INSTRUCTIONS FOR VALVE GEAR PROGRAMS Ver. Q.1

   These valve gear programs were written betweem 1986 and 2000 by
            Charles J. Dockstader   P.O. Box 3111
            California Valley, CA 93453-3111   Tel 805 475 2519

The programs have been placed in Public Domain and are FREEWARE. The
programs can be copied and distributed. The author accepts no
responsibility for any claim arising from the use of the programs.

The programs have had many changes and updates. See Update.TXT file.

The computer system requirements to run the programs is an IBM or
compatable computer with EGA or VGA graphics using two page graphics,
MSDos 3.3 or higher, 640K memory and a hard drive. A math coprocessor,
MSDos 6+ and a fast computer are desirable but not necessary. Two Icons
have been added for use if run under Microsoft Windows. These programs
were created using Borland's Turbo Pascal 5.5.

A design procedure has been added to some of the programs. The programs
can be used to examine valve gears and their characteristics. The programs
can also be used to check or change designs.

Mouse control has been added to most of the programs. The left button is
the point button and when clicked on the green characters, that function
is selected. The right button is similar to the enter key and is used to
exit some parts of the program or to skip over some keyboard inputs. The
right button is also used to enter graphics in the dimensional menus.

The default dimensions used in these programs are in inches for 1.5 inch
scale or close to this scale. All the dimensions can be changed in order
to change the design or the scale. Units other than inches can be used.
Dimensions for fixed pivot points, mounting points and cylinder center
lines are measured from the center of the main driver.

  Note: The internal default or starting dimensions using the name NOMINAL
are not necessarily a proper design. The programs will start using the
internal default unless an external set of user defined dimensions are
saved by the user as a file named DEFAULT. This DEFAULT file must be saved
with the program on the same drive and directory.

When using scales other than 1.5 and dimensions other than inches, the
graphics valve motion can be zoomed and panned to correct for off screen
scaling problems.

Unless otherwise noted, the keys are not case or shift sensitive.

The graph of the Oval Diagram has a vertical scale that can be changed
so that scales other than 1.5 can be adjusted to fit the graph. The graph
of the Sine Diagram, valve travel versus driver rotation, also has a
vertical scale that can be changed. The simulated steam diagram or graph
of cylinder pressure versus piston travel does not require vertical
scaling.

FROM THE MAIN MENU

The 1 key sets the driver position or angle. The main use of this key is
    in the graphics motion to set the driver at some specific angle
    after the H or hold key has been pressed. The angle of rotation for
    the driver pin is like a vector. 0 or 360 degrees is forward, 90
    degrees is up, 180 degrees is back and 270 degrees is down. Thus the
    angle decreases as the driver rotates forward.

The 2 key recalculates the center for the reverse arm and then recenters
    it. The reverse arm (reach rod or the yoke in Baker gear) is the
    lever that changes the valve gear between forward and reverse.
    Note: It may be necessary to use the 2 key after loading data from
       disk to recenter the reverse arm.

The 3 key is used to set the reverse arm to some specific position. The
    dimension shown for the reverse arm is the horizontal distance from
    the main driver center to the pivot point of the reach rod and the
    reverse arm. The reverse arm position can be changed as a dynamically
    changed variable. See 8 key below for dynamically changed variable
    key functions.

The 4 key enters the menu that contains the dimensions of the valve gear.
    The R key will return all 4 key changed dimensions to the starting
    normal and also turns off F6, F7 and resets F5 functions in graphics
    motion. Select the item that is to be changed using lower case. Enter
    new dimensions or use the Enter key to default past that dimension.
    Using the upper case key will bring up the graphics screen and show
    the dimension selected in Red/Green color with all other lines Gray.
    Note: If dimensions have been saved using the name 'DEFAULT' then
       the programs will use these dimensions as start up and the R key
       will use these DEFAULT dimensions.
    Note: Dimensional values for the levers, rods and pivots must be
       reasonable for the design of the valve gear. If dimensions are too
       large or too small the graphics may have abnormal movement or the
       program may terminate. If the program terminates, any dimensions
       that have been changed would be lost unless they have been saved to
       disk. If the program terminates, it may be necessary to reboot the
       computer and restart the program. It is difficult to protect the
       program from this type of bad data. Thus abnormal dimensions should
       not be placed in the program.
    Note: In the dimensional menus, when using scales other than 1.5,
       and using the upper case letters to locate the placement of a
       dimension, the graphics might be off screen.

    The O key (Baker only) enters the menu that contains the dimensions
       of the Baker pivot mechanism. The R key will return all changed O key
       dimensions to the starting normal. The R key also turns off F6, F7
       and resets F5 functions in graphics motion. See notes in 4 key.

    The dimensions can be changed dynamically. See 8 key below.

The 5 key enters the menu that contains the dimensions of the piston,
    valve and cylinder. The R key will return all changed 5 key dimensions
    to the starting normal and also turns off F6, F7 and resets F5
    functions in graphics motion.  See notes in 4 key.
    The dimensions can be changed dynamically. See 8 key below.

The 6 key (all programs do not have this function) enters the menu that
    contains the pin and lever wear dimensions.  Used to show the effects
    of loose and worn pivots and bearings. If the F7 function in graphics
    motion is enabled the 6 key will be disabled. The R key will return
    all 6 key changed dimensions to zero and also turns off F6, F7 and
    resets F5 functions in graphics motion. See notes in 4 key.

The 7 key (all programs do not have this function) enters the design
    function. One must have some starting layout of what is wanted. This
    would include basic dimensions of the cylinder, steam port size,
    desired lap and lead, stroke, frame dimensions, axil positions and
    valve gear mounting positions. In the design some dimensions are of a
    different form than those in the internal data files. These dimensions
    are transformed when they are transfered to the internal data files.

    To first see how the design works, use the C + ENTER key to step thru
    the design. New data is entered or the C key will preset aproximate
    dimensions or do a calculation as needed. If an error is entered, the
    E + ENTER key will return the design to the main menu for a restart.
    Near the end a T key is needed to transfer the new data to the internal
    data files. Some calculations are done after the T key because these
    calculations require the internal math using the internal data files.

    A good design normally requires going thru the design more than once.
    Reenter the design and step thru using the ENTER key or reenter new
    data as needed. In some designs the entered and calculated data is
    interreactive so one must reenter the design and step thru to correct
    this interreaction.

    The dimensions adjusting the reverse arm, lifting arm and lifting
    link are set using the data input at the main menu 4 key. These
    dimensions are not set by the design program equations. They can be
    adjusted before or after the design. If after then the design must be
    reentered to correct effects of the lifting link.

The 8 key plots the sine diagram or valve travel versus driver rotation.
    First change the vertical scale or default to 1.5 using the ENTER key.
    Select the number of plots in a family. 9 plots maximum. Then give
    dimensions of reverse arm for each plot. The first three plots may
    be defaulted to center, forward-nominal and reverse-nominal. Use the
    Enter key to default. Dimensional data of lap and lead is placed on
    the screen if the plot with the reverse arm at center is selected.

    The F7-F10 key turns on the dynamically changed variable so that up to
       4 dimensions can be varied while the graph is displayed. The last 4
       variables changed in the change menus become the dynamically changed
       variables. Use the F1 to F4 keys to set the increment size. Use the
       Cursor keys to change the dimension. While the F7-F10 function is
       operational, the 6 key (pivot error) in the main menu is disabled.

    The F1 key sets the step to 1.0 inches. F2 to 0.1, F3 to 0.01 and
       F4 to 0.001 inches.

    The F5 or F6 key turns off the dynamically changed variable.
The 9 key plots the oval diagram or valve travel versus piston travel.
    First change the vertical scale or default to 1.5 using the ENTER key.
    Select the number of plots in a family. 9 plots maximum. Then give
    dimensions of reverse arm for each plot. The first three plots may be
    defaulted to the center, forward-nominal and reverse-nominal. Use the
    Enter key to default. Dimensional data of lap and lead is placed on
    the screen if the plot with the reverse arm at center is selected.

    See 8 key above for dynamically changed variable key functions.

The 0 key (all programs do not have this function) plots a new plot of 8
    or 9, which ever was plotted last, to make a comparison of changes with
    respect to the previous plot of 8 or 9. The previous plot is shown as a
    broken line. This overplot function is not valid if the stroke is
    changed because the horizontal scale is changed distorting the last plot.

The - key runs the simulated steam diagram. Various keys can be used to
    control the action of the graphics motion. The keys are not shift
    sensitive.

    The  simulated steam diagram uses four different equations to
    simulate the cylinder pressure versus piston movement. One equation
    for each function, admission, expansion, exhaust and compression.
    These are simple equations which approximate the pressure in the
    cylinder of an engine while running with open throttle. The equations
    do not account for throttle setting, boiler  pressure, steam passages,
    restrictions, wire drawing, loss of heat, piston head clearance,
    speed, draw bar load, etc..

    The C key will Clear the screen.

    The H key Holds or stops the motion. Any key restarts the motion.

    The F key will toggle the Front steam diagram on or off. Use the C
       key to clear the screen.

    The R key will toggle the Rear steam diagram on or off. Use the C
       key to clear the screen.

    The E key will cEnter the reverse arm.

    The < or > key moves the reverse arm towards reverse or forward in
       small increments.

    The ( or ) key moves the reverse arm to normal reverse or normal
       forward. The normal set dimension for the reverse arm is in the
       4 dimensional menu.

    The S key will slow the plotting so it can be observed on a fast
       computer.

    The K key will change the background color. Black/white.

    Any other key will exit to the main menu.

       Normal reverse or normal forward are preset positions in the program
       and are not specific cutoff positions.

    The < and > keys will move the reverse arm farther than the ( and )
       keys normal position, depending on the reverse arm maximum setting.
       The maximum set dimension for the reverse arm is in the 4 dimensional
       menu.

    Note:  Error in graph and cutoff data is +/-0.5 %.

    See 8 key above for dynamically changed variable key functions.

The = key starts the Graph of Port Opening and Closing Points. The first
    graph is in forward motion with piston percent travel on the
    horizontal and reverse arm position on the vertical. The reverse arm
    being centered at the bottom and normal forward at the top.

    The F key will plot the forward graph.

    The R key will plot the reverse graph.

    The B key will plot both forward and reverse graphs.

    The C key will clear screen and replot the last graph.

    The K key will change the background color. Black/white.

    See 8 key above for dynamically changed variable key functions.

    Note:  The large amount of computation required for this graph can
       take up to 12 seconds to cycle for each keystroke using a 486 66 and
       up to 10 minutes per keystroke using a 286 8.

    Note:  Error in graph is +/-0.5 %.

The G key enters the valve gear graphics motion. Various keys can be used
    to control the action of the graphics motion. The keys are not shift
    sensitive unless noted. The graphics motion of the valve gear can be
    graphically displayed with the driver moving in steps. The number of
    steps can be 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048 or 4096 per
    driver revolution. 16 being the normal starting number with 22.5
    degrees per step. 4096 steps is 0.0879 degrees per step.

    The pivot points are displayed as small circles.  A fixed pivot point
    is shown with an X at its center. Levers and rods are shown as lines
    between pivot points. The cylinder, piston and valve are outlined so
    the steam and exhaust port action can be observed. The graphics pixel
    display can distort the edge of the ports. Zooming will enlarge the
    ports, reduce the distortion and increase the step calculation time.

    When the graphics valve motion is zoomed in, the original display is
    expanded beyond the edge of the screen. The time required by the
    computer to determine what part of the graphics is on screen is
    increased and the step time may be many times the original step time.

    The bottom lines in the graphic screen contain key words with one
    capital letter in green representing the key for that function.

    The E key will cEnter the reverse arm.

    The F key or Fine, will decrease the step size by a ratio of two.

    The C key or Course, will increase the step size by two times.

    The U key will pan Up.  D-Down. R-Right. L-Left.

    The I key will zoom In. O-Out. Zooming in increases the calculation time
       and zooming more than 8 times produces the loss of some graphics.

    The N key will zoom to Normal start. The P key to Previous from Normal

    The V key will expand the vertical scale to correct for the vertical
       compression of a 24 pin printer when printing the graphic screen.

    The A key will turn on and off the steam thru the cylinder.

    The 1, 2, 3, 4 or 5 keys zoom and pan to preset positions.

    The 6 key pans so that the 1st. ref. point is centered on the screen.

    The 7 key pans so that the 2nd. ref. point is centered on the screen.

    The Cursor keys move the reference points in 1.0, 0.1, 0.01 and 0.001
       inch steps. The X Y coordinates are displayed on the graphics motion
       screen. The distance between the reference points is also displayed.

    The F1 key sets the step to 1.0 inches. F2 to 0.1, F3 to 0.01 and
       F4 to 0.001 inches.

    The F5 key turns on the first reference point, the F6 key turns on
       the second reference point.

    The F7-F10 key turns on the dynamically changed graphics variable so
       that up to 4 dimensions can be varied while the graphics motion is
       running. The last 4 variables changed in the change menus become the
       dynamically changed variables. Use the F1-F4 keys to set the increment
       size. Use the Cursor keys to change the dimension. While the F7-F10
       function is operational, the 6 key (pivot error) in the main menu
       is disabled.

    Only one function of F5-F10 is active at any time.

    The H key Holds or stops the motion and restarts the motion. This
       allows other keys to zoom, pan, change reference point, change reverse
       arm or goto main menu while the motion is held.

    The S key Steps the motion while in hold. Lower case for normal
       direction. Upper case reverses its direction. The number to the right
       of the word Step is the step size in degrees. Caps Lock will reverse
       the S and s keys.

    The < or > key moves the reverse arm towards reverse or forward in
       small increments.

    The ( or ) key moves the reverse arm to normal reverse or normal
       forward.

    The K key will change the background color. Black/white.

    Any other key will exit to the main menu.

    Normal reverse or normal forward are preset positions in the program and
       are not specific cutoff positions. See 4 dimensional menu to change.

    The < and > keys will move the reverse arm farther than the ( and )
       keys normal position, depending on the reverse arm maximum setting.

    Note: While operating under Dos.
       To dump graphics to a printer, a program like "GRAPHPLUS" is required
       if Dos 3.x is used. If Dos 5.x or higher is used, the Dos "Graphics"
       command can be used. Call "Graphics" before running the Valve Gear
       Programs. The Graphics command has been added to a RUNG.BAT file.
       Use RUNG.BAT instead of RUN.BAT to start programs for graphics
          printing.
       Use the Shift PrintScreen to dump the graphics screen.
       Note: Dos graphics command is for a printer with a line spacing of
          x/216 (9 pin). Printers using line spacing of x/360 (24 pin) are
          distorted. Use the V key to expand the vertical to adjust for the
          compression of the vertical on the 24 pin printer.

    Note: While operating under Windows 95.  (or Windows 3.1)
       To dump text or graphics to a printer, first bring up the desired text
       or graphics screen. If graphics, use the K key to bring up a white
       background, not required for text. If graphics motion, also use the V
       key to expand the vertical. The V key will help correct the distortion
       some printers create when the printer compress the vertical from what
       is seen on the graphic screen. If the text or graphics is a window and
       not full screen, click the Windows tool bar FULL SCREEN button or the
       hotkey ALT-ENTER to make the text or graphics full screen. Hotkeys
       must be active to use. Use the Windows hotkey ALT-PRINTSCREEN to copy
       the active text or graphics screen to the Windows Clipboard. Use the
       Windows hotkey ALT-ENTER to change to a window so Windows buttons are
       available. Start the word processor and adjust the left and right
       margins so the text or graphics right side is not cut off. Paste the
       Clipboard to the word processor and print the text or graphics. Click
       on the Minimize button of the word processor or use ALT-TAB to return
       to the Valve Gear program. Click the Windows tool bar FULL SCREEN
       button or the hotkey ALT-ENTER to make the graphics full screen. A
       paint program can also be used to paste and print the graphics but not
       text. There are other methods of copying the text or graphics to the
       Clipboard. With the text or graphics in a window (use the hotkey
       ALT-ENTER if necessary) click on the icon of the Valve Gear program in
       the upper left corner. Pick edit, mark, then mark the area to copy.
       Click the icon again and pick edit, copy. Enter the word processor,
       then paste and print.

    Note: Percent cutoff is displayed in the upper right corner along with
       reverse arm position, driver angle and valve position from its center.
       Error in cutoff % is +0.5 -1.0 %. If step is less than 2 deg then
       error is +/-0.1 %. Cutoff is not computed when the step is > 22
       degrees and on some programs > 5 degrees.

The R key is used, while in the main menu, to change the position of the
    reference points on the graphics motion screen to any XY coordinate.
    The reference points can also be moved while in the graphics motion.

The B key is used to turn on and off a Beep. This Beep will sound when most
    computation errors occure. The errors occure from bad data in the math
    equations. When a divide by zero, a square root of a - number, a tangent
    or arctan at +/- 90 degrees occure, a small error is forced by the
    program to satisfy the equations. A Beep is sounded and the computation
    continues. Some programs use a loop in the computation. Bad data can make
    this loop endless. If the loop has greater than 1000 cycles, the loop is
    terminated and the program is returned to its main menu. The bad data
    must be fixed to continue. The program finds most errors but there are
    still some errors that can terminate the program. While running new data
    or using the dynamic change variables, the Beep will alert one to the
    presence of an error. Not all errors will produce the Beep.

The N key is used to change the name of the dimensional data to be saved. The
    program starts with the name "NOMINAL". This name can be changed to any
    eight characters. The name can also be changed while saving data.

The S key saves to disk the dimensional data. The return key will default
    to drive C. The program will list the names which have previously been
    saved using the proper extension. Then data can be given a new name.
    Eight characters or less. Do not add an extension. The program will add
    the extension. The last zoom, pan and reverse arm positions are also
    saved in the data.

    The programs will start using an external set of user defined
    dimensions if the user saves a file named DEFAULT. This DEFAULT file
    must be saved with the program on the same drive and directory.

    Caution... Using a name that has already been used will overwrite
                the old data file.

    Each valve gear program uses a different extension. The extensions are:

  Baker       Inside  Admission  .IBK   Baker       Outside Admission  .OBK
  Cramptom    Outside Admission  .OCR   Hackworth   Outside Admission  .OHA
  Hackworth2  Outside Admission  .OH2   Joy1        Outside Admission  .OJY
  Marshall    Outside Admission  .OMA   Southern    Outside Admission  .OSO
  SouthernBKY In Adm  Indep CO   .ISB   Stephenson  Inside  Admission  .ISP
  Stephenson  Outside Admission  .OSP   Walschaert  Inside  Admission  .IWL
  Walschaert  Outside Admission  .OWL   Young       Inside  Admission  .IYO
  CP #229     Out Adm Riding CO  .OCP   Corliss Rey.Rotary Valve IndCO .COR
  Caprotti    Rot Cam Pop Valve  .PCP   Franklin    Osc Cam Pop Valve  .FRA
  R-C-Type    Rot Cam Pop Valve  .PRC   Woolf       Outside Admission  .OWO
  WRiverStmBoat  Fixed CO  Pop V .WRS   WRiverStmBoat Calif. CO  Pop V .WRC
  Corliss I-S Rotary Valve IndCO .COS

The L key loads dimensional data from disk. The return key will default to
    drive C. The program will list the names which have previously been
    saved using the proper extension. Enter the name of the desired data
    file. Do not add an extension. The program will add the extension.
    Entering a name that does not exist will terminate the program.
      Note: Loading new data may require resetting the reverse arm
    position. Use the 2 key to reset the reverse arm.

The I key brings up the general instructions. To back one page, use Page Up
    or Left Mouse at top lines. Back one line, use Up Arrow or Left Mouse
    near top. Forward one page, use Page Down or Left Mouse at bottom lines.
    Forward one line, use Down Arrow or Left Mouse near bottom. Exit, use
    any key or Right Mouse.

The J key, if present, brings up special notes and instructions.

The Q key twice will exit the program.

NOTES

  There are four events in the steam cycle of a steam engine. They are
admission, expansion, exhaust and compression. The timing of these four
events are referenced to the piston position in the cylinder as percent
of piston travel.

  The oval diagram is a plot of valve travel on the vertical scale vs
percent of piston travel on the horizontal scale. There are two sets of
these four events on the oval diagram. One set for each cylinder end. One
set uses the 'Front Steam Port Open' and the 'Front Exhaust Port Open'
lines. The second set uses the 'Rear Steam Port Open' and the 'Rear
Exhaust Port Open' lines.

  1 ADMISSION
  Admission starts when the steam port just opens and ends when the steam
port just closes. Admission on the oval diagram is the part of the oval
starting as it crosses the 'Steam Port Open' line and ending as it
recrosses the same line.

  2 EXPANSION
  Expansion starts when the steam port just closes and ends when the
exhaust port just opens. Expansion on the oval diagram is the part of the
oval starting as it crosses the 'Steam Port Open' line and ending as
it crosses the 'Exhaust Port Open' line.

  3 EXHAUST or RELEASE
  Exhaust starts when the exhaust port just opens and ends when the exhaust
port just closes. Exhaust on the oval diagram is the part of the oval as it
crosses the 'Exhaust Port Open' line and ending as it recrosses the same
line.

  4 COMPRESSION
  Compression starts when the exhaust port just closes and ends when the
steam port just opens. Compression on the oval diagram is the part of the
oval starting as it crosses the 'Exhaust Port Open' line and ending as it
crosses the 'Steam Port Open' line.

OTHER TERMS

  CUTOFF
  Cutoff is the point when the steam port just closes, admission ends and
expansion begins. Cutoff is expressed as the percent of piston travel from
one end, to when the steam port just closes. 100 percent being its full
stroke. Depending on load and speed, cutoff is controlled on a steam engine
to reduce the amount of steam admitted into the cylinder and then allows the
steam to expand. When less steam is admitted and then allowed to expand,
efficency of the engine increases.

  LEAD
  Lead is the distance that the valve is open when the piston is at either
end of its travel. Lead on the oval diagram is the vertical distance between
the 'Steam Port Open' line and the tangent point of the oval, tangent to the
vertical left or right edge line of the graph.

  The purpose of lead is to admit steam before the piston reaches the end
of its travel. The steam pressure in the cylinder is then increased at the
start of the piston stroke, increasing efficiency and output power. This is
true only while the engine is running. At start, lead decreases output power
because the piston is forcing the crank backwards.

  LAP
  Lap is the distance that the valve must travel in either direction to just
open the steam port, starting its travel from its center position. Lap on
the oval diagram is the vertical dimension above or below the center or '0'
of the valve travel scale to one of the 'Steam Port Open' lines.

  The purpose of lap is to keep both intake and exhaust valves closed after
admission producing expansion. Steam expansion after admission uses some of
the heat energy of the expanding steam, increasing engine efficency.

  In a steam engine using a simple valve (a single piston or D valve), lap
also produces compression after exhaust. Some compression is desirable
because it helps to slow the piston at the end of its stroke. Expansion and
compression are tied together, changing one changes the other.

  Using a more complex valve system, Corliss or a D valve with riding cutoff,
expansion can be varied while maintaining only a small compression.

  EXHAUST CLEARANCE
  Exhaust clearance is the distance the valve must move to just close the
exhaust port starting its travel from its center position. Exhaust clearance
on the oval diagram is shown by the distance between the 'Exhaust Port Open'
lines and the '0' line of the valve travel scale. Changing exhaust clearance
will slightly effect expansion and compression.

  EXHAUST LAP
  Exhaust lap is the negative value of exhaust clearance. Most engines are
designed with zero exhaust clearance (zero exhaust lap).

SOME CONCEPTS

  The direction of driver rotation in these valve gear programs is
clockwise for forward. When discribing the driver angular movement of the
main crank pin, zero degrees is to the front, 90 degrees is up, 180 degrees
is to the rear and 270 degrees is down. The driver angle decreases while
going forward.

  The oval diagram, with the gear set at center, should be a closed loop
with equal lead at each end and pass thru the center of the graph.

  The sine diagram of a radial gear with three plots, center, forward,
reverse, should pass thru a common point on the zero and 180 degree lines.
This point should be above the port open line and shows the constant lead
of a radial gear.

  The sine diagram of a link motion with three plots, center, forward,
reverse, should form a small triangle on the zero and 180 degree lines. The
triangle should point to the valve travel center line. The point should be
at the intersection of the valve open line and the zero and 180 degree lines,
showing no lead in forward or reverse. The amount the center plot is above
the valve open line shows the lead with the gear at center.

  The steam diagram should be symmectrical between the front and rear port
plots.

  The graph of port opening and closing points will show the symmetery or
lack of symmetery between the front and rear port opening plots. Also the
symmetery between forward and reverse port opening plots.

  No valve gear that uses swinging or pivoted levers has a perfect steam
distribution.

  A valve gear that is called 'radial' has a constant lead. This means that
when the piston is at either end and the reverse lever is moved from full
forward to full reverse, the valve does not move. The valve opening or lead
is constant. This is shown on the oval diagram where every plot of a family
(different reverse arm positions) are all tangent, at the same point to the
vertical left or right edge line of the graph. Also on the sine diagram all
plots will cross at the same point, this point should be on the 0 and 180
degree lines.

  The design in most valve gears is a compromise of several distortions.

  In general, the shorter the length of a swinging rod and the larger the
angle of swing, the greater is the distortion added to the valve gear from
that rod.

  If exhaust clearance is positive, then both the front and rear exhaust
ports are open when the valve is at its center position.

  A short main rod produces more distortion in the valve gear because it
swings thru a greater angle. As the rod becomes shorter, the crank angle
moves away from the 90 degree points when the piston is at the center of its
stroke.

  Adjusting levers to reduce one distortion will often increase another
distortion.

  The four events can be more easily seen on a plot of valve travel vs driver
rotation since the events are not compressed at the beginning or the end of
the piston travel. This plot is similar to a sine wave and is linear in time.
This plot distorts the timing events due to the angularity of the main rod.
When the piston is at 50 percent travel, the main crank pin is less than 90
degrees or greater than 270 degrees. When the reverse arm is centered,the
sine wave crossing point is less than 90 or greater then 270 degrees.

  Don't try to make the forward gear and reverse gear or the front end and
rear end sections of the oval diagram symetrical above or below the 'Port
Open' lines. What should be symetrical is the points where the oval diagram
crosses the 'Port Open' lines. The crossing points should be symetrical left
and right of the 50 percent piston travel point. These crossing points are
the starting points of the four events in the steam cycle; admission,
expansion, exhaust and compression.

  On the sine diagram don't try to make the peaks of the sine symectrical
in forward and reverse gear or the front and rear ends. When the reverse
arm is at its center position, the peaks should be the same height and
centered about the zero and 180 degree lines showing equal lead at each
end. If the center position oval diagram is closed and passes thru the
center of the oval diagram, the sine diagram should cross the valve scale
'0' line less then 90 and more than 270 degrees. The angle less than 90
or more than 270 is about one half the maximum angle that the main rod is
above or below the horizontal.

  Lead on the sine diagram is the distance the plot is above the 'Steam
Port Open' lines at the zero and 180 degree lines.

  Cutoff on the sine diagram is the point when the plot just recrosses
the 'Steam Port Open' line. Percent cutoff on the sine diagram must be
computed, it cannot be read directly. Use the oval diagram for % cutoff.

  In viewing the sine diagram of a radial gear using a family of different
reverse arm poisitions, each plot should cross the zero and 180 degree lines
at the same point, showing constant lead.

  In viewing the sine diagram of a non radial gear, the family should form a
small triangle centered on the zero and 180 degree lines.

  Some Walschaert valve gears have the radius rod lifting link inside the
radius of the radius rod. Make the radius rod extension negative and move
the reverse arm pivot.

  Some Walschaert valve gears do not have a lifting link. Make the lifting
link 0, move the bellcrank down, on the main menu use the 2 key to recenter
the gear, move the radius rod extension so it's end is on top of the
lifting arm end, again recenter the gear using the main menu 2 key. The
lifting link in the graphics motion will rubberband.

  If the reverse arm bellcrank faces to the rear, make the lifting arm
negative and move the bellcrank pivot.

  A design of Walschaert valve gear will position the radius rod on the
link for a specific maximum percent cutoff for forward motion. To find the
reverse arm position corresponding to this position-
A. In the main menu use the R key to set the first reference point
   horizontally to the same horizontal dimension as the link center pivot.
   Then move the reference point vertically so it is below the link center
   pivot by the radius or dimension that the link block would be below the
   link center pivot.
B. Use the 3 key to change the reverse arm position. Enter the same value
   as shown. This will activate the dynamic variable for the reverse arm
   position.
C. Use the G key for graphics motion.
D. Use the F5 key and the 6 key to pan so the first reference point is at
   the center of the screen.
E. Use the I key to zoom in. Several times.
F. Use the H key to hold the graphics motion.
G. Use the s and S keys to step the driver angle to swing the link so the
   link passes thru the reference point. Use the F and C keys to change
   the driver step size.
H. Use the F7 key to turn on the dynamic variable.
I. Use the F1 to F4 keys to control the increment size and the up and down
   arrow keys to move the reverse arm until the radius rod is in line with
   the reference point. If the maximum forward/reverse limit of the
   reverse arm position is set too small, the reverse arm and radius rod
   movement will be limited. To change the limit, go to the dimensions
   under the 4 key in the main menu.
J. When the proper radius rod position is achieved, return to the main
   menu. Subtract the reverse arm center position from the forward set
   reverse arm position.
K. Use the 4 key and set the reverse arm normal position to the value
   obtained in J.
L. The ) key in graphics motion should now move the reverse arm to the
   designed maximum forward percent cutoff.
This concept can be used on other valve gears.

  Some Stephenson valve gears have the valve stem in line with the piston
rod. Direct motion. Make the upper part of the rocker negative. Make both
rocker parts equal and long. Move the rocker pivot up for the long rocker
parts. Move the valve down. Move the valve seat down. Rotate the eccentrics.

  If the reverse arm bellcrank faces to the rear, make the lifting arm neg.

SOME ADJUSTMENTS


  The following adjustments are general statments and apply to some of the
valve gears. There are many more adjustments and on any one valve gear, the
adjustments react with each other.

  Adjusting the length of the valve rod or the valve stem moves the valve so
that the lead is equal at both ends when the reverse arm is at its center.

  Adjusting the backset at the top of the combination lever, with the reverse
lever centered, adjusts the center crossover of the oval diagram. Most
engines use zero backset on the combination lever.

  Adjusting the backset of the link crank adjusts the symmetry between the
front and rear steam port opening or closing points.

  Adjusting the eccentric rod length also changes the symmetry between the
front and rear steam port opening or closing points. The eccentric rod length
should be adjusted after the link crank backset because in practice it is
easer to change and is usually adjusted to compensate for tolerence buildup
of the other parts in the valve gear.

  Adjusting the eccentric crank length will change the angle of the eccentric
crank pin, advancing or retarding the oval or sine diagrams in time, or the
horizontal position of the sine diagram. When the eccentric crank length and
the eccentric circle are properly adjusted on a radial gear, with the piston
at either end of its travel, the radius rod can be moved from full forward to
full reverse without the radius rod moving the valve.

  Making adjustments so that the engine will run in reverse as well as it
runs in forward is usually a compromise that degrades the forward operation.

A GENERAL DISCRIPTION OF THE WORKING PROCESS OF THESE PROGRAMS.


  These programs are compiled using Turbo Pascal by Borland.
The programs run independently of each other and of other programs so they
do not need a parent program to run. They do need a disk operating system
and use MS DOS. Dos 6+ being preferred. All programs work in a similar manner.

  Using a Walschaert valve gear for discription, the internal default
dimensions of levers, rods, diameters, angles, vertical and horizontal
positions etc are stored in a table inside the program. To start the valve
gear program, these stored dimensions are transferred to the internal
default variable dimensions. External default dimensions can also be created
and used. Using the graphics motion G key in the programs main menu, the
program will start by setting the driver rotational angle of the main crank
to 3 o'clock or zero degrees as defined as a mathematical vector. The main
crank angle can also be started or set to any angle from the main menu. Most
calculations in the program use trig. The center of the main driver is
defined as XY coordinates 0,0. All other coordinates are referenced to the
0,0 at the main driver. The main crank pin and eccentric crank pin XY
coordinates are calculated. The cross head pin XY coordinates are calculated.
The expansion link pivot XY coordinates were defined by the stored variables.
The XY coordinates of the link foot are calculated. The XY coordinates of the
center of the link arc are calculated. The reverse arm/lifting arm pivot XY\
coordinates were defined. The reverse arm is set to mid gear or some other
position. The lifting arm end XY coordinates are calculated. The valve stem
vertical position was defined.

  The next process is one method of solving simultanious equations on a
computer. When several pivots depend upon each other, that is each one
requires the solution of the other one to obtain its solution, then this
process can be used to find their solutions. All valve gear programs do not
require this process. This is a partial explanitation.

    Using the link, radius rod and combination lever as an example. The link
  block position is not known and the position of the combination lever is
  not known. Select a point on the link for the link block that is known to
  be below its true point. The true point being unknown. The lifting link
  would then be longer than its defined value. With the link block position
  approximated, calculate the position of the combination lever. Then
  calculate the length of the lifting link and compare with its defined
  length.
    This position is not true because the lifting link is too long. Move the
  link block up some small increment and recalculate. Check to see if the
  lifting link is too short. If too long then continue to increment the link
  block up and recalculate. Repeat until the lifting link is too short. When
  too short, increment the link block down one increment, or back one
  increment. Reduce the size of the increment. Usint the smaller increment
  size, increment the link block up until the lifting link is too short
  again. Increment the link block down one increment.
    Keep repeating the previous procedure until the desired error in the
  length of the lifting link has been reached. This process will force the
  length of the lifting link to converge on the true length of the lifting
  link. This is then the proper solution for the position of the link block
  and combination lever. Calculate the valve horizontal position.

  Some cases require the incrementation of a second approximated point inside
the loop of the incrementated first approximated point.

  All of the XY Coordinates are now known in decimal units. Scaling factors
are determined from zoom in or zoom out. Offset factors are determined from
pan up, down, left or right.  Multiply all X coordinates by a horizontal
scaling factor and add a horizontal offset factor. Multiply all Y coordinates
by a vertical scaling factor and add a vertical offset factor. All the XY
coordinates are then changed from decimal type numbers to integer numbers.
The integer numbers are now used to plot lines, arcs and circles to the
screen. The screen requiring integer numbers which correspond to screen
pixel positions.

  The cylinder, piston and valve outline dimensions are changed to integer
XY coordinates and include the scaling and offset factors. These are then
plotted to the screen.

  The dimensional position of the reverse arm is printed to the screen.
  The angle of the driver main crank pin is printed to the screen.
  The center of the valve and the center of the cylinder or valve ports are
compared and their difference is printed to the screen as valve position.
  As the driver angle is incremented, the dimensions of the valve edge and
the port edge that opens the valve for steam are compared and their
differences are temporally saved. When the driver is steped to the next
position, the previously saved value is moved and saved and the new value is
saved. When the previous value is + or steam port open and the new value is
- or steam port closed, cutoff has occurred. The previous driver angle was
also saved. Knowing the two driver angles and the two valve positions, the
driver angle at cutoff can be calculated using interpolation. Then calculate
the piston position at cutoff and the % of cutoff. The % cutoff is then
printed to the screen.

  The screen is actually two screens. All plotting is done on one screen that
is not visible, while the other screen is viewed. When plotting is finished,
the screens are interchanged. The non visible screen is then erased and
replotted. Thus the plotting distortions are not seen as each XY coordinate
is changed.

  The keyboard is now scanned for any key inputs. If a key has been pressed,
the function for that key is performed, variables changed, or what ever is
required for that key function. Any key that does not have a key function
will direct the program back to the main menu.

  If the program has not reentered the main menu it is now looped back to
the begining of the graphics motion. The driver is incremented one step and
all coordinates are recalculated and replotted using any new values that have
been changed by the keyboard.

  If up to four variables have been changed in the change menus, a flag is
set for each variable. While the graphics motion is running the Fx keys will
use these flags and turn on the printing of these variables to the screen.
The arrow keys, using these flags, will increment these selected varables
and the variable changes will be recalculated and plotted as the graphics
motion is running.

  There are three lines of text at the bottom of the graphics motion screen.
This text has green highlighted characters which are the controlling keys
for the graphics motion. These characters are also the pick points for
mouse control using the left button. The right button is used as a default
key similar to the Enter key to skip or exit a procedure.

  The program has four graphs showing some of the characteristics of the
valve gear. Each graph uses the same equations as the graph motion, with
the reverse arm and driver being set or stepped in a predetermined sequence.
More calculations are preformed to obtain the data needed to produce each
graph.

  The internal dimensions used are for a scale of 1.5 inches to the foot.
Dimensions for other scales can be used. Dimensions must be in decimal form,
like decimal inches or decimal feet or centimeters, not feet and inches.

For another valve gear computer program see: MODELTEC Aug/Oct 1993
  Locomotive Valve Gear Simulator by Allan K. Wallace PhD.
  Write to   Allan K. Wallace PhD. 31A Birkinshaw Ave. Trainmere 5073
  South Australia    Email  allanw@appdes.com.au
    Dr.Wallace's program is shareware.

The concept for the graph of the valve port opening and closing points
came from the programs of Dr. Wallace of South Australia.

References

    Vitkovits, Stephen Jr.
      Valve Gears A Practical Approach to Analysis and Design
      Live Steam Magazine, Traverse City, Michagan 49685-0629
      December 1982 to April 1985

    Jukes, Fred     101 Valve Motions
      Railway and Locomotive Historical Society
      Bulletins 88, 89, 90, 91

    Grimshaw, Robert    Locomotive Catechism
      Norman W. Henley Publishing Co., New York, New York 1908
      Locomotive Reprints, Anaheim, California 1978

    Mc Shane, Charles    The Locomotive  Up To Date
      Griffin and Winters, Chicago, Illinois 1900

    Zeuner, Dr. Gustav   Translated from the fourth German edition
      by J. F. Klein    Treatise on Valve-Gears
      E.&F.N. Spon, 16, Charing Cross, London.
      35 Murray Street, New York.     1884

    Peabody, Cecil H.   Valve-Gears for Steam-Engines
      John Wiley & Sons, New York.
      Chapman & Hall, Limited, London.    1898

    James, Walter H.  &  Dole, Myron W.    Mechanism of Steam Engines
      John Wiley & Sons, Inc., New York.
      Chapman & Hall, Limited, London.    1914

    Furman, Franklin DeRonde     Valves and Valve Gears
      John Wiley & Sons, Inc., New York.
      Chapman & Hall, Limited, London.    1915

    Hurst, Charles     Valves and Valve Gearing
      Charles Griffin and Co., Limited, London.  1919

    Evans, Martin     Model Locomotive Valve Gears
      Model & Allied Publications Ltd.
      13/35 Bridge Street Hemel Hempstead, Herts. 1962

    The Baker Locomotive Valve Gear,    Manufactured by The Pilliod Co.
      Toledo, Ohio,  Swanton, Ohio,   Vol. 3  May 1951

    International Correspondence School textbook on
      Marine Engineering, vol. II 1900.