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Power Steering For A Sierra Steering Column - Preparation

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  • Power Steering For A Sierra Steering Column - Preparation

    Although I have postponed the fitting of a power steering column to my Cabrio, until after I get it through the IVA test - it would be just another item they could find an issue with - I thought I'd share how I have prepared it ready for installation. Its not for everyone, as it requires some minor, but significant welding, and the use of a lathe. However, all the preparatory work in the enclosed photos can be carried out by anyone: and the difficult bits of welding the Sierra column sections in a lathe can be taken to any decent machine shop, and will not cost the earth. Thanks go to Lee Hunter for identifying that this modification actually works and blazing the trail.

    A standard Sierra Adjustable Column + Inner Shaft.


    Corsa C EPAS Fixed Steering Column.







    This is an Electric power steering column from a Corsa C - it comes with the ECU attached to the column, and is known as EPAS (Electric Power Assisted Steering).




    A special torxx socket is required to undo the centre bolt.



    The EPAS assembly can be dismantled to this stage by pulling apart friction fit connections - it does require some effort, but there is only friction holding it.



    Removing the inner shaft from the upper column assembly is more difficult. I used an angle grinder to carefully cut away the outer case - it is then discarded.



    The Corsa has a lower link with two u/js, which is splined to the output shaft of the EPAS column. I simply cut the splined section off the u/j with the trusty angle grinder. A 1mm thin slitting blade makes this very easy.



    I want to retain the Sierra columns reach adjustment, so have shortened the Sierra's lower outer shaft, and welded the two triangular sections closer to each other, and then fitted a shortened inner triangular section. This provides 50mm of reach adjustment with the white nylon bush sliding in either one or both of the outer triangular sections. A spin off is that this column is truly collapsable.

    Note: This is the only variation from the pioneering system fitted by Lee Hunter. Lee chose to weld the Sierra's inner triangular shaft direct to the splined boss, making the overall steering column assembly fixed. Given that probably most drivers want the steering wheel pushed away from them in a Cabrio, reach adjustment may not be a big issue, so it is probably a good compromise - ( and, it will simplify installation too).

    As the Forum will prevent me from adding more Photos to this posting - I'll continue with the upper assembly in Part 2 !

    Last edited by Mike; 03-10-12, 07:53 AM.

  • #2
    Re: Power Steering For A Sierra Steering Column - Preparation Part 2

    Now to the upper assembly arrangement.



    Note the collar on the shaft inside the outer case. This is exactly the same diameter as the inner one of the Sierra's shaft.



    The collar above is used to support the spring loaded bearing alignment collar (castellated) and controls the minimum length the Sierra column assembly can be easily reduced to. Therefore cut the shaft 15mm below this collar, to allow it to fit over the EPAS input shaft, but inside the outer casing. This is a nice fit, and helps control the later alignment when welding it all together.



    Shaft cut to length



    This shows how the collar controls the overall length.



    The upper section of the Corsa's inner shaft is exactly the same diameter as the inner one of the Sierra's. All that is required is to turn the centre section down to the same size, to allow the Sierra shaft to slide fully ove the Corsa shaft. It can then be drilled pinned, and welded for safety. The splined section can then be fitted to the EPAS input shaft, and the steering shaft assembly is complete.



    The standard Sierra outer column can now be attached, along with its cowling and standard reach / height adjuster.

    Voila - an adjustable Power steering column which is completely inter-changeable with a standard Sierra adjustable column.

    Installing the column in the car has only one significant challenge. How to provide an adjustable support (reach and height) for the power steering motor which will move in height and reach. Lee hunter has demonstrated that a fixed Corsa EPAS column will fit in a Cabrio, and the motor mounting is certainly easier. However, I have ideas for how the motor support can be made adjustable, but the development of this will have to wait until after I get my Cabrio through IVA!
    Last edited by Mike; 01-10-12, 04:14 PM.

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    • #3
      Re: Power Steering For A Sierra Steering Column - Preparation Part 2

      Looking good Mike, have you tried it in the car yet ?

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      • #4
        Re: Power Steering For A Sierra Steering Column - Preparation Part 2

        great work Mike.

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        • #5
          Re: Power Steering For A Sierra Steering Column - Preparation Part 2

          Hi - This looks a very elegant solution. Just a word of warning though. I'm sure I heard somewhere that any welding on a steering column would result in a fail in SVA (and similarly IVA). It could have been MoT as well or instead. Sorry I can't be any more specific, but it might be worth a bit of research. Cheers - Dave

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          • #6
            Re: Power Steering For A Sierra Steering Column - Preparation Part 2

            Section 2.2 (c) inappropriate modifications or repair esepecially by welding, or evidence that excessive heat has been applied.....

            But what might be considered inappropriate by some inspectors , is open to debate.
            MOC member since 05/97
            1984 Marlin Roadster SWB.
            1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
            Three core radiator, Renault Clio vented front discs.
            The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

            Loads of Marlin Reference can be found documents here or there.

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            • #7
              Re: Power Steering For A Sierra Steering Column - Preparation Part 2

              I too heard that rumour Dave and looked through the IVA manual for the answer and couldnt find anything, I also heard it was ok if the joint was sleeved and staked. I guess its down to the tester to assess whether the welding is of a sufficiently high standard? I also infer from the manual that any steering system taken in its entirety from a production vehicle that was type approved is ok - so welding a bit in would change that. The only thing I can find in the manual is that ..."In cases where an intermediate shaft is used, it will be connected to the steering column at one end and the steering rack or box at the other, by means of universal joints and/or flexible couplings.

              The MOT testers manual talks about 'inappropriate' modifications and repairs, and potential damage caused by heating. (as Steve points out).

              I would have thought that almost any kit car going through IVA would have some sort of lengthening or shortening required? So I guess the answer is in the hands of those who have recently been through the IVA test?

              Comment


              • #8
                Re: Power Steering For A Sierra Steering Column - Preparation Part 2

                Originally posted by dave.kitson View Post
                Hi - This looks a very elegant solution. Just a word of warning though. I'm sure I heard somewhere that any welding on a steering column would result in a fail in SVA (and similarly IVA). It could have been MoT as well or instead. Sorry I can't be any more specific, but it might be worth a bit of research. Cheers - Dave
                I think this applies to the steering linkage rather than the column. I think every Marlin on the road has had the steering column modified and most by welding?

                MOT Steering extract.jpg

                Comment


                • #9
                  Re: Power Steering For A Sierra Steering Column - Preparation Part 2

                  Originally posted by dave.kitson View Post
                  Hi - This looks a very elegant solution. Just a word of warning though. I'm sure I heard somewhere that any welding on a steering column would result in a fail in SVA (and similarly IVA). It could have been MoT as well or instead. Sorry I can't be any more specific, but it might be worth a bit of research. Cheers - Dave
                  Hi Dave

                  Thanks for your kind words - the credit for the concept is due to Lee Hunter.
                  For the very reasons you suggest, I had decided to postpone fitting the adapted steering column until my Cabrio gets through IVA - its just one less item they could light upon as a failure.
                  As it will be my life which depends on the robustness of the column, I have gone to considerable lengths to ensure the components work in the same way as they did on their donors, and that all welded parts have been welded by a professional welder from a local engineering company.

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                  • #10
                    Re: Power Steering For A Sierra Steering Column - Preparation Part 2

                    Good point Dave especially when safety is in question, however the sleeve that is welded on my column was a press fit the welding is just the braces side of it. On with my third column for a cabrio doing Terry's now.

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