Question: What is the true origin of the Constructicons? "Heavy Metal War" claims they were built on Earth by Megatron, but "The Secret of Omega Supreme" shows them already on Cybertron before the war on Earth began. Is this a legitimate mistake or is there a reason behind it?
Answer: This was actually one of many errors in Transformers, the Constructicons MUST have been built on Cybertron, the only transformers genuinely built on earth were the dinobots, reason being Vector Sigma has to give personalities to each and every robot, else they end up like the dinobots, very simple and dumb. For reference watch the episode "The Key to Vector Sigma" which introduces the Stunticons and Arielbots - both Megatron and Optimus Prime have to go to Vector Sigma to get decent personality traits installed, prior to this the new robots are controlled by remote controllers and have no AI.
Chosen answer: Archangel and the Firm provided fuel and armaments. Dom and Hawke would have had to transport them to the lair to refuel and rearm.
Grumpy Scot