Terminology query

[Tim StevensParticipant @timstevens64731]

Please, what is a Weighshaft?

I need to know to make sense of the recent ME article on making a Garrett 4CD Tractor (p797)

Thanks

Tim

Edited By Tim Stevens on 25/11/2015 11:20:15

[Tim StevensParticipant @timstevens64731]

[JasonBModerator @jasonb]

It's the bit that goes in the weightshaft bracket

 

Part of the stevensons valve gear. The rod from the reversing lever attatches to an arm which is fitted to one end of the weightshaft, the one pointing down on the bottom left of this pic.

The shaft then runs through the bracket and has the lifting link lever (forked arm) on it which inturn has the lifting links pivoting on its end and these lift the expansion link to engage the forward or reverse eccentric

Edited By JasonB on 25/11/2015 11:32:53

[Tim StevensParticipant @timstevens64731]

Thanks for that (but it should have been the editor's job, I suspect)

So is the origin of the name anything to do with the 'Shaft which alters the way it goes along' and then mis-spelt by someone who thought it ought to be cleverer than that?

PS the article does say weigh- and not weight- in several places …

Tim

[julian atkinsParticipant @julianatkins58923]

hi tim,

the term weighshaft is derived from an old meaning of 'weigh' as in to 'raise up' as in 'weigh the anchor'.

the weighshaft is the means by which the radius rod in walschaerts gear is moved, or the expansion link moved in stephensons gear. in fullsive raising up these parts can be quite heavy and require a lot of effort, and a counterbalance is often added to the weighshaft with stephensons gear to assist the 'raising up'.

cheers,

julian

[Martin KyteParticipant @martinkyte99762]

Is it not a variant on way and meaning motion. Weigh shafts in marine engines are part of the starting gear. We talk of motion work and valve gear. Giving weigh or way to someone meaning to allow them to continue in motion. So the weigh shaft is that which gives motion to whatever it is attached to.

regards Martin

[JasonBModerator @jasonb]

Posted by Tim Stevens on 25/11/2015 12:06:10:

Thanks for that (but it should have been the editor's job, I suspect)

He would probably have said its something to do with the Milkyweigh

[John Stevenson 1Participant @johnstevenson1]

Naw,

He's a genuine hazelnut guy

[BazyleParticipant @bazyle]

So it doesn't have anything to do with counterbalancing the weight of the links? Not a problem in models but how do they do that full size or is it just brute strength?

[JasonBModerator @jasonb]

May be why the reversing levers are so long to give about a 3:1 advantage

[Neil WyattModerator @neilwyatt]

A weighshaft is any shaft that moves back and forth, rather than rotating. It's a very common item in control gear, such as valve gear.

While it's not feasible for Diane (or me) to include a glossary for every article, you can find a definition in the 'Workshop A-Z' HERE – a little something I put together for just these situations!

Neil

[JasonBModerator @jasonb]

Posted by Neil Wyatt on 25/11/2015 14:40:44:

A weighshaft is any shaft that moves back and forth, rather than rotating.

But the weighshaft does rotate and not move back & forth

The lever hanging off the end moves back & forth and the lifting link lever moves up and down but it's the shaft that rotates

[KWILParticipant @kwil]

Stick to stars and electronics Neil

[Neil WyattModerator @neilwyatt]

Posted by JasonB on 25/11/2015 16:00:43:

Posted by Neil Wyatt on 25/11/2015 14:40:44:

A weighshaft is any shaft that moves back and forth, rather than rotating.

But the weighshaft does rotate and not move back & forth

The lever hanging off the end moves back & forth and the lifting link lever moves up and down but it's the shaft that rotates

Rotation is to move in a circle, a weighshaft only moves in an arc of a circle, or it would be a crankshaft. Craknkshafts rotate, weighshafts sway gracefully back and forth.

To be absolutely exact a weighshaft translates linear motion in one plane into linear motion in another, parallel plane.

 

Edited By Neil Wyatt on 25/11/2015 16:46:31

Edited By Neil Wyatt on 25/11/2015 16:57:27

[JasonBModerator @jasonb]

"weighshafts sway gracefully back and forth."

Are we looking at the same thing, weighshaft on a traction engine does not sway back and forth gracefully or not

[Neil WyattModerator @neilwyatt]

<missed smiley alert>

Neil

[Howard LewisParticipant @howardlewis46836]

On some, (mostly the later locomotives), full size engines, the forces involved were so great that using a reversing lever (Johnson bar in U S A) was not feasible, and so brought about the screw reverser, which delivered greater forces, and allowed more precise setting of the valve gear for expansive working.

Howard

[Brian GParticipant @briang]

Or the steam reverser, a device which sometimes gained a reputation for allowing much less precise setting of the valve gear for direction, let alone expansion.

Brian

[Chris GunnParticipant @chrisgunn36534]

Tim, as the author of the article in question, I am sorry if the descriptions have given rise to any confusion. I am using the descriptions that appear in the drawings, which in this context are pretty standard, weighshafts are mentioned in many articles covering locomotive and traction engine construction. I felt that this was better than using "non standard" descriptions which may have caused more confusion.

Chris Gunn

[Tim StevensParticipant @timstevens64731]

Please don't worry, Chris

I just came across a word which was new to me and I felt that I needed to find out more. Which I did. This was a term which my dictionaries and Wiki etc were silent about, so thanks for prompting the question.

Regards, Tim

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