Introduction: General Grievous Costume With Moving Mechanical Extra Set of Arms
The basic construction is a black pullover from an old cheap store-bought halloween costume, and foam-core assemblies attached with velcro. There's a PVC 'backpack' that has mechanical arms with elastic bands that can flip up giving the General an extra pair of arms.
Step 1: Foam Core Assemblies
This costume was built by eye so you need a decent picture to start from.
The foam core assemblies are sized for a child, but of course could be made larger for an adult. They are cut from paper patterns and most are bilaterally symmetric. Some sections are pre-painted and 'weathered' with dilute black tempera paint to give shadowed 3D effect. I used hot-glue to assemble them, but other glues are fine. When dry, they are aligned onto the body-suit with velcro on the assembly and the suit. The suit velcro should be sewed on (or stapled if you're hasty).
Step 2: PVC Clips
I developed this PVC clip to attach some of the to the PVC tubes on the backpack (described in an upcoming step). If you wish to skip the backpack, you can just use velcro for everything. The PVC clips are described in detail on the creatrope website and in this instructable.
These clips are useful because the allow anything that attaches to the PVC to be removable.
I used these clips in several places in this costume.
The roundish neckguard is held on to the PVC backpack using these clicks. On the secondary arms the forearm 'greaves' use these clips.
Step 3: BackPack
The backpack is a PVC assembly that allows the mechanical arm to flip up. It needs to be customized to your wearer and size so dimensions wouldn't mean much unfortunately. A linear joint made from a dowel rod that slides within a PVC connector is used to hold the rotating arms in position. I constructed rotating joints from PVC and dowels describe inGeneral Grievous Costume (and in a future instructable).
Don't glue anything until you're satisfied with the motion and mechanism. Be aware the the elastics moving the arms in an unglued PVC harness can cause the harness to break apart.
The arms of the back rotate using a short lever arm that is tied with a strong exercise elastic to the base of the backpack in back. I simply tied the elastic to the base to allow for an adjustment in tension. The arms are prevented from over-rotating with a carefully place stop at each the shoulders. Please exercise caution when releasing the arms as they can move fast and someone could be injured. I instructed my son to always do it with his back to a wall and look side to side.
He was able to release the arms himself, and them restore them into position.
To prevent the arms from colliding during rotation, one is slightly offset (farther back) than the other.
Step 4: Mask
The mask is fairly straightforward. I found a technique for curving the foam-core by rubbing it against a pole which worked nicely (just like you'd curve paper). See the second photo for the final mask; I was able to make 'eyes' with red felt behind the eye holes that looked good. The mask is light and easy to wear.
Add detail using dilute black tempera paint.
Add an elastic band to hold it in position.
My original plans were to vacuum form the mask, but time ran out.
Step 5: Complete the Look
The cape and light-sabers complete the look. You probably will not be able to use the arms without getting the cape out of the way. It serves two purposes. It hides the unwieldy backpack and it discourages others from triggering the mechanism. I think it's an effective costume without the backpack so give it a try!
If you like this costume, please check out my other instructables and halloween builds at Creatrope Halloween.
Some of them are in instructables as well.
Godzilla / T-Rex