At 06:28 PM 10/4/2000 -0500, Rick Chasteen wrote:
><snip>
>I have recently been mixing sythtetic grease with synthetic motor oil to get
>a less viscous lubricant for my hubs. It works for me and I see no
>disadvantages. Do any chemical or petroleum engineers care to comment?
I am neither chemical or petroleum engineer, but I'll comment: fools rushing in where angels fear to tread.
1) Because both the synthetic oil and the synthetic lube are engineered products, I wouldn't be confident that I knew enough to be sure that the additives won't eat each other. Mixing is not something I would do.
2) 20 years ago, I discussed this with a fine mechanical engineer who worked on aircraft stuff (cargo doors for passenger ject, for example), and he suggested just using a particular light, high temperature range, mil-spec grease. I found an ounce or so a week ago, and it still looks and feels fine, but I'm sure I lost the spec. Smells bad.
3) Again, the underlying issue is that I have no idea what the relation is between unloaded friction and loaded friction. The first is sort of like "static friction," the resistance to starting motion between two things that are at rest. The latter is sort of like "dynamic friction," the sliding friction between two things that are moving. It is not a perfect analogy, but those old enough to have used slide rules will get it immediately. You're close to where you need to be, and trying to move the slider just a smidge. More and more force, and then it breaks loose and overshoots.
4) So, I decided to ride a bit more and worry a bit less. I use Phil, becasue I like the feel better than that of Park, but I have no idea if it is actually 1% - or 50% - better or worse.
harvey sachs
mclean va