I’ve seen a few of these. The piping is always curved–semicircular, approximately–before the spigot. Why? Does this configuration keep the full water pressure from striking the spigot valve?
I’m thinking that the curvature of the piping actually serves to increase the pressure before the fluid exits the nozzle… But, I’m not entirely sure on that. But, if you think of your own experiences with a regular garden hose, if you bend the end of the hose, doesn’t that serve to make the pressure rise, and the water to shoot farther?
Or, it could just be for decoration. Who knows.
“Far better is it to dare mighty things, to win glorious triumphs, even checkered by defeat, than to rank with those poor souls who neither suffer much nor enjoy much because they live in the gray twilight that knows neither victory nor defeat.” Theodore Roosevelt
I’m not sure if I understand the question, but it sounds like something you would do to reduce friction in the pipe. You want to get as much water and pressure to the nozzle as possible, so you’d avoid sharp corners. Since the water would be moving rapidly in the pipe you want to maintain laminar flow, turbulence can consume a lot of energy in a fluid flow.
Boy, you physics people really make things complicated…laminar flow, pressure increase, jeez…
To put it bluntly, the bends are there so you can aim the thing.
The nozzle on top of the truck is called either a “deck gun,” “monitor,” or “master stream,” depending on where you are. They (usually) flow from about 350 gallons per minute (gpm) to around 1000 gpm, some go upwards of 6000 gpm. If you look at the bends, there is a swivel at the end of each bend. One swivel lets you swing the gun left/right, the other lets you swing it up/down.
Some have a handle to move them, others have a wheel that turns a worm gear. I personally like the kind with the worm gear, you don’t have to stand there with it.
They can also be removed from the top of the truck and placed on a ground base. Hose is run to the base so you can place the deck gun away from the truck and closer to the incident, since parking a fire engine too close to a fire makes the paint bubble and the windows break.
Some links:
http://www.tft.com/products/product.asp?ID=XFT-NJ http://www.elkhartbrass.com/prfirede.htm
Jeremy
Self-Declared SDMB Resident Fire Service Expert
Forgot to add…
We do try to get a laminar flow just before the water leaves the nozzle. There is a fitting just before the nozzle itself called a “stream shaper.” Its a tube about 8" long with vanes inside, straightening the water before it enters the reduced diameter of the nozzle tips.
Jeremy…
Nobody ever calls me after they’ve done something smart.