Originally posted by pops1
One clown has a write up on bowls on his web site. It is the funnest BS lack of knowledge piece I have ever seen.
Pops, do you have a link to that site? I've got a little time to kill at work today.
Thanks!
I'm no expert this could be totally wrong.
I know many of you have been the PWC guys do this. they get on the front of the ski and pop the jet out of the water and just start hoseing everything down. Well when i see them do this they dont move much. If the impellers was pulling like some say it does then they would still moving.. right? makes sense to me.
Wasn't there some old guy named Newton that explained all this a few centuries ago??
You got that right!
Originally posted by superdave013
Pops, do you have a link to that site? I've got a little time to kill at work today.
Thanks!
My point going back to the 95% number( Hyp. Number) if some percent is forward pull/thrust the balance is the byproduct of the jet turbine effect. I have asked two friends both Hyd Engineers & 10 other very qualified people this same question and all say it can be calculated. I have yet to see any analysis.
I submitted intake & bowl pressures, nozzle exit sizes and flow rates to our fire people and got 4780 GPM out of that one from one race boat. Would like to see what kind of Analysis could be arrived at on this. I also wanted the board to think a little different on the impeller. Remember the Aroria Pump test boat I talked about in a past string. That boat had a all tubular encased bowl and thrusted 2-3 feet above the waterline. According to one of the test persons involved it ran great, and knowing him I have no reason to doubt.
Is that not a high percent of forward pull with no wall to push on.
Now with a fire pump this ratio and design changes also, as the exit port is almost at a 90 degree with a swift wrap to create very high pressure. Smaller inlet larger diameter longer sweep to the vane.(Ride duration/Higher Thrust)
Another question was swarf compount angle found in our impeller! It is there to allow the higher volumn and surface pitch control. Remember we have a bigger entry mouth then others so it must control a larger water column (Volumn).Yet My wife say's I have just a bigger mouth.
Remember- Make the front purrrddy and let the backside do the work!
JetHydro, yes my responses are jackass like at times. But some repeat posts deserve it. Like the post...
"If you shoot a hose at a wall it will push you back. That's why when you raise the divertor out of the water you loose speed."
Nozzle thrust has nothing to do with the wall. Or shooting the jet into water. Same no matter, wall or no wall, water or not water.
Neither do fire hoses have thrust bearings or impellers. I mentioned that to illustrate why a jet pump's thrust is different than a prop's. On the other hand, angle of thrust does impact forward thrust. Some mentioned up angle affects aero lifting so less water drag. Some mentioned digging the hull so more water drag. Both influence speed and one tends to cancel the other.
But don't forget this: The higher you go the less forward thrust you have. This basic trig as in the total thrust times the cosine of the divertor angle equals the forward thrust. Most likely the main reason you loose speed with excessive up nozzle. Consider the extreme...a nozzle pointed vertical. How much speed would you get??? Zippo. Old faithfull.
"Isn't the surface of the blade slightly concave? Jer what effect would this have on the water moving over the blade?"
Omega, I haven't looked at blade geometry closely, but my guess is all mixed flow impellers could be called concave depending on what axis or viewing angle you're talking about. There's a definite twist as you travel down flow even with a Berkeley. More later...
Jet4fun, thanks for the example. And yes, a jet pump does not "pull" or suck itself across the water.
Cyclone, nozzle reaction can (and has been) calculated.
jer
Hey guys, do these pull or push the boat??
http://www.***boat.com/image_center/...c01500-med.jpg
Originally posted by LVjetboy
Cyclone, nozzle reaction can (and has been) calculated.
jer
So can the "relatively negative" acceleration of the lake water introduced into the intake. I.E. 'bricks'
but noone seems to believe me. The math works.
On the other hand i will say again anyone who says that the impeller pulls the boat thru the water is just pullin your chain, Jer. They, like me, must like the graphs.
"Jim Lee will sell some Torque T-Shirts"
Remember that, Jer?
Did you convince anyone?
You know with me, on almost all of the points you are preaching to the choir. Sometimes in a rather enlightning way, even for a choir.
You bring the facts as described by (un)common sense and science as well as a very visible demonstration to back up all that you say.
On the other hand, observations and suppositions are the mother of discovery. IMHO if the present state of the jetdrive to improve it will take just that. Another way of looking at things.
Some of the seemingly prepostrous statements i have read on the pump and HP/Q discussions has given me reason to ponder and explore new possibilities.
mikeT
Originally posted by superdave013
Hey guys, do these pull or push the boat??
Yes.
Originally posted by superdave013 [/i]
[B]Hey guys, do these pull or push the boat??
:
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