Talk:Pump-jet

Clogging-up and efficiency

Jets don't clog up, with a properly designed jet unit, they rarely clog. In 10years of jet boating I have never experienced a clog jet unit.

The efficiency of a jet is rarely discussed by any owner of a jet, it is only mentioned by other boat owners, probably because they really don't understand jets.

There are enough commercial boats sizes ranging from 5 metre to 50 metres that use marine jet propulsion, and I'll bet ecomony is the reason they use them.

Torpedoes

A classic use of pump-jets is in modern, heavy-weight torpedoes. This fact was included in the torpedo article for ages - until someone (accidentally?) deleted it. Examples of torpedos which use pump-jet propulsion include the the American Mark_48_torpedo and the British Spearfish_torpedo.

Rename to Water-jet?

I've never heard of a pump jet. Shouldn't this be removed to water-jet?--Sturmvogel 66 (talk) 17:48, 11 January 2010 (UTC)

Well, considering it is normal to have articles at their most common name, and the first line of this article says "or, more commonly, water-jet", I think that moving it to Water jet would be a prudent thing to do. -SidewinderX (talk) 12:06, 29 June 2010 (UTC)

I have written an article on the history of water-jet propulsion. May I introduce it here? —Preceding unsigned comment added by Downypilt (talk • contribs) 16:47, 15 October 2010 (UTC) "History" should perhaps come under "Source"?

Invention

PT-76 article say, that PT-76 tank has pump-jet design in the end 1940-sХодок (talk) 09:38, 20 March 2010 (UTC)

possible contradiction

In the advantages section, it lists a higher rotational speed before cavitation onset due to higher dynamic pressure (which makes sense from fluid dynamics), but in the disadvantages section it states an increased chance of cavitation. Seems contradictory to me. Under what conditions do each of these occur? Cowbert (talk) 21:50, 19 August 2011 (UTC)

Between the time you read it, and today, the advantages section line had somehow been changed to read static pressure. Which doesn't make sense. So I changed it. 220.224.246.97 (talk) 17:39, 11 February 2013 (UTC)

Increases entrained weight

WHAT. Water, underwater, is weightless. Archimedes' principle!

Even then, I'd agree if this 'entrained water' was the leaden drag mass, but this is the propelling mass!

Removed the statement. 220.224.246.97 (talk) 17:41, 11 February 2013 (UTC)

Kitchen Rudder

This is NOT an udder but a early version of the reversing bucket. LOL! ThomasHarrisGrantsPass (talk) 05:07, 3 April 2013 (UTC)

First known cephalopods swam with a reciprocating pump jet

I would like to see a source on this statement; that's a paper I'd like to read :) — Preceding unsigned comment added by 108.70.59.227 (talk) 00:28, 15 August 2013 (UTC)

Inventor

I believe the statement that William Hamilton invented the pump-jet propulsion source is in error. The first practical pump-jet (water-jet) boat was designed, patented (US 2,276,193), manufactured and sold commercially in 1938 by James Keenan Hanley as the proprietor of Prospect Fire Engine Company and later dba Hanley Engineering Services, both of Prospect, Ohio. The boat was a fire-fighting vessel destined for use by the Wheeling, WV fire department. It featured forward and reverse jet outlets as well as what may have been the first use of bow and stern thrusters which allowed it to pivot 360 degrees within its own length. In the 1942-1943 time period Hanley also designed and manufactured more than 100 pump-jet-powered fire-fighting boats of a more advanced type for the US Coast Guard, then a part of the US Navy. After the war, he designed and manufactured a compact water-jet propulsion unit called the Hydrojet, that could be installed in a wider variety of vessels. Curiously, he doesn’t seem to have patented his commercially-produced Hydrojet, but was awarded patents on several variations and accessory equipment. Hanley manufactured several versions of the Hydrojet until his death in 1965, and formed at least two associations with complimentary engine manufacturers, but the Hydrojet was not a commercial success, as its performance was soon leap-frogged by William Hamilton’s efforts. However, there was a definite connection between them. William Hamilton was shown an article about the Hydrojet from the April, 1953 issue of Popular Mechanics, built and tested a replica, then went on to make several improvements to Hanley’s design before abandoning the centrifugal pump concept in favor of an axial turbine pump, which his company still produces. REFerences; George Philip Hanley, “Firefighters From Prospect”, HYK Publishing, Rochester, MI ISBN 0-9615817-1-9 David S. Yetman, “Without A Prop”, Dog Ear Publishing, Indianapolis, IN ISBN 0-978-160844-475-5

Curmudgeon38 (talk) 20:20, 18 January 2016 (UTC)

There is no statement in the article that that William Hamilton invented the pump-jet propulsion. Rather, it refers to the first person to achieve a commercial product. It does call him a "New Zealand inventor", but that's referring to his identity, not that he was the inventor of the product. - BilCat (talk) 20:30, 18 January 2016 (UTC)

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Efficiency

Water jet propulsion is inefficient at low speeds, is it not? Because at low speeds, there's a lot of unused energy in the jet. The wider the jet, the greater the efficiency, but the less max propulsive speed. WorldQuestioneer (talk) 17:59, 8 October 2020 (UTC)

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