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ragnarhairybreeks
Samba Member
Joined: October 26, 2009
Posts: 1890
Location: Sidney B.C. Canada
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 Posted: Tue Dec 25, 2012 1:13 pm Post subject: |
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| Jon_slider wrote: |
http://www.vanagon.com/syncros/faq/syncro-faq.htm
How does the Vanagon Syncro's viscous coupling work?
The viscous coupling is constructed of a series of metal plates. Half the plates, (plates 1, 3, 5, 7, etc.) are connected to the input drive shaft coming froward from the transmission. The other half of the plates (plates 2, 4, 6, 8, etc.) are connected to the front differential. These plates are enclosed in a chamber with a very unusual silicon fluid. When the rear wheels and front wheels are moving at the same speed, all the plates move at the same speed, nothing special happens, and little power is transmitted through the coupling. But, when the rear wheels begin to lose traction and spin, the plates connected to the driveshaft begin to spin faster than the plates connected to the front differential. This causes a shearing action in the silicon fluid, which almost instantly heats and thickens, becoming much more viscous. This now highly viscous fluid locks the two sets of plates together and power is transmitted to the front differential and thus the front wheels. VW says this happens as quickly as 1/4 turn of the spinning rear tire.
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That old "the fluid thickens upon heating" canard raises its head again 
read: http://www.syncro.org/sitephotos/Galleries/peschke_viscous_coupling_article/index.htm
cheers
alistair
_________________
'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
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WestyBob
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Joined: June 11, 2004
Posts: 2346
Location: Portland, Oregon
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| Posted: Tue Dec 25, 2012 1:35 pm Post subject: |
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Alistair ... I doubt most will be reading the booklet on Xmas day and likely not at all so could you enlighten us on the key phraseology that makes your point ? |
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syncrodoka
Samba Member
Joined: December 27, 2005
Posts: 12005
Location: Santa Cruz, CA
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syncrodoka
Samba Member
Joined: December 27, 2005
Posts: 12005
Location: Santa Cruz, CA
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| Posted: Tue Dec 25, 2012 1:52 pm Post subject: |
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| Jon_slider wrote: |
Running mismatched tires on a Syncro will "damage" the Viscous Coupling.
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I would substitute "can" for "will". The van will also drive differently which could pose a issue for the driver on a road.
It is not advised for the vehicle components, tires and possibly safety. |
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ragnarhairybreeks
Samba Member
Joined: October 26, 2009
Posts: 1890
Location: Sidney B.C. Canada
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| Posted: Tue Dec 25, 2012 3:41 pm Post subject: |
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| WestyBob wrote: |
Alistair ... I doubt most will be reading the booklet on Xmas day and likely not at all so could you enlighten us on the key phraseology that makes your point ? |
Bob,
a short explanation of VC mechanism, via GKN:
http://www.gkndriveline.com/drivelinecms/export/si...s-engl.pdf
cheers
alistair
_________________
'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
http://shufti.wordpress.com |
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WestyBob
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Joined: June 11, 2004
Posts: 2346
Location: Portland, Oregon
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| Posted: Tue Dec 25, 2012 4:19 pm Post subject: |
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Thanks Mario & Alistair.
So aside from reaching the 'hump' mode where some thermal pressure seems to be involved, exactly how would a VC fail ? Natural viscuous material aging and breakdown (excessive thinning) or aging plate deformation or ? |
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syncrodoka
Samba Member
Joined: December 27, 2005
Posts: 12005
Location: Santa Cruz, CA
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| Posted: Tue Dec 25, 2012 4:57 pm Post subject: |
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To help visualize what the fluid in the VC is doing I liken it to Oobleck(a mixture of corn starch and water) where it is both a liquid and solid. It is in a viscous form until activated then it acts more like a solid. This is of course a very crude comparison but it helps to understand it a little better.
Link
The plates can wear so that it is harder for it to activate, the fluid gets contaminated from the metal of the plates wearing off over time and the seals fail so that the fluid leaks out are some of the failures types that I am aware of. I don't know how the aggressive VC type failure comes about.
I apologize for wandering off topic but the info is interesting. |
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ragnarhairybreeks
Samba Member
Joined: October 26, 2009
Posts: 1890
Location: Sidney B.C. Canada
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| Posted: Tue Dec 25, 2012 6:11 pm Post subject: |
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I disagree, the silicone is not a shear thickening mix (oobleck for example).
No time for more right now, but the hump is achieved by a sort of fluid throttling/uneven local pressure gradients between plates.
cheers
alistair
_________________
'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
http://shufti.wordpress.com |
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syncrodoka
Samba Member
Joined: December 27, 2005
Posts: 12005
Location: Santa Cruz, CA
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| Posted: Tue Dec 25, 2012 6:33 pm Post subject: |
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| syncrodoka wrote: |
| To help visualize what the fluid in the VC is doing I liken it to Oobleck |
| syncrodoka wrote: |
| This is of course a very crude comparison but it helps to understand it a little better. |
I am outta here. |
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insyncro
Banned
Joined: March 07, 2002
Posts: 15086
Location: New York
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| Posted: Tue Dec 25, 2012 7:44 pm Post subject: |
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| ragnarhairybreeks wrote: |
I disagree, the silicone is not a shear thickening mix (oobleck for example).
No time for more right now, but the hump is achieved by a sort of fluid throttling/uneven local pressure gradients between plates.
cheers
alistair |
Please take your opinions to the VC thread.
I believe my last post to it that includeds Seth Drew's video explains quite a bit.
This thread is about lifting Syncros and suspension.
Thank you kindly  |
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Jon_slider
Samba Member
Joined: April 11, 2007
Posts: 5091
Location: Santa Cruz, Crowdifornia
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| Posted: Tue Dec 25, 2012 10:38 pm Post subject: |
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> a short explanation of VC mechanism, via GKN:
http://www.gkndriveline.com/drivelinecms/export/si...s-engl.pdf
"The “Hump” mode is activated when the coupling achieves 100% filling due to fluid thermal expansion thereby amplifying a hydraulic throttling effect between the plates"
again
"fluid thermal expansion"
imo, the reason the fluid expands, and the reason the pressure inside a partially filled VC rises, is because the air portion of the fill, expands as it gets heated by the shearing of the plates rotating at different rates.
when the pressure inside the VC rises, from the hot air expanding, the plates bind and engage the front wheels
so, the point is, IF you get big tires, to add ground clearance, after lifting your wheel wells with taller springs, you will also have the expense of a tire carrier, since a Syncro NEEDS to run matched tire sizes, otherwise the VC WILL overheat, which can ruin it.
And you should add the cost of big brakes to stop the bigger heavier tires.
Or, if youre feeling lucky, just buy 4 tires that match, and carry a mismatched spare. Lots of people never get a flat tire.
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My Soapboxes: Inflation; Handling; Gearing; Decoupling; Swepco |
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DeadSetMonkey
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Joined: April 15, 2010
Posts: 532
Location: Denver, CO
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| Posted: Wed Dec 26, 2012 7:36 am Post subject: |
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I plan to keep all 5 tires the same size, and to rotate every 3000miles, no matter what I do with the suspension.
I'll figure out spare tire storage.
Back to lifting questions.
T3 bushings? Burley bushings? Urethane? Rubber?
Seems to me everyone agrees that urethane is the way to go.
D
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'90 Syncro Westy 2.5Subi Turbo, BFGs 215/75/15 Rheins |
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Brianfromutah
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Joined: May 30, 2012
Posts: 150
Location: Utah, Heber City
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| Posted: Wed Dec 26, 2012 8:43 am Post subject: |
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Back to lifting questions.
T3 bushings? Burley bushings? Urethane? Rubber?
Seems to me everyone agrees that urethane is the way to go. |
I was also thinking about doing some bushings as well and was wondering the same question.
I was thinking of just getting the kit from VC...
http://www.van-cafe.com/home/van/page_944_1232/front_suspension_bushing_kit.html
although they look like regular rubber to me...
Also, for someone on a tight budget (like me) are there specific bushings that wear more than others that perhaps i could spend the extra money to get the upgraded bushings?
_________________
'89 Westy Syncro w/ '09 Subaru 2.5 |
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j_dirge
Samba Member
Joined: August 08, 2007
Posts: 4641
Location: Twain Harte, CA
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| Posted: Wed Dec 26, 2012 9:37 am Post subject: |
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| DeadSetMonkey wrote: |
I plan to keep all 5 tires the same size, and to rotate every 3000miles, no matter what I do with the suspension.
I'll figure out spare tire storage.
Back to lifting questions.
T3 bushings? Burley bushings? Urethane? Rubber?
Seems to me everyone agrees that urethane is the way to go.
D |
Not everyone agrees that urethane bushings are the way to go.
Most people who have installed them.. like them.
I, for one, like the ones I installed.. but admitteldy only installed them in two locations. Rear swing arms.. and the power stearing rack.
However, there is a considerable cost difference between OEM style rubber and performance urethane.
So lets have an honest discussion about this..
The OEM rubber bushings lasted for 20 yrs.. and they provde a surprsingly nice ride and remarkeablygood handling for such a cumbersome vehicle.
Urethane will likely last very long as well and some specific handliong characteristics may feel improved/different. But a new vanagon owner driving two tuned vanagons (all other things equal) side by side.. one with new urethane bushies and one with new rubber.. probably could not tell the difference.
Only your budget can make your decision for you.
I think most of us who have messed with our suspenssions would be honest enough to admit that there is a law of diminishing returns that applies here.
I recommend taking a step step approach and do you own cuase and effect analysis as you tune and mofify your own suspension.
Having put $1000s into my own suspension, I can hoestly say that (in 20/20 hindsight) my OEM suspension was really pretty damned good.. and new shocks and good tires were 95% of the equation. (maybe more)
So then the question becomes.. how much money is that last 5% worth to you?
_________________
-89 GL Westy, SVX.. finally.
-57 pan f/g buggy with a 67 pancake Type 3 "S"
"Jimi Hendrix owned one. Richard Nixon did not"
-Grand Tour, Season 1, episodes 4 and 5
| danfromsyr wrote: |
those are straight line runs with light weight race cars for only 1/4mile at a time..
not pushing a loaded brick up a mountain pass with a family of 4+ inside expecting to have an event free vacation..
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fairweather
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Joined: August 26, 2007
Posts: 663
Location: Aspen, CO
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| Posted: Wed Dec 26, 2012 9:50 am Post subject: |
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| j_dirge wrote: |
Having put $1000s into my own suspension, I can honestly say that (in 20/20 hindsight) my OEM suspension was really pretty damned good.. and new shocks and good tires were 95% of the equation. (maybe more)
So then the question becomes.. how much money is that last 5% worth to you? |
You're not going to get a more honest and concise answer than this. |
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danbar
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Joined: October 16, 2011
Posts: 464
Location: North Bend, WA
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| Posted: Wed Dec 26, 2012 11:17 am Post subject: |
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On the Rubber vs Urethane front there's also comfort vs performance to consider. Rubber dampens vibrations that urethane transmits. You will have a somewhat more abrasive ride on rough surfaces with urethane than with rubber. Urethane is more responsive and stiffer in the corners though. There is no perfect solution, it's finding what you want your suspension to do for you.
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'88 SCA High/Pop-top Syncro camper
'61 Meyers Manx |
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snowsyncro
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Joined: January 11, 2009
Posts: 1557
Location: East Preston, Nova Scotia, Canada
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| Posted: Wed Dec 26, 2012 12:42 pm Post subject: |
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This seems like an appropriate place to raise a question about rear trailing arm bushings, that I have never seen answered.
The pivots for the arms are not co-axial. So when the arm swings, the plane of the arm changes, introducing camber to the wheels. As a result, the bushing centre does not stay concentric with the sleeve that holds the bushing in place, and the bushing is compressed. The stock bushings appear to be designed for this, because they provide a radius for relief at both ends. The urethane bushings that I have seen do not have this radius.
Has anyone noticed any binding as the arm goes through its range of travel, with the aftermarket bushing, or are the forces so small they are insignificant?
RonC |
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j_dirge
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Joined: August 08, 2007
Posts: 4641
Location: Twain Harte, CA
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| Posted: Wed Dec 26, 2012 1:08 pm Post subject: |
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| snowsyncro wrote: |
This seems like an appropriate place to raise a question about rear trailing arm bushings, that I have never seen answered.
The pivots for the arms are not co-axial. So when the arm swings, the plane of the arm changes, introducing camber to the wheels. As a result, the bushing centre does not stay concentric with the sleeve that holds the bushing in place, and the bushing is compressed. The stock bushings appear to be designed for this, because they provide a radius for relief at both ends. The urethane bushings that I have seen do not have this radius.
Has anyone noticed any binding as the arm goes through its range of travel, with the aftermarket bushing, or are the forces so small they are insignificant?
RonC |
I have firm rear swing arm polyU bushings from Burley in the custom 16 inch swing arms he built for me.
I understand the point you raise.
I have not observed any apparant binding. The polyU bushings are 2 piece.. where as the OEMs are one piece. I'd suggest/speculate that the break between halves allows a fair bit of flex and can accomodate the variation in the differing "planes" of the mounting bolt centerlines. (admittedly not the "designed" intent in making the bushings 2 piece)
It should be noted, however, I have only 8-10k miles in on them.
I pulled the bolts after our summer trips.. I saw no signs of wear to sleaves, bolts, or hangers. And no apparant deformation the polyU bushing at all.
We carreid a good deal of weight, drove some crappy roads.. did a little fire-road type dirt.. but nothing extreme. And I have not had the van air-borne, yet..
well...
OK.. maybe a a couple inches. 
But I have not attempted to clear the Snake River Canyon, yet. 
_________________
-89 GL Westy, SVX.. finally.
-57 pan f/g buggy with a 67 pancake Type 3 "S"
"Jimi Hendrix owned one. Richard Nixon did not"
-Grand Tour, Season 1, episodes 4 and 5
| danfromsyr wrote: |
those are straight line runs with light weight race cars for only 1/4mile at a time..
not pushing a loaded brick up a mountain pass with a family of 4+ inside expecting to have an event free vacation..
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syncrodoka
Samba Member
Joined: December 27, 2005
Posts: 12005
Location: Santa Cruz, CA
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| Posted: Wed Dec 26, 2012 1:42 pm Post subject: |
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| snowsyncro wrote: |
The stock bushings appear to be designed for this, because they provide a radius for relief at both ends. The urethane bushings that I have seen do not have this radius.
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I have removed the stock bushings from many trailing arms and they showed no real sign of the radius that the stock bushings have when new.
I have burley's rear trailing arm bushings on my truck and they have shown no signs of binding and it has many miles on it. I have had the rear end apart for various reasons and the cycling of the trailing arm was never an issue, it is something I have been interested in knowing. No squeaking either which had been one of my biggest concerns going in. |
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FrankenSubySyncro
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Joined: May 03, 2007
Posts: 638
Location: Vancouver, WA.
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| Posted: Wed Dec 26, 2012 2:29 pm Post subject: |
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I have spent way too much on my suspension but here are the most significant improvements. I am sitting around 20.5" from wheel center to fender lip.
E load range tires (225/75/16) helps a lot with the cross winds on the highway and handling in the corners. Also has enough sidewall to air down and work well offroad. (not recommended for stock motor)
Adjustable shocks in the rear, ProComp MX6 with or without remote reservoir, I have tried both. I adjust them to the softest setting for off road and the stiffest for on road. The non reservoir are about $100 each and the reservoir are about $200 each. I wish I could find an off the shelf set for the front but so far the only ones I have seen are the GW Fox shocks but are $$$$.
I had .org and OME to start but the springs were too stiff for my tintop. I have not tried the GW lift springs but friends with tintops did not like them while others with westys did.
"Serious offroading" is a relative term here. If you want to do serious offroading, get another vehicle and sleep in a tent.
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Syncronize it!
1987 Franken Syncro (converted 2WD auto)
2004 2.5 SOHC Subaru
F & R lockers, decoupler, SS, 6.17 R&P
Trans Cooler
EMPI race prepped 930 CVs and axles
Bilstein coilover front, rear ProComp MX-6066R shocks, 14" hypercoil springs
30x9.5 15" BFG Muds
Custom skid plates
Nose job (custom front bumper) http://www.flickr.com/photos/subyvanagon/sets/72157624970330925/ |
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