GrumpyGel said:
Presumably you meant to write "The fluid in this one is much LESS viscous".

Incidentlly, I'm sure this has been said before and I could find it searching through an umpteen page VCU thread, but what size holes do you drill and how far in from the edge of the VCU are the hole centers? Do you used "normal" drill bits, or a form of more 'flatter tipped' so as not to damage the plate on the inside of the case?
Click to expand...
Err yes, less vicious (pun intended) in an ideal world we would use a perfect shaped drill and would stop in time to avoid hitting the disks but in my case they get hit and who knows what swarf ends up in side. That's all part of the compromise doing it this way. There are other comprises doing it by cutting and welding. As for the drill size it depends on what thread bolts/nozzles you plan to use. Standard thread uses a smaller drill than fine or extra fine as the grooves made by the tap are deeper. There are tables available to tell you what to use.
I pick a spot half way between the shaft and the edge to drill. Go to near the edge and you'll hit the side wall, to near the centre and the bolt won't fit.
 
Hi all, it is interesting with the comments re fluid 'weight' / no.
I can quite understand a lightweight fluid being absolutely fine in a snow / ice / wet grass condition, but personally do not believe the same vcu would be capable of the appropriate performance in a hard surface situation like a rocky path - not BOULDERS LOL - but a hard shale.
There is a HUGE difference.
A VCU that is capable of traction is snow is not necessarily appropriate in hard surface conditions, whereas, a VCU set properly per manufacturers specs would perform superbly in hard surface situations AND in low necessary 'grip' situations such as snow / ice / wet / etc.
There is no one 'less' solution - ie - a low grip apparently working vcu in 'low grip' conditions is not correct - a VCU that performs correctly in designed condition is perfectly suited to low grip conditions - that is how it is designed to work. IN snow / ice - you could probably put tomato ketchup in and it would do the job...:eek:
:D
 
Joe_H said:
Hi all, it is interesting with the comments re fluid 'weight' / no.
I can quite understand a lightweight fluid being absolutely fine in a snow / ice / wet grass condition, but personally do not believe the same vcu would be capable of the appropriate performance in a hard surface situation like a rocky path - not BOULDERS LOL - but a hard shale.
There is a HUGE difference.
A VCU that is capable of traction is snow is not necessarily appropriate in hard surface conditions, whereas, a VCU set properly per manufacturers specs would perform superbly in hard surface situations AND in low necessary 'grip' situations such as snow / ice / wet / etc.
There is no one 'less' solution - ie - a low grip apparently working vcu in 'low grip' conditions is not correct - a VCU that performs correctly in designed condition is perfectly suited to low grip conditions - that is how it is designed to work. IN snow / ice - you could probably put tomato ketchup in and it would do the job...:eek:
:D
Click to expand...
Good point Joe. It takes a lot more torque to push a car up a rocky slope than along a flat snowy road. I know my last VCU home brew job worked great on rocky conditions cause I tested it in a quarry. That's why I'm not worried about the latest one being as good as i can swap them if needs be.
 
GrumpyGel said:
Presumably you meant to write "The fluid in this one is much LESS viscous".

Incidentlly, I'm sure this has been said before and I could find it searching through an umpteen page VCU thread, but what size holes do you drill and how far in from the edge of the VCU are the hole centers? Do you used "normal" drill bits, or a form of more 'flatter tipped' so as not to damage the plate on the inside of the case?[/QUOTE

The steel ball that sits in the hole where the unit was originally filled can be drilled out with a core drill bit. Once the ball comes free the hole may be drilled with a suitable ordinary drill bit to take a tap to thread the hole for a plug or grease nipple.
Click to expand...
 
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jonaf said:
How the VCU works: https://www.landyzone.co.uk/attachments/viscous-engl-pdf.57718/
"The degressive locking characteristics (viscous mode) can be tuned by fluid viscosity, number and size of plates, and fluid filling percentage "
"The “Hump” mode activation is tuned by the fluid filling percentage"
Click to expand...
Yes, all noted, and has been discussed at length :)
Viscosity is most important - as well as ALL the other parameters. It does not mean that your unit is as per original. I fail to see exactly what you are intending to show by the oft' quoted GKN pdf ?
What works on snow / ice / wet does not a fully working VCU make. I honestly doubt the weight of fluid you are using produces a suitable VCU as per original.
:)
 
jonaf said:
How the VCU works: https://www.landyzone.co.uk/attachments/viscous-engl-pdf.57718/
"The degressive locking characteristics (viscous mode) can be tuned by fluid viscosity, number and size of plates, and fluid filling percentage "
"The “Hump” mode activation is tuned by the fluid filling percentage"
Click to expand...

I also think you are very much confusing the following -

"The “Hump” mode activation is tuned by the fluid filling percentage"

Whilst the above is 'true' (within certain parameters) - it also does not at all mean that a single entity (ie - fluid filling percentage ) regardless of the weight of the silicone in any way controls the 'hump mode in respect of manufacturers design figures and performance' - it means that the fluid fill percentage to obtain a certain figure is directly related to the Viscosity!!. NOT 'any' viscosity! - a major difference. - fluid fill V viscosity produces A hump mode and A certain performance - however - unless related to the design parameters of BOTH viscosity AND fluid fill will only produce a unit with indifferent performance. That is the biggest issue that most re-conditioners face. It seems to work, is passes with flying colours the OWUT but simply does not perform in the manufacturers desired way in all conditions. I had a superb OWUT pass -re-con VCU that was utterly crap on the road / off road. I am sure that in certain conditions a vcu can be filled with a level and weight of fluid that performs in certain conditions, but not in others.
Sorry mate if we are confusing things or there is a case of 'lost in translation'
Joe :)

 
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The proof of the pudding is the eating, Joe.H. Your are welcome to try and follow me throug the mudholes and up the hills in the Norwegian woods any time.
By the way: What is the viscosity of the fluid in a brand new OE VCU? Has anybody drained one and compared it to fluids with a known centistoke number?
 
jonaf said:
The proof of the pudding is the eating, Joe.H. Your are welcome to try and follow me throug the mudholes and up the hills in the Norwegian woods any time.
By the way: What is the viscosity of the fluid in a brand new OE VCU? Has anybody drained one and compared it to fluids with a known centistoke number?
Click to expand...
Yes, Bell Engineering has performed extensive tests to reproduce the manufacturers specification. Speak to them. :)
You are also welcome to follow me up the shale and small rock roads in the Portuguese hills :D
Joe;)
 
Joe_H said:
Yes, Bell Engineering has performed extensive tests to reproduce the manufacturers specification. Speak to them. :)
You are also welcome to follow me up the shale and small rock roads in the Portuguese hills :D
Joe;)
Click to expand...

I doubt Bell are going to share their trade secrets with us. To me it is not really important to know because I have found the way to make my VCUs work the way I want them to. Just like Bell Engineering have.
 
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I have to say, it doesn't really matter what you put in it or how much. The important thing is whether it works or not.

I suspect that you Portuguese VCU Joe just didn't have enough fluid in it to get to Hump - mode regardless of its viscosity - but I'm not starting another war of words here!
 
GrumpyGel said:
I have to say, it doesn't really matter what you put in it or how much. The important thing is whether it works or not.

I suspect that you Portuguese VCU Joe just didn't have enough fluid in it to get to Hump - mode regardless of its viscosity - but I'm not starting another war of words here!
Click to expand...
Or the guy filled it with some cheap crap that might be a bit like VCU fluid but not quite. How many people are going to even notice never mind complain about it?
 
GrumpyGel said:
I have to say, it doesn't really matter what you put in it or how much. The important thing is whether it works or not.

I suspect that you Portuguese VCU Joe just didn't have enough fluid in it to get to Hump - mode regardless of its viscosity - but I'm not starting another war of words here!
Click to expand...
Grumpy ;)
No, that is not the case - that is a ridiculous statement and one you cannot quantify as to 'works or not'. The fill level is NOT the issue in itself - it is directly related to the viscosity AND the fill level. - period. :) - I think you may have had too much 'sauce' this evening - and it shows :(
Or, are you intending to say that you can put any old crap silicone in of any 'weight' and the results are directly related to fill level ? - I hope not - but hey ..... that seems to be your intention - however misguided.
Snow and ice and mud are one thing, correct operation in all conditions are another.. people who fill it with the incorrect fluid are - usually - going to say it works. I say TOTAL UTTER Bollox... :D
It may - in certain loose conditions do something. - I think your 'conclusion' - if that is what it is, is completely uninformed and incorrect... (sorry mate but -) put ketchup in and it is the fill level that makes the VCU the desired object..:rolleyes:

NOT a cat in hell's chance old boy. - AND you know it.:)

Define works ? - just because some snow merchant says it is 'ok' means nada.
I am absolutely amazed at your naivety. GG.... (but can see the relationship between 'intake' of 'fluids' and outtake) :( :(
 
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GrumpyGel said:
Ibut I'm not starting another war of words here!
Click to expand...
Joe_H said:
Grumpy ;)
No, that is not the case - that is a ridiculous statement and one you cannot quantify as to 'works or not'. The fill level is NOT the issue in itself - it is directly related to the viscosity AND the fill level. - period. :) - I think you may have had too much 'sauce' this evening - and it shows :(
Or, are you intending to say that you can put any old crap silicone in of any 'weight' and the results are directly related to fill level ? - I hope not - but hey ..... that seems to be your intention - however misguided.
Snow and ice and mud are one thing, correct operation in all conditions are another.. people who fill it with the incorrect fluid are - usually - going to say it works. I say TOTAL UTTER Bollox... :D
It may - in certain loose conditions do something. - I think your 'conclusion' - if that is what it is, is completely uninformed and incorrect... (sorry mate but -) put ketchup in and it is the fill level that makes the VCU the desired object..:rolleyes:

NOT a cat in hell's chance old boy. - AND you know it.:)

Define works ? - just because some snow merchant says it is 'ok' means nada.
I am absolutely amazed at your naivety. GG.... (but can see the relationship between 'intake' of 'fluids' and outtake) :( :(
Click to expand...
I would quantify whether it works or not as whether wheels on both axles are spinning if you're stuck! If you're stuck and the back wheel(s) aren't spinning, then the VCU doesn't work. I believe this is what you found and concluded much the same.

What the car is driving on definitely has NOTHING to do with whether the VCU "works" or not. Whether its flat dry tarmac on a sunny day, a steep incline of wet grass, 3' of snow or 3' of gravel or 3' of shale - they don't change the characteristics of a VCU - in exactly the same way they do not change the characteristics of a diff lock.

They also don't greatly change the characteristics of how the VCU should operate. They impact more on other factors such as tyre choice and suspension setup.

A VCU has a viscous mode and a hump mode. Hump mode essentially locks the coupling. As you can attain hump mode with differing CST level silicone fluids, it therefore implies that you can put different CST fluids in and drive a Freelander over anything in hump mode (assuming you have grip for the surface). So, that quantifies that it "will work".

The lower the CST level, presumably the more often you will need to use hump mode. There will be much reduced torque transfer in viscous mode.

TBH I would have thought low CST levels of 15.000 and 30.000 would not have been any good in a Freelander's VCU - but if someone's been driving Scandinavian winters and been muddy forest hunting for a number of years successfully, then that rather shows the opposite.
 
Alibro said:
Or the guy filled it with some cheap crap that might be a bit like VCU fluid but not quite. How many people are going to even notice never mind complain about it?
Click to expand...

I've seen many people claiming that 100K silicone oil will work in the VCU and will give a good OWUT. However on the slippery stuff, it's pants as it never actually locks. Simply because the fluid used in the VCU isn't a silicone oil. It's a dedicated non-Newtonian fluid. This is silicone based but has properties that ordinary silicone oil simply can't achieve.
 
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Nodge68 said:
I've seen many people claiming that 100K silicone oil will work in the VCU and will give a good OWUT. However on the slippery stuff, it's pants as it never actually locks. Simply because the fluid used in the VCU isn't a silicone oil. It's a dedicated non-Newtonian fluid. This is silicone based but has properties that ordinary silicone oil simply can't achieve.
Click to expand...
As with all things in life, our reconned VCU's are a compromise, but if done right they are good enough for long enough that for most people the compromise is worth making. For the rest they buy OEM made by GKN and pay the premium.
I'm happy with the compromises I've made so far with the ones I've reconned but it remains to be seen how good the latest one is doing it the cheaters way. Note I didn't say the easy way as it probably requires more time and effort than cutting, cleaning and welding (and grinding and welding and grinding etc etc etc)
 
Nodge68 said:
I've seen many people claiming that 100K silicone oil will work in the VCU and will give a good OWUT. However on the slippery stuff, it's pants as it never actually locks. Simply because the fluid used in the VCU isn't a silicone oil. It's a dedicated non-Newtonian fluid. This is silicone based but has properties that ordinary silicone oil simply can't achieve.
Click to expand...
Where is your source for this information?
I'm happy to be disproved, but I believe that once again this is another "fact" about the VCU that's actually totally untrue.
My source for stating this, other than every other reputable documentation about Viscous Couplings, is the GKN document relating to their Viscous Couplings. It clearly states "Silicone fluid is optimised with specific additives for lifetime performance" - so it IS using a Silicone fluid as the primary/sole operating material and the diagram clearly highlights the fluid as "Silicone Fluid".
 
Alibro said:
As with all things in life, our reconned VCU's are a compromise, but if done right they are good enough for long enough that for most people the compromise is worth making.
Click to expand...
... and who's to say the combined resource of LZ members' research and development, hasn't produced a better VCU than the original?

I said above that its easily quantifiable to say whether it works or not - but whether the GKN, Bells or one of the now many home built VCUs is "best" is more difficult to quantify. So, if you're VCU is working well for you, congratulate yourself because there is nobody out there that can quantify GKN's, or anyone else's as better - therefore you have created THE BEST Freelander VCU :)
 
GrumpyGel said:
I would quantify whether it works or not as whether wheels on both axles are spinning if you're stuck! If you're stuck and the back wheel(s) aren't spinning, then the VCU doesn't work. I believe this is what you found and concluded much the same.

What the car is driving on definitely has NOTHING to do with whether the VCU "works" or not. Whether its flat dry tarmac on a sunny day, a steep incline of wet grass, 3' of snow or 3' of gravel or 3' of shale - they don't change the characteristics of a VCU - in exactly the same way they do not change the characteristics of a diff lock.

They also don't greatly change the characteristics of how the VCU should operate. They impact more on other factors such as tyre choice and suspension setup.

A VCU has a viscous mode and a hump mode. Hump mode essentially locks the coupling. As you can attain hump mode with differing CST level silicone fluids, it therefore implies that you can put different CST fluids in and drive a Freelander over anything in hump mode (assuming you have grip for the surface). So, that quantifies that it "will work".

The lower the CST level, presumably the more often you will need to use hump mode. There will be much reduced torque transfer in viscous mode.

TBH I would have thought low CST levels of 15.000 and 30.000 would not have been any good in a Freelander's VCU - but if someone's been driving Scandinavian winters and been muddy forest hunting for a number of years successfully, then that rather shows the opposite.
Click to expand...

Hi GG, I think there are two things very wrong with your hypothesis that throw virtually everything else in your comments here into deep question.
First is viscosity - as in the viscous mode of operation of the VCU. the operation of the viscous mode - which is designed to be progressive ! - is directly related to the 'weight' of the fluid given a set amount of plates. You even have a test to confirm that as Tony demonstrated and also a figure to test on based on Landrover spec (the rotating test measuring static load.)
The hump mode of operation you also appear to be presuming is a constant applied 'locking force' - as in - when in effect the coupling is effectively locked - I disagree. With higher viscosity fluids the hump mode when activated will have a far higher eventual shear limit than the 'hump mode' with very low viscosity fluid. In other words, the hump mode of a low viscosity fluid will have a form of hump activation but a far lower break away force - it will not cause a 'lock up action' of = force to the higher weight fluid, it will cause an increase in tightening only that more than likely WILL be overcome by the torque of the engine / drive. Hence what appears to work on snow and ice and soft mud will not work effectively on shale / rock.
Viscous modes and Hump modes are not all equal across differing fluids and will not be overcome and made equal by altering quantity :)
There are also other factors at play in areas such as rate of hump activation and perhaps more importantly de-activation.
It is therefore not "easily quantifiable to say whether it works or not"
A veritable minefield.
Joe:)
 
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