#2
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Re: Amount of tanks
How big are the pistons you're using? The 3/4" bore 1" stroke cylinders used in the AM shifters take a whole lot less air than the 2" bore 24" stroke behemoth from Bimba.
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#3
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This is a difficult question to answer because we don't know what size cylinders you are going to use, and how much you are planning on using them. If you only plan on actuating the cylinder once, then you need to figure out how much volume of air is required to fill the cylinder at 60PSI and you can calculate the volume of the storage cylinder. Some small amount of calculations later you can find out how many storage cylinders you need. Now the rules state that you can only have 4 storage tanks (identical to the 2 supplied in the kit of parts) - refer to The Robot section, <R84>.
If you need more air, then it is time to start thinking about including the compressor on your robot. Then you might be able to reduce the amount of storage cylinders you have depending on how often you want to use your cylinders during a match. Hope this helped! ![]() |
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#4
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Re: Amount of tanks
Quote:
- It's a thought |
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#5
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Re: Amount of tanks
i would use all 4 storage tanks unless you have a major weight problem
if you're extending/retracting your pistons a lot the air gets used up fast and the air compressor really drains your battery, so you want to have lots of air stored |
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#6
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Re: Amount of tanks
just add all 4 of em
just make sure you could take one out if you need to loose weight. |
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#7
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Re: Amount of tanks
You could do what 675 is toying with: A T-valve between the tanks and the pump. Add all 4 tanks. Charge in the pit, close T valve, disconnect pump (which ISN'T mounted to the robot), go to compete. As long as you have the regulation valve for the system at 60psi, you could charge the tanks at a higher pressure (we've been using 110psi for testing) which gives you more use out of the actuators.
Also, no mounted tank = Less weight and less power sap. |
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#8
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Re: Amount of tanks
Quote:
As long as you're not using too much air, I think it's a good idea to have the compressor off-board, to save weight. Two years ago(?) we used pneumatic shifters, which were the only pneumatics on the robot. It used two of about the smallest cylinders available, and two air tanks. This was plenty for us for a match. |
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#9
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Re: Amount of tanks
Depends on how much you'll use your pneumatics. If its only a few time a match you might be good with two. But if it is constant you might want one OR two AND a compressor aboard. Overall it comes to usage. If you know you won't even use two tanks, put three to be safe. Worst come to worst how many time a match will you use your pistons and prepare for the answer to that question. I suggest though a compressor and one or two accumulators though.
Pavan. |
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#10
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Re: Amount of tanks
Just to echo what everyone else is saying, to me (and I know how the "we need to shave off just .1 lbs. AHHHHHH) you should always put all four tanks on (you never, EVER, want to run out of air, its really not very fun, so you should play it safe) and if you're going to be using the pneumatics for, say something like scoring, you need to put the compressor on too; because that air will be gone really fast (note last comment about running out of air)
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#11
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Number of tanks relates to how often you use them.
Quote:
If your system won't be actuating many times a match, you should figure out how much air pressure you're using each time, and base how many accumulators you need on that. A compressor may be unnecessary depending on the amount of air you're spending a match. Losing the compressor is a significant chunk of weight, so I suggest figuring out whether you're going to need to refill your accumulators. |
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#12
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Re: Amount of tanks
Give someone a fish, and they can eat for a day. Teach them to fish and they will eat for a lifetime. I’m going to answer the question I’m sure you meant to ask, which is “How do I determine how many tanks to use based on my selected actuators (pistons) and their usage?”
First some background you need to understand:
For each tank, d=2.0, L=6.0, volume = 6 in^3/pi (at 120 psi). Suppose you want to run your actuators at 60 psi; the amount of air in each tank is equivalent to 6 x (120+14.7)/(60+14.7), or 10.82 in^3/pi at 60 psi. You will leave 6 in the tank – after that the pressure will drop below 60 – so you have 10.82-6=4.82 in^3/pi usable air at 60 psi. Suppose you are using ¾ inch bore actuators. That’s 9/64 or .14 in^3/pi per inch of stroke. So each tank gives you 4.82/.14=34.27 stroke inches. For a 4 inch stroke actuator, that’s 8 strokes, or 4 cycles (extend and retract = 1 cycle) Now suppose you are using 1-1/2 inch bore actuators. That’s 9/16 or .56 in^3/pi per inch of stroke. So each tank gives you 4.82/.56=8.56 stroke inches. For a 4 inch stroke actuator you will get 2 strokes (1 cycle). For the 2 inch bore actuator, it is 1 in^3/pi per inch of stroke. So each tank gives you 4.82 stroke inches, and you can only get 1 stroke out of a 4 inch stroke actuator. Now try running the actuators at 30 psi. Using the calculations above at 30 psi, usable air in the tank is 12.08 in^3/pi at 30 psi. Scaling by 12.08/4.82, you get about 2.5 times as many cycles per tank. You should be able to use the information for different combinations of pressures and actuators. I usually put it in an Excel spreadsheet so I can see the sensitivity to different changes. Good Luck. Last edited by Gary Dillard : 09-01-2008 at 11:16. Reason: clarification |
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