Hippo
Lord Hippo
Its not the same test. The one wheel up test puts a known force on the vcu.
Force is the most important bit. Without a known reference of force applied, a test would be invalid. Force is key to understanding how the test works.
The one wheel up test supplies a time to turn 45 degrees to the horizontal. That means the test turns 45 degrees, and stops at the horizontal. The time taken to do this is measured, as a reference of force applied. The bar should start turning before the test, so it takes up the slack in the transmission and starts to apply the force to the vcu.
The force measurement is the pressure applied by the weight, due to the length of the bar, compared against a fixed reference = gravity. Betterer known at torque. If you hold a 2kg object close to your chest, its weight is a certain amount. If you hold the same 2kg object at arms length, it feels heavier, but the weight is still the same amount. Why? The answer to this is key to why a known force is so important. Torque = force x distance.
The weight of an object changes with distance. Thats why the same 2kg weight feels heavier at arms length. Bit like when you were at school and did balancing. 10kg at 1m balanced perfectly with 2kg at 5m on a sea saw. The one wheel up test uses the same principle. A known weight on the end of a bar of known length. The known length is the measurement of the distance between the pivot point (drive shaft wheel nut) to the connection of the weight on the end.
The best way to display the results are to measure torque at a certain point, depending on the angle. That means
Torque = weight x gravitational acceleration x (length of weight to pivot x cos Angle)
For a 1.2m bar and 4kg weight:
Torque = 4 x 9.8 x (1.2 x cos Angle) = torque in Nm
Measuring torque (force applied) is the bet thing to do. Torque against time is even betterer.
Buts its too complicated so after much debate we settled for the time to turn 45 degrees to the horizontal, with a known weight and known length of bar (distance from pivot to weight). The torque graph I posted above shows the torque applied verses angle, which is nearly the same during the test of 45 degrees to the horizontal. Hence weight and length factors still count. Cos Angle is taken out as were timing in seconds the amount of time it takes to turn.
Physics experts on ere such as young porky will have spotted a fundamental problem with this test. The weight of the bar needs to be taken into account too. The bar applies a varying force as it turns. At 3 oclock its force is greater (maximum) than 2ocolck. We can take out this factor by performing the test several times, each time with a different weight. Subtract one result from the other to give the weight factor only, with no bar weight factor. Hence 6kg result 2kg result = 4kg only known weight applied.
Sadly this isnt an option as very few do the test anyway. Why? Not really sure myself. They either cant be bothered or dont think its worth doing. I appreciate some may feel its not something they can do. Some wont have a big enough socket. Some argue it wont work. Some argue a better test is appropriate. A common theory of changing the vcu at 70k seems to win most views. Why? Because a number have failed around or above this mileage. Without testing theyre happy to pay for a replacement when they may not need it. Bit like changing all Jatco autos at 100k miles as they suffer failures at that mileage.
I can confirm my vcu works ok. Last tested a few weeks ago. Ive posted my results loads on times on ere, and other forums. Tried to get other forums involved in the testing too. Tested vcus on other peeps vehicles anorl. One of which compared nearly the same to mine, and he still changed it. After years of debate (including a few arguments) we still dont have enough test results. Without that vital input, were stuck.
Force is the most important bit. Without a known reference of force applied, a test would be invalid. Force is key to understanding how the test works.
The one wheel up test supplies a time to turn 45 degrees to the horizontal. That means the test turns 45 degrees, and stops at the horizontal. The time taken to do this is measured, as a reference of force applied. The bar should start turning before the test, so it takes up the slack in the transmission and starts to apply the force to the vcu.
The force measurement is the pressure applied by the weight, due to the length of the bar, compared against a fixed reference = gravity. Betterer known at torque. If you hold a 2kg object close to your chest, its weight is a certain amount. If you hold the same 2kg object at arms length, it feels heavier, but the weight is still the same amount. Why? The answer to this is key to why a known force is so important. Torque = force x distance.
The weight of an object changes with distance. Thats why the same 2kg weight feels heavier at arms length. Bit like when you were at school and did balancing. 10kg at 1m balanced perfectly with 2kg at 5m on a sea saw. The one wheel up test uses the same principle. A known weight on the end of a bar of known length. The known length is the measurement of the distance between the pivot point (drive shaft wheel nut) to the connection of the weight on the end.
The best way to display the results are to measure torque at a certain point, depending on the angle. That means
Torque = weight x gravitational acceleration x (length of weight to pivot x cos Angle)
For a 1.2m bar and 4kg weight:
Torque = 4 x 9.8 x (1.2 x cos Angle) = torque in Nm
Measuring torque (force applied) is the bet thing to do. Torque against time is even betterer.
Buts its too complicated so after much debate we settled for the time to turn 45 degrees to the horizontal, with a known weight and known length of bar (distance from pivot to weight). The torque graph I posted above shows the torque applied verses angle, which is nearly the same during the test of 45 degrees to the horizontal. Hence weight and length factors still count. Cos Angle is taken out as were timing in seconds the amount of time it takes to turn.
Physics experts on ere such as young porky will have spotted a fundamental problem with this test. The weight of the bar needs to be taken into account too. The bar applies a varying force as it turns. At 3 oclock its force is greater (maximum) than 2ocolck. We can take out this factor by performing the test several times, each time with a different weight. Subtract one result from the other to give the weight factor only, with no bar weight factor. Hence 6kg result 2kg result = 4kg only known weight applied.
Sadly this isnt an option as very few do the test anyway. Why? Not really sure myself. They either cant be bothered or dont think its worth doing. I appreciate some may feel its not something they can do. Some wont have a big enough socket. Some argue it wont work. Some argue a better test is appropriate. A common theory of changing the vcu at 70k seems to win most views. Why? Because a number have failed around or above this mileage. Without testing theyre happy to pay for a replacement when they may not need it. Bit like changing all Jatco autos at 100k miles as they suffer failures at that mileage.
I can confirm my vcu works ok. Last tested a few weeks ago. Ive posted my results loads on times on ere, and other forums. Tried to get other forums involved in the testing too. Tested vcus on other peeps vehicles anorl. One of which compared nearly the same to mine, and he still changed it. After years of debate (including a few arguments) we still dont have enough test results. Without that vital input, were stuck.