A new chapter about my VC

Post by **manxman** » 06 Feb 2008, 18:11

double checked on a grassy slope this morning, it is buggerd!!

dont think all the weight was on the bars, some was on the front wheels they just wern't helping, and the back were touching a bit as it drove off in the end.

Luckily I've got a spare VC in stock.

I guess I need to take the front diff right out to swap it over? or can I replace it in situ?

I'll keep chucking money at it till it's sorted don't worry I'm not giving up...... Any one want to buy Rallye Golf?

Post by **HarryMann** » 06 Feb 2008, 20:53

Can change it in situ or by removing diff.. either.

Loosen diff refill plug first! Drain diff... Driveshafts and rear mounts have to be disconnected, lossen front mounts, angled down and slightly sideways, remove rear cover, don't lose the ring that goes between VC and rear bearing (grease to hold when replaced) use a good liquid sealant (I used orange anaerobic jointing compund), check mounting rubbers for delamming, ensure those long through bolts are put back with all washers in the right place, etc.
Refill diff (2.5 litres? check first)

Think there is a blow-by-blow pictorial artcile on web (american)... possibly linked in our Wiki

Post by **manxman** » 06 Feb 2008, 22:30

Thanks again for your advice, looks like I've got a job this weekend.

I've liberated the one from my spare front diff, came out dead easy on the bench!

What sealent was my next question but youve answered that.

Cheers, I'll let you know how I get on.

http://www.syncro.org/VCTest.html

Post by **HarryMann** » 07 Feb 2008, 00:35

That's all good stuff on syncro.org about VCs except this, which, IMHO, is total "Balls".. and invented to maybe illustrate 'effective viscosity' or some such concept..

[img:500:452]http://www.syncro.org/sitephotos/VCtemp.JPG[/img]

No fluid even 'unique patented silicon fluid' has a temp~viscosity curve like that... it is what happens as temp and therefore internal pressure rises, but the vertical axis of that graph is not viscosity!

Probably an idealised schematic of Transmitted Torque Vs Temp

Post by **syncrodoug** » 07 Feb 2008, 08:50

Curious to know what happens when the temperature is less than -30 degrees - the 'apparent viscosity' appears to be rising. Or perhaps it's just an artistic embellishment!

Post by **toomanytoys** » 07 Feb 2008, 10:29

natural thickening of the fluid.....

Post by **HarryMann** » 07 Feb 2008, 22:38

No use speculating as that graph isn't Viscosity Vs temperature..

Silicon fluids (siloxanes) are used because they can be designed with a wide range of viscosities (e.g. higher than most fluids), are stable and can have quite low temp ~ viscosity gradients (viscosity reduces with temperature steadily, the opposite of what we think we want for a VC, but at a slower rate than most fluids)... they're also not very good lubricants (so shear and heat up quickly)
They would need to change phase to produce that difference, which they don't, or not at these temps and pressures...

Rheological fluids, those responding to magnetic fields, can be made to behave in the way one might wish, and these are in fact used in some power transmission, clutch and barke systems these days.

The primary driver of VC action is pressure (due to air gap being reduced by mixing, and expansion of the fluid)... until then, the viscosity is reducing as temp increases...

Aidan will tell you what the seals look like to contain this pressure (up to 100bar safety limit), you can tell how strong the unit needs to be to contain that pressure by picking one up !

Get the air gap too small and that 100bar can be exceeded

Post by **manxman** » 11 Feb 2008, 19:29

Did the job on Sunday, now have 4WD and don't need to put Rear diff lock in to pull off my grassy test slope, of drive along rocky test beach, were I did before, so success all round

Got some pictures of most of the proccess,but I'll start a new thred with them.

Post by **HarryMann** » 11 Feb 2008, 22:26

Great stuff, great feeling when you have all that traction

Like chalk and cheese aren't they - a syncro that works and one that doesn't

I'll then take the info from your thread and make sure we have it in the Wiki and see if Jenny can also put it on the Syncro website. If you have pictures to then we can host for you if you send them to:
syncronauts@ntlworld.com
and send back the links.

Post by **manxman** » 11 Feb 2008, 23:09

you can use the imageShack links from here (see other thred), if you can lift them, or I can email you the photos.
If you want them emailing, what size would you like? (took them at 10mp)

Post by **HarryMann** » 12 Feb 2008, 00:15

Images look very good thanks... ideal size. Will prob. transfer them to Wiki database so they're always there and links never get broken, thanks v.much for writing up..

Yes, change the prop bolts & nuts to the proper spec as CJ says... well spotted