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  1. Robert Clark

    How long would inductor hold energy disconnected from battery but current flowed in alternate path

    Thanks for the response. You want the switch so rapid that the field doesn’t collapse. There are also “make-before-break” switches that can switch to the alternative current flow pathway before the battery is fully disconnected: Transfer switch 101. Closed transition A closed transition is a...
  2. Robert Clark

    How long would inductor hold energy disconnected from battery but current flowed in alternate path

    Usually this question is asked in regards to just disconnecting the battery, like in the attached image. In that case the answer is just milliseconds. But in the analogous scenario for a capacitor, it could hold the charge for significant time because the charge would be held on the parallel...
  3. Robert Clark

    Force produced by pressurized water exiting a hose or pipe?

    3DDave, I intend to! By the way look at one of the numerous videos of people using pressure washers on the net: Pressure Washer Buying Guide | Consumer Reports. https://youtu.be/6g3IYVsBc6k Just from normal use you sometimes get bends in the hose. It doesn’t seem reasonable that this...
  4. Robert Clark

    Force produced by pressurized water exiting a hose or pipe?

    Rputin, the pressurized water can certainly provide a lifting force even to carry a heavy payload, as shown in the videos in the first post. The question is how much lifting force? By the way, pressure washers are in common use nowadays and anyone can do a simple test to find out which is the...
  5. Robert Clark

    Force produced by pressurized water exiting a hose or pipe?

    Littleinch, the point is to produce a lift force with a water jet, like in the videos in the first post. So you would need to know what is the max force possible. The hose has to be bent rearward to be able to make the lifting force. The problem is which is the correct value for the thrust...
  6. Robert Clark

    Force produced by pressurized water exiting a hose or pipe?

    The only obvious difference between the two cases is that the water bottle rocket case exits out to the open air, while in the force on a pipe bend case it remains inside the pipe. I thought I was taking that into account though in the pipe bend analysis by restricting the pipe diameter down...
  7. Robert Clark

    Force produced by pressurized water exiting a hose or pipe?

    ...And here is the answer using the online calculator at the link: https://www.lmnoeng.com/Force/ForceBend.php We'll restrict the diameter at after the bend to make the scenario like the water bottle rocket case. I was surprised to see that the force was still much higher than the water bottle...
  8. Robert Clark

    Force produced by pressurized water exiting a hose or pipe?

    Here is the water bottle rocket analysis for one pressure washer: We’ll use the first equation shown there which amounts to F = (mass flow rate)*(exit velocity). Take for example this pressure washer: PowerShot PS4240 4200 PSI at 4.0 GPM Cold Water Gas Pressure Washer with HONDA GX390...
  9. Robert Clark

    Force produced by pressurized water exiting a hose or pipe?

    Well known examples of the force produced by pressurized water exiting a pipe: JetLev Water Propeled jet Pack. https://youtu.be/n0109liIZGQ Hovering Car. https://youtu.be/s-2BN6FLDjA I need to calculate the maximum for the thrust produced when the hose or pipe is bent rearward. Since this...
  10. Robert Clark

    How does a pump trade flow rate for head, i.e., pressure?

    Rputvin, thanks for responding. Yes, for a hose held aloft thousands of feet in the air extending horizontally for a distance of several miles, you would have to get FAA approval. However, since this is for region that extends from a lake, pond, creek, etc. in the direction towards a forrest...
  11. Robert Clark

    How does a pump trade flow rate for head, i.e., pressure?

    That video is of airplane water or fire retardant drops which are only minimally slows the spread of the large forest fires.
  12. Robert Clark

    How does a pump trade flow rate for head, i.e., pressure?

    California firefighters ‘stretched to limit’ as devastating blazes become the norm. https://apple.news/ARNc_w8E1QVu_TuCHsVxJhg Robert Clark
  13. Robert Clark

    How does a pump trade flow rate for head, i.e., pressure?

    In addition to the application of fighting fires far away from any available water source, there is also this extremely important application: https://www.worldvision.org/clean-water-news-stories/walk-water-6k Robert Clark
  14. Robert Clark

    How does a pump trade flow rate for head, i.e., pressure?

    1503-44, those huge pumps I mentioned can put out 375 GPM. This compared to a common 2” fire hose which might put out 250 to 350 GPM: #60 - Double Jacket Fire Hose Comparison: 2 inch Fire Hose vs. 1¾ inch vs. 1½ inch. “2-inch double-jacket fire hose: large volumes, difficult handling 2-inch...
  15. Robert Clark

    How does a pump trade flow rate for head, i.e., pressure?

    3DDave, keep in mind the hose and therefore the distance from the water source to the location of the fire suppression, is VERY far away. Now consider what kind of scenario where the only water source would be so far away, AND why the hose would have to be held so high aloft necessitating the...
  16. Robert Clark

    How does a pump trade flow rate for head, i.e., pressure?

    As LittleInch suggested, perhaps I should say where this is coming from. Take a look at this video: Drone Could Help Firefighters By Putting Out Fires. https://www.youtube.com/watch?v=Bm2BVTTir4c Now imagine this with much, MUCH longer hoses, and going both vertically and horizontally. I...
  17. Robert Clark

    How does a pump trade flow rate for head, i.e., pressure?

    I’m thinking of performance curves like this: https://www.enggcyclopedia.com/wp-content/uploads/2011/09/pump-curve2.jpg From the web page: https://www.enggcyclopedia.com/2011/09/pump-performance-curves/ It is notable that the relation between head and volume flow rate isn’t exactly an...
  18. Robert Clark

    How does a pump trade flow rate for head, i.e., pressure?

    For my application, maximizing head is more important, even at the sacrifice of flow rate. I’m referring to pumps used in pressure washers, such as: SIMPSON Cleaning MS60763-S MegaShot Gas Pressure Washer Powered by Kohler RH265, 3100 PSI at 2.4 GPM...
  19. Robert Clark

    How does a pump trade flow rate for head, i.e., pressure?

    A pump’s power is a product of its pressure rise times volume flow rate. Commonly, a pump is specified by giving the pressure rise, or head, it can provide and the flow rate, such as in gallons per minute(GPM). But some pumps provide the user with a chart that shows how the pressure rise can...

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