This has been a three-year off-again, on-again project.
The Holden harmonic balancer is a complicated assembly of a dozen parts. Its job is to damp out torsional vibrations in the crankshaft. A heavy inertia disc is sandwiched between two rubbers, and secured to the hub by six rivets and a special washer at the front of the unit. The inertia disc acts as a flywheel, and torsional vibrations in the crankshaft hub cause the rubbers to deform. The rubbers are not perfectly springy, and absorb the torsional vibrations.
But like everything else, the grey motor harmonic balancer gives trouble over time. The timing case oil seal wears a groove in the hub, which then leaks. The rubbers fall to bits, and the inertia disc comes loose. Or the rivets loosen and the pulley comes loose and rattles.
How hard can it be to disassemble a few harmonic balancers, reproduce the rivets and the rubbers, sleeve or hard-chrome the hubs, and reassemble?
There's quite some work to it . . .
The first challenge was in reverse-engineering the rubbers and getting moulds made for reproduction rubbers. And then there was the issue of what durometer rating was closest to the original. I wanted to do it in a more exact manner than just the "sink the thumbnail into the rubber" method. Fortunately I was able to get some original rubbers measured for their durometer rating.
The rivets, it turns out, were designed in sensible imperial dimensions. But I still had to guess-timate the overall length of the rivet, because they get peened over at the factory.
I needed to design some assembly tooling to hold the parts in the right relationship, compress the rubbers, and peen the rivets over with star-shaped drifts to duplicate the original assembled appearance.
A goodly amount of time with a sandblaster cleaning parts, some etch primer, and -
(view from rear)
(view from front)
Rob
