Dave Perry:

This patch adds main gear rotations about the fuselage attach points that keep the wheels in contact with the ground as the compression increases and decreases.  I also rotated the main fairings and wheels 4 degrees so the wheel axles are horizontal sitting on the ground.  The left and right main gear struts, wheels, and fairings were adjusted to be mirrored (symetric) in the c172p.ac.  I also increased the rpm boundary between the Propeller and Propeller.slow selects.

Aircraft/c172p/Models/c172p.xml

@@ -891,24 +891,27 @@
  <!-- Airframe -->
 
  <animation>
+
    <type>select</type>
    <object-name>Propeller</object-name>
    <condition>
      <less-than>
        <property>engines/engine[0]/rpm</property>
-       <value>200</value>
+       <value>500</value>
      </less-than>
    </condition>
+
  </animation>
 
  <animation>
+
    <type>select</type>
    <object-name>Propeller.Slow</object-name>
    <condition>
      <and>
        <greater-than>
          <property>engines/engine[0]/rpm</property>
-         <value>190</value>
+         <value>400</value>
        </greater-than>
        <less-than>
          <property>engines/engine[0]/rpm</property>
@@ -916,6 +919,7 @@
        </less-than>
      </and>
    </condition>
+
  </animation>
 
  <animation>
@@ -1212,15 +1216,15 @@
  
  <animation>
    <type>rotate</type>
-   <object-name>fairing2</object-name>
+   <object-name>fairing3</object-name>
    <object-name>RightWheelStrut</object-name>
    <object-name>RightWheel</object-name>
-   <property>gear/gear[2]/compression-norm</property>
+   <property>gear/gear[2]/compression-rotation-deg</property>
-   <factor>1.9</factor>
+   <factor>1.0</factor>
    <center>
      <x-m>0.711</x-m>
-     <y-m>0.474</y-m>
+     <y-m>0.4518</y-m>
-     <z-m>-0.708</z-m>
+     <z-m>-0.70</z-m>
    </center>
    <axis>
      <x>1.0</x>
@@ -1231,15 +1235,15 @@
 
  <animation>
    <type>rotate</type>
-   <object-name>fairing1</object-name>
+   <object-name>fairing2</object-name>
    <object-name>LeftWheelStrut</object-name>
    <object-name>LeftWheel</object-name>
-   <property>gear/gear[1]/compression-norm</property>
+   <property>gear/gear[1]/compression-rotation-deg</property>
-   <factor>-1.9</factor>
+   <factor>-1.0</factor>
    <center>
      <x-m>0.711</x-m>
-     <y-m>-0.474</y-m>
+     <y-m>-0.4518</y-m>
-     <z-m>-0.708</z-m>
+     <z-m>-0.70</z-m>
    </center>
    <axis>
      <x>1.0</x>

Aircraft/c172p/Nasal/action-sim.nas

@@ -17,6 +17,10 @@ var navLights = props.globals.getNode("controls/lighting/nav-lights", 1);
 var instrumentsNorm = props.globals.getNode("controls/lighting/instruments-norm", 1);
 var instrumentLightFactor = props.globals.getNode("sim/model/material/instruments/factor", 1);
 var panelLights = props.globals.getNode("controls/lighting/panel-norm", 1);
+var dhR_ft = props.globals.getNode("gear/gear[2]/compression-ft", 1);
+var dhL_ft = props.globals.getNode("gear/gear[1]/compression-ft", 1);
+var propGear1 = props.globals.getNode("gear/gear[1]", 1);
+var propGear2 = props.globals.getNode("gear/gear[2]", 1);
 
 # Associate Nodes
 
@@ -28,6 +32,8 @@ var filteredCDI0 = propNav0.getNode("filtered-cdiNAV0-deflection", 1);
 var filteredCDI1 = propNav1.getNode("filtered-cdiNAV1-deflection", 1);
 var filteredGS0  = propNav0.getNode("filtered-gsNAV0-deflection", 1);
 var filteredGS1  = propNav1.getNode("filtered-gsNAV1-deflection", 1);
+var right_main_rot = propGear2.getNode("compression-rotation-deg", 1);
+var left_main_rot = propGear1.getNode("compression-rotation-deg", 1);
 
 
 var init_actions = func {
@@ -43,6 +49,25 @@ var init_actions = func {
 
 var update_actions = func {
 
+#  Compute compression induced main gear rotations
+#
+#  constants
+   var R_m = 0.919679;
+   var h0 = 0.63872;
+   var theta0_rad = 0.803068;
+   var radTOdeg = 57.295779;
+
+#  Right main
+   var delta_h = dhR_ft.getValue()*12/39.4;
+   var right_alpha_deg = ( math.acos( (h0 - delta_h)/R_m ) - theta0_rad )*57.295779;
+
+#  Left main
+   var delta_h = dhL_ft.getValue()*12/39.4;
+   var left_alpha_deg = ( math.acos( (h0 - delta_h)/R_m ) - theta0_rad )*57.295779;
+   
+    
+
+  # outputs
     if ( navLights.getValue() ) {
        instrumentLightFactor.setDoubleValue(1.0);
        #  Used double in case one wants to later add the ability to dim the instrument lights
@@ -54,11 +79,12 @@ var update_actions = func {
        panelLights.setDoubleValue(0.0);       
     }
 
-  # outputs
     filteredCDI0.setDoubleValue( cdi0_lowpass.filter(cdiNAV0.getValue()));
     filteredCDI1.setDoubleValue(cdi1_lowpass.filter(cdiNAV1.getValue()));
     filteredGS0.setDoubleValue(gs0_lowpass.filter(gsNAV0.getValue()));
     filteredGS1.setDoubleValue(gs1_lowpass.filter(gsNAV1.getValue()));
+    right_main_rot.setDoubleValue(right_alpha_deg);
+    left_main_rot.setDoubleValue(left_alpha_deg);
 
     settimer(update_actions, 0);
 }

Aircraft/c172p/c172p.xml

@@ -96,13 +96,13 @@
             <location unit="IN">
                 <x> -6.8 </x>
                 <y> 0 </y>
-                <z> -20 </z>
+                <z> -19.5</z>
             </location>
             <static_friction> 0.8 </static_friction>
             <dynamic_friction> 0.5 </dynamic_friction>
             <rolling_friction> 0.02 </rolling_friction>
-            <spring_coeff unit="LBS/FT"> 4000 </spring_coeff>
+            <spring_coeff unit="LBS/FT"> 1800 </spring_coeff>
-            <damping_coeff unit="LBS/FT/SEC"> 1000 </damping_coeff>
+            <damping_coeff unit="LBS/FT/SEC"> 600 </damping_coeff>
             <max_steer unit="DEG"> 10 </max_steer>
             <brake_group> NONE </brake_group>
             <retractable>0</retractable>
@@ -111,12 +111,12 @@
             <location unit="IN">
                 <x> 58.2 </x>
                 <y> -43 </y>
-                <z> -17.9 </z>
+                <z> -15.5 </z>
             </location>
             <static_friction> 0.8 </static_friction>
             <dynamic_friction> 0.5 </dynamic_friction>
             <rolling_friction> 0.02 </rolling_friction>
-            <spring_coeff unit="LBS/FT"> 4400 </spring_coeff>
+            <spring_coeff unit="LBS/FT"> 5400 </spring_coeff>
             <damping_coeff unit="LBS/FT/SEC"> 1600 </damping_coeff>
             <max_steer unit="DEG"> 0.0 </max_steer>
             <brake_group> LEFT </brake_group>
@@ -126,12 +126,12 @@
             <location unit="IN">
                 <x> 58.2 </x>
                 <y> 43 </y>
-                <z> -17.9 </z>
+                <z> -15.5 </z>
             </location>
             <static_friction> 0.8 </static_friction>
             <dynamic_friction> 0.5 </dynamic_friction>
             <rolling_friction> 0.02 </rolling_friction>
-            <spring_coeff unit="LBS/FT"> 4400 </spring_coeff>
+            <spring_coeff unit="LBS/FT"> 5400 </spring_coeff>
             <damping_coeff unit="LBS/FT/SEC"> 1600 </damping_coeff>
             <max_steer unit="DEG"> 0.0 </max_steer>
             <brake_group> RIGHT </brake_group>