Shim for viscous coupler (2nd post)
Gonis
Band Wagon
Hello, I searched forum for answers, but didnt found anything. So, about the issue:
Im planing to install wagon's VC to my project car, and decided to test it before installation. The way I am testing it:
1. Fix VCU to the table.
2. Mount 32mm socket with long light bar.
3. Put some weigth on the end of the bar.
4. Let it spin the VCU from 1h to 4-5h position and see how much time it takes.
The problem is, that I dont know how much torque I should use (bar length x weigth x g) and how long it should take to spin VCU. Only resource I found is video of Land Rover Freelander VCU test, but I dont know if the result should be the same as wagons VCU.
In video using ~60Nm torque it takes about 12s to turn VCU about 45deg. My VCU resulted in about 7s using ~50Nm torque. So there is two options: wagons VCU is softer than Freelanders, or my VCU just simply worn out.
Can somebody test a wagons healthy VCU and share the results?
I cant do the e-brake test, because I didnt made brakets for shaft yet and I am not using any e-brake in my project car.
Thank you in advance.
Im planing to install wagon's VC to my project car, and decided to test it before installation. The way I am testing it:
1. Fix VCU to the table.
2. Mount 32mm socket with long light bar.
3. Put some weigth on the end of the bar.
4. Let it spin the VCU from 1h to 4-5h position and see how much time it takes.
The problem is, that I dont know how much torque I should use (bar length x weigth x g) and how long it should take to spin VCU. Only resource I found is video of Land Rover Freelander VCU test, but I dont know if the result should be the same as wagons VCU.
In video using ~60Nm torque it takes about 12s to turn VCU about 45deg. My VCU resulted in about 7s using ~50Nm torque. So there is two options: wagons VCU is softer than Freelanders, or my VCU just simply worn out.
Can somebody test a wagons healthy VCU and share the results?
I cant do the e-brake test, because I didnt made brakets for shaft yet and I am not using any e-brake in my project car.
Thank you in advance.
Comments
So, I mounted that VCU and it seemed to be worn out. I had another one VCU, which gave the same bentch testing results, but on car it worked like a charm. So these tests on bench are worthless. It needs to be tested on car.
In that case I have another question about VCU. I read somethere that it is possible to shim VCU and make it more aggresive, but I cant find exact information where it needs to be shimmed and what kind of shim to use. Maybe someone knows more about this?
As for making the VC more aggressive, I assume you mean making it lock up more quickly. That can probably be accomplished by using a higher viscosity PDMS fluid. It may not be practical, however. Greater resistance in the VC will make it behave more like a solid shaft, creating drag and tire-scuffing in turns. I rebuilt my VC with fluid which I believe to be 10k cSt greater than the stock fluid. This is just a guess based on the fluid that came out of the unit compared visually to what I replaced it with. The drag is quite noticeable under normal driving when compared to driving with the RWD disengaged. Kind of like driving with the brake on. The VC is designed to allow a certain amount of slippage, reducing that slippage affects driveability.
Yes, making it stiffer will result in increased drag and decreased durability of VCU. The drag issue can be solved with using slightly different tires, that will compensate some difference in transfer ratios between front and rear. After that, the lock up can be the same as factory, but maximum resistance should be inceased.
It can be achieved by using more viscous fluid, but somewhere I read about using shim (unluckely I cant find the source anymore). I dont know which would be better in all aspects.
so a car with said fluid or shim would make for a car only tracked or something?
The "drag" I referred to is created by insufficient slippage of the VC when turning, similar to a solid shaft situation.
The VC consists of a stack of 79 (iirc) plates of 2 different styles (see picture). The plates are stacked alternately, 39 splined to the shaft, 40 splined to the housing. The metal ring keeps the shaft-splined plates separated, creating .008 in. clearance between each plate and the one next to it. This space is filled with the PDMS fluid. Driving force is transmitted by the drag created by the fluid between the plates when one set of plates is rotating at a different speed from the other. The amount of torque transmitted is determined by the total surface area of the plates, and the viscosity of the fluid (this is a simplified explanation). To increase the torque capacity of the VC, the total surface area of the plates must be increased by increasing their diameter or increasing the number of plates. I don't see any way that a simple shim could change this.