Power Steering

[GreatOldOne]

I've been inspired by Lee's PAS conversion to his cabrio - I'm going to attempt the same thing to Vikki.

To this end, I've just bought a Corsa C EPS steering column, a spare BMW column and the correct plugs for the power steering ECU.

My plan is to make this so there is no need to have a manual override control - most of the conversions I've seen use a small box of tricks with a 555 timer chip in it to create the speed pulses the ECU expects. This is ok, but it can lead to wooly feedback according to some sources on the Internet.

My idea is to take the pulses from the diff and the coil, sample them using a microprocessor and then output corrected pluses for the desired amount of assistance for a given speed.

Considering that anything over about 10 mph at the sportster steering is light enough, I think I can get away with turning assistance completely off at anything over that speed, and have a gradual reduction of assistance from 0-10mph.

In fact, I know that it's possible, as whilst I was researching it all, I came across this post on a VW website:

http://www.vwgolfmk1.org.uk/modules....209&highlight=

So there's a chap out there thats already done essentially what I had in mind - something that's completely programable to all wheel sizes, engine speeds and driver requirements.

Now all I need is the bits to be delivered, and I can start to experiment!

[GreatOldOne]

Well, the parts have arrived. You've all seen an e30 column, so I won't bore you with that - but here's the Corsa column:



I have divested the top part of the column of it's sleeve and tilt mechanism. I won't be using those. I did save the inner splined tube that slides over the input shaft, as it may come in handy later on. I have no idea what the black donught type sensor is for, as there is nowhere to plug it in on the EPS ECU. I assume it must be a steering angle sensor that clipped to the top of the column...



Anyone know how to cut splines?

[Mike]

Hi GOO

Why do you want to cut splines?
As you've said, you have the splines for the top part of the column, and if you cut the end off the lower link U/J you have the splines already made for the bottom of the Corsa column, and with a safety bolt already fitted. You can then weld the bottom part of your BMW column to the cut off spline.

The bit I am struggling with is how to maintain the adjustability I currently have in the Sierra column, both Forward/Back and Up/Down. To do this I need to allow the Corsa motor to move in both plains whilst offering some torque resistance for the motor to push against?

Lee took the simpler route of making his column fixed.

Have you offered your Corsa section to your footwell? I have found the Corsa section makes my column 25mm too long if I cut the Sierra column where I would ideally choose.

[GreatOldOne]

The splines comment was more of a joke than something I actually want to do.

No, I haven't offered up the column yet - been too busy this weekend.

As for the adjustability, I'm keeping mine fixed. Have you thought about getting the adjustable corsa column to replace the sierra adjuster altogether?

[Mike]

Originally Posted by GreatOldOne

The splines comment was more of a joke than something I actually want to do.

No, I haven't offered up the column yet - been too busy this weekend.

As for the adjustability, I'm keeping mine fixed. Have you thought about getting the adjustable corsa column to replace the sierra adjuster altogether?

Mmmmmmm....................

I have thought about the adjustable Corsa column, (and have not ruled it out totally) but the problem keeps coming back to the column being too long.

I'm not sure what the Sportster is like, but in a Cabrio the steering wheel is pushed closer to the driver than you might choose. Therefore anything that makes the column longer is not ideal.
Currently, I am thinking about cutting and carving the Sierra column to give me back the 35mm I want, but even that is not straight forward, hence why I am still thinking/?playing about with ideas.

Was your donor BMW column adjustable for height and length?

The problem with keeping the Corsa adjustability is having to marry all the Sierra electrics to the new Corsa switch gear - not my strong point!

[Mike]

GOO

This site might be of interest to you?

http://www.migweb.co.uk/forums/other...ut-please.html

Mike

[denniswpearce]

Interesting reading, but why do you guys want to change to power assisted steering ?

I like the directness / positve feel of it. Very little movement ( similar to a kart ) and you feel everything. Was a bit thrown by it when I bought it having been used to all the feel taken out by modern steering systems.
Just don,t let go of the wheel when you are driving or you could be in the ditch or the car coming from the opposite direction.

[GreatOldOne]

It's more for low speed manoeuvring Dennis - trying to park etc - is annoyingly heavy. I plan on programming my controller to shut the assistance off completely once I'm above 10mph or so.

Mike - that's an interesting thread... I'll keep an eye on it, but as I have an arduino to play with, I'll give it a go myself first. I've already got the logical design worked out - just need to prototype it and give it a go.

My BMW column is not adjustable. I'm not sure BMWs of the time had that option... I plan on chopping my second BMW column down so I have the original mounting plate and it'll bolt straight into the marlin bracket. I'll strip the casing away about an inch or so after that, and then machine the splined sleeve so that it'll slip onto the BMW shaft and then weld it.

Some brackets from the eps casing to the BMW column case will hold the top portion together. Then I'll fab some brackets fro the mounting holes on the eps case somewhere on the chassis - probably hanging from the top of the foot well.

I'll make another cut to what's left of the BMW column so I have the bottom bearing , splines and a stub of the steering rod. Weld the rod to a section of the universal coupling that came with the eps, clamp the bottom part of the BMW column in the mount bolted into the firewall and slip the other end onto the eps splines. The BMW splines marry up with the BMW UJ in the engine bay.

Simples.

[alackofspeed]

The "doughnut" is a coiled up ribbon that connects to the airbag.