Series 3 Electric Power Steering

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Tube fitted to the power steering unit.

Tube being welded to existing Corsa bracket.

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Trial fit to bulkhead mock up.

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Thanks for the positive comments.

Next it gets a bit tricky, I have to join the remains of the Land Rover column to the input shaft of the power steering unit. The male splines you can see in the last picture would normally have a matching female part bonded to it with some kind of thermoplastic glue. The is part of the Corsa collapsible column arrangement. The female part was actually two parts welded together, one part with the female splines the other part with male splines and a thread to mate with the steering wheel.

I've machined away the weld and separated the two parts, now I need to substitute the old Corsa part for the Land Rover part and mate this to the female Corsa spline.

I hope to achieve this with a combination of press fitting, pinning and welding. The design will be such that any one of the retention methods will be sufficiently strong so I hope I will have layers of redundancy.
 
impressive work, i can't see a problem, your doing such a well engineered job i can't see it failing at all, the pas motor part is the most likely failure but that's irrelevant if it fails as you will still have full steering control
The only thing you have altered is the splines/joints it's just like fitting an aftermarket steering wheel boss
 
Started work on mating the Land Rover shaft to the Corsa shaft.

As mentioned this will be pinned, welded and press fitted.

Measuring the torque on the standard Land Rover steering it can be as high as 30Nm, this is worst case with the vehicle stationary, tyres down at around 20psi and a firm grippy surface. If the power steering is working then this max torque figure will be very much less and obviously when driving even lower still.

The plan is to join the two shafts you see below.

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The top one is the Corsa shaft that has been removed, you can see some splines on it, this shaft was pressed into the small stubby shaft below and welded together, none of the parts are hardened. I want to fit the longer Land Rover shaft seen below into the small stubby one.

Land Rover shaft has been roughed out, the turned down part will be pressed into the Corsa part.

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If I can get an interference fit of 0.02mm the joint should be capable of transmitting over 200Nm of torque. Once assembled this will also be drilled and pinned, a 4mm diameter silver steel pin should give me a safety factor of 4 so I will put in a couple just in case. Finally where the shafts butt up to each other they will be TIG welded together.

The challenge will be getting the two shafts pressed together with a 0.02mm interference fit, plan at the moment is to put one in the oven at 200 c and the other in the freezer then assemble in a hydraulic press, think I will try a dummy run first just to make sure I can do it without undue distortion.
 
A bit more progress, the Corsa shaft has been mated with the Land Rover shaft. I was a little concerned about possible distortion using a press with a the 0.02mm interference fit so called upon some help and managed to get some liquid nitrogen to cool the Land Rover shaft. The Corsa shaft was heated to 200 C in the oven and both parts simple slid together with no force.

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A small "V" weld prep was then machined in and the two shafts TIG welded together.

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I light skim in the lathe after welding. I still need to drill a couple of holes for the dowel pins.
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Next on the list is the outer column, here the cut down column has been welded to the previously manufactured boss.
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Once its welded up its back into the lathe, the shaft is clocked to run true and the end face of the flange is skimmed to remove any distortion. At the same time a small taper is also machined into the protruding stub, this is located into a detail in the Corsa EPAS motor to make sure everything is coaxial.

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Both parts fitted to EPAS on bulkhead mockup. Just need to sort out a detail to allow the steering lock to work and I think thats most of the fabrication work done.

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A bit of an update,

Detail added to upper column to allow the steering lock to work.

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Torque tube and bulkhead plate finalised

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Parts ready to fit, steering box is now a sealed unit so it needs venting, this will be done via the small reservoir.
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Hopefully this will all be bolted into place in the next few weeks.
 
Christ! No wonder series came without power steering, Brummie car makers wouldn't go to that much trouble just to make it easier to steer. For people with weak arms, they made minis.

Col
 
No video I'm afraid but I did measure the torque required, previously needed 30Nm of torque when stationary, with maximum assistance dialed in it now needs 5Nm.

After a few tentative shuffles on the drive followed by a couple of short runs up and down the street I've eventually been for a proper hours drive and I love it, in fact I'm still smiling. I gradually upped the assistance level to max and it just works.

Driving in a straight line its barely detectable but come to a slow tight corner and its just so easy. One thing you do notice is the almost total absence of kick back through the steering, now this may be due to the rebuilt steering box, when I set it up I was surprised by how much preload you needed on the adjuster to get the recommended turning torque I suspect that my existing box was well overdue a service.

I guess the lack of feed back could be seen by some as a negative aspect to this mod but for me it just makes it easier to drive and should give Miss Kane the confidence to venture out as well.

The upgraded servo has also been an eye opener. I already had 11" brakes and a servo but they still took quite a push. The larger servo has transformed the brakes and dramatically reduce the pedal effort. I now find it much easier to modulate the effort and it seems less likely to lock up. The servo only just about fits in the space, there are only a few millimeters to spare next to the wing but its been well worth the effort.

Obviously power steering on a Series isn't for everyone but I'm struggling to see and downsides yet.

Since I started this I've found a few companies that do a similar conversion, if I new that at the beginning I think I would have just brought one.
 
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