That center Prop question

Mark Chirnside

Mark Chirnside

Member
Mark I am only quoting from your article in ADB. summer 2020:
In case of a propeller with slip of 14% (three bladed as in Stephen Pigott proposed notebook) this means it is working at 86 per cent of it maximum efficiency whereas a propeller with a slip pf 11.7 per cent ( four bladed as in Stephen Pigott proposed notebook) is working at 88.3 of its maximum efficiency.

Mike, I did not dispute the figures given.

I can only repeat myself:

It must be remembered that they sought to maximise efficiency and minimise vibration.
 
J

James Murdoch

Member
I recall having a discussion on this topic here around the start of the year:all the evidence points to the central propeller being three-bladed. There is primary source evidence to support this argument, firstly, an engineering notebook (commonly referred to as the Pigott evidence) from J.Brown & Co Clydebank, and secondly the H&W notebook published in 2006.

I recommend reading through the thread, some great arguments were made.


[Moderator's note: Edited post, as per the member's request. JDT]
 
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Mike Spooner

Mike Spooner

Member
I recall having a discussion on this topic here around the start of the year:all the evidence points to the central propeller being three-bladed. There is primary source evidence to support this argument, firstly, an engineering notebook (commonly referred to as the Mignot evidence) from J.Brown & Co Clydebank, and secondly the H&W notebook published in 2006.

I recommend reading through the thread, some great arguments were made.

Do you mean Stephen Pigott and not Mignot notebook?
 
J

James Murdoch

Member
Hi Mike, yes I did. My predictatext decided to take a bit of creative license with my phone (I have a relative with that surname so I guess that's why lol). I am unable to edit the post now, if a mod could, I would be most grateful. Thanks for pointing that out Mike.
 
Mike Spooner

Mike Spooner

Member
When looking at Stephen Pigott papers from the University of Glasgow Archives & Special Collections. He has calculated two proposed centre propeller for Olympic & Titanic a three bladed and four bladed propeller. The one thing stand out in his calculation that is the slip ration in %. Where the Three bladed propeller is -14% and as four bladed is -11.7%. Therefore I can only think is the reason why the four bladed propeller was use on Olympic. As for Titanic if a three bladed centre propeller was used I can only think it was more on a comparison between the two ships.
For correct propeller design on a new class of ship is not an easy task indeed.
Mark list of 21 H&W ships using the combination propulsion system is food for thought. As there is about 50% split between three and four centre bladed propeller. However if I have time before going on holiday for few weeks I look what class of ships they were.
As for this weekend is the Kempton Museum steam up for the worlds biggest working triple expansion steam engine. Similar to Titanic but different application pumping water to London in the past. But when visitors see the size of the engine 60 feet high including the water pumps, Then tell them the Titanic where ever bigger they are amaze at the size. We have also a good working DVD of Titanic engines, boilers and propellers etc. Come to think about it I must check if a three or four bladed centre propeller is used in the DVD?
 
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Mike Spooner

Mike Spooner

Member
I never take a computer on holiday, but I will read Sam Halpern new book: Prelude To An Allision with great interest.

Cheers Mike
 
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Mike Spooner

Mike Spooner

Member
Checking the centre propeller on a DVD video it shown a four bladed centre propeller with S W. Halpern signature!
 
Samuel Halpern

Samuel Halpern

Member
Checking the centre propeller on a DVD video it shown a four bladed centre propeller with S W. Halpern signature!
Hmmm? I never produced any DVD. I did create an animation showing Olympic's props turning, and that had a 4-bladed central prop. If you open this link: Speed and Revolutions you can see the animation in the second image of the article. (And yes, it has my name on it.) If someone produced a DVD with some of my material in it without my knowledge, it would not have been the first time.
 
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Mike Spooner

Mike Spooner

Member
Hmmm? I never produced any DVD. I did create an animation showing Olympic's props turning, and that had a 4-bladed central prop. If you open this link: Speed and Revolutions you can see the animation in the second image of the article. (And yes, it has my name on it.) If someone produced a DVD with some of my material in it without my knowledge, it would not have been the first time.
Thanks for the reply.
 
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