Uwe i agree on everything you have said i was also just as sceptical! But after him providing me with some scientific reasons as to why and how the rack would fail im not really willing to take the chance. This text was writen up by him, "Power steering obviously has assistance from hydraulic pressure pushing on a piston attached to the rack bar, that's why the steering is lighter. The way this assistance is controlled is in the valve. What it has is a thin bit of metal effectively attached to the end of the column known as the torsion bar, or T-Bar. This is designed to twist as you turn the wheel and in doing so it opens up various orifices which allows hydraulic fluid to flow. This is the clever bit in power steering as controlling these edges and openings is what aids the 'feel'. Anyway, as you can imagine the more force needed to turn the wheel the more the T-Bar twists and so the more assistance you get, the T-Bar normally twists the most at parking when the steering is heaviest. Now imagine you have removed the hydraulic part, all you'll be left with is a very soft T-Bar with no assistance, so you will be continually winding this up until it hits its stops. All will be designed to have some durability with no hydraulics which is why they have stops but won't be designed to run permanently in this condition....hence an MOT failure. To add some numbers to the equation a typical colum stiffness is about 10 Nm/deg, which is quite stiff. A typical T-Bar stiffness is about 1.75 Nm/deg, obviously quite soft. Now join the two in series and you'll have 1.5 Nm/deg which is 15% of the stiffness of what a manual rack would be (as it doesn't have a torsion bar!). The best way to feel this is with the engine off and then try steering the wheel, you'll notice a very soft initial stiffness and then it will be bloody heavy. This can be done on any hydraulic power steered car." Bellow is a pic of different types T-bars Lots of different sizes and they will vary in diameter from 3 to 5mm. For hydraulic power steering this is the only mechanical link between the steering wheel and rack, most stiffness comes from the hydraulics unless you've removed that of course... They will have some durability, there will be stops at about 3 to 4 deg to stop the torsion bar turning too far but use it for long enough and it will break. There will be nothing connecting the steering wheel to the rack, you can imagine the rest. I even found an article on the web about analysis into a failed torsion bar and it was caused by torsional overload, but when I paste the link it doesn't work for some reason. Durability aside you will also have 6 to 8 deg of free play in the steering...that can't feel very clever. What you want to do is either fit a proper manual rack, which will have a slower ratio, or take the power steering valve apart and weld it up. There are also things to do with the hydraulics that can add weight. I mentioned this topic to a couple of guys at work and we had a good chuckle about it...but what do we know we only have about 45 years of power steering tuning and design experience between us. To be honest in my opinion the driving experience of a failed power steered rack is so bad I can't understand why people are doing it. You can take the rack apart and weld it up which would be much better but bloody heavy. We have done it to one of our racks at work which we use to asses where the effort contributions are coming from i.e. if you have a manual rack and the centre weights are still too light then you are a bit buggered and have to change the chassis. " There is more i can post up but this is the bulk of the text. Andrew
Hi, Demlotcrew- your contact / info spells out what needs to be done when converting a Power rack to Manual. Its all in the ''weighting'' and therefore, you need to know how to balance the end rods to create the right feel at the wheel. The people I have been discussing this with said that Power to manual is not the problem, it can be done, but its how much your willing to spend to obtain the right balance and thus feel to the rack. A power rack with the central clip/washer removed and then packed with grease, and the holes plugged has been used by numerous racers and I have not heard of a rack failing, but the feel of this sort of conversion does leave a lot to be desired. 215M3- Ok, not a Cell sump as such, but more of a collector set low down inside the tank feeding the fuel outflow. Where is planned to sit this Tank / Cell in the car please ? Regards, The Gorilla.
In the spare wheel well. I have provided dimensions for depth and diameter. It will be a 65ltr tank so i have been told. I will have an access plate and the filler will be on the rear panel where the numberplate is located. The internal collection is so a swirl pot is not required, because this is effectively an internal swirl pot and works in a similar way.
I gave him the ZF part number of the M3 rack and this is the responce today. "The word from ZF is: Understands why you would want heavier steering for racing and less power loss from the pump. Also having a compliant steering feel on-centre is up to you (fair enough) but more importantly the T-Bar is designed not to fail as it has 3 deg stops. BUT, he raised an issue I didn't know about and that is that the pinion and rack design is different on a power steering rack and is designed to react loads through the hydraulics. He says you will get accelerated wear so the yoke spring will need tightening often but he said the life expectency of the rack may be as low as 5000km." So its good news about the failure issue but bad about the accelerated wear. I might just try and tighten up my 210k mile old RHD rack. Andrew
Ok back on subject. I have order 2 cells today. Alex will build one first and we will test fit before any more are built. 2 will definately be built. Should anyone that has mentioned interest pm me. I have ordered mine with internal collection and fuel sender unit. The sender unit has a specific resistance and if used with a stack type system can be programmed in. If it is being used with thw instrument cluster or separate gauge then a resistor will need to be added to the line. These are pence in value though.
i replied on the 14th, but have sent another with a little mor einfo this time. The pumps are something that can be decided later on.
Karl It gives me scope if i decide to race the car. If i had a small tank and wanted to compete in an endurance then i would need to pit all the time. If i decided to drive to the Ring then again i would need to fill up all the time. The extra weight in making the cell bigger is marginal to the inconvenience of a smaller cell. They come foam baffled so if you only want 20 ltrs in the tank then it won't slosh around. It also means when doing track days the car can get there with a full tank and almost last a whole day as well. If you want a smaller tank i'm sure Alex can make one to suit the size but less ltrs. I have ordered the first one and he will build it and send it to me to make sure if fits before building any others.
?? when have you been the last time on a track day? 65Liter for the whole day? You are having a laugh! (or you don't put your foot down hard enough..... )
Just trying to get my head around what size tank. My car is trailered and most track sessions are half an hour (unless open pit but can get quite hard to keep going at full speed). 9 mpg and most tracks are 2 miles long. about 10-15 laps per session so really at 60 ltr tank is about half a day. Anything wrong with that calculation. Karl
The other thing to look at is the tank can be run till it is down to it's last ltr without the fuel surges. I did do croft, full day, and needed to fill up when the tank got down to a quarter but did not use a huge amount of the full tank.
So are you wanting a larger tank. If so i'm sure they could build you a larger tank. But the more fuel in the tank the heavier the car will be. If you have too much weight in the rear will that have an effect? An extra 20-25 litres is what 20kgs? Why don't you have a word with Alex as he was very help on the phone and he may come up with something that would suit.
No definately not a bigger tank - maybe even smaller. Filling after every session is not a problem. Karl
Did this tank ever get made ? I'm looking for something and came across this thread ? any pics of a installed unit ?
