Slag & Sludge always had vaguely similar lower legs, formed from the rear of their beast modes, so it comes as little surprise to find them sharing parts on their Power of the Primes versions. They share robot legs, arms, hands, combiner connectors & guns. The arms have black paint on the forearms, as per the original Sludge but this will have an effect later. The unique pieces here are the body and head: From early pictures I thought that Slugs's chest appeared to form Sludge's back but in hand it's obvious they're different pieces, but I could see that maybe this was the plan at one stage. It's somewhat of a surprise not to see the combiner connector in Sludge's chest: done in black that would have made for a decent simulation of his Diaclone pilot's compartment. Instead there's an area painted black with a 5mm peg hole in it for mounting Sludge's Prime Armour on. The wings, formed from the front of the dinosaur body, are still there but sit slightly lower than we're used to with Sludge. The head, modelled on his animation bucket like design, can turn freely on Sludge which is the only change in articulation to Slug. His only real weapon is his gun, identical to Slug's. It would be nice to have something closer his original and I'm sure Shapeways will provide. It would also be nice to have his sword. However since I've doubled up on my Dinobots so I can have them individually and as Volcanicus I have a spare set of weapons from those combined so Sludge gets Snarl's sword.
Transformation: Remove the gun and Prime armour. Raise the arms, fold the hands into the forearms and fold the wings closed across his chest. Rotate the waist 180° then transform the legs just as you did for Slug. The back of the wings, now the front of the dinosaur, tabs into Sludge's robot feet. Rotate the biceps 180° then bend the elbows and swing the shoulders back so the bottom of the feet on what is now the front legs are level with the feet on the rear legs. Raise the flap on the Dinosaur's neck, which is down the robot's back/underneath the dinosaur, and fold the neck over the robot's head closing the flap to conceal it. Rotate the mid neck joint so the head is the right way up.
Bar some slight colour differences, the back is grey instead of chromed silver and the front lower dinosaur legs are now painted black thanks to his forearms not being stored under the dinosaur, this isn't a bad go at doing a new Transformers Brontosaurus, a beast mode that's been frequently skipped when the Dinobots were re-released. Before his Film and Platinum Editions, the last time Sludge was a Brontosaur was in the Gold Boxed Classics line, when only he, Grimlock & Snarl were released. These later two also appear in G2 but Sludge is replaced by Slag, creating a further link between the two, and the only appearance of a Sludge between then and Age of Extinction is as a Dimetrodon in the Wal*Mart exclusive Dinobots line. The head's nice, complete with opening jaw. Forelegs are identical to Slug except Slug's inner leg is the outside of Sludge's resulting in the loss of two 5mm peg holes. The new back legs worry me: solid units made out of clear plastic. I'd have made them in grey plastic like the original! A pair of Titanmaster footpegs are on top of the shell, with a 5mm peg hole on each side for the gun and Prime Armour. In theory either could fit in the 5mm looking hole on the top of the back of the neck but the earlier feels a bit loose, and already has stress marks on mine, while the latter is a bit too small for a 5mm peg.
Sludge also forms a limb for the Dinobot combiner Volcanicus.
Leg Mode: Start from the dinosaur mode, fold the tail back, fold the forelegs along the sides of the dinosaur, then fold the neck back onto the back of the dinosaur. Initial pictures showed the dinosaur head upside down in this mode, putting a lot of people off, but the swivel mid neck allows it to be put the right way up. Fold up the combiner connector.
Arm Mode: Start from the dinosaur mode, transforming the rear of the dinosaur into the robot legs and tab them together. Repeat with the neck and forelegs as above.
Generally really happy with Sludge. Very good modern interpretation. The back legs worry me, but I'll be careful with them.