Testing a Viscous Coupling

Grumpy - expanding on your idea of checking wear in the IRD bearings have a look at this article. I am not very knowledgeable about this technique - others on here will be, but I am sure this could be adapted fairly easily to construct some form of IRD bearing monitor, which could be checked with a vibration phone app.

It would help if I could link the article :o

http://www.academia.edu/5873884/MICROCONTROLLER_BASED_NON_INVASIVE_WIRELESS_SENSOR_NETWORK_TO_MONITOR_HEALTH_OF_DIESEL_GENERATOR_DG_SETS

lol, I did wonder if I'd missed something. There's a lot to read there, won't be able to get through it today - but I will read it at some time. I've never built electrical circuits, but I'm a programmer by trade.

My current 'project' is a 109 SSW and I've ripped the wiring loom out and am replacing it with a network of Arduino micro processors (eg 1 micro processor in the dash connected to switches and another in the engine bay connected to relays for lights). However, in the tradition of not finishing 1 project before you get the next, I've got my eye on this Freelander. It would give me a 4WD setup to put some monitoring on - such as the suggested remote temp sensors pointed at IRD bearings & VCU - but rather than making circuits (which I don't understand) I'm sure there are components for Arduino micro processors that can be purchased. Hopefully there is an equivalent of the PIC suggestion from an earlier post. Plus, I can also learn how to change head gaskets :)

Have a look at this, Grumpy, as a simple Vibration monitoring system.

http://www.jameco.com/Jameco/pressroom/recipe4.html?CID=vibrationsensor

Calibration would be a pain, but a starting point???

Jeepers, could end up with a Freelander with more monitoring wires than a patient in ICU!

From MadSci Network;

The phenomenon you are asking about is called dilatent rheology [the harder you stir, the thicker it gets] A cornstarch/water slurry is not a solution, but a suspension [or dispersion, if you prefer] of a solid in a liquid. At a certain ratio of cornstarch to water, the critical PVC is approached. PVC is an abbreviation for "Pigment Volume Concentration", a term widely used in the paint industry, and meaning simply the ratio of pigment {starch} in the total volume. Exactly at the CPVC, there are no voids [the starch particles are in contact with each other and the water fills the interstitial space]. At this point, it cannot be said if you have a 'solid' or a 'liquid' the application of pressure [motion, stress, stirring] perturbs that and the flow characteristics change -- the water is 'squeezed out' [into adjacent areas] leaving the starch behind as a damp solid. This is the same phenomenon that you see when walking along wet sand at the beach: your footsteps look dry behind you, even though they were made in wet sand. Other than simple water solutions, most systems exhibit thixotropic behavior. There is little commercial appeal for dilatent ones. Send me a note if you'ld like more info and refs Ken Johnsen @ MSN
No mention of heat. Just particles in suspension that are very close to each other. When these fluids are placed under stress they act like a solid as the particles have no time to move out of the way. It is noteworthy that this Chemist thinks there is little commercial appeal for dilatent fluids.

Jim

To return to the OPs question.......

As the failure of the VCU can lead to catastrophic failure of the rest of the drive train....

Is the "wheel up" test considered a suitable, easily carried out, test to check for progressive failure of the VCU, specifically the "thickening" or "loosening" of the contents, such that some form of qualified decision can be taken to replace the offending article prior to a very expensive result - in some cases complete destruction of the IRD and rear diff?

IMHO- yes it will provide the info needed, if you have a suitable baseline to compare to and are confident there are no other drivetrain issues on that particular vehicle that could affect it. Quite simply, you've just got more variables than if you take it out and test it on a bench!

Interesting video of a Honda vcu rebuild - he states quite clearly that there should be NO air gap....

It also looks like spare parts are available for them.

Also found this on Choosing the silicone oil although it is, again described as "oil". It also seems that different peeps use differing viscosities.