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Peter-RB
30th Oct 2016, 11:18
Has anyone noticed just how twitchy this new addition is to cars, my car has Power Steering via a small pump and is so smooth in operation that you hardly notice ,..but Mrs P R-B has a new BMW with this "Electric " steering and I find it seems to be a step backwards from Hydraulic Pwr Steering...anyone noticed..?

cattletruck
30th Oct 2016, 11:37
A work colleague had a Jap supercar that had electric steering because the engine was at the back. He said you couldn't tell the difference unless the battery was on its last legs.

Try turning off the radio, the cabin fan, the lighting, the i-drive system, the reverse camera, dim the console and your electric power steering will back to normal.

G-CPTN
30th Oct 2016, 11:45
I have owned cars with hydraulic power steering which was imperceptible in use, and now have a car with electric power steering which is 'twitchy' such that with reduced concentration it wanders across the carriageway - though 'wanders' is, perhaps, too vague - it 'darts'.

DirtyProp
30th Oct 2016, 11:59
Drive-by-wire.
Made by Airbus, perchance...?

Loose rivets
30th Oct 2016, 12:20
G-C That sounds horrible! . Has your car got Run Flat tyres? I'm told that makes a difference to tracking.

I drove back from London last night in the BM 635d. I had been surprised to learn it only had conventional steering* and find it rather ordinary in use.

Diverting a moment re G-C's comment, one thing the car has that's incredible is the Lane Drift system. When selected ON it shows the road on the Head Up Display. When a camera locks onto the white lines, two deltas point to the top of the symbol. If you drift to a white line - in either direction - without signalling, you'll get a stick-shake - or more correctly, a simulated rumble strip. Last night in the fog I was very glad the system seemed to be able to see through it. (mostly mist with patches of fog so not too bad.) I still don't know if it'll quit when the fog gets bad, but by then one is usually crawling with eyeballs pressed against the glass.

I'm a tracking fanatic and have spent ages with this car and others thinking about getting the whole car rail-accurate, at least on the flat. As hinted, these run-flats are reputed to be bad on tracking anyway, though I can't see how a more rigid tyre would make it worse.

I had a Toyota Supra (before Colin Chapman messed about with it) and it was utterly perfect. Hardly move the wheel, yet it would seem to go just where you were planning. The steering swivels were made by Lockheed, a bit like a couple of large eggs that unscrewed to repack. Supreme design. Why on Earth have we not got better steering now? Oh, wait. So:mad:g front wheel drive. The public were sold on that simply to allow the makers to plonk a unit in, in about 60 seconds. 'It'll grip better.' Yeh, and slide into infinity when the wheels do un-stick.


* A couple of 640s I tried out were Three stage sports with steering that was acutely modified.

andytug
30th Oct 2016, 12:43
Don't think the "twitchiness" is purely down to the electric steering, it might be a combination of things. Tyre pressures can be critical in this, worth adjusting +/- a pound or two and see if it makes any difference.
A lot of cars seem over-assisted to me, just had a Fiat 500 as a hire car which was borderline twitchy, but also had a "city" button on the dash that made the steering so light that it was dangerous for me, but for an elderly person it might be ideal.

Loose rivets
30th Oct 2016, 13:04
This business of fly by wire in cars is something that needs standardising around the world. Just been talking to an ex police Class I driver and he was caught out by the throttle on a Polo suddenly introducing power as you were coming to a standstill. It was endemic on the type. Nothing happened in this instance but one always wonders what might have happened.

My MB E500 Sports had Fly by wire brakes which were so good you'd look in the mirror while braking. (how silly is that? :p) But when you suggested servicing your own brakes MB tecs would throw up their hands. 'You can't to that, the hidden battery could chop your fingers off.' And so it could, if you were daft enough to work on such a system without a manual.

A friend's car here in the UK would suddenly turn hard one way! I put the issue to this forum back then, but I still couldn't help her resolve the issues with her garage. No fault found. The worst three words in any kind of engineering - especially aircraft maintenance. Teckies old and new are often not skilled enough in electronics fault-finding to ensure safety in vehicles. Intermittent faults can be a headache for people with years on the electronics workbench behind them.

VP959
30th Oct 2016, 13:15
I've owned cars with electric steering since 2005. Only once did I ever notice a problem, and that was , it turned out, caused by a faulty sensor and was fixed by a recall.

I went from a Merc SLK (with hydraulic power steering) to a 2nd generation 2005 Prius with electric power steering, and the only thing I noticed was that the Prius steering was silent. The feel was much the same, and, apart from the fault that was fixed by a recall, I couldn't find fault with it.

I've since owned two more Prius's, and still have one, their Plug-In version. My wife has a Yaris hybrid, also with electric steering, and neither of us have ever felt that the steering being electrically assisted, rather than hydraulically assisted, felt any different at all.

Ancient Mariner
30th Oct 2016, 13:31
The only "problem" I've noticed with electric power steering is the lack of feedback versus hydraulics.
Apart from that I could not tell the difference. If some of you can, you are probably allergic to electricity or your car has a problem.
Per

VP959
30th Oct 2016, 13:40
If you look at how most electric power assist steering works, then the steering wheel shaft runs straight through the assist motor, with a solid mechanical connection to the rack, so it's not "fly by wire", the steering wheel is still directly mechanically connected to the front wheels.

I can't speak for the other systems, but the system I looked at a few years ago (one with a motor in the footwell, surrounding the steering shaft) just has a thinned-down section of this shaft, with rotary position sensors at either end. This detects the very small twist in the shaft as the steering wheel is turned and resistance is encountered by the steering rack, and applies just enough electric assistance, in the correct sense, to take out the twist. The sensors were very similar to the engine torque sensors found on the engine input shafts to a helo MRGB.

If the electrics fail, then just like a hydraulic system, there is a back up, as the shaft is strong enough to drive the rack directly, the steering would just feel very heavy.

G-CPTN
30th Oct 2016, 13:49
If the electrics fail, then just like a hydraulic system, there is a back up, as the shaft is strong enough to drive the rack directly, the steering would just feel very heavy.
Without the engine running, the steering is 'solid' - ie I cannot turn the wheels with the car stationary.

VP959
30th Oct 2016, 14:09
Without the engine running, the steering is 'solid' - ie I cannot turn the wheels with the car stationary.
Just been and checked mine. Challenging, as there is an electric steering lock, enabled by the power button, so the steering does appear to be locked with the car turned off and stationary.

However, according to the manual, the steering will just revert to non-power assist in the event of a failure with the vehicle moving. I assume there's an interlock that prevents the anti-theft automatic steering lock being applied under such a condition.

If I get a chance tomorrow I'll pick a safe area and turn the power off with the car in motion and see what happens, then report back here.

Ancient Mariner
30th Oct 2016, 15:31
If you that, VP959, do not turn the ignition off or push the stop/start button. You have to make the engine stop by other means. Good luck.
Per

Peter-RB
30th Oct 2016, 15:40
Thank you Chaps, but Ancient Mariner has it , its the lack of feedback I am missing, whereby the Hydraulic PS returns to straight just by slightly releasing my grip on my car steering wheel, with this new Beemer you need to action and turn to return to the path you desire,, wow..! hows this got passed by the Safety Guys at the MOT or even the EU -TuV....

I have just tried free wheeling without the engine turned on, as strong as I am I cannot turn the darned wheel...Mrs PRB has no chance at all.

Surely this is slightly dangerous...need to ask a question of my local Beemer Garage..

VP959
30th Oct 2016, 16:26
I remember, years ago, having the belt that drove the power steering pump fail on my old 2.8 litre Granada. That, too, was a real challenge to steer - I barely managed to get home (about 2 miles or so) but there is no way I'd have taken it out again like that.

I think the lack of feel isn't so much the method of providing power steering assistance as the way modern car front wheel geometry is set up. I remember having a Citroen GS may years ago, and one of the points made at the time was that the you could have a blow out on a front tyre and not notice an effect on the steering. That, too, had really a really "dead" feel to the steering, and gave very little feedback to the driver.

Maybe a lot of modern cars are set up in the same way, as a way of helping to prevent loss of control if a front tyre blows? I don't know for sure, but I did have a front wheel go flat on the Merc SLK I had. I drove for around 2 or 3 miles before another motorist flagged me down. There was no way I could feel that the front tyre was flat, and by the time I stopped the side walls of the tyre were shredded, it had got that hot.

VP959
30th Oct 2016, 16:29
If you that, VP959, do not turn the ignition off or push the stop/start button. You have to make the engine stop by other means. Good luck.
Per
I'm not sure if it will actually let you turn the power off while in motion, thinking about it. I rather suspect it won't. The other problem is that turning off the power automatically engages the transmission lock, as the pin that locks it is held out by power and a spring pushes it back into the lock when the power goes off.

Perhaps not a good idea to do a test as I suggested earlier............

G-CPTN
30th Oct 2016, 16:52
In the 1960s, there was an interlock on the steering lock.
You had to remove the key before the lock would engage - simply turning off the ignition wasn't enough - but, now that the key is no longer located on the steering column . . .

Loose rivets
30th Oct 2016, 17:02
This thing was quite nice on the rare occasions it would compete a journey without the need to go to the menders. But one thing I was told was 'normal' was the need to turn the steering back to centre. I'll never know the truth.

However, it seems one of the tracking parameters is caster. This is the function that powers the return. Okay, so it might be that a force does it instead, but again, I don't know. All I know is, I hated that dead characteristic on this car.

http://img.photobucket.com/albums/v703/walnaze/Cars/DashboardE500Sport013.jpg (http://smg.photobucket.com/user/walnaze/media/Cars/DashboardE500Sport013.jpg.html)

One fine spring day I set out in my MK10 Jag for Norwich. I'd not seen another car on the A140 (those were the days) but during a long sweeping left turn a lorry came in the opposite direction and at the worst possible moment there was a bang and the steering failed. I heaved on the wheel and just managed to get it contained. A new belt was fitted at Norwich airport.

It may have been the same 10, I had the later one, erm, later, but it exploded on a pub forecourt with total steering failure. The top of the box had blown off and the fluid sent over the landlord's nice tarmac. There were just enough studs/nuts left to tack the lid back on and I made my way gingerly home. If I remember correctly, the thing that engaged into the worm gear was part of the lid. So nice to have the right tools in the boot.

There was an upgraded set of studs and nuts as a spare part. The days before recalls, obviously. Oh, and no one in my family screws the steering around while stationary. At least, not while I'm looking.


.
.

VP959
30th Oct 2016, 17:07
In the 1960s, there was an interlock on the steering lock.
You had to remove the key before the lock would engage - simply turning off the ignition wasn't enough - but, now that the key is no longer located on the steering column . . .
Indeed. In my case there's no key, just something that senses that the remote is inside the car, plus a power button. I already know that turning the power off locks the transmission, as I've done it in my drive, before putting the parking brake on, and the car does the classic roll a bit then the wheels lock up, like older US cars when people were in the habit of not using the parking brake when stopping, and relying on the transmission lock.

I have no idea how the steering lock works on my car, except that it definitely does lock up the steering wheel with the power off. I did see the insides of the old steering motor on my first 2005 Prius (the one that was recalled for a defect in the torque sensor). I didn't see a lock, but it was clear that the steering shaft went straight through the motor, and the system relied on sensing the torque in that shaft (from trying to steer the car) to set the amount and direction of power assistance (not unlike the way the bobbin valve does the same with a hydraulic assistance system).

jimtherev
30th Oct 2016, 17:50
Yes, there does seem to be a 'sweet spot' related to tyre type / pressure. A few weeks back the steering on my Auris hybrid felt 'strange'... not quite so accurate and a bit inclined to hunt from side to side. Cheapest solution, not really believing this would work, bring tyre pressures back from 31 to 33 psi. (Hadn't checked for weeks.) Instant gratification. Pin-sharp steering and feel restored.
Just for fun, I then pumped both fronts up to 36. Another sort of 'feeling strange': now hyper-sensitive to steering movement.


At least I now know what to look for - or at least where to start.

andytug
30th Oct 2016, 17:57
Could be there's a tyre pressure "sweet spot" for every car, might even differ from tyre to tyre on the same car.
Apart from anything else under inflated tyres increase fuel consumption and tyre wear so a few coppers every fortnight to check them at the local garage will pay for itself and more.

My Vauxhalls Zafira (not exactly a sports car) starts to feel less "sharp" and slightly slower when even 2-3psi lost from the fronts. The number of cars you see with expensive low profile tyres that are visibly under pressure always amazes me.......

vapilot2004
30th Oct 2016, 18:27
The cars I have driven with the electric power assist had a centering issue and the breakout force seemed to need tweaking, making the car more squirrelly than others with the standard hydraulic assist.

Out of all the cars I have spent time behind the wheel in, save a few exotics, the BMW always seems to have the best steering feedback, giving the driver, once used to it, the best control. At speed, in my better halve's Sportwagon, I can even feel the paint on the edge of the road, and small road imperfections that would have never been noticed in other cars.

G-CPTN
30th Oct 2016, 18:41
The number of cars you see with expensive low profile tyres that are visibly under pressure always amazes me.......
Indeed, and then when you point out the lack of pressure to the driver, the reply is usually "Low profile tyres, Mate!" I just slink away.

Loose rivets
30th Oct 2016, 18:57
I changed Castor for caster. :O


Yes, there does seem to be a 'sweet spot' related to tyre type / pressure.

I've always run front tyres at a higher pressure. Two or even four psi more for the big engine lumps. Now, the computer is monitoring the pressures and I don't think it stores each tyre but just reports on a sudden departure from the set's pressure. But that's just another thing I don't know.

I've been fed so much duff gen in the last few weeks! I guess the only way to know is to pump the fronts up a bit more and see what the computer says - and see how it steers.

tdracer
30th Oct 2016, 19:20
Most new cars are incorporating electric power steering for a simple reason - efficiency. Getting rid of the hydraulic power steering pump is worth ~3-5% fuel burn. While the lack of feedback is the big slam on electric power steering, not all electric PS systems are created equal. My 2000 Honda S2000 has electric power steering (one of the first cars to incorporate it), and the steering is fantastic - best I've ever used in a road car. I also have a 2007 BMW 328xi - which has very nice hydraulic steering. A while back, I had a 3 series BMW loaner while mine was being serviced and it had electric steering. It did a really good job of convincing me I didn't want to trade my 2007 in on a new one :ugh:

Ancient Mariner
30th Oct 2016, 20:46
I remember, years ago, having the belt that drove the power steering pump fail on my old 2.8 litre Granada. That, too, was a real challenge to steer - I barely managed to get home (about 2 miles or so) but there is no way I'd have taken it out again like that.

I think the lack of feel isn't so much the method of providing power steering assistance as the way modern car front wheel geometry is set up. I remember having a Citroen GS may years ago, and one of the points made at the time was that the you could have a blow out on a front tyre and not notice an effect on the steering. That, too, had really a really "dead" feel to the steering, and gave very little feedback to the driver.

Maybe a lot of modern cars are set up in the same way, as a way of helping to prevent loss of control if a front tyre blows? I don't know for sure, but I did have a front wheel go flat on the Merc SLK I had. I drove for around 2 or 3 miles before another motorist flagged me down. There was no way I could feel that the front tyre was flat, and by the time I stopped the side walls of the tyre were shredded, it had got that hot.

Had a GS X3, I think. Orange and black. Lovely little car with its four pot air cooled boxer.
Fantastic car, I miss it.
Per

G-CPTN
30th Oct 2016, 21:10
When power-steering was first introduced in the UK to the majority of cars, it tended to be 'over-active' (like many American cars).

In time, the PS was refined on many vehicles such that it wasn't possible to tell (other than acceptable effort).

Maybe, with the introduction of electric PS it will take time to refine the response?

rogerg
30th Oct 2016, 22:18
The MGF/TF have had electric steering from day one, I have not heard of many complaints.

crippen
31st Oct 2016, 01:32
They are just getting ready for when the do away with the driver.:{

Brian Abraham
31st Oct 2016, 03:56
Never noticed any difference between hydraulic or electric. Perhaps I'm too ham fisted.

Stanwell
31st Oct 2016, 04:23
I've certainly noticed.
I drove my brother's Holden Commode a while back. .. It was a worry.
Perhaps I'm too much of a driver.
On the other hand, perhaps I don't play enough arcade games. :ooh:

MG23
31st Oct 2016, 04:28
Without the engine running, the steering is 'solid' - ie I cannot turn the wheels with the car stationary.Same with our Subaru. But it has more weight on the front wheels than the weight of the entire car I drove in the UK. Based on my experience of driving one of my old cars with the power steering drivebelt disconnected, as soon as it gets moving, it would probably turn OK without the steering assist, just not as easily.

And this thread is odd, because I was thinking about how well the electric steering works on the way back from work on Friday. It's staggeringly better than the my girlfriend's old Buick where you could wobble the steering wheel like you were in a 1960s movie as you drove along the road, and the car would keep going straight without reacting to the steering wheel movements at all.

MG23
31st Oct 2016, 04:30
Just been talking to an ex police Class I driver and he was caught out by the throttle on a Polo suddenly introducing power as you were coming to a standstill.

That seems to be normal these days: our Honda does it, too. The ECU turns the fuel off as you're braking, and has to turn the fuel back on when you stop. You can feel the car suddenly try to pull away, and have to press harder on the brake to stop.

andytug
31st Oct 2016, 09:50
Think all modern cars do that, if in gear and throttle completely closed the fuel injectors shut off until around 1500rpm (petrol) then get turned back on again to avoid a stall, so the impression is a sudden lack of the engine braking you were getting up to that point.

Loose rivets
31st Oct 2016, 10:39
RPM? Ah, I'd got a vague memory of 15mph. But vague.

Manual I guess the clutch could be brought into play, but with automatic, only us left-foot breakers would already have the brakes slightly on.

I know we've talked about this before, but just a mention at this juncture:

A while back I called the local IAM (institute of advanced motorists) about the observation deal they do. Anyway, I asked if I could do it in an automatic. No problem. Then I asked if I could left-foot brake.

The answer sounded a bit like Aaaaaaaaaaaaaagh! NO! Never heard of anything like it! Time taken to get breath back.

I drove around Colchester trying to right-foot brake and just gave up. The loss of that tight immediacy with braking an automatic was just not acceptable to me.

It all started in 1961 with a Olds 88 6ltr thing. Try manoeuvring that about while the choke was still in and you'd hit 90mph in yer garage.

Back then we did a kind of survey. A surprising number of people did L-F-Brake

G-CPTN
31st Oct 2016, 10:49
Tell them that left-foot braking is standard for Formula One drivers.
It is faster (as you well know).

GearDown&Locked
31st Oct 2016, 12:01
Tell them that left-foot braking is standard for Formula One drivers.
It is faster (as you well know).

First time I drove an automatic, I was nearing a crossroad and pressed on the "clutch" ... the car stopped completely in a couple of feet.:eek:

Damn good brakes that Merc!:ouch:

ShyTorque
31st Oct 2016, 12:15
You guys have power steering? Wow, I'm jealous. But I do have relatively high upper body strength.

You'll be telling me you've got servo assisted brakes next.

GearDown&Locked
31st Oct 2016, 12:24
My current means of transportation even adjusts de brake pads to the disks in order to clean them if you take the foot off the throttle when itís raining... :cool:

Loose rivets
31st Oct 2016, 15:25
I expect they got the idea from me.:p

Out Of Trim
31st Oct 2016, 17:43
I drove a very cheap new car the other day. A Dacia Sandero; a petrol 3 cylinder engine apparently built by Renault. Every time I dipped the clutch the ECU added about 200 rpm.

I wondered why the revs went a little too high every time I pulled away!

BigEndBob
31st Oct 2016, 17:52
I have a later model BMW Z4.

The electric steering gives very little if any feedback.
Most important thing is to ditch the runflats, they are dreadful.
Before the car would drift towards on coming traffic.
They are just too hard, the sidewalls are 1/2 inch thick.

Nice set of Goodyears improves the car stability a lot.

MG23
31st Oct 2016, 18:20
My current means of transportation even adjusts de brake pads to the disks in order to clean them if you take the foot off the throttle when itís raining..

The Subaru uses the brakes to prevent wheelspin. It's pretty weird hearing the ABS chattering away on a crappy road surface while driving with your foot nowhere near the brake pedal.

andytug
31st Oct 2016, 19:25
Land Rovers since the first Freelander use a similar system for "Hill Descent Control", the Abs works backwards so the car goes downhill at a steady 4mph without locking any wheels or speeding up, feet off the pedals all the way. Very weird to sit in one doing it.

RAT 5
1st Nov 2016, 10:44
The Subaru uses the brakes to prevent wheelspin

Which one? I have a 2012 XV. Excellent car, but does it do this?

I've not driven a hi-perf car with electric steering so can't compare to my older hydraulic sports cars. I did drive a 2004 Honda Jazz of father-in-law, 34000km's. What was very disconcerting was the steering did not self centre when rolling out of a corner. It was very tiring as you had to position the car very accurately with every twitch. The local dealer told me it was a known wear problem. £400 or so to replace, but I hope they designed out this fault.

Blacksheep
1st Nov 2016, 15:54
I drive a Honda CRV with electric steering and 'all wheel' drive. The steering is very precise and one can 'feel' the road through the wheel. I don't know if the precision is just the work of the steering or if the stability assist system (VSA) is responsible for keeping it right on the line. The only time I've been aware of VSA assistance is when cornering on icy roads in the winter.

One thing I find interesting is the way the steering activates when you press the power-up button. If the steering is not dead ahead, it immediately moves to the centered position as the car becomes live.

Una Due Tfc
2nd Nov 2016, 00:01
I drove the new electric steering 911 on a track....hated it. It just doesn't communicate what's going on as well as a hydro system. I've always been very wary of that car with that big pendulum out back ready to make a fool of you when you get cocky. But it saves weight, and thus crucially fuel, so, like turbocharged smaller engines, they'll become more prevalent. Boo.

Speaking of small turbo engines, they're tested at very low rpms, where the turbo is normally off boost. At motorway speeds the 1.6 turbo is probably using more fuel than the 2.0 normally aspirated. Turbo engines sound crap, hence why the new 2.0 turbo Golf R and various turbo Audis pump a synthetic engine noise through the speakers because they sound nowhere near as good as the old 3.2 V6 and 4.2 V8 they did. Boo.

My new car has that radar cruise control, big help in poor visibility, I can "see" a car in my instrument cluster well before I do with my eyes in fog. Very handy. The active braking pulled me out of the poo one night when I stupidly got distracted, would have rear ended someone otherwise. My insurance is cheaper because the car has this, that incident demonstrates why...

vapilot2004
2nd Nov 2016, 07:15
I believe electric steering is technically electric power assisted steering and the mechanical connections remain. We've not gone the way of drive by wire yet (throttle by wire yes, and in some hybrids, partial braking by wire) in the steering department, of this I am almost positive.

So feedback is likely through the mechanical rack and pinion that remains, whether the vehicle is hydraulically boosted or with electric assist. Are we agreed?

Is it possible there is a zone (1-2 deg or less) of artificial feel where the wheel is technically connected to nothing? I ask this due to the odd 'breakout' forces I've experienced on a few hired American cars with electric assist.

andytug
2nd Nov 2016, 07:39
It depends, my car is the same setup as the old engine powered hydraulic pump ones, but with an electric pump replacing the engine driven one, so it's still hydraulic really. "Proper" electric power assistance has the motor round the steering wheel shaft as previously described and no hydraulics.

Loose rivets
2nd Nov 2016, 11:24
I was astonished to read back there that the information might be gleaned from the torque-derived difference in a calibrated length of the column. Just what is that steel like?

Okay, it's easy to measure minute changes on a shaft but not so easy outside the lab. All that vibration on the point of focus . . . sheeeesh.:rolleyes:

That section has to be able to take full steering load, not just on the road but in an emergency, including veering away from say, a tree, while in rough ground. People get a lot of strength when that adrenalin pumps in. I know I did on that heavy MkI0's old fashioned powered-steering box. Or should I say, powered until that moment, steering box.:ooh:

VP959
2nd Nov 2016, 11:46
I believe electric steering is technically electric power assisted steering and the mechanical connections remain. We've not gone the way of drive by wire yet (throttle by wire yes, and in some hybrids, partial braking by wire) in the steering department, of this I am almost positive.

So feedback is likely through the mechanical rack and pinion that remains, whether the vehicle is hydraulically boosted or with electric assist. Are we agreed?

Is it possible there is a zone (1-2 deg or less) of artificial feel where the wheel is technically connected to nothing? I ask this due to the odd 'breakout' forces I've experienced on a few hired American cars with electric assist.

There's a dead zone, I'm sure, on either electric or hydraulic assistance. With a hydraulic system it's the small amount of movement before the shuttle valve operates in either direction to provide hydraulic assistance, with an electric system it's the small amount of deliberate hysteresis built in to stop the electric assist "hunting" around the "no assistance required" point. My guess is that the characteristics of the latter are variable from one make to another, depending on how the manufacturer perceives their target market.


I was astonished to read back there that the information might be gleaned from the torque-derived difference in a calibrated length of the column. Just what is that steel like?

Okay, it's easy to measure minute changes on a shaft but not so easy outside the lab. All that vibration on the point of focus . . . sheeeesh.:rolleyes:

That section has to be able to take full steering load, not just on the road but in an emergency, including veering away from say, a tree, while in rough ground. People get a lot of strength when that adrenalin pumps in. I know I did on that heavy MkI0's old fashioned powered-steering box. Or should I say, powered until that moment, steering box.:ooh:

It's pretty well-proven technology, that's been around for decades in helicopters. Take a look at the input shafts to the MRGB on a twin and you'll find that the torque sensor (used for the cockpit display and as a FADEC input on newer types) is just such a relative twist measurement system. In the helo case it's dealing with a shaft that's continuously rotating at very high speed, so far more demanding than the steering torque sensor on a car.

Sensing torque on a shaft with a limited rotational range isn't at all hard to do. It's just some strain gauges bonded to the shaft thinned down section that are used to to measure the very tiny deflection (twist) in the steering shaft with increasing torque. When I looked at the unit on the steering motor they took out of my car when it was recalled, the torque sensor seemed to be within a plastic case about 2" in diameter and maybe 1" thick, around the shaft. I understand that much of the space was taken up by a flexible cable wrapped several times around the shaft to transmit the signal out to the motor control electronics (that's what I was told by the technician doing the job).

MG23
2nd Nov 2016, 16:09
Which one? I have a 2012 XV. Excellent car, but does it do this?Forester. I'm pretty sure the XV doesn't do that; it's just software, so probably one way they differentiate between the different models for different market segments.

Loose rivets
2nd Nov 2016, 16:34
Thanks, VP. I guess I'm getting to be quite a dinosaur. In my day outer threads had to climb along an inner helical gear against a calibrated spring and then send a message to the torque gauge and/or modify the VP prop's control valve setting.

VP959
2nd Nov 2016, 16:59
Thanks, VP. I guess I'm getting to be quite a dinosaur. In my day outer threads had to climb along an inner helical gear against a calibrated spring and then send a message to the torque gauge and/or modify the VP prop's control valve setting.
Strain gauge measurement is now dirt cheap and incredibly sensitive and accurate. I recently bought a very cheap strain gauge sensor, intended for use in cheap digital scales, plus a 24 bit amplifier and analogue to digital converter PCB, all for the princely sum of £5, including postage, from China.

I didn't expect much for that price, but when I hooked it up and tested it I found that it was very, very accurate, stable and sensitive, better by far than the strain gauge instruments we used to use on A/C components years ago, and that cost many thousands of pounds.

I doubt that an enhanced, more reliable, sensor, suitable for use as a car steering torque sensor, would cost more than £10. It might even be a lot cheaper than that.

Peter-RB
2nd Nov 2016, 17:39
My wife's car with the Electric steering is the BMW Z4, I have driven the thing 160 miles today and have to admit it has tired me out, I really do not like the feel of the steering and without feel or seemingly no self centring on corners I am looking forward to doing the same journey next week in my Jaguar S Type. which never tire me at all. Sad really, a brand new Beemer beaten by an old Jag.:ok: