And we have a model subframe which is really promising! OpenSCAD for the win!

model/subframe.scad

@@ -1,10 +1,88 @@
 // tricycle.scad: 
 
+include <Library/BentSim/Bike_accessories.scad>
+
+include <Library/SprocketGenerator2/files/Sprocket_Generator_v2_example_10.scad>
+
 module subframe () {
-    translate([0, 180, 109])
-        cube([50, 25, 230], center = true);
+    // front leg (supports cross-shaft, epicyclic, motor
+    translate([-25, 1820, -550])
+        color("grey")
+        cube([50, 25, 230]);
+    // bottom bracket leg
+    translate([-25, 1690, -578])
+        color("grey")
+        cube([50, 25, 310]);
+    // wheel leg
+    translate([-70, 1430, -593])
+        rotate([0, 5, 0])
+        color("grey")
+        cube([25, 75, 363]);
+    // front upper
+    translate([-25, 2000, -385])
+        rotate([70, 0, 0])
+        color("grey")
+        cube([50, 25, 330]);
+    // central upper
+    translate([-25, 1700, -275])
+        rotate([82, 0, 0])
+        color("grey")
+        cube([50, 25, 370]);
+    // rear leg
+    translate([-25, 1200, -515])
+        rotate([-23, 0, 0])
+        color("grey")
+        cube([50, 25, 344]);
     
-    cube([50, 25, 
+    // wheel
+    translate([0, 1467.5, -450])
+        rotate([0, 0, 90])
+        // Pierre Rouzeau's wheel is beautifully modelled and parameterised, but it doesn't seem to be scaled as I'd expect...
+        scale([0.70, 0.70, 0.70])
+        wheel(rim=451, spoke_nbr=0);
+        
+    // bottom bracket
+    translate([-25, 1680, -390])
+        color("black")
+        rotate([0, 90, 0])
+        cylinder(h=68, r=26);
+    translate([-35, 1680, -390]) 
+        color("silver")
+        rotate([0, 90, 0])
+        sprocket(teeth=82, roller=7.9, pitch=12.7);
+        
+     // left crank
+     translate([-44, 1680, -395])
+        color("black")
+        cube([12,20,150]);
+        
+     // left pedal
+     translate([-120, 1670, -265])
+        color("black")
+        cube([70,40,15]);
+        
+     // left pedal shaft
+     translate([-120, 1690, -257.5])
+        color("silver")
+        rotate([0,90,0])
+        cylinder(h=80,r=4);
+        
+     // right crank
+     translate([44, 1680, -535])
+        color("black")
+        cube([12,20,150]);
+        
+     // right pedal
+     translate([58, 1670, -525])
+        color("black")
+        cube([70,40,15]);
+        
+     // right pedal shaft
+     translate([44, 1690, -517.5])
+        color("silver")
+        rotate([0,90,0])
+        cylinder(h=80,r=4);
+        
 }
 
-subframe();
+subframe();