Steering Gears, RMS Titanic

[gearcutter]

Interesting gear profile on these gears, apparently part of the mechanism used to drive the steering system of the Olympic-Class liners such as the RMS Titanic.

I'm not sure what the profile would be called. Double Herringbone perhaps?

This reference refers to the gears as 'Wilson-Pirrie' type.
"The steering gears for the Titanic were built by the machine shops at Harland & Wolff and were of the Wilson-Pirrie Type and were situated on C Deck under the after end of the Poop Deck."

https://www.encyclopedia-titanica.org/community/threads/steering-gear.17386/

 

[tbuelna]

I'm assuming the intent behind this type of tooth form was to minimize backlash in the steering system. Not really a double herringbone, which would have a "W" profile rather than a "Z" profile. Maybe it minimized backlash by allowing the pinion to float axially so it could make local contact on both sides of a tooth as it passed thru mesh. The contact points on opposing flanks of a Z-helical(?) tooth would be offset along the face width, and would likely be constantly moving as the pinion continuously re-positioned itself in response to the opposing axial mesh forces. Not a good approach for high load/speed gear drives, but would work for a very low speed steering gear mechanism where minimal free-play is a concern. Simpler and more reliable than the spring-loaded scissor gear approach commonly used for this application at the time.

 

[RolMec]

It must be an ISSUE to get the alignment right for such gears, and also the manufacturing, at the time. Esp. the pinions look strange to me, the plain hub w/o keyway or bolting bores or anything to fix it somewhere of the straight pinion, and the nonfinished "dead end" gearcutting of the beveled pinion.
I'd rather like to have smbdy have a look, smbdy specializing in the details of open gear engineering of that time, lest not to fall to a digital mockup ;-)

Roland Heilmann
Lpz FRG

 

[mfgenggear]

manufacturing must of being a nightmare. to get these gears to perfectly line up. something lost in past. never seen such intricate pattern.

 

[Compositepro]

The gears appear the be castings with little to no post machining, so they could not be very close tolerance. I would guess that with this design the gears match better as they wear. Wooden gears were still being made when these gears were made.

 

[mfgenggear]

good point, but the spacing error vs the tooth and tooth space clearance had to be perfect so the teeth would not self destruct.

 

[gruntguru]

If they were castings with no post machining it might be possible to "lap" them into a reasonable mate - especially if they are hunting.

je suis charlie

 

[tbuelna]

Take a look at pages 1-4 of this September 1921 issue of Machinery. Provides a nice description of form end milling large external herringbone gears. Figure 1 shows a partially shrouded pinion similar to the one on the right in the OP photo above. Figure 3 shows the indexing mechanism used on the milling machine.

 

[gearcutter]

tbuelna - I followed the link but am unable to open anything displayed on that page. It appears to be a place for leaving reviews about the book.

 

[3DDave]

Gearcutter - it may be a browser setting interfering with your view as the full book appears for me. It is part of the Google project that scanned millions of books, in this case from the Princeton library. Try another browser or a different computer.

 

[gearcutter]

Well this is quite odd; I had considered myself to be somewhat savvy around computers. I might have reassess that view
I have tried opening that link on a PC from IE, Chrome & Firefox and all I see is the opportunity to leave a review.
Are you using a mobile device?

In Chrome, this is all I'm seeing -

 

[3DDave]

Win 7 on a Dell laptop, Firefox and Chrome both work. Here's the entire link that I pasted into Chrome:

https://books.google.com/books?id=2IhNAAAAYAAJ&pg=PA1#v=onepage&q&f=false

I hope it isn't a regional limitation; I'm in the U.S. There must be some consideration about international copyrights, though the page indicates it is freely distributable. It is over 1200 scanned pages or I would download and attach it here.

 

[gearcutter]

There must be some sort of geo-blocking going on as I'm only able to view the book, in what Google calls, 'Snippet View'.

 

[tbuelna]

gearcutter-

Sorry the link didn't work for you. I checked it before submitting the post and it worked OK for me. Like 3DDave I still run Win 7 Pro on my Dell workstation and use the current Firefox browser. Definitely worth a read to see how these types of gears were machined 100 years ago.

Here a link to another scanned version (from University of California library) of the same document:

https://books.google.com/books?id=BMY7AQAAMAAJ&pg=PA1#v=onepage&q&f=false

 

[MikeHalloran]

I downloaded the latter link.

It was very illuminative about how to machine herringbone gears with an end mill, and also of how to construct a machine to do so.

Then it went on to hundreds of pages on all sorts of machinery and related subjects like laying out factories and hiring people and on and on.

Wow.


Mike Halloran
Pembroke Pines, FL, USA

 

[Windward]

I hope a tangential comment will be interesting. I have sailed on some ancient Great Lakes ore boats that used this kind of steering gear. They rattled like crazy, but that was after sixty years or more of use. One of my jobs was to grease the gears and other moving parts every day. You always get some on you.

The most interesting part of these old steam-driven steering gears was the control valve that operated the steam cylinders. It would take an electrical signal from the pilot house and direct steam to the cylinders until the new rudder position was achieved. Then it would cut off the steam. It was entirely automatic. It had an internal worm gear and some other parts, and it was just a small part compared to the rest of the gear. Less than the size of a 1/4 HP induction motor. Truly an ingenious mechanism. I believe you can see them on the museum ships in Toledo, Ohio, the SS Willis B. Boyer and the SS Col. James M. Schoonmaker.

Modern steering gears are generally hydraulic. I have seen them with a Rapson Slide.