VCU Torque test results

Bife · Sep 12, 2024

@seraphin 's results also show a linear trend with 1/time
Only 3 points so not conclusive but pretty good

VCU Torque test results

stolen from Aulro... Testing is accomplished by keeping the housing stationery and having the hub rotate with a constant speed of 75 rpm. Temperature is being measured by means of a thermo coupling on the outside of the housing. Torque transfer in Nm vs. temperature (C) at a speed difference...

www.landyzone.co.uk

Bife · Sep 12, 2024

To give some idea of how (in)accurate my method is:

@Hippo : 6.1 kg gives 25 s, so my prediction for 10 kg is 15 s, his actual 10 kg value is 12 s, 'error' = 3 s

@mrblockpaving: 6 kg gives 7 s, so my prediction for 10 kg is 2.4 s, his actual 10 kg value is 2.4 s, 'error' = 4.6 s (but timing errors at such low times will be big)

@seraphin: 6.1 kg gives 30 s, so my prediction for 10 kg is 18 s, his actual 10 kg value is 12 s, 'error' = 5 s

Above should be warning not to use a sledgehammer to open peanuts, as its not totally accurate, but what's 5 seconds either way?

Obviously 5 s becomes more significant at lower times, but if we have low times we dont have to be worried anyway

GrumpyGel · Sep 12, 2024

What I find amazing is that, like, windows are solid... but we can see out of them.

Blows my mind.

Can someone please explain?

And like, how does turning that round thing in front of the seat on the right make the car go left or right? Unbelievable. Its like magic.

Hippo · Sep 16, 2024

Bife said:
...
We could do exactly the same thing if we change the stick length L, to give comparisons for different stick lengths by changing W1 and W2 for L1 & L2 in my equation (1) above, keeping the Weight the same:

t2 = t1 x (L1/L2) Equation (2)

For example to 'change' times with a 100 cm bar to a 120 cm to make valid comparisons, just multiply the times for a 100 cm bar by 100/120, or 5/6 (0.833)
...

Why are you trying to undo all the work we have done on vcu testing with maths nonsense?

You can't compare 5kg at 1.2m with 8kg at 1.2m, by multiplying the result to convery one to the other. 5kg at 1.2m doesn't put enough force on the vcu to proove its NOT stiffening up.

To do the test correctly you have to apply enough force to get the vcu to turn in its linear mode. If it can't do this its a sign its stiffening up. Thsts what the test id looking for.

Hippo · Sep 16, 2024

Bife said:
...
All I'm trying to do is work out how to compare a 5 kg test result with an 8 kg result, for example, or a 1 m bar result with a 1.2m result, not describe the whole operating range of the VCU

You can't compare results of different applied force. You are over complicating the test with rpm nonsense.

The test is designed to be done where the results are on the linear line of my graph. If the time creeps into the non linear curve of the graph, something has changed. Often the vcu stiffening unless the brakes are catching.

Hippo · Sep 16, 2024

Avocet1 said:
Er... OK... but that seems an odd thing to do? Surely what we're interested in, is the operating range of the VCU?! Indeed, one o the most frequent criticisms of the OWUT is that it is carried out way outside the operating range of the VCU, at such low toques and speeds that a slightly binding brake can make a big difference.

I'm sure you can regard the difference between a 5 and 8kg weight s being linear, but where it actually matters, we should be using a 50 or 80 kg weight!

Incidentally, Hippo's original graphs in that link I posted, were some way off being linear. Arguably linear at the higher weights, but way off at the lower ones:

View attachment 325794

The results of 8kg to 14kg are linear. Its what we call the straight line. We're looking to see if the 8kg 1.2m result creeps up the curve to the left of the 8kg result, which indicates stiffening or brake binding.

26kg is the highest weight I have put on a vcu doing the test. In another test we put over 50kg which was over 400Nm. Problem is thats not easily repeatable on a diy basis. Results were facinating.

Hippo · Sep 16, 2024

Bife said:
That's because the plot above is time vs weight, NOT one over time (1/time) vs weight. I wouldnt say that graph is linear anywhere

And yes, it would be nice to be able to investigate the behaviour under operating conditions and torques and rotations etc, but that is pretty much impossible so @Hippo cleverly developed a benchmark test that can give an indication of a ****ed or getting-****ed VCU. its pretty much like looking at the oil in a gearbox for metal particles - the metal particles dont cause the gearbox failure but they show it is happening.
This is not infallible, for example my VCU is still working even though it gives very quick times, but the OWUT identified it was a slack VCU and even though it is working it almost certainly isnt working in the same way as a stiffer one would

At the end of the day, if the VCU is stiff at low shear rates (RPM) then it is pretty much sure to be ****ed (probably more so) at the higher RPM when you are driving, and so it is an excellent way of checking if the VCU is OK or on its way out or ****ed

A test doesnt have to give accurate values, or even nothing other than trends with no absolute values, to give very useful information

My result graph has a near enough straight line for results 8kg to 14kg. Thats linear and straight enough for us.

Vcu's have been tested on and oft road. Put sensors on the props with counters measuring both props. I have toys at work that can do this. I have also monitored the abs. It all points to the OWUT being good enough for what we need. DIY preventative monitoring.

If you wheel spin the front wheels from stationary, the rears will turn after 1/3 rev of the front wheels spinning. Thats on a healthy origional and replacement gkn vcu.

Hippo · Sep 16, 2024

Bife said:
Simplifying all the above, I think that:

1. to convert (roughly) tests done for a stick of 1.2 m (or any other length) with a weight of 5kg to be able to compare them (at least roughly) with tests done with a 1.2 m stick (or any other length as long as its the same) BUT with an 8kg weight we can simply times them by 5/8 (0.625)

2. Similarly, to 'change' times with a 100 cm bar to a 120 cm to make valid comparisons, just multiply the times for a 100 cm bar by 100/120, or 5/6 (0.833) to give a value you can compare with the 120 cm bar result

3. To 'change' times with a 100 cm bar with 5 kg to a 120 cm bar with 8 kg to make valid comparisons, just halve the times for a 100 cm bar with 5 kg to give a value you can compare with the 120 cm bar with 8kg result

NB!!! Above only roughly works, but I think enough to give a 'feel' for comparisons between values

This is all wrong. 5kg weight at 1.2m bar doesn't put enough force on the vcu to see if its turning fast enough. Its the crux of what we're looking for: is the vcu turning ok or stiffening. If its ok it will be in the linear zone.

Its like timing a car 0 to 60mph and multiplying the result to give the 0 to 100mph result, but max speed of the car is 90mph.

Hippo · Sep 16, 2024

GrumpyGel said:
What I find amazing is that, like, windows are solid... but we can see out of them.

Blows my mind.

Can someone please explain?

And like, how does turning that round thing in front of the seat on the right make the car go left or right? Unbelievable. Its like magic.

You can see out of some windows but not see in. How can a transparent window not be transparent?

Hippo · Sep 16, 2024

Bife said:
To give some idea of how (in)accurate my method is:

@Hippo : 6.1 kg gives 25 s, so my prediction for 10 kg is 15 s, his actual 10 kg value is 12 s, 'error' = 3 s

@mrblockpaving: 6 kg gives 7 s, so my prediction for 10 kg is 2.4 s, his actual 10 kg value is 2.4 s, 'error' = 4.6 s (but timing errors at such low times will be big)

@seraphin: 6.1 kg gives 30 s, so my prediction for 10 kg is 18 s, his actual 10 kg value is 12 s, 'error' = 5 s

Above should be warning not to use a sledgehammer to open peanuts, as its not totally accurate, but what's 5 seconds either way?

Obviously 5 s becomes more significant at lower times, but if we have low times we dont have to be worried anyway

So thats proof its a load of rubbish. Plotting the results in a different way tells us nowt.

We film the test as it makes it easier to time stamp when to start and stop the timer. This reduces inaccuracies. If my result of 8kg at 1.2m increased from 16 seconds to 21, that would be enough to warm me somefink was different. I would repeat the test many times to confirm.

Hippo · Sep 16, 2024

The reason why the OWUT One Wheel Up Test is so important is because many years ago we had Freelander 1 owners come on ere with cracked ird's and rear diff's. They wanted to know why this happened. We wanted to know how to avoid it happening. Hence the test was created. Pic's below of what we're trying to avoid.

Freelander 1 - Cracked Freelander 1 IRD

Ere's some photo's of a broke'd Freelander ird (intermediate reduction drive). Think of it as a fixed ratio transfer box which takes the drive from the gearbox and passes it to the front wheels via a diff, and also to the rear wheels via the pinion gear. Unfortunately this one has failed...

www.landyzone.co.uk

Bife · Sep 17, 2024

Hippo said:
So thats proof its a load of rubbish. Plotting the results in a different way tells us nowt.

We film the test as it makes it easier to time stamp when to start and stop the timer. This reduces inaccuracies. If my result of 8kg at 1.2m increased from 16 seconds to 21, that would be enough to warm me somefink was different. I would repeat the test many times to confirm.

Fair enough
But 5 seconds difference between results for different VCUs is a completely different thing to 5 seconds between results for the same VCU.

Bife · Sep 17, 2024

Hippo said:
You can see out of some windows but not see in. How can a transparent window not be transparent?

Handbags Gentlemen, please

Hippo · Sunday at 10:45

Bife said:
Handbags Gentlemen, please

The fing that concerns me about your vcu is when you said it was too hot to touch. The correct fluid fails quickly when getting too hot. Somefink for you to monitor.

Hippo · Monday at 07:53

Bife said:
Fair enough
But 5 seconds difference between results for different VCUs is a completely different thing to 5 seconds between results for the same VCU.

Early on when testing started we had access to Freelanders with an origionsl gkn manufactured vcu on low miles. Gkn was used by LR on the track when building the Freelander 1. So thats our go to datum for how a 'good' vcu should perform. If the OWUT test is repeated correctly across different vcu's, it should give us comparable results. We're looking out for stiffening vcu's that resist being turned, compared to the origional gkn results. Stiffening vcu's put a greater strain on the transmission with something going bang if they don't get removed.

Bife · Monday at 19:10

Hippo said:
The fing that concerns me about your vcu is when you said it was too hot to touch. The correct fluid fails quickly when getting too hot. Somefink for you to monitor.

It was too hot to hold, as in for a long time comfortably, not too hot to touch. I think the pain threshold temperature is surprisingly low, under 50 C.
Anyway I will continue to monitor it, to check it doesnt get too stiff, with the test

EDIT, I would have said it was hot, not painful, so around 40 C. Probably not doing it any good, but then again we were an hour roaring around and I wont do that very often at all. And here 35 C during summer is very usual and we get 40 pretty much every year for some time

VCU Torque test results

Bife

Active Member