Geodark
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Yeah, think that is going to be my Saturday morning stuff. Going to go out and check tyre pressure now I think - haven't needed to check them for the last 6 months and the batteries are gone in the tpms!
VCU Torque test results
- Thread starter The Mad Hat Man
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Geodark
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Just done the OWU test, car cold and cold outside, Car been stood all night so VCU totally cold. did 3 tests and got between 50 seconds and 115 seconds using 6kg weight (all i had handy) This is a recon VCU I have just stuck on bought from Ebay. Those timings seem ok?
Geodark
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my maths is crap - its should have been 50 seconds and 75 seconds, not 115! stil havent had enough coffee - just to clarify - timings were from just under a minute to 1 minute and 15 seconds.
GrumpyGel
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How long was the bar - that's a pretty slow time I believe if its a 6kg weight on a 1.2m bar.
Geodark
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1.2m bar, vcu I took off and sent back was 45 seconds from what I can remember. dodgy reckon you reckon? I will keep an eye on it and if it starts getting any worse I will order another one and from Bell this time instead of Ebay. What do they say danger time is - over 90 seconds?
GrumpyGel
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My take on it is that its not a precise art!
Any time over a minute and you have to be prepared to replace it sooner rather than later - 90 seconds would definitely be change it. That is with a 5kg weight though, the times would be less with 6kg on - those who can do the sums, such as @Hippo may provide more advice.
Geodark
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Will keep an eye on it and give it a weekly check, if it starts getting any worse I will grab another one. Hopefully it will last till after xmas - dont think the wife would be happy if I started to spend more money haha.
Might try after a drive this time in case the discs hadn't released properly or anything like that.
Might try after a drive this time in case the discs hadn't released properly or anything like that.
GrumpyGel
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I picked up a scrap Freelander a while ago. It hadn't been used for quite a while and I never drove it.
I did a 1WUT on it and it came back as 3 minutes! After a few more goes it went down to 2 minutes. As it happens the IRD on that looked in OK nick. I've got it im my garage for when I'm brave enough to go back to 4WD
Geodark
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This had been stood since Friday evening - dont know if that makes any difference, will give it a check one night this week. Will give it a drive round the block first to make sure the liquid is distributed Off to cook dinner and crack open a few beers this afternoon I reckon
Off to cook dinner and crack open a few beers this afternoon I reckon 
Alibro
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If they put too much fluid in it can be over tight, also maybe they didn't clean it out thoroughly enough and it will need a couple of hundred miles to properly mix the new fluid through it. The old fluid may still be in between the plates making it more sticky than it will be after some use.
Geodark
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Never thought of that. Its only done 30 miles in the last week. I will keep an eye on it and see how it goes.
Just for a reality check - Just done mine again at 140k miles ambient 8C 1.2 bar - after a run round the block and a couple of roundabouts to just stir things up
5Kg 30s
8kg 13s
Mine at 130k miles ambient 20c was
5kg 28s
8kg 12s
My daughter's new GKN with 10k miles on it - same setup (don't remember ambient but it was summer) was
5Kg 24s
8kg 12s
We would encourage you to use 5kg and 8kg on a 1.2m bar so we can collect as wide and consistent a database for ourselves as possible.
both Mad Hat Man and Hippo have tried to get people to just DO THIS TEST and REPORT YOUR RESULTS but with poor response.
Pardon my shouting (not directed at you personally) but it's a reasonable request to an intelligent and interested audience and I cannot understand why more people don't just do it.
5Kg 30s
8kg 13s
Mine at 130k miles ambient 20c was
5kg 28s
8kg 12s
My daughter's new GKN with 10k miles on it - same setup (don't remember ambient but it was summer) was
5Kg 24s
8kg 12s
We would encourage you to use 5kg and 8kg on a 1.2m bar so we can collect as wide and consistent a database for ourselves as possible.
both Mad Hat Man and Hippo have tried to get people to just DO THIS TEST and REPORT YOUR RESULTS but with poor response.
Pardon my shouting (not directed at you personally) but it's a reasonable request to an intelligent and interested audience and I cannot understand why more people don't just do it.
What does the car feel like when you drive slowly on full lock? Mine slows down slightly, as if a brake was binding. My one-wheel-up test was only done with 5kg at 1.2m but in quite cold weather, and I think it took something like 50 seconds.This had been stood since Friday evening - dont know if that makes any difference, will give it a check one night this week. Will give it a drive round the block first to make sure the liquid is distributed
If you do that in reverse and it is even more marked I would think yours is getting past it
A OWUT of under a minute seems to be just acceptable, however 30 seconds is better. With times approaching 1 minute, it suggest that the transmission is being loaded up, your dragging when tuning proves as much.
Yes, I think that was the conclusion the group came to at the time. It's not great, I know, but I'm going to just continue monitoring it for now, as I need to be careful about how much more I throw at this car. It was only a stopgap and just at the minute, it's a bit of a money pit. I've already chucked more at it than it's worth! I'll try to post back on here with updates as it progresses. Irritatingly, it had a reconditioned VCU not long before I got it. I don't think this one has done 12,000 miles yet!A OWUT of under a minute seems to be just acceptable, however 30 seconds is better. With times approaching 1 minute, it suggest that the transmission is being loaded up, your dragging when tuning proves as much.
Last edited:
Hippo
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If you test a vcu outside of its linear response you will not get precise comparable times.
The origional idea of the test was to collate results. This didn't happen fast enough so the next best thing to do is test yer own vcu regular, to see if its result times start to change. If they do then something is happening...
The length of bar (pivot to weight distance) and the weight used, make up the force applied during the test.
Bar length x weight x angular velocity = force in Nm
A 1.2m bar with 5kg provides:
1.2 x 5 x 9.8 = 59Nm, which isn't enough force to test a vcu in its linear responce.
If you wish to use 5kg you need to make the bar longer, at nearly 2 meters to apply the ideal force.
The graph below shows the responce of a vcu with various weights on a 1.2meter bar. The graph is made up of two parts. A curve section and a straight line section, joined together. The straight line section is where you need to test the vcu. It will provide a regular reliable time which is comparable. The straight line section is where the vcu test times provide a clear linear proportional responce.
OneWheelUpTestResultGraph 3paXgcc
If you test a vcu on the curved section you are testing it where it doesn't provide a linear responce. Times measured will vary by up to a third. Occasionally more. You will not get comparable consistent results. That is why peeps post up times which vary by up to a third. When repeating the same test straight away, result times vary by too much. Its a pointless result if this happens.
The OWUT One Wheel Up Test is designed to apply a known force to the vcu. That force must be greater than 90Nm. The easy figure to use is the origional 8kg weight on a 1.2m bar.
1.2 x 8 x 9.8 = 94Nm
If you test in the linear section of the graph you will get more reliable results.
When you first start the test you have to start the bar turning just before 45 degrees. This is to allow the force applied to take up the strain and start applying said force to the vcu, to overcome its internal resistance against the force applied. 5kg at 1.2m only applies two thirds of the force needed. This means the way you let go of the weight before 45 degrees has a potentially more noticeable affect/importance on the result. Drop it to start and it will kick start the test and provide a faster time as the force applied becomes initially stronger. Let go gently and the time will decrease. Faster times are created by tricking the force applied into being more forceful. It's hard to put into words. You don't get the same problem when testing in the linear section with enough force, where increases in force applied don't change the result time by much. But a failing vcu will give a more noticeably result time which stands out.
There are too many peeps changing their vcu for recon's only to find the variation in test times by not applying enough force during the test, means your recon and old vcu can provide the same test time.
When a working vcu starts to fail its time will increase noticeably. You don't get this if yer not applying enough force. Theres too much room for variation in results if yer not putting enough force on the vcu.
A vcu only needs to be turned one full rotation for it to mix the fluid inside fully. The Turnip Test is also a valid test to perform.
When applying force to a vcu you have to overcome its internal resistance against that force, in order to test it. The force applied is whats needed to turn the vcu. To do this we apply enough force to test in the linear section of the graph. To ensure a fair test we start the bar turning just before 45 degrees in order to start turning the vcu before the test starts.
If you apply 94Nm of torque (8kg on a 1.2meter bar) or more you will be applying enough force to the vcu to be able to test it in its straight line linear section of the graph where applied force gives a proportional result. Hence why 8kg on a 1.2m bar is preferred.
The origional idea of the test was to collate results. This didn't happen fast enough so the next best thing to do is test yer own vcu regular, to see if its result times start to change. If they do then something is happening...
The length of bar (pivot to weight distance) and the weight used, make up the force applied during the test.
Bar length x weight x angular velocity = force in Nm
A 1.2m bar with 5kg provides:
1.2 x 5 x 9.8 = 59Nm, which isn't enough force to test a vcu in its linear responce.
If you wish to use 5kg you need to make the bar longer, at nearly 2 meters to apply the ideal force.
The graph below shows the responce of a vcu with various weights on a 1.2meter bar. The graph is made up of two parts. A curve section and a straight line section, joined together. The straight line section is where you need to test the vcu. It will provide a regular reliable time which is comparable. The straight line section is where the vcu test times provide a clear linear proportional responce.
OneWheelUpTestResultGraph 3paXgcc
If you test a vcu on the curved section you are testing it where it doesn't provide a linear responce. Times measured will vary by up to a third. Occasionally more. You will not get comparable consistent results. That is why peeps post up times which vary by up to a third. When repeating the same test straight away, result times vary by too much. Its a pointless result if this happens.
The OWUT One Wheel Up Test is designed to apply a known force to the vcu. That force must be greater than 90Nm. The easy figure to use is the origional 8kg weight on a 1.2m bar.
1.2 x 8 x 9.8 = 94Nm
If you test in the linear section of the graph you will get more reliable results.
When you first start the test you have to start the bar turning just before 45 degrees. This is to allow the force applied to take up the strain and start applying said force to the vcu, to overcome its internal resistance against the force applied. 5kg at 1.2m only applies two thirds of the force needed. This means the way you let go of the weight before 45 degrees has a potentially more noticeable affect/importance on the result. Drop it to start and it will kick start the test and provide a faster time as the force applied becomes initially stronger. Let go gently and the time will decrease. Faster times are created by tricking the force applied into being more forceful. It's hard to put into words. You don't get the same problem when testing in the linear section with enough force, where increases in force applied don't change the result time by much. But a failing vcu will give a more noticeably result time which stands out.
There are too many peeps changing their vcu for recon's only to find the variation in test times by not applying enough force during the test, means your recon and old vcu can provide the same test time.
When a working vcu starts to fail its time will increase noticeably. You don't get this if yer not applying enough force. Theres too much room for variation in results if yer not putting enough force on the vcu.
A vcu only needs to be turned one full rotation for it to mix the fluid inside fully. The Turnip Test is also a valid test to perform.
When applying force to a vcu you have to overcome its internal resistance against that force, in order to test it. The force applied is whats needed to turn the vcu. To do this we apply enough force to test in the linear section of the graph. To ensure a fair test we start the bar turning just before 45 degrees in order to start turning the vcu before the test starts.
If you apply 94Nm of torque (8kg on a 1.2meter bar) or more you will be applying enough force to the vcu to be able to test it in its straight line linear section of the graph where applied force gives a proportional result. Hence why 8kg on a 1.2m bar is preferred.
Thanks Hippo, that's all useful stuff! I would have to look back through my posts on here to remember what weight I used. Will try to do it again one day when I have more time, and document it a bit better. Couple of observations though:
1. We're trying to apply a "torque" rather than a "force" to the VCA in this test.
2. Velocity doesn't come into it. Your later calculations don't have velocity in them.
3. The torque (in your example) of 94 Nm is ONLY being applied when the bar is horizontal. Obviously, to provide a constant torque, you'll need something like a big clock spring. If you hang the weight on the bar and you put the bar vertical, there will be zero torque applied. If the 1.2m bar is at 60 degrees above the horizontal, and you have your 8kg weight on the end, you'll be applying 0.6 X 8 X 9.8 = 47Nm. (Because at 60 degrees, the weight is only 0.6m away from the centre of the hub). At 45 degrees, you'll be applying 0.85 x 8 x 9.8 = 67Nm. At 30 degrees you'll be applying 1.04 x 8 x 9.8 = 81.5 Nm. At 10 degrees you'll be applying 92.5 Nm and at 0 degrees, when the bar is horizontal, you'll be applying the full 94 Nm. (obviously all these neglect the weight of the bar itself, which would be messy to factor into the calculation)! Not that this detracts from the test in any way. As long as we all do the same thing, we're comparing like with like.
1. We're trying to apply a "torque" rather than a "force" to the VCA in this test.
2. Velocity doesn't come into it. Your later calculations don't have velocity in them.
3. The torque (in your example) of 94 Nm is ONLY being applied when the bar is horizontal. Obviously, to provide a constant torque, you'll need something like a big clock spring. If you hang the weight on the bar and you put the bar vertical, there will be zero torque applied. If the 1.2m bar is at 60 degrees above the horizontal, and you have your 8kg weight on the end, you'll be applying 0.6 X 8 X 9.8 = 47Nm. (Because at 60 degrees, the weight is only 0.6m away from the centre of the hub). At 45 degrees, you'll be applying 0.85 x 8 x 9.8 = 67Nm. At 30 degrees you'll be applying 1.04 x 8 x 9.8 = 81.5 Nm. At 10 degrees you'll be applying 92.5 Nm and at 0 degrees, when the bar is horizontal, you'll be applying the full 94 Nm. (obviously all these neglect the weight of the bar itself, which would be messy to factor into the calculation)! Not that this detracts from the test in any way. As long as we all do the same thing, we're comparing like with like.
Hippo
Lord Hippo
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1. A torque is a turning force. Some times called a twisting force. We're just after an easy to do comparable test. It's been going on for 10 years and currently has 114,000 views on my youtube.
2. Angular velocity is assumed to be constant as we're using gravity as our source of energy. Not perfect due to angles i agree but it's the same for everyone doing the test (even those who are up side down) so its an eggcepted oft set we ignore. Hence why Nm applied needs to be in the linear range where theres enough to get the vcu turning. If weight and bar length are the same then the tests are the same in theory between members.
3. Yer but no but. We refer in general to the force applied at the horizontal only. Reason being it would be too complicated to include applied force as the bar turns, in the name. We could also take into account rate of eggcelleration anorl as the angular velocity varies slightly as opposed to being constant. It all counts but makes it even more complex. Hence refering to the bar length and weight only. That's enough for peeps to follow. We refer to Nm at the horizontal to remind peeps of the forces involved. Some are daft enough to use a wheel nut instead of the drive shaft nut. So again a differing measurement if not following the test correctly. Not everyone realises at first just how much force we're using. Plastic broom handles have been hurt when used for these tests. I've had weights up to 26kg on my vcu before.
To apply a constant known force we put a rope over a tree branch and pulleys with weight on it. The rope was wrapped round a make shift wheel to take the rope, secured ro my hippo's wheel. This gave us a 1meter diameter or 50cm bar with end result of hundreds of Nm force applied constantly to my vcu via the rope. We put enough in to see the vcu "activate" as it would when working in real life. Considering all the messing about with vcu's i've done over the years... it was quite magical to see it happen in our test in front of us.
1. A torque is a turning force. Some times called a twisting force. We're just after an easy to do comparable test. It's been going on for 10 years and currently has 114,000 views on my youtube.
2. Angular velocity is assumed to be constant as we're using gravity as our source of energy. Not perfect due to angles i agree but it's the same for everyone doing the test (even those who are up side down) so its an eggcepted oft set we ignore. Hence why Nm applied needs to be in the linear range where theres enough to get the vcu turning. If weight and bar length are the same then the tests are the same in theory between members.
3. Yer but no but. We refer in general to the force applied at the horizontal only. Reason being it would be too complicated to include applied force as the bar turns, in the name. We could also take into account rate of eggcelleration anorl as the angular velocity varies slightly as opposed to being constant. It all counts but makes it even more complex. Hence refering to the bar length and weight only. That's enough for peeps to follow. We refer to Nm at the horizontal to remind peeps of the forces involved. Some are daft enough to use a wheel nut instead of the drive shaft nut. So again a differing measurement if not following the test correctly. Not everyone realises at first just how much force we're using. Plastic broom handles have been hurt when used for these tests. I've had weights up to 26kg on my vcu before.
To apply a constant known force we put a rope over a tree branch and pulleys with weight on it. The rope was wrapped round a make shift wheel to take the rope, secured ro my hippo's wheel. This gave us a 1meter diameter or 50cm bar with end result of hundreds of Nm force applied constantly to my vcu via the rope. We put enough in to see the vcu "activate" as it would when working in real life. Considering all the messing about with vcu's i've done over the years... it was quite magical to see it happen in our test in front of us.
Ah! The wheel with the rope round it is a brilliant idea! Yes, that would give you a pretty constant torque. (Although how on earth did you get a metre diameter wheel into the wheelarch)?! Did you have something like a tractor wheel bolted to the outside of the road wheel to get it clear of the bodywork or something? Just out of interest, when you use the rope, is your graph a straight line? Does the VCU (or should I say, does a healthy VCU!) have a linear characteristic, or is there a step in it above a certain speed? When you say you've had enough torque on there to "activate" it, I'd always imagined that these things had a fairly linear response so that the faster the speed the greater the torque and that torque would be proportional to the speed, but does there come a speed where it suddenly just "locks"?
This is all interesting. The Freelander replaces a Nissan X-Trail and they have a completely different 4WD system. There's a multi-plate clutch in the nose of the rear diff which is electrically actuated, so you can have a switch on the dash for 2WD, "Auto" and "Lock". I thought that was a better system than the viscous one that LR use, and true enough, it was one of the few parts of the X-Trail that never gave us a minute's bother in the whole time we had the car, but from the little bit of driving on mud and wet grass that I've done, the Freelander does seem to have better traction!
Thanks you so much for doing this. It's a really valuable resource.
P.S. I think you can neglect acceleration completely. Certainly at the speeds I've been looking at, it's been negligible. If anything, if you wanted to "finesse" it more, might the weight of the bar itself be the next thing to try and account for?
