As far as I know, Cluster Rocket's animation has a default trail-effect of the missile itself
Use this model for your dummy unit Abilities\Spells\Other\TinkerRocket\TinkerRocketMissile.mdl OR Cluster Rockets <Missile>
🔨 Hive's 3D Viewer has been updated! 🔨 It now supports MDX1100 which should fix a lot of issues when viewing HD models in our 3D Viewer. We encourage you to check it out for yourself and report any issues you find in the Site Discussion board.