Add engine model and stability analysis to loader

Introduced a parametric engine model and its placement in the assembly. Added a comprehensive weight distribution and stability analysis module, including center of gravity and tipping load calculations. Updated wheel assembly logic for improved rear wheel placement and included new engine and analysis parameters in the configuration file.

Author: dorkmo

LifeTrac-v25/mechanical_design/openscad/lifetrac_v25.scad

@@ -89,6 +89,19 @@ FRAME_Z_OFFSET = GROUND_CLEARANCE;
 // Calculate wheel X offset - wheels positioned outside the outer panels
 WHEEL_X_OFFSET = TRACK_WIDTH/2 + SANDWICH_SPACING/2 + PANEL_THICKNESS + WHEEL_WIDTH/2 + WHEEL_CLEARANCE;
 
+// =============================================================================
+// ENGINE CONFIGURATION
+// =============================================================================
+
+ENGINE_HP = 25; // Desired horsepower (e.g., 25HP V-Twin)
+// Estimate engine weight (kg) based on HP (approximate for small engines)
+// Base 30kg + 1.2kg per HP
+ENGINE_WEIGHT_KG = 30 + (ENGINE_HP * 1.2); 
+
+// Engine Position (Middle near back)
+ENGINE_POS_Y = 400; // Forward from rear of frame
+ENGINE_POS_Z = FRAME_Z_OFFSET + 200; // Height above frame bottom
+
 // =============================================================================
 // LOADER ARM DIMENSIONS - PARAMETRIC CALCULATION
 // =============================================================================
@@ -1777,6 +1790,173 @@ module base_frame() {
     mid_stiffener_plate(800, FRAME_Z_OFFSET + 100, FRAME_Z_OFFSET + 825 - 25.4);
 }
 
+// =============================================================================
+// ENGINE
+// =============================================================================
+
+module engine() {
+    // V-Twin Engine Representation
+    // Dimensions approx for 25HP engine
+    eng_width = 450;
+    eng_depth = 400;
+    eng_height = 450;
+    
+    translate([0, ENGINE_POS_Y, ENGINE_POS_Z])
+    {
+        color("DimGray")
+        union() {
+            // Crankcase base
+            translate([0, 0, 100])
+            cube([eng_width, eng_depth, 200], center=true);
+            
+            // Cylinders (V-Twin)
+            for (rot = [-45, 45]) {
+                rotate([0, rot, 0])
+                translate([0, 0, 200])
+                cylinder(d=120, h=150, center=true);
+            }
+            
+            // Flywheel/Fan cover
+            translate([0, -eng_depth/2 - 20, 150])
+            rotate([90, 0, 0])
+            cylinder(d=250, h=50, center=true);
+            
+            // Muffler
+            translate([0, eng_depth/2 + 50, 150])
+            cube([300, 100, 100], center=true);
+        }
+    }
+}
+
+// =============================================================================
+// WEIGHT DISTRIBUTION & STABILITY ANALYSIS
+// =============================================================================
+
+module calculate_cog() {
+    // --- WEIGHT ESTIMATES (kg) ---
+    w_frame = 350;      // Chassis, panels, crossmembers
+    w_wheel = 40;       // Tire + Rim + Motor (x4)
+    w_arm = 180;        // Arms + Crossbeams + Cylinders
+    w_bucket = 120;     // Bucket + QA Plate
+    w_engine = ENGINE_WEIGHT_KG;
+    w_operator = 90;    // Operator on rear deck
+    w_fluids = 40;      // Hydraulic oil + fuel
+    
+    // Max Load Calculation (Tipping Load)
+    // We calculate moments about the FRONT AXLE
+    
+    // --- POSITIONS (Y, Z) relative to World Origin ---
+    // Frame: Centroid approx middle of machine
+    pos_frame = [MACHINE_LENGTH/2, FRAME_Z_OFFSET + 300];
+    
+    // Wheels:
+    // Front axle Y is calculated in wheel_assemblies
+    front_axle_y = WHEEL_BASE - WHEEL_RADIUS;
+    // Rear axle Y is calculated in wheel_assemblies (re-calculating here for logic)
+    rear_axle_y_target = LIFT_CYL_BASE_Y + WHEEL_RADIUS + 100;
+    
+    // Re-calculate wheel positions to match wheel_assemblies logic
+    _front_y = WHEEL_BASE - WHEEL_RADIUS;
+    _rear_y_target = LIFT_CYL_BASE_Y + WHEEL_RADIUS + 100; // Moved forward of cylinder
+    _min_wb = WHEEL_DIAMETER + 50;
+    _max_rear_y = _front_y - _min_wb;
+    _rear_y = min(_rear_y_target, _max_rear_y);
+    
+    pos_wheels_front = [_front_y, WHEEL_RADIUS];
+    pos_wheels_rear = [_rear_y, WHEEL_RADIUS];
+    
+    // Engine
+    pos_engine = [ENGINE_POS_Y, ENGINE_POS_Z + 200];
+    
+    // Operator (Standing on deck at rear)
+    pos_operator = [-200, 300]; // Behind machine
+    
+    // Arms (Dynamic based on angle)
+    // Centroid approx 40% along arm
+    arm_cg_dist = ARM_LENGTH * 0.4;
+    pos_arm = [
+        ARM_PIVOT_Y + arm_cg_dist * cos(ARM_LIFT_ANGLE),
+        ARM_PIVOT_Z + arm_cg_dist * sin(ARM_LIFT_ANGLE)
+    ];
+    
+    // Bucket (Dynamic)
+    // At tip of arm
+    pos_bucket = [
+        ARM_PIVOT_Y + ARM_LENGTH * cos(ARM_LIFT_ANGLE),
+        ARM_PIVOT_Z + ARM_LENGTH * sin(ARM_LIFT_ANGLE)
+    ];
+    
+    // --- MOMENT CALCULATION (About Rear Axle for CoG Y) ---
+    // We use World Y=0 (Rear of frame) as reference datum.
+    
+    moment_frame = w_frame * pos_frame[0];
+    moment_wheels = 2 * w_wheel * pos_wheels_front[0] + 2 * w_wheel * pos_wheels_rear[0];
+    moment_engine = w_engine * pos_engine[0];
+    moment_operator = w_operator * pos_operator[0];
+    moment_arm = w_arm * pos_arm[0];
+    moment_bucket = w_bucket * pos_bucket[0];
+    moment_fluids = w_fluids * (MACHINE_LENGTH * 0.3); // Tank usually near back
+    
+    total_weight_empty = w_frame + 4*w_wheel + w_engine + w_arm + w_bucket + w_fluids; 
+    total_moment_empty = moment_frame + moment_wheels + moment_engine + moment_arm + moment_bucket + moment_fluids;
+    
+    cog_y_empty = total_moment_empty / total_weight_empty;
+    
+    // --- TIPPING LOAD CALCULATION ---
+    // Tipping happens when moment about Front Axle is zero.
+    // Counter-balance moments (behind front axle) vs Load moments (in front)
+    // Distances relative to Front Axle
+    
+    // Note: Positive distance = Behind axle (Counter-weight)
+    //       Negative distance = In front of axle (Load)
+    
+    // Sum of counter-moments (Weight * Distance from Front Axle)
+    // We want the machine to stay flat, so Sum(Weight_i * (Front_Y - Y_i)) > 0
+    
+    tipping_moment_capacity = 
+        w_frame * (_front_y - pos_frame[0]) +
+        2 * w_wheel * 0 + // Front wheels have 0 moment arm
+        2 * w_wheel * (_front_y - pos_wheels_rear[0]) +
+        w_engine * (_front_y - pos_engine[0]) +
+        w_operator * (_front_y - pos_operator[0]) +
+        w_fluids * (_front_y - (MACHINE_LENGTH * 0.3)) +
+        w_arm * (_front_y - pos_arm[0]) +
+        w_bucket * (_front_y - pos_bucket[0]);
+        
+    // Load is at bucket position. 
+    // Load Moment = Load_Weight * (pos_bucket[0] - _front_y)  <-- Distance in front
+    // Tipping occurs when Load_Moment = Tipping_Moment_Capacity
+    
+    load_dist_from_axle = pos_bucket[0] - _front_y;
+    
+    // If load is behind axle (e.g. fully raised and back), it won't tip forward
+    tipping_load_kg = (load_dist_from_axle > 0) ? (tipping_moment_capacity / load_dist_from_axle) : 9999;
+    
+    rated_load_kg = tipping_load_kg * 0.5; // 50% of tipping load is safe rating (ISO standard)
+    
+    // --- VISUALIZATION ---
+    // Draw CoG Sphere (Empty)
+    color("Magenta")
+    translate([0, cog_y_empty, FRAME_Z_OFFSET + 400])
+    sphere(d=100);
+    
+    // Console Output
+    echo("=========================================");
+    echo("STABILITY ANALYSIS");
+    echo("=========================================");
+    echo("Engine HP:", ENGINE_HP);
+    echo("Engine Weight:", w_engine, "kg");
+    echo("Total Machine Weight (Empty):", total_weight_empty, "kg");
+    echo("CoG Y Position (Empty):", cog_y_empty, "mm from rear");
+    echo("Front Axle Position:", _front_y, "mm");
+    echo("Rear Axle Position:", _rear_y, "mm");
+    echo("Wheelbase:", _front_y - _rear_y, "mm");
+    echo("Load Distance from Front Axle:", load_dist_from_axle, "mm");
+    echo("TIPPING LOAD (at current arm reach):", tipping_load_kg, "kg");
+    echo("RATED OPERATING CAPACITY (50%):", rated_load_kg, "kg");
+    echo("=========================================");
+}
+
 // =============================================================================
 // WHEEL ASSEMBLIES
 // =============================================================================
@@ -1785,13 +1965,36 @@ module wheel_assemblies() {
     if (show_wheels) {
         // Wheel positions - outside the outer panels with clearance
         // Wheel centers at Z=WHEEL_RADIUS so bottom of wheel touches Z=0 (ground)
-        // Front wheels moved back so front of tire aligns with front of machine body
-        front_wheel_y = WHEEL_BASE - WHEEL_RADIUS;  // Front of tire at Y=WHEEL_BASE
+        
+        // Front wheels: Standard position relative to frame front
+        front_wheel_y = WHEEL_BASE - WHEEL_RADIUS;
+        
+        // Rear wheels: Moved forward of cylinder mount
+        // Cylinder mount is at LIFT_CYL_BASE_Y
+        // We want rear axle > LIFT_CYL_BASE_Y
+        // Add clearance for cylinder body and wheel rotation
+        rear_wheel_target_y = LIFT_CYL_BASE_Y + WHEEL_RADIUS + 100; 
+        
+        // Check for collision with front wheels
+        // Ensure minimum wheelbase
+        min_wheelbase = WHEEL_DIAMETER + 50; // 50mm gap between tires
+        
+        // Let's calculate the max Y the rear wheel can be at without hitting front wheel
+        max_rear_y = front_wheel_y - min_wheelbase;
+        
+        // Use the target, but clamp to max
+        final_rear_y = min(rear_wheel_target_y, max_rear_y);
+        
+        // Warn if we couldn't meet the "in front of cylinder" constraint due to space
+        if (final_rear_y < LIFT_CYL_BASE_Y) {
+            echo("WARNING: Rear wheels could not be placed in front of cylinder mount due to lack of space!");
+        }
+        
         positions = [
             [-WHEEL_X_OFFSET, front_wheel_y, WHEEL_RADIUS],   // Front left
             [ WHEEL_X_OFFSET, front_wheel_y, WHEEL_RADIUS],   // Front right
-            [-WHEEL_X_OFFSET, 0, WHEEL_RADIUS],               // Rear left
-            [ WHEEL_X_OFFSET, 0, WHEEL_RADIUS]                // Rear right
+            [-WHEEL_X_OFFSET, final_rear_y, WHEEL_RADIUS],    // Rear left
+            [ WHEEL_X_OFFSET, final_rear_y, WHEEL_RADIUS]     // Rear right
         ];
 
         for (i = [0:3]) {
@@ -2249,6 +2452,7 @@ module lifetrac_v25_assembly() {
     if (show_frame) {
         base_frame();
         control_housing();
+        engine();
     }
 
     wheel_assemblies();
@@ -2264,6 +2468,7 @@ module lifetrac_v25_assembly() {
 // =============================================================================
 
 lifetrac_v25_assembly();
+calculate_cog();
 
 // Ground plane reference at Z=0 (shifted down slightly so wheels visibly touch it)
 color("Green", 0.2)

LifeTrac-v25/mechanical_design/openscad/lifetrac_v25_params.scad

@@ -125,6 +125,19 @@ _calc_base_y = _attach_y_world - (_attach_z_world - LIFT_CYL_BASE_Z) / tan(_targ
 // 5. Clamp Y to valid frame range (0 to WHEEL_BASE/2)
 LIFT_CYL_BASE_Y = max(50, min(WHEEL_BASE/2, _calc_base_y));
 
+// =============================================================================
+// ENGINE CONFIGURATION
+// =============================================================================
+
+ENGINE_HP = 25; // Desired horsepower (e.g., 25HP V-Twin)
+// Estimate engine weight (kg) based on HP (approximate for small engines)
+// Base 30kg + 1.2kg per HP
+ENGINE_WEIGHT_KG = 30 + (ENGINE_HP * 1.2); 
+
+// Engine Position (Middle near back)
+ENGINE_POS_Y = 400; // Forward from rear of frame
+ENGINE_POS_Z = FRAME_Z_OFFSET + 200; // Height above frame bottom
+
 // =============================================================================
 // BUCKET DIMENSIONS
 // =============================================================================