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Postby MartyBartfast » Mon May 27, 2013 5:03 pm

Nuke wrote: Having no handbrake lever, how does it meet the requirement for at least two independently controllable braking systems ? I'm interested.



If it's anything like my Passat it has a button, and no I don't like it - I don't have the same confidence it it as I do with a direct mechanical linkage between my left hand and the brake disks/drums.
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Postby Nuke » Mon May 27, 2013 6:35 pm

MartyBartfast wrote:If it's anything like my Passat it has a button, and no I don't like it

So no graduation? Press the button and it slams full on? I would not like to use that if my foot brake ever failed - it would spin you right out of control. Better to be braking more gently and rear-end the guy in front than to go across the road and meet one coming the other way.

Also, the legal requirement for the secondary brake is that it should hold on ~ a 1 in 6 gradient. That is one helluva force and I would never apply a conventional handbrake that hard just for parking on the flat, which is most of the time. I would be concerned about wearing out and fatiguing the components. But presumably a button-brake does that very time.
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Postby MartyBartfast » Mon May 27, 2013 7:19 pm

Nuke wrote:
MartyBartfast wrote:If it's anything like my Passat it has a button, and no I don't like it

So no graduation? Press the button and it slams full on?


Don't know as I've never tried it, but there is logic in the circuitry such that you can do a hill start with the "hand" brake on and it will gradually release the brake as the engine takes up the strain so it's not outside the wit of the programming to realise that if you hit the button while stationary it goes full on immediately, but if you hit the button while moving it applies the brake more gradually - I wonder if you'd be allowed to pass the driving test hill start component with one of these though?

These type of brakes are quite common nowadays so clearly the fulfill all the legal requirements.
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Postby wyliecoyoteuk » Mon May 27, 2013 8:18 pm

Nuke wrote:
wyliecoyoteuk wrote:My current car has no keyholes in the door or dash.
It has a start button, and no handbrake lever. The speedo has a digital readout.

And the advantages are ? Having no handbrake lever, how does it meet the requirement for at least two independently controllable braking systems ? I'm interested.

Well, The parking brake is electronically operated, requires no physical effort, and is separate from the footbrake system. Most cars these days have several braking systems. In fact I did have a Xantia 8 years ago that had 2 seperate processor unitts for each, and four processors for the suspension system.
My current vehicle has proximity sensors for the keys, tied into the alarm system, it unlocks when I put my hand in the door handle, and locks when I walk away.
When I switch off the engine, the handbrake engages (unless I override it).
When I accelerate, the handbrake disengages.
There is a manual override switch.
You need to look right at and read your speedo; but I can see the angle of my analog speedo needle in the corner of my eye, like I know where 30mph is.

That's nonsense. I have a large clear numerical display, which is far easier to read, and is accurate in MPH and KPH, which having recently returned from a French trip in a vehicle with an analogue speedo, I can confirm it is far easier to follow.
And the first thing I would do with a car like yours is put in a hard-wired engine kill switch because of stories like this [I don't normally read the Grunaiad btw] :-

more nonsense.
There are at least 3 ways to disable the engine, he only had to switch the ignition off. It is far more likely that the disabled adaptions were faulty.
http://www.guardian.co.uk/world/2013/feb/13/french-driver-200kmh-car-chase?CMP=SOCNETTXT6966

Despite my old banger having an old-fashioned ignition switch, I put in a kill switch anyway as part of a home-brew anti-theft arrangement, but don't tell anyone. :wink:

sadly, that would probably render the vehicle inoperable. The built-in immobiliser is far more effective anyway.
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Postby MartyBartfast » Mon May 27, 2013 8:33 pm

wyliecoyoteuk wrote:
Nuke wrote:
wyliecoyoteuk wrote:
There are at least 3 ways to disable the engine, he only had to switch the ignition off. It is far more likely that the disabled adaptions were faulty.



Yes, it also seems bizarre that after driving over 100 miles at up to 125 mph, once "his petrol tank spluttered empty" he then felt the need to drive into a ditch rather than just wait for it to roll to a stop.

I think there's more to this than is being reported in that story.
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Postby guy » Mon May 27, 2013 8:57 pm

If both braking systems rely on electronic control, what happens if the electrical system fails at speed?

"They were so primitive, they still thought digital watches were a pretty neat idea". So wrote Douglas Adams ca. 1980 in the days when you could hardly find an analogue watch to be sold. They tried digital speedos in cars, too. We all tried, we really did, but both soon fell by the wayside in favour of the more effective analogue displays. History does tend to repeat itself, so today it looks like a case of here we go again.
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Postby MartyBartfast » Mon May 27, 2013 9:18 pm

guy wrote:If both braking systems rely on electronic control, what happens if the electrical system fails at speed?


You do a "Casey Jones" and slam it in reverse :shock:
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Postby wyliecoyoteuk » Mon May 27, 2013 9:24 pm

guy wrote:If both braking systems rely on electronic control, what happens if the electrical system fails at speed?

Simple really, the electronic systems control the servo pumps. if the electronics fail, they stop controlling the servo. if the servo fails, you have to use brute force on the brake pedal.
I have experienced similar controlled shutdown in a system undergoing successive hydraulic failure.
First the steering gets heavy, then the brakes, and finally (if you have hydraulic suspension) the suspension.
The system fails in a manageable manner because the fluid supply is prioritised.
At no point is manual override eliminated.
The systems do not rely on electronic control, it is used as an enhancement, not a replacement.
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Postby MartyBartfast » Mon May 27, 2013 10:03 pm

wyliecoyoteuk wrote:The systems do not rely on electronic control, it is used as an enhancement, not a replacement.


The handbrake system is fully electronic, all there is on the dash is a small button, which could be pressed by my little finger, to activate the handbrake. Once it's been pushed the electrics do everything.

Not the same for the footbrake though.
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Postby Nuke » Mon May 27, 2013 10:58 pm

wyliecoyoteuk wrote:
[Nuke said] And the first thing I would do with a car like yours is put in a hard-wired engine kill switch because of stories like this :-http://www.guardian.co.uk/world/2013/feb/13/french-driver-200kmh-car-chase?CMP=SOCNETTXT6966

more nonsense.There are at least 3 ways to disable the engine, he only had to switch the ignition off. It is far more likely that the disabled adaptions were faulty.


Yes indeed, the disabled controls were faulty, somehow jamming the throttle wide open. But the point of the story is that the engine start/stop was not contolled by any ignition switch, but by an electronic start/stop button, and this button would not stop the car. because, unlike an ignition switch, it did not act directly but was only one of many inputs to the car's micro-processor This story got a lot of coverage at the time and I gather that he did push the start/stop button but the micro-processor thought it was a bad idea to cut the engine in the outside lane of a motorway at 125mph, so his frantic button pushing was ignored.

wyliecoyoteuk wrote:
[Nuke said] Despite my old banger having an old-fashioned ignition switch, I put in a kill switch anyway

sadly, that would probably render the vehicle inoperable. The built-in immobiliser is far more effective anyway.

You've lost me there. The very point of my "kill" switch, or more accurately my anti-theft switch, is to render the vehicle inoperable.

As for a built-in immobiliser being more effective, (i) my car never had one in the first place; and (ii) how would you know how effective my immobiliser is? One thing is certain, a thief would not know where to start with it, because it is a unique design, my own, and not a standard fitting. It would even take me about an hour's work to override it, and that is with my own circuit diagram to hand. OTOH, it is fairly common knowledge how to override the built-in immobiliser of my wife's car (a popular type I shall not name) within a minute - and from the outside.
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Postby wyliecoyoteuk » Tue May 28, 2013 6:24 am

MartyBartfast wrote:
wyliecoyoteuk wrote:The systems do not rely on electronic control, it is used as an enhancement, not a replacement.


The handbrake system is fully electronic, all there is on the dash is a small button, which could be pressed by my little finger, to activate the handbrake. Once it's been pushed the electrics do everything.

Not the same for the footbrake though.


Yes, mine is the same, but the footbrake is not electronic, although there are several electronic braking assistance systems.
Last edited by wyliecoyoteuk on Tue May 28, 2013 6:35 am, edited 1 time in total.
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Postby wyliecoyoteuk » Tue May 28, 2013 6:33 am

@nuke, a disabled vehicle with third party adaptions is not exactly a good example.
Without knowing the details of the adaptions, it is not possible to comment further.
For my vehicle to do that, there would need to be several separate failures, most of them mechanical, I.e. clutch, gearstick, accelerator, brake pedal.
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Postby guy » Tue May 28, 2013 10:16 am

One very good reason to kill a petrol engine is to kill the high-voltage pulses from the controller to the spark plugs, as if these continue after a crash there is a risk of an ignition lead sparking and igniting petrol vapour.

Any electronically-controlled petrol engine without a controller kill switch is a ticking time bomb.

Makes us turbo-Diesel freaks a bit smug. And my brother with his old classic and its mechanically-driven magneto.
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