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#16
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Re: Placing a Tank after a solenoid valve
We actually did this in 2008 and it was legal, but it's possible the rules have changed so this sounds like a good Q&A to me.
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#17
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Re: Placing a Tank after a solenoid valve
Mechanically locking a cylinder and keeping the valve open won't do anything.
Once you have 60 psi air in the area of the cylinder it can fill it will stop flowing. Adding low pressure volume does nothing but make your compressor work harder for no reason. The reason you have high pressure storage is the change in volume of the air as it expands to a lower pressure acts as energy storage. Without the expansion just oure volume does nothing. Please rethink your plan and consult a mentor that has some experience in fluid dynamics. |
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#18
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Re: Placing a Tank after a solenoid valve
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Since the shuttle stays in the same position the pressure on the working side of the valve can vent back through the valve. So yes tanks on the working side of a commonly used FRC solenoid will vent assuming as you noted that there aren't any check valves added into the system. Last edited by Mr V : 13-01-2014 at 16:58. |
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#19
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Re: Placing a Tank after a solenoid valve
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#20
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Re: Placing a Tank after a solenoid valve
Think of this way. You use cylinder that has more stroke than you need. The start position is mid way in the cylinder. You effectively use part of the cylinder as the accumulator. And you don't have that pesky 1/4 tube slowing things down. If the vent valve can dump all the pressure, you should be legal. If it doesn't then the design is not legal regardless of the legality of the individual parts.
This is safer than using a big spring for your stored energy since you can relieve the pressure, getting rid of the stored energy. The catapult is ultimately going to have the stored energy to throw the ball at the required speed regardless of the method used. So the wise thing to do is thing about how to safely handle that energy. |
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#21
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Re: Placing a Tank after a solenoid valve
For those interested this was actually a prototype from 2008 which was the first thing we tested after kickoff. This is an 8" with a 1 1/2" bore and it shoots the ball about 7ft ish into the air.
If anyone would like more info on it let me know and maybe we can post a vid or something along those lines. EDIT: DISCLAIMER - This was legal in 2008, we haven't looked into it's legality in 2014. Last edited by Richard.Varone : 13-01-2014 at 20:49. |
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#22
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Re: Placing a Tank after a solenoid valve
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#23
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Re: Placing a Tank after a solenoid valve
I am looking at this more from a safe design that plans for failures view. If the system dump valve is downstream from a regulator(s) that potentially could plug in a failure, then the valve couldn't release all system pressure. I believe that is what the original rule was addressing. With working regulators, system pressure would be released.
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#24
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Re: Placing a Tank after a solenoid valve
Q/A Q62 addresses this.
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#25
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Re: Placing a Tank after a solenoid valve
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The trick is selecting an appropriate reservoir volume that balances the need for a fast stroke with the time needed to recharge the reservoir after venting for retraction. |
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#26
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Re: Placing a Tank after a solenoid valve
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#27
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Re: Placing a Tank after a solenoid valve
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EDIT: Also we've found that in a system like this it's vital to not have any fittings on the other end of cylinder Last edited by Richard.Varone : 14-01-2014 at 20:52. |
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#28
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Re: Placing a Tank after a solenoid valve
In rereading this thread and thinking always about safe operation, the precharged and locked cylinder makes me wonder what happens when the vent plug valve is opened. (I do a lot of "what if" analysis. Sorry, but that is what I do) So these are my questions as I consider operation...
1. Is there ever a chance that the locking cylinder could release the piston as system pressure is vented? 2. Is there a mechanical lock that prevents uncontrolled movement when the robot is powered down? 3. Is the robot carried off the field with the cylinder under pressure and what happens if the robot is accidentally dropped or shocked? 4. When the cylinder moves, is the movement exposed to the outside of the robot? 5. Knowing that the PVC storage tanks have failed in the past (from external forces), are they being used as intended with rigid fittings to a moving cylinder? Did I miss anything? |
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#29
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Re: Placing a Tank after a solenoid valve
Not sure if this was directed towards me or just in general but:
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This setup had potential to be pretty dangerous and extreme caution should be taken into it's design and execution. While it was able to be dry fired we never recommended it, hitting the ball acted as a dampener taking a lot of the stress of the shot. Another point in the safety of a device like this is to attach a rope from the robot to the end of what ever is on the piston. Now in terms of safety, this years ball is half the size, and with our testing we were able to use a cylinder half the size which makes for a safer implementation ![]() |
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#30
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Re: Placing a Tank after a solenoid valve
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If we go this route, we won't use a recocking mechanism that is capable of overpressurizing the low pressure side of the system. If your team does so, I would highly suggest installing a pressure relief valve set at 60psi between your solenoid and the catapult cylinder. This will help keep you legal and safe. |
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