

| Subject: | Re: <Syncro> viscous coupling fluid ! |
| Date: | Mon, 10 Feb 1997 19:00:03 -0800 |
>| However it all seems very simple to me. A Viscous Coupling is a COUPLING, >| not a differential. A DIFFERENTIAL PROVIDES SLIP UNDER LOAD (ie cornering) >| A VISCOUS COUPLING LOCKS UP UNDER LOAD AND provides SLIP under NORMAL >| CONDITIONS. The two are completely opposite. Well, since I was the one that started it this time, I would like to clarify what I was talking about. I didn't mean replace the diff with a VC, but instead to couple the two. The VC transmit load with a threshold is past; in the Syncro, we are looking at a temperature/pressure threshold that is an inherit properity of the silicone fluid used. What creates the heat is the friction within the silicone liquid as two plates start spinning at unequal rates. If I understand the VC correctly, there are no mechincal "connections" when the silicone is a liquid, the two disks are allowed to turn, one driven by a connection to the engine, the other by the front wheels as they are turned by the ground as the car is moved forward by the rear drive wheel. When the back wheels slip, the plate powered by the main driveshaft starts spinning much faster than the plate driven front wheels, and the VC locks up (now I am not sure how this works, whether the silicone actually fills some gap between the plates and transmits the power from the enigne across itself or if it merely pushes some gears together). All very nice, but the specifics of how the VC works can be left aside in this case, because all I want is the locking up action when the two sides spin at greater than 6% difference. Maybe my idea/dream was not clear its first iteration. I do not want to replace the diff with a VC, but instead add a VC across the two output shafts of the diff itself so that when either of the two output shafts were to spin at greater than 6% of the other, it would lock up and ineffect, lock the differential. I cannot see where this could be a problem on a vanagon, maybe the VC should lock up at somewhere about a 25% difference in speed or something (have to be careful not to get the difference great enough to snap components when the silicone fluid solidifies though I guess). Still I do not see why one could not join the VC concept with a differential to provide an automatic locking diff. But I am not the right type of engineer to attempt this. Nor do I have access to a machine shop to fabricate the pieces. So it will remain a pipe dream (unless someone hands it to some off road race design team and they for some reason implement one and give me a second as a favor for daydreaming ;) ). What did interest me was hearing that the VC could be replaced with one of those neat pull buttons to make it locking (well, it was not offered here, I know that, so an order from I guess Austria would be necessary, but hey, I would have three knobs and all three green dots would light up when I had true AWD right?). To be serious, has anyone looked into importing one/a set of these? Locking front diff and transfer box? Looking at the current setup, I would expect the one change needed would be a different front final drive. Anyone started this research? If I ever get some free time, it would be something I would persue... dave
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