[SystemSafety] Another runaway car

[Simon Struck]

On 02/14/2013 03:11 PM, Bernd Sieker wrote:
> On 14.02.13 14:38, michael.ellims at tesco.net wrote:
>>
>> You should be able to turn off the ignition at any time, there is
>> usually a relay for the fuel pump however if it’s software controlled...
>
> In Germany there is a requirement that the engine must not be able to
> run unless the key is in the ignition and rotated to the "running"
> position, but I don't know if there is still a requirement that it be a
> direct mechanical/electromechanical (relay) link to an ignition (petrol)
> or injection (diesel) shutoff. If it's software-controlled ... who knows?

Turning the key into off-position mechanically locks the steering, does 
it? So simply turning the engine of might lead to further problems...

Simon

>
>>
>> Failing that, the vehicle can be put into neutral, that’s almost
>> always a mechanical shift unless you have paddles on the steering
>> wheel. Then I have no idea.
>
> If the gear is under (torque) load, it may not be easy to force a manual
> gearbox into neutral, although it may be possible with brute force. But,
> as below, if this was a specially adapted vehicle for a disabled driver,
> it was probably an automatic transmission, where Neutral may be
> electronically disabled above a certain speed (and, of course, no
> mechanical clutch pedal, either).
>
>>
>> The service brakes should be able to overpower the engine, esp. at
>> high speed as the torque at the wheels is lower (i.e. high gear) and
>> the front brakes should be able to apply >> 3000Nm per wheel on a
>> vehicle that size. Note it shouldn’t matter if the throttle is open as
>> regulations require an energy reserve to allow the brakes to be
>> applied 9 times with no engine power. However if you keep using that
>> up - then no power brakes.
>
> I agree. The problem arises if the brakes are (a) overheated from
> several half-hearted braking attempts or (b) there is insufficient
> suction, if braking assistance is vacuum-powered, and the vacuum is
> taken from the intake manifold: At fully open throttle there is very
> little "vacuum".
>
> Many modern petrol (and all diesel) engines use a mechanically driven
> suction pump. In that case even at full throttle there should be enough
> "vacuum" for the power brakes. Unassisted brakes should in theory be
> always available, but may require force beyond the driver's capabilities
> in some cases.
>
> Will be interesting to follow this.
>
>
> Bernd
>
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M.Sc. Dipl.-Ing.(FH) Simon Struck          / __\/ _\  /__\
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