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Discussion Starter #1 (Edited)
So I have converted my s1 to electric pas which means passing the earth wire up the column is a no can do. I dont want the preferential earth down the column to the epas drive motor in case it gets damaged.

So my thoughts are earth route is steering wheel to centre column shaft then from column shaft to the turn signal spring wrapped around the inner shaft, then from the spring connect a wire to chassis earth.

Also wondered about fitting a carbon brush and carrier from a washing machine motor but more effort that maybe over the top.

Anyone seen this solution or a better one ?
 

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Wow, tell us more about the "pas" (Power Assisted Steering?) system that you installed. Does it accept your original Alfa steering wheel?

I would think that the manufacturer of the pas would have made some provision for controlling the horn. Or was that the "the preferential earth down the column to the epas drive motor" I didn't understand your concern about "in case it gets damaged" - in case what gets damaged? The drive motor? Without seeing how this thing goes together, it's tough to comment.

So my thoughts are earth route is steering wheel to centre column shaft then from column shaft to the turn signal spring wrapped around the inner shaft, then from the spring connect a wire to chassis earth.
Well, yes, the cancelling spring could act as a brush. And since the spring is only attached to a plastic part on the TS switch, you could pull a signal from it. The few milliamps that a horn relay draws isn't going to heat up the spring. You would need to electrically isolate the collar that the spring rides on from the steering shaft, with the shaft supplying the ground to the horn switch (if that makes any sense).
 

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Discussion Starter #3
The EPAS is actually a home grown installation taken from a Vauxhall Corsa B here in the UK. Yes the top section is in fact the original shaft etc so same steering wheel and controls, only change will be the horn earth.
See this link to my restoration post to save repeating. I can put some more pics if your interested


The concern is around potential internal gear or bearing damage the same as the Burman can suffer with a dodgy earth which I find surprising because the current is so low as you say. Is it really the case arc damage has been seen or is it just bearing fatigue.
I havent cracked the Epas itself so not sure what might suffer if anything.
I thought the spring runs directly on the shaft ? this is what I need to get rotary contact translated to a fixed point, the idea is the current takes the path of least resistance so goes via the spring as opposed to into the guts of the epas.
Does this make sense ?
 

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But Mad North-Northwest
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The concern is around potential internal gear or bearing damage the same as the Burman can suffer with a dodgy earth which I find surprising because the current is so low as you say. Is it really the case arc damage has been seen or is it just bearing fatigue.
Nah, that's bunk. Someone on here posted lower shaft bearing damage on a Burman one time and said it was due to horn grounding. No freakin' way: that's just wear and tear on the bearings from either improper lubrication or water in the box. The horn circuit uses a relay and the current through the switch is incredibly small, like 200 mA: that's not going to hurt anything.

Also the steering shaft rides on a metal bearing in the aluminum steering support. If you're really worried just make sure you've got bare metal somewhere where the support bolts to the under-dash mounting points and that'll be your ground path.
 

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Discussion Starter #5
Thanks for that. Couldnt see the small current being an issue plus normally needs to arc across a gap as well. So your suggesting the continuity is from inner shaft through the upper steady bearing to the steel column tube then into the alloy casting to the body attachment ?
Sounds like a plan , I guess its a pay off bearing vs spring as conductor.
 

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But Mad North-Northwest
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I mean, what I'm saying is there are multiple ground paths. If you want to be sure you're not grounding through the box you can ensure a good ground form the support to the body.

But that said, in a stock Burman box you've got grounding through both the top and bottom bearings, as well as (probably) from the big rocker arm to the casing. There's a LOT more total metal area there than through the small connection point at the horn switch. I'm certain there's no problem for the tiny horn circuit current...we're talking milliamps to drive the relay coil here.
 

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So your suggesting the continuity is from inner shaft through the upper steady bearing to the steel column tube then into the alloy casting to the body attachment ?
Uhhh - I'm not sure quite what I'm suggesting. Again, without seeing how this thing goes together, it's tough to design something.

I thought the spring runs directly on the shaft ? this is what I need to get rotary contact translated to a fixed point, the idea is the current takes the path of least resistance so goes via the spring as opposed to into the guts of the epas.
Yes, on an un-modified Alfa, the spring rides on the shaft. But to use the cancelling spring to pick up a signal, you would need to insulate the surface that the spring rides on from the shaft; otherwise it would always be grounded and your horn would always sound.

gubi said:
Someone on here posted lower shaft bearing damage on a Burman one time and said it was due to horn grounding. No freakin' way
Oh, now I see what Legin was worried about. Sure, gubi is right - the amount of current that flows through the steering column to trigger the horn is infinitesimal. And even if the horn circuit ran on 20,000 volts, unless you lived in Mumbai, your horn relay is drawing current so seldom that the damage just wouldn't accumulate. There's no way power to the horn circuit could damage the lower bearing, or anything else.
 

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Discussion Starter #8
Uhhh - I'm not sure quite what I'm suggesting. Again, without seeing how this thing goes together, it's tough to design something.



Yes, on an un-modified Alfa, the spring rides on the shaft. But to use the cancelling spring to pick up a signal, you would need to insulate the surface that the spring rides on from the shaft; otherwise it would always be grounded and your horn would always sound..
Needs to be rubbing the shaft all the time otherwise I dont achieve a slip ring connection.

I need to look more closely at the horn / wheel arrangement as Im probably confusing myself.
 

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Discussion Starter #9
Right I think Im getting there. The bit I missed is that the column already is the ground and the black wire up the centre connected to the relay effectively the hot terminal.
So I get what your saying. I need some insulation between a sleeve and the centre column but they rotate in unison. The spring runs on the conductive but isolated sleeve. The sleeve is connected to the horn wire and the the spring to the relay.

Agree ?
 

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But Mad North-Northwest
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Now you're confusing me :LOL:

Yes, wire up the shaft is +12V hot. That connects to the horn switch. When the horn switch closes it connects that wire to the steering wheel boss / shaft, which are grounded.

Are you using a stock steering wheel? You should just be able to connect that wire to the existing terminal on the wheel.
 

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Discussion Starter #11
Yes stock wheel. This confused me , maybe it still does. So the task is to connect the 12v hot to the steering wheel switch without passing a wire up the columns centre.
Not possible because the epas is in the middle.
So the 12v would come from the relay to the spring.
The collar under the spring would be connected to the horn wire and the collar is insulated from the column shaft.
Short of it is the spring and collar plus and external wire to relay replace the current black wire up the shaft.

I think.
 

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But Mad North-Northwest
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Yes stock wheel. This confused me , maybe it still does. So the task is to connect the 12v hot to the steering wheel switch without passing a wire up the columns centre.
Not possible because the epas is in the middle.
Ah, I didn't realize that the EPAS didn't use a hollow shaft. Yeah, that's a problem, you'll need to figure out some sort of a way to get around that. Does the unit attach to the existing Burman shaft somehow or does it completely replace it?

You can't be the only one who's had this issue, maybe talk to other folks who have retrofitted the same EPAS unit?
 

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But Mad North-Northwest
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I mean, it's not stock, but you could wire the horn to a button under the dash or in the center console. My TR7 used to actuate the horn by pressing in on one of the column stalks, and that was stock :LOL:
 

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Discussion Starter #14
Yeah it could but I want the stock look as far as possible. I think the spring sleeve will work fine. I just need to machine up a sleeve with a ptfe internal liner and its done. I had a TR7 V8 my last big restoration in 1988 !
 

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Discussion Starter #15
Gubi, The upper an lower sections are original burman but the middle is bespoke and modified epas cut and shut in place. Sounds like Im hacking my car but the reality is this and the 501 colour will be only mods and the epas is done so it could be reversed without recourse to the welder.
 

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So the 12v would come from the relay to the spring.
The collar under the spring would be connected to the horn wire and the collar is insulated from the column shaft.
Yes, sounds like you've got it. Think of the problem as trying to duplicate the function of that wire that used to pass through the hollow steering shaft. Instead of providing a path to ground simply through the wire to the horn button (when it's pressed), now the current needs to go from the relay through a wire connected to the cancelling spring, to an insulated collar on the shaft and then from the collar to the horn button switch.
 
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