Re: T-12 Cylinder Cant
| September 23, 2021 07:17PM |
|
mrwalsh85 Wrote:
--------------------------------------------------
> On a related note . . .
>
> It was my understanding that piston center-
> lines should be aligned with the centerline of
> the driving axles. If the T12 was straightened
> out, and as such, higher than the CL of the dri-
> ving axles, this could be problematic, correct?
> I could see some "waddling" of the locomotive
> occurring under power.
Herb Kelsey Wrote:
--------------------------------------------------
> Right Mr. Walsh. Here is my assumption and,
> my not being a mechanical engineer means I
> AM assuming, but most locomotives have the
> piston on the same level as the center of the
> drivers. On the T-12's the center-line of the cyl-
> inders is raised above the center-line of the main
> driver's axle. This is possibly due to clearance
> problems for the 4-wheel lead truck. So to cre-
> ate four equal power stroke events per revolution
> I think the cylinders would be angled downward
> to align the piston rod with the main driver's center.
> Setting up the valves to get four equal strokes
> would seem to be difficult if the components
> weren't aligned.
Waddle you know, Herb -
There is also a discrepancy created by the unequal surface areas of the two sides of the piston, due to the diameter of the piston rod: on the backward stroke steam is pushing on the full face of the piston – the area of which is π × the square of the radius of the piston – but on the forward stroke steam is pushing on the area of the piston minus π × (radius of piston rod)×(radius of piston rod), so the forces are not equal unless the valve timing is adjusted slightly to allow a bit more full-pressure steam to enter the cylinder on the forward stroke. Cant or no cant, the crosshead guides have to absorb the upward and downward thrust of the main rod due to its angle above or below the crosshead at the peak of the power thrust, a problem which can't be avoided . . . *
- Sincerely, Willie (Wm. Claude Johnson-Barr III, Esq.)
"Not All Who Have Cell-Phones Do Twitter *
"Not All Those Who Ponder Can Think . . . "
* Only TWITS Twitter!
* Right, Bill?
--------------------------------------------------
> On a related note . . .
>
> It was my understanding that piston center-
> lines should be aligned with the centerline of
> the driving axles. If the T12 was straightened
> out, and as such, higher than the CL of the dri-
> ving axles, this could be problematic, correct?
> I could see some "waddling" of the locomotive
> occurring under power.
Herb Kelsey Wrote:
--------------------------------------------------
> Right Mr. Walsh. Here is my assumption and,
> my not being a mechanical engineer means I
> AM assuming, but most locomotives have the
> piston on the same level as the center of the
> drivers. On the T-12's the center-line of the cyl-
> inders is raised above the center-line of the main
> driver's axle. This is possibly due to clearance
> problems for the 4-wheel lead truck. So to cre-
> ate four equal power stroke events per revolution
> I think the cylinders would be angled downward
> to align the piston rod with the main driver's center.
> Setting up the valves to get four equal strokes
> would seem to be difficult if the components
> weren't aligned.
Waddle you know, Herb -
There is also a discrepancy created by the unequal surface areas of the two sides of the piston, due to the diameter of the piston rod: on the backward stroke steam is pushing on the full face of the piston – the area of which is π × the square of the radius of the piston – but on the forward stroke steam is pushing on the area of the piston minus π × (radius of piston rod)×(radius of piston rod), so the forces are not equal unless the valve timing is adjusted slightly to allow a bit more full-pressure steam to enter the cylinder on the forward stroke. Cant or no cant, the crosshead guides have to absorb the upward and downward thrust of the main rod due to its angle above or below the crosshead at the peak of the power thrust, a problem which can't be avoided . . . *
- Sincerely, Willie (Wm. Claude Johnson-Barr III, Esq.)
"Not All Who Have Cell-Phones Do Twitter *
"Not All Those Who Ponder Can Think . . . "
* Only TWITS Twitter!
* Right, Bill?
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488 stops for water at Los Pinos tank on closing day Oct. 1979. Photo courtesy Don Richter
The NGDF was started by Don Richter and is currently operated in his memory by Nathan Holmes and others. Others who have contributed to the upkeep of this board are (in no particular order): Charles McCandless, Everett Lueck, Ted Wilton, Cole Adams, James Bane, John Moellmer, Jon Bentz, Linn Moedinger, lloyd lehrer, Rod Jensen, John Craft, Steven Forney, Herb Kelsey, Bill Ramaley, Russ Sperry (El Russo Loco), Josh McNeal, John West, Jim Armstrong, Bob Bergstrom, Greg Scholl, Blake Forbes Doug van Veelen and Mark Fuller.