An open letter to Austen

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I don't think there is an "ideal" owner test. It's just a matter of finding, if that is possible, a test that, hopefully, will give some form of repeatable, consistent guidance to the user as to whether they are ok or need to take the car for a more detailed analysis or whether it is totally gazoobered!
A minimum test would be to show that the VCU was not "good".
 
austen said:
Rather than measuring torque, which without a controlled machine, and calibrated torque wrench is very inaccurate, we measure by "feel", We can say if its acceptable, not acceptable or on the verge, its impossible to give a definitive pass or fail. The VCU slowly deteriorates so you have to weigh up the cost to change vcu and the extra wear you are causing to the drive train as time goes by.
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I really dont know a whole lot about this, but Shirley once a month say, lifting a wheel and using a torque wrench ( preferably a spring one ) will at least give you some idea of any changes occurring to your VCU. :)

Wouldn't it ??
 
austen said:
but torque reading is affected by the rate, weight and way the force is applied, especially on something that is designed to slip
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Exactly.

Just read MHM post on how to test torque of VCU which obviously I should have read first :rolleyes:

However I still think and if I had a freebie I'd test the theory, that using a torque wrench after taking up the slack in the drive train I'd measure the force required to turn the wheel.
Not that I believe doing this will indicate the conidtion of the VCU but doing so every 1000 miles I may discern any difference and or deterioration.

That would work wouldn't it?
 
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Bromsgrove Defender said:
Exactly.

Just read MHM post on how to test torque of VCU which obviously I should have read first :rolleyes:

However I still think and if I had a freebie I'd test the theory, that using a torque wrench after taking up the slack in the drive train I'd measure the force required to turn the wheel.
Not that I believe doing this will indicate the conidtion of the VCU but doing so every 1000 miles I may discern any difference and or deterioration.

That would work wouldn't it?
Click to expand...

Not sure how repeatable it would be, i.e you lean on it a biot faster or a bit quicker than a month ago and it gives you a different reading. In theory you could push it with your little finger for long enough and it will slip, ok thats a little extreme of an example but you know what i mean. For example when i remove a vcu, if the prop bolt is tight i can see and feel the VCU slip while i'm pulling on it, the VCU then tests to be fubared, the next car i come to the bolt is no where near as tight, when i undo that bolt the vcu doesn't test but checks out perfect. But its how i apply the pressure that causes the slip.
 
If it were just a case of removing my vcu and working bearings, then fitting another vcu wiff it’s own bearings, to do the one wheel up test as below in my video, severals times wiff different vcu’s, then putting my vcu/bearings back afterwards, wiff no damage to my hippo, then I’ll volunteer my hippo for the testing. It’s a v6 though. Doesn’t matter if it takes all day. Can appreciate it’s a business etc.

As for values on and off…
The video below, shows my results from the one wheel up test. Result for that was 8kg x 9.8 gravitational acceleration x 1.2m bar = 94.08Nm. I have results from different weights somewhere too.

Results below from testing the same vcu, on it’s own, not connected to ma hippo.
Hippo said:
Rough time 22 seconds, 10.2kg, bar 0.35m, to turn 45 degrees and stop at horizontal.
10.2 x 9.8 x 0.35 = 35Nm

Have also done it at different weights, turning the same 45 degrees and stopping when horizontal, and found 60 seconds for 5.2kg, bar 0.37m
5.2 x 9.8 x 0.37 = 19Nm
Click to expand...
Would agree wiff the above comment about force on a torque wrench. Tried the same myself. If you push harder you can get it to click sooner.
 
Hippo said:
If it were just a case of removing my vcu and working bearings, then fitting another vcu wiff it’s own bearings, to do the one wheel up test as below in my video, severals times wiff different vcu’s, then putting my vcu/bearings back afterwards, wiff no damage to my hippo, then I’ll volunteer my hippo for the testing. It’s a v6 though. Doesn’t matter if it takes all day. Can appreciate it’s a business etc.

As for values on and off…
The video below, shows my results from the one wheel up test. Result for that was 8kg x 9.8 gravitational acceleration x 1.2m bar = 94.08Nm. I have results from different weights somewhere too.

Results below from testing the same vcu, on it’s own, not connected to ma hippo.
Would agree wiff the above comment about force on a torque wrench. Tried the same myself. If you push harder you can get it to click sooner.
Click to expand...

where abouts are you? quickest and easiest way is to fit vcu with bearings each time.
 
austen said:
Not sure how repeatable it would be, i.e you lean on it a biot faster or a bit quicker than a month ago and it gives you a different reading. In theory you could push it with your little finger for long enough and it will slip, ok thats a little extreme of an example but you know what i mean. For example when i remove a vcu, if the prop bolt is tight i can see and feel the VCU slip while i'm pulling on it, the VCU then tests to be fubared, the next car i come to the bolt is no where near as tight, when i undo that bolt the vcu doesn't test but checks out perfect. But its how i apply the pressure that causes the slip.
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Ok I can see where your coming from.

But

What about (for the sake of argument) timing through say 90 degrees. or possibly for greater accuracy 180 degrees.
And record the average torque of say three consecutive attempts.
 
Bromsgrove Defender said:
Ok I can see where your coming from.

But

What about (for the sake of argument) timing through say 90 degrees. or possibly for greater accuracy 180 degrees.
And record the average torque of say three consecutive attempts.
Click to expand...

My suggestion (based on Hippos's test) is do time it through 45 degs, with a known weight and extension bar. Do this for a range of vcu and we get an easily repeatable result, that joe blogs can do with minimal tools, no need for a torque wrench. I will try and give a range of acceptable times.
 
I would agree that Hippo's test would be the best one that every owner can carry out, it was the test I used as I found the tippex test a waste of time. I used a 1.2m bar and 8kg of weights = 45 degrees approx 20secs.
 
One of the problems that we have us that the torque varies, depending on the angular displacement of the bar, so the test would have to be carried out over the same angle every time. For example if the bar was vertical, then the torque being applied would be zero, with max torque when horizontal. The other point to be considered would be the initial torque would be that to overcome the resistance of the complete rear drive system.
 
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The clock and graph below show torque on the bar as it turns from 12 o’clock (vertical) clockwise through 3 o’clock (horizontal), then to 6 o’clock (vertical). The one wheel up test only times the bar passing through the red arrow phase, which is 45 degrees.

As the bar starts turning, during the green and red arrow phase, the torque placed on the vcu via the wheel and rear diff increases. When the bar is at 3 o’clock, the torque is at its highest value. If the bar were to continue turning through the blue phase, the torque would decrease.

The one wheel up test is challenged wiff the above varying torque issue. Also as said above, the test also faces the challenge of the initial slack taken up by the rear diff, and the initial phase of torque required to turn the rear diff and vcu. To overcome these problems it’s best to start the bar turning during the green arrow phase. This will allow for transmission slack to be taken up, then the vcu will start to turn/slip. All of our timed measurements so far have taken place during the red arrow phase only. I start mine where the black dot is on the green arrow. As the bar passes into the red arrow phase, I start counting the time. I stop counting when the bar gets to the end of the red arrow.

Timing only the 45 degrees during the red allow phase means the torque is nearly the same throughout the test. This is more precise than starting the test at 12 o’clock, passing through both the green and red arrows. Starting the bar turning before the red time counting phase, means the bar has had time to start turning the rear diff and vcu, which means it’s already at a steady speed ideal for measuring the test. The speed of the bar is controlled by the weight on the end of the bar, and the effect gravity has on the weight. It would be ideal to know the weight of the bar too, as this has a slight effect on the results. The heavier the bar, the faster the bar will turn.

AcIP2Aa.jpg

WheelTorqueGraph AcIP2Aa
 
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I don't wish to appear rude... And I am not taking the ****.

:eek:

I am genuinely interested....


Can someone explain in laymans terms what you are talking about? :)
 
OK DN. basically we are talking law of levers here.
if the bar is vertical then it doesnt matter how heavy the weight is, it wont turn.
The maximum turning effort is when the bar is horizontal.

so the turning moment varies between 0 when the bar is upright, to maximum when the bar is horizontal.

So the turning moment varies depending on the angle, so the angle that the bar turns is critical in determining what the Torque is that is being applied..

Understumbles?
 
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The Mad Hat Man said:
OK DN. basically we are talking lay of levers here.
if the bar is vertical then it doesnt matter how heavy the weight is, it wont turn.
The maximum turning effort is when the bar is horizontal.

so the turning moment varies between 0 when the bar is upright, to maximum when the bar is horizontal.

So the turning moment varies depending on the angle, so the angle that the bar turns is critical in determining what the Torque is that is being applied..

Understumbles?
Click to expand...


:rolleyes:

OK understumbles so far... And this applies to which bit of the vehicle under what circumstances?
 
Dartmoor Navigator said:
:rolleyes:

OK understumbles so far... And this applies to which bit of the vehicle under what circumstances?
Click to expand...


If yu are trying to design a test that measures the Torque required to turn a wheel or the VCU, you need to know what the Torque is - if it varies depending on the angle that the torque is applied, then you need to identify exactly what it is during the angle that you are turning the item....
 
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