Food for thought

[quest]

years ago I tore down a free 2.0 sohc stazz motor. The balance shaft had "wobbled around" in there to the point, where there was no rear bearing left nor the bore for the shell to sit in! Beat to just an irregular shaped hole.
Could never understand how a motor can still operate to that point, and not lose pressure to the crank and lock up long before
For a brief moment I thought, "get rid of those shafts"

[ProZac]

I'm not even close to being a guru on the topic of vibration and engine dynamics, but I don't think the last paragraph is accurate from that article ProZac posted.. althought the first two paragraphs make perfect sense.

Firstly it is stated that there is a "potent" lubrication problem.. why is this considered to be the case? If due to the shafts spinning at twice engine rpm, then that doesn't make sense, given that a turbo spinning at perhaps 10 times balance shaft rpm doesn't seem to have these lubrication dramas due to rpm?

Secondly, countering a wave at a 180 degree phase IS balancing (or perhaps more appropriately, cancelling) it out, so it's not "merely masking" the vibration as the last paragraph claims. Perhaps a sound engineer can shed more light on this, because sound is basically vibrations through a medium such as air or water or a speaker cone. Masking the vibrations is essentially the same as balancing them.

I likewise don't really agree with the lubrication problems they talk about, but I think what they're trying to get at is that you have to lubricate a pretty beefy chunk of metal spinning at twice the speed of the crankshaft, and it seems like that'd be a hard thing to do. In reality, I think with correctly specified oil and oil pressure within spec, it's really no drama. I advised my work to leave the shafts in an evo engine build recently for the reasons outlined in the article RZ posted, plus they really do make for a smoother engine.

I can also see what they mean when they say 'masking' the vibration, as you're not curing the source of the vibration, you're adding another component that counters it. However, the harmonics are inherent to the design, and can't be cured conventionally by balancing, so the shafts are a good solution.