Saturday, April 10, 2010

Bender's eyes - the good ones

I discussed how attempting to cast the eyes from cement did not work as well as planned. Ideally I wanted weld-ments, but did not have enough of the pressure cylinders to make that work. I returned to the casting option, but with a different media than cement. If I'd been able to use my furnace, I'd have made them from aluminium to begin with, but that was not an option, so instead I chose to cast the eyes from "bog" - a.k.a. Automotive putty.

I kept the fixtures I made for the cement eyes, and the eye plates.
The idea of sand molds didn't appeal with using bog, so I looked for an alternative mold. Whilst shopping with my darling wife, I found some cheap Christmas decorations. They were plastic balls which measured 85mm across, and had a clearly defined mold line from their manufacture. I bought three of them and cut them carefully along the mold line to get hemispheres. I mixed up some bog, filled one of the hemispheres, and placed it on the eye-plate with a fixture already secured.
A couple of notes on the above procedure:

-- I've been keeping my bog in a refrigerator so it's cold, and not going off as fast. (I also keep all my glues, and expensive solvents in the same fridge)

-- I sprayed the eye-plate with a light oil as a form of mold release to stop the bog sticking to the plate... However I did not spray any oil on the fixture since I wanted maximum adhesion to this part.

-- A reasonably thick section of curing bog gets VERY hot. I'd seen similar exothermic reactions when working epoxy with the rockets, so I knew I could cool the mold from the outside with water, and not cause any damage to the casting. If anyone else tries thick castings based on resins, they should not leave the casting unattended during curing, and keep flammables away. If possible, do the casting in layers to distribute the heat effects.

Once the putty had cured, I removed the decoration halves (some popped off neatly, others needed to be cut away), and sanded out any irregularities caused by the thin plastic warping with the hot putty, or due to the weight of putty.

The end result after repeating the above with another three eye castings was two sets of eyes. I decide not to bother with making up the third eye-plate since I was running out of bog at the time.
Top view of bog eyes mounted on plate.

front view of good eyes on plate.
This photo demonstrates how the eye-plate bolts to the head. In this shot I was testing the exposed length of the eye fixtures to ensure they would not foul against the surface of the head. The eye-plates are held to the head by a single bolt on the centreline of the plate, and the head. A second "prong" is also there to prevent rotation of the eye-plate which engages with a hole located 25mm (1") below the holding bolt.

No comments:

Post a Comment