Hippo
Lord Hippo
Thanks. Lot of reading but it will give a firm understanding of the problems we face. Would be good to be able to fit/adapt someone else's product to suit our needs. Perhaps even work backwards from the vcu temp graph with our One Wheel Up Test and Turnip Test results, to work out an idea setup (and if it's possible).Bed time reading.....
Design Analysis and Experimental Evaluation of an MR Fluid Clutch
If you are considering an MRF type application, then a product by BASF - their Basonetic MRF5020 seems to be most suitable - NOT Damper fluid which is a different animal - categorised by BASF MRF2040.
There may also be a problem when the material isnt new, in that because the fluid does not comply with a true brownian principle (the particle size is too big) it could possibly form a sediment over a couple of months. This is not a problem when new as it is readily re-dispersed. But might be if a vehicle was laid up over winter.
If any of you are maths wizards then MR fluid behavior in the shear mode can be modelled by the following formula:
Where = shear stress; = yield stress; = Magnetic field intensity = Newtonian viscosity; is the velocity gradient in the z-direction.
Great thread and I've often scratched my head trying to think of a simple way to make the FL a selectable 4x4.
It's just struck me that to do this it needs to be in addition to the VCU and work in tandem with it. If you don't then there's all the issues around IRD and diff failure to contend with.
I had a boat trailer a few years ago that had electrically operated drum brakes. They were brutal as they were either on or off and would haul the car to a stop at slower speeds. They were just electro magnets on a lever that ran against a back plate to create the torque to operate the lever and then the drum brake.
So there are electro magnets that can "slip" on a mating surface and suffer minimal wear. What if you split the FL prop in front of the VCU and add in a small flywheel/electro magnet coupling? Providing the magnets were strong enough and the flywheel diameter big enough (using available space) it would provide sufficient torque to the VCU.
Operating the 4x4 could be at the flick of a switch or linked to traction control and for the rally team could have a disengage micro-switch on the handbrake lever!
My two penneth worth
Edit. Just thought of a very good reason why it won't work, you'd need to make an electrical connection to something that is rotating in a hostile environment. Not impossible but quite a hurdle..
It's just struck me that to do this it needs to be in addition to the VCU and work in tandem with it. If you don't then there's all the issues around IRD and diff failure to contend with.
I had a boat trailer a few years ago that had electrically operated drum brakes. They were brutal as they were either on or off and would haul the car to a stop at slower speeds. They were just electro magnets on a lever that ran against a back plate to create the torque to operate the lever and then the drum brake.
So there are electro magnets that can "slip" on a mating surface and suffer minimal wear. What if you split the FL prop in front of the VCU and add in a small flywheel/electro magnet coupling? Providing the magnets were strong enough and the flywheel diameter big enough (using available space) it would provide sufficient torque to the VCU.
Operating the 4x4 could be at the flick of a switch or linked to traction control and for the rally team could have a disengage micro-switch on the handbrake lever!
My two penneth worth
Edit. Just thought of a very good reason why it won't work, you'd need to make an electrical connection to something that is rotating in a hostile environment. Not impossible but quite a hurdle..
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Great thread and I've often scratched my head trying to think of a simple way to make the FL a selectable 4x4.
It's just struck me that to do this it needs to be in addition to the VCU and work in tandem with it. If you don't then there's all the issues around IRD and diff failure to contend with.
I had a boat trailer a few years ago that had electrically operated drum brakes. They were brutal as they were either on or off and would haul the car to a stop at slower speeds. They were just electro magnets on a lever that ran against a back plate to create the torque to operate the lever and then the drum brake.
So there are electro magnets that can "slip" on a mating surface and suffer minimal wear. What if you split the FL prop in front of the VCU and add in a small flywheel/electro magnet coupling? Providing the magnets were strong enough and the flywheel diameter big enough (using available space) it would provide sufficient torque to the VCU.
Operating the 4x4 could be at the flick of a switch or linked to traction control and for the rally team could have a disengage micro-switch on the handbrake lever!
My two penneth worth
Edit. Just thought of a very good reason why it won't work, you'd need to make an electrical connection to something that is rotating in a hostile environment. Not impossible but quite a hurdle..
tiz easy (theoretically). replace silicone lube with mrf and place an electromagnetic coil around the vcu. on switching the coil on, this will magnetise the mrf and doesnt need to be in contact
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Hippo
Lord Hippo
Too late. It's mine. I pulled it out earlier. It's sat drying by the radiator.I know where there's a cheap one
...
sijwhite
Active Member
Too late. It's mine. I pulled it out earlier. It's sat drying by the radiator.
Have the doors fallen off?
be a tad difference between dampners 'n a vcu unit ..
.. centrifugal force ..
what might that do to metal particals suspended in a liquid ?
~~~~~~~
and does anyone know just what causes the vcu liquid to loose its' properties ?
i.e. loosing its' ability to change physical state from liquid to solid at a given temperature
is it heat ? .. time ? .. production quality of the 'new' liquid ?
seen it written that the vcu needs 'exercise' to stay healthy
i.e. to engage 4wd once in a while
any scientific evidence for that ?
~~~~~
rekon i'd rather have an extra lockable-from-cab coupling between the ird and vcu
de-couple for constant 2wd and saving on vcu wear 'n tear ..
re-couple for winter or off-roading ..
used to have a lockable rear diff on a hgv .. ( for snow and ice traction )
was air operated .. swith in-cab ..
problem: need air compressor and attachments ..
and leaving it 'on' when on a dry non slip surface .. meant ..
screwed rear diff and big hole in bank account ..
~~~~~
nice thing about the vcu ..
it's automatic .. few moving parts .. doesn't depend on being hooked up to sensors
or require hydraulics or electrical wiring ..
and no doubt cheaper to replace than a haldex coupling ..
~~~~
imho .. a temp sensor on/in the ird unit .. with in-cab display
would suffice in keeping-an-eye-on the condition of the vcu unit
stress equals heat .. ird starts to run hotter than 'normal .. good chance the vcu is kaputsky
( or another componenet in the drive-train ) .. or as near as ..
.. centrifugal force ..
what might that do to metal particals suspended in a liquid ?
~~~~~~~
and does anyone know just what causes the vcu liquid to loose its' properties ?
i.e. loosing its' ability to change physical state from liquid to solid at a given temperature
is it heat ? .. time ? .. production quality of the 'new' liquid ?
seen it written that the vcu needs 'exercise' to stay healthy
i.e. to engage 4wd once in a while
any scientific evidence for that ?
~~~~~
rekon i'd rather have an extra lockable-from-cab coupling between the ird and vcu
de-couple for constant 2wd and saving on vcu wear 'n tear ..
re-couple for winter or off-roading ..
used to have a lockable rear diff on a hgv .. ( for snow and ice traction )
was air operated .. swith in-cab ..
problem: need air compressor and attachments ..
and leaving it 'on' when on a dry non slip surface .. meant ..
screwed rear diff and big hole in bank account ..
~~~~~
nice thing about the vcu ..
it's automatic .. few moving parts .. doesn't depend on being hooked up to sensors
or require hydraulics or electrical wiring ..
and no doubt cheaper to replace than a haldex coupling ..
~~~~
imho .. a temp sensor on/in the ird unit .. with in-cab display
would suffice in keeping-an-eye-on the condition of the vcu unit
stress equals heat .. ird starts to run hotter than 'normal .. good chance the vcu is kaputsky
( or another componenet in the drive-train ) .. or as near as ..
DD3
New Member
It's not like LR to spot obvious mistakes...
By the time yer saved up the D4 will be starting to age and be a betterer buy.
Na - don't like them electric hand brakes!!
DD3
New Member
Yes the pillock did! Rather wet and cold after climbing out the window! Apparently fitting the tow rope wasn't fun
Was this in recent floods or has he just driven it into a river - or both?
DD3
New Member
Assume vehicle was right off?
