Harmonic Balancers

[ardiesse]

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.


Exploded view.

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, a light coat of etch primer, and -


view from rear.


view from front.

(Finally sorted out how to link images)

Rob

[Blacky]

love your work mate you and Harv should both be awarded the NASCO gold star for services rendered to the early Holden tragics of Australia

I am just about to rip the front off the motor in the ute to change the cam and see if I can figure out why it PISSES oil out even when parked I have about 5 good harmonic balancers in a box in the shed so will pick the best one I have and speedy sleeve it and hopefully after I get it back together it wont leak from there at least

[In the Shed]

Onya Rob,
We appreciate the effort you have gone to in detailing your work with the aim of keeping the old grey original. We're the rivets available off the shelf or did you have to make them?

Regards
Stephen

[ardiesse]

Blacky -

Your oil leak sounds like Joe's in his ute, so I'd suspect that you're leaking oil between the front engine mount plate and the block. When you've pulled the camshaft out, remove the front engine mount plate too, and check that the mating face is flat - and it may take some work with a press to make it flat.

Stephen - No, I had to measure up the rivets and do a dimensioned sketch. One of the mechanical engineers at work kindly turned my sketch into a proper drawing, and then I had a small run of them made.

Rob

[Blacky]

yeah , got a freshly surface ground front plate ready to go in mate

[Harv]

The balancer really came up a treat. Did you use one of the old Holoriv riveters?

Cheers,
Harv

[thebrotherj]

yeah , got a freshly surface ground front plate ready to go in mate

Yes, Rob was right about my leak. My discovery on tear down was likely more to do with the front main bearing cap not being flush with the front of the block... and I suspect the wrong sealant used on the last rebuild also.
On reassembly, I was at pains to make sure the front cap tensioned down flush, using a steel ruler. My plate proved dead flat with the straight edge test, so I left it alone, and used Permatex No.4 on the gasket, it’s the one that cures hard.

My balancer had a decent ridge from the timing case seal but I’ve seen worse so i took a punt on it, made sure the timing cover was loose before hammering the balancer on so it self centred, then torqued to spec.

Not a drop so far... but I haven’t run the motor for terribly long! I’m sure it’ll be fiiiine right?....






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[ardiesse]

Harv,

I've never heard of the Holoriv riveter. No, I used the antediluvian 30-ton press hiding in the dark next to the welding bay at work. (And I thought it was a big press until I went to bus museum in Leichhardt last weekend and saw its 60- and 100-ton brethren)

Joe,

You'll be fine, as far as I can tell. But I did see the condition of your balancer's rubbers and thought, "Hmm. You could do with a reconditioned one."

Rob

[thebrotherj]

Joe,

You'll be fine, as far as I can tell. But I did see the condition of your balancer's rubbers and thought, "Hmm. You could do with a reconditioned one."

Rob

I turned a blind eye to that when my first credit card bill came in from all the engine rebuild costs Hey, it was revving smoothly and not leaking (much) from the seal before so i figured I’d suck it and see.

When you’ve got a production line happening for the reco balancers, I might be your first customer? I’m very impressed by your efforts there also, well done.


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[Harv]

Holoriv riveter by Coxhead. Mainly used for brake shoes, though the star-patterned mandrel caught my eye as similar to the harmonic balancer.

Optimized-Holoriv.JPG (687.06 KiB) Viewed 671 times

Gotta love a 100t press... the brother-in-law has one at work that straightened the FB towbar tongue like butter.

Cheers,
Harv

[Craig Allardyce]

PM sent Rob.