diff --git a/clockworkLibrary.scad b/clockworkLibrary.scad
index 9c0d5d9..8f45e22 100755
--- a/clockworkLibrary.scad
+++ b/clockworkLibrary.scad
@@ -229,6 +229,7 @@ module drum(
 {
 	flangeWidth=min(drumHeight/3,rimWidth/2);
 
+	if (drumHeight != 0 ) {
 	difference()		// makes the center hollow & includes holes to attach string
 	 {
 		union() 	// builds the drum with flanges
@@ -254,6 +255,7 @@ module drum(
 	}
 
 	}
+	}
 }
 
 module escapementWheel(