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Steam & Excursion > Young Valve Gear

Date: 09/16/22 16:53
Young Valve Gear
Author: gbmott

What were the claimed advantages of Young and did those fail to materialize or were there offsetting disadvantages?  Something clearly prevented it's widespread adoption.


Date: 09/16/22 17:49
Re: Young Valve Gear
Author: LarryDoyle

Basically, the Young Valve Gear is the same as a Walschaerts, except that instead of taking its motion from an eccentric crank on the main driver, it takes its motion from the crosshead on the opposite side of the engine, thus claiming reduced unbalanced weight.

If you were Mr. Young, of course the advantage was that you received a royalty for each engine built with it.  And, if you were the same Mr. Young that was also the Motive Power Supt. for the CNW (or was it UP - I forget) ......  Well, that road briefly favored the Young Valve Gear.

A disavantage was that it was more expensive and difficult to maintain, as a worker had to work on both sides of the engine to set valves.  It was not widely used.


Date: 09/16/22 18:11
Re: Young Valve Gear
Author: train1275

O. W. Young worked for the C&NW.

Date: 09/17/22 07:51
Re: Young Valve Gear
Author: LarryDoyle

train1275 Wrote:
> O. W. Young worked for the C&NW.

Thank you.


Date: 09/17/22 09:16
Re: Young Valve Gear
Author: timz

One claimed advantage: it allowed longer valve travel.
Dunno why that would be.

When it was new, think they said its valve-motion
curve was more symmetrical.

Date: 09/17/22 15:22
Re: Young Valve Gear
Author: LarryDoyle

Studying working animated schematics of Walschaert and Young valve gears at various cutoffs, I can see no difference in the performance of one over the other as far as the engineer (or the bean counters) were concerned.  The Dockstadter animations make the Young look more complicaed, but remember its showing BOTH sides of the locomotive while the Walschaerts is only showing the right side.  Though I do agree that Young did reduce counterbalancing issues at the main driver, I do not see what the added complexity of transversing left/right motions was worth.

Walschaert = KISS.  I.E. "Keep it Simple, Stupid"


Date: 09/17/22 17:45
Re: Young Valve Gear
Author: wcamp1472

To me, the argument that eliminating the Walschaert crank
is an inconsequential amount of weight.

There's also possible "patent expenses" with  the Young...so, the varoius configurations
 of Walschaert valve gears were available without paying royalties to the patent holders.

Interestingly the  PRR's T-1s, using the Caprotti system, also used cross-powered
valve gears ...left side cross head operated the valve events of the right side.

However, the Caprotti system used miniature Walschaert links for variable
cut-offs and reversing.  

Later, improved Franklin poppet valve gears used oscillating cams, as well a rotary cams.
As I understand it, the new T-1, #5550, will be equipped with a variant of Franklin's
rotary cam scheme --- using lighter weight titanium valves and valve return springs.

The cam is driven by a 'return crank' on the main drivers.  A 'return crank' has it's
upper end at the center of the axle's center, instead of off-center --- or 'eccentric' crank.
Thus, the right-angle gears produce rotary motion to drive the cam shaft.

Back at the close of steam, poppet valves were closed with coil springs --- At high rotative
speeds you can get 'valve-float' ----- where the valve poppet never fully closes onto it's
seat until popped open again by the rapidly turning camshaft.

The old cure was to use stiffer 'return' springs ----- which, at medium track speeds, battered
the hardened valve-seat inserts...ruining the valve seat inserts.. pieces sent flying out the 'stack..

By using lighter ( than comparable steel components) titanium valve poppets and springs.
requiring less powerful return springs --- which should add hours of service life to the
valve seats for the proposed #5550.

We'll see..



Edited 4 time(s). Last edit at 09/17/22 18:19 by wcamp1472.

Date: 09/18/22 18:49
Re: Young Valve Gear
Author: tomstp

Wes, while you are "at it" what about Baker valve gear?.  Doesn't it have less pins( 2 on each side) which eliminates some slop after the gear wears?     Thanks in advance.

Date: 09/19/22 05:49
Re: Young Valve Gear
Author: wcamp1472


I don't know about the "number of pins & slop", but after the ready
availability of 'needle' roller bearings, Baker used them on all it's
loco valve gears.

Before that, they were equipped with plain, sleeve bearings, and
that wear could get excessive....especially with so many pivots 
between the eccentric crank and the valve stem.

Although Baker used only  2 frames ( the long frame used with locos that had 4-wheel 
pilot trucks and short frame gears used on switchers & 2-wheel pilot trucked engines..).

The pivot points for ALL Baker gears are virtually the SAME dimensions...
used on switchers, up to the biggest passenger & freight engines...

Once they adopted the needle bearings, the Baker valve gears lasted from
rebuild to rebuild... a very high amount of miles.   Storehouses only needed 
to keep one type of Baker valve gear parts on hand for their entire,
Baker-equipped fleet.

The two variables: the 'lead' and the total stroke of the spool are determined
on the drawing board for each specific class.  The 'tead'  ( amount that the valve port 
is open, with the piston at a dead-center) expressed as a fractional-inch,
like 1/4",  5/8", 1/2", etc., is determined by the 'combination levers' dimensions,
and the spacing of it's 3 pivot pins ---- to suit the specific port widths, valve travel, 
et cetera.

The combination lever is moved by the piston and its cross head.
So, even with the engineers's reverse lever handle in it's centered position,
the valve & its ports are still opened and closed at the end of each stroke.
Allowing for steam admission, or exhaust --- even on 'centered' reverse levers.

The total valve travel is determined by the designers' dimensions of the valve ports,
the eccentric crank, it's pivot spacing, and the diameter of the 'crank circle'....  
And, the Baker gear allows for various cut--off lengths ( shortens the admission times) -
-- to close the ports after a certain number of degrees of driver rotation.

The variable cut-offs are advantageous at high track speeds, when the extreme 
steam ( gas) temperature allows for beneficial power down the full length of
the stroke.  That's the huge advantage of superheating the steam after 
it leaves boiler.

So, over time, many RRs adopted the Baker gear for all of the engines in their fleets....
whether passenger, switcher, of freight dedicated.  One set of Baker parts
fit all the engines, only the gear's combination lever, the union link, the eccentric crank
and the reach rod ( from gear-frame to valve stem's cross head)  were different
dimesions for each class of engines in a fleet.  Again, each of those levers, port
dimensions, and pivots was determined on the drawing boards by the loco designers.

"Valve setting" meant restoring the tight tolerances of the designers,
per their drawings.. Over many miles, plain sleeve bearings and Wakschaert links
& blocks get badly worn.

Baker gears, after the adoption of the rolling-element bearings, lasted many
hundreds of thousands of miles longer than Walschaert-driven valves and
the associated wear rates.

And, only one set of Baker gear parts fit every Baker-equipped loco,
regardless of loco class, manufacturer, or driver diameter..

The biggest risk to Baker gears in today's environment is the temptation
to over-lubricate the needle bearings by applying grease too often and at sxtreme pressures.

They should only br lubricated very sparingly, and do not force grease into the bearings.
the delicate needles need to be able to freely move and spin....too much grease locks them
and leads to premature bearing failure.  Once a year would be plenty!




Edited 1 time(s). Last edit at 09/19/22 06:09 by wcamp1472.

Date: 09/19/22 06:24
Re: Young Valve Gear
Author: train1275

Agreed with what is posted above regarding Baker gear,  but then, so why  did roads like ATSF and NYC and others who ran  super steeds use Walschaerts ?
What was their thinking ?

Edited 1 time(s). Last edit at 09/19/22 06:25 by train1275.

Date: 09/19/22 07:06
Re: Young Valve Gear
Author: wcamp1472

For as many reasons as there were CMOs...


( NYC's Niagaras and others were equipped with Bakers...).

Date: 09/20/22 09:55
Re: Young Valve Gear
Author: timz

It seems there are Young valves, and Young valve gear.


The earlier article


Edited 1 time(s). Last edit at 09/20/22 10:58 by timz.

Date: 09/20/22 11:23
Re: Young Valve Gear
Author: wcamp1472

From the Railway Age article cited, above:"The Young valve is lighter dueto the packings
being carried in the valve bushing instead
of the valve and this feature also permits the valve to be
 much simpler in construction."

It's a virtual impossibility to have the packings in the valve bushing.

"Packing" is the railroaders' term for what is commonly known as piston rings, rod seals, etc.
So, what they're saying is that the spool valves' seals are a series multiple rings
(surrounding the valve) carried next to each other, in the entire length of the bushing .... ?
I'm not from Missouri, but Show Me, how to put the multiple sets of packing rings in the
valve bushing !

That smacks of advertising Bull Crap.... from back in the day.

And speaking of misrepresentation...
The article's so-called indicator card renditions are fictional, also.
An indicator card has one pencil and records pressures for one end of a cylinder.
( the trace approximates a profile of a high-top 'sneaker')
You can't  get two traces on one graph..

The two traces shown in one graph in the article are manually drawn on one sheet...
no 'indicator' makes records with two pencils and In two directions simultaneously.  
These are fictitious renditions of what an indicator card could look like....
but, one piece of paper is required for each end of one cylinder.
 It's a P/V trace of one stroke...

It can be done today,  using a dual-trace oscilloscope,  but back then,
it was paper on a drum ( string to cross head) and a pencil ( moved by  pressure cylinder)
for the vertical trace..

Indicator Cards were common on slow rpm, factory ( stationary ) steam engines.
On locomotives at 70-per, that could be 5 to 7 revolutions per second...
Too fast for spinning drums and bouncing pencils..


Edited 4 time(s). Last edit at 09/20/22 14:47 by wcamp1472.

Date: 09/20/22 13:38
Re: Young Valve Gear
Author: LarryDoyle

wcamp1472 Wrote:

> That smacks of advertising Bull Crap.... from back
> in the day.

As stated in my post above, Young valve gear is simply a rearrangement of Walschaerts' parts.      Smoke, Mirrors, and advertising hyperbole.

Longer valve travel?  Ya get that simply by changing the relative lengths of various lever arms.  The MOTION is still the same!

Take a look at these schematics and diagrams of valve events from the Dockstadter program.  The "tennis shoes" Wes describes are nearly identical - slight variatiions are due to minor variations in the dimensions of the parts in the drawing, not to differences inherent in the motions themselves.  The steam diagrams are virtually the same!



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