Electric Handbrake / Emergency brake - Why? 10

[NickJ67]

Whats the reason for manufacturers moving towards electrically actuated, push-button handbrakes these days?

Having recently had to deal with one as fitted to the VW Passat, I have to say that it alone would prevent me from buying/leasing what is otherwise a pretty good car - such a pain to use when maneovering on a steep slope. I have also had the entertainment of watching my neighbor having to deal witha malfunctioning one on her Renault Scenic (non-release scenario).

Seems to me that they must be more expensive to fit and more prone to malfunction than a good old fashioned cable and lever arrangement - what am I missing? Am I a luddite....?

Regards

Nick

 

[rmw]

Hogwash,

I grew up in hilly terrain driving manual transmissions and have driven my share of manuals all through my adult life even after I began to drive automatics well into adulthood and I rarely if ever used the hand brake or emergency brake to assist me on a hill take off. Probably because they were located in such a way that they were intended for parking, not hand use.

I commonly drive manuals in countries other than the USA and likewise, I managed to get going on hills without having to resort to the hand brake or emergency brake. If I remember correctly, in England with the RH drive cars, the hand brake is on the same side as you are trying to shift with.

But I never would say never, and there have been a few occasions where it came in handy and I used it but they were rare. So it is not like I haven't done it or don't know how. It just wasn't taught to me when I was learning to drive as a technique and I just didn't practice it. Now, riding the clutch...... well that's another topic.

I have driven tractor trailers with manuals ranging from 10 speeds to 18 speeds and motor coach sized buses all with manuals ranging from 7 speeds to 4 speeds all with air brakes and there was no "hand brake". Plenty of that driving was in the Rocky Mountains. The parking brake as mentioned in my previous post was a pneumatic device that was either full application or off, not something that could be manipulated as a 'hill asssit'. In those beasts, you just had to have the skill to get off the brake and feather the fuel without killing the engine or breaking the passengers necks. And, no I never broke any necks, but yes, I did kill a few engines over the years. Embarrasing.

So I'm not buying it.

I did have one vehicle that had hand brakes and I say brakes as it was an Impy Sporster metal body dune buggy built on a shortened VW frame and the emergency/parking/hand brake was two handles (yes, between the seats), one connected to each rear wheel. When grabbed and yanked in a tight turn, it would make that DB spin on a dime. Fantastic.

Maybe I need to go back and learn how to drive all over again.

rmw

 

[GregLocock]

Damn so I can't take my driving test in my Aston Martin? (Old british sports saloons often had fly-off handbrakes on the outer side of the driver's seat).

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[btrueblood]

Rmw,

I learned to drive in tractors and dump trucks, and had quite a bit of off-public-road time on them before taking my driver's exam. During my first trip in a manual-transmission car for driver's ed course, I naturally did a heel-and-toe (or more likely just a quick-dip start) on a hill. The instructor chuckled, said he remembered now what my last name was (brother and sister had both driven with him), and made me go back and demonstrate a parking-brake start on a hill. He claimed that not doing it that way during a driver's test would result in points off.

Nowadays, on some hills around where I live, I still use the handbrake to start off. Not so much in my pickup truck, as it's got a foot-applied e-brake. An e-brake start is a little easier on the clutch, I think. I also tend to leave a good 10 feet or more when stopping behind a truck on a hill, just in case that driver isn't very good at hill starts and rolls back a bit. I've seen a few cars take a roll-back hit around here.

 

[swall]

btrueblood--thanks for reminding me why I never used the parking brake to get going on hills--most of the cars I have owned had the foot actuated parking brake.

 

[btrueblood]

It's do-able with the foot-actuated parking brake, but you've gotta have timing. Once you have timing, why bother...

 

[patprimmer]

Remember, we are a set of engineers here with an interest in automotive. I would suggest the average skill level of those commenting is well above average.

When I had a manual transmission company car, I was quite amazed at how many could not actually drive it when it had to do pool car duty and that was in Aus. I believe from anecdotal evidence it is even worse in the USA, but better in Europe.



Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[rmw]

I think that the ability to drive a manual transmission is virtually a lost art in the USA.

I read one newspaper account of a Greyhound Bus driver who was having trouble with one (Greyhound - an all automatic tranny bus company bought Trailways, an all manual tranny bus company and inherited a lot of buses with manuals) and a woman passenger came off the seats and volunteered to drive it (from Roanoak, VA to NYC) and he let her. He was fired upon their arrival.

I'd say the vast proportion of the population can't drive manuals and as soon as my generation dies off, that goes way up.

Some of the little fuel efficient "wind-up" cars are bringing it back somewhat, however.

rmw

 

[dicer]

Yeah funny stuff. Looks like the way it is heading, you will soon have zero control over the nice new vehicle you are driving. A major solar flare or some sort of emp and you will be out of control, no way to steer or stop.
Saying nothing about the repair costs for all the little electric specialty boxes, and transducers.

 

[GregLocock]

To be utterly boring about that, car companies track total cost of ownership, and attempt to correlate that (and many other things) with purchasing decisions made by their customers.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[Hauge]

I worked att VCC (volvo car corporation) with sourcing of a electric handbrake and can provide some insight.

The two main arguments were:
1: Interior Design/Safety
2: Old lady´s and such havent got the muscle to safely apply/disengage the handbrake.
other arguments:
3: You could incorporate some safety features such as hill start assist, automatic apply at red lights, connect the brake to the car theft system etc.
4: more freedom in packaging

At that time (10 years ago)it was hard to interpret the legality rules regarding handbrakes. Yes it was to be standalone , yes it was to give this retardation and be able to hold a car in a certain slope and it should be functional below 30 km/h.

one question we discussed a lot was the potential problem with wheel lockup when applying the brake... whas that acceptable even in low speeds ? ... the law didnt say.. just minimum retardation

Another question was how hard the brake should be applied: too hard always would give certain problems and too loose would give other. That brought us to next problem: How was the brake force measured and was it a reliable method ?
Other problems were safety related since the brake NEVER NEVER EVER was allowed to engage by itself when driving.

All the designs we looked att incorporated some kind of microprocessor with a watchdog.

We focused/looked on three designs.

One german design didnt really have force control and applied full brake always ... skipped immediately (the design didnt really allow for force control)

One american design consisted of a motor and a screw that pulled one wire which was divided into two wires with a "lever" (cant come up with the english word for it now). Basically you replaces the brake handle with an electric motor with a gear.
Seemed reliable enough.. however the product wasnt mature enough.

Another german design was really sexy it pulled both wires with the same force guaranteed. It had a REAL force sensor, instead of the other solutions that measured current draw/voltage.
It also used a internal tilt-sensor that changed the applied force depending on circumstances and actively monitored it.
Renault was to use that one and had already paid for the tooling.

Before i left VCC it was decided that electric handbrake had to wait a year or two pending more studies. (That was my opinion too)

Another issue/question was.. since its marketed as a safety thing it really has to be safe. What happes if the damn car starts to roll anyway.. for example a ferry:
The system pulls the brake cables to a certain tension, but on a ferry that might not be enough. Should the e-brake have a manually controlled maximum tension mode for the ferry event and can we trust the user to remember that?
Ok we probably cannot... what do we do about that?
One idea was to use the new type of ABS sensors that can sense small movements (hall sensor instead of a VR) and let the brake tension the cables if it moves, but they draw current and modern cars have already problems with battery life (current draw) when the car is turned off

End of post (my first one)

 

[GregLocock]

Interesting. So how did you deal with the flat battery conundrum? Car is left at the airport for six weeks with the headlights (or interior light) on. Annoyed driver returns that he needs more than just a jump start as his car has rolled into the ditch.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[BrianGar]

The thing I hate is that I now have to bring my laptop c/w vagcom outside whenever I need to change the rear pads in one of these 'yokes', callipers can no longer be wound back with the force+rotation method, and instead have to be wound back gismotronically. Hmmmmmm....

My opinion driving 'stick shift' all my life is that it is horrible. No feel from a button and it feels like it will break at any given time, without notice. Now, in what mode it will break in Im not sure.

Ive also heard of 'a good few' passats giving hell problems with the rear callipers already.

Pat, you mention hill starts, very true, and it is this Im talking about for a feel aspect.
But having said that, I rarely use the handbrake on a hill any way, Instead move my foot swiftly off the brake onto the accelerator , while at the same time bite the clutch, while at the same time give it revs. All that happens in .25 of a second amazingly...
When driving a button handbrake car, that all goes out the window, because on some(cant remember) they will auto apply handbrake if you are on an incline. Now thats annoying if your used of using my method described above.

BG

 

[NickJ67]

Hauge,

Thanks for your very interesting post - just the sort of insight I was hoping for when I started the thread.

It's also highlighted some interesting "cultural differences" in hand brake use.

Nick

 

[patprimmer]

If the electrical had brake still pulls a cable,a ratchet could still be incorporated that is released by a solenoid.

A built in hill holder solves another problem.

Another way is for the hand brake to be disengaged by the solenoid or linear motor or whatever while the brake is applied by a spring, like some truck brakes.

I still like a fly off handbrake between the front seats just behind the shift lever and I expect I always will. I still drive for fun at times and convenience or mindless foolproof operation can take a back seat, however I expect I am in a shrinking minority from a marketing point of view.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[patprimmer]

Hauge

If that is your first post, I look forward to many more. Very well done.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[rmw]

Agree with Pat there Hague. Well done.

Pneumatic braking systems had or have the ability to stay engaged when the air system went "flat" which is more typical than not.

Once the air system is re-established, the brakes don't just automatically release, it takes some action - full application of air pressure on the brakes for example in the case of one I am thinking of - to release the brakes.

I always wondered what the mechanism inside that cylindrical brake actuator was that accomplished that, but never took one apart to find out because some part or parts of it were spring loaded and loaded with enough force to do bodily harm. My respect for life and limb overcame my natural curiosity. It is one of the few things I never took apart just to see how it ticked.

rmw

 

[patprimmer]

rmw

I am pretty sure it is a coil spring that applies the brakes and air pressure releases them so an air line failure results in a screeching stop rather a runaway truck.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[BrianGar]

rmw, Indeed, its a coil spring inside the actuator, a very hefty one too. Been there, done that, broke a double glazed window investigating one once.

BG

 

[evelrod]

The failed air brakes can be released manually, but it's a time consuming and difficult job. Like Brian, BTDT more than once.

Rod

 

[jmw]

I had one of the newer Audi's out as a loan while mine was being serviced and this had an electrically operated "handbrake"....
It was bugger to figure out how to get away from initial switch on but every time I braked to a halt, it automatically applied itself. The engine also shut off.
Then when I pressed the accelerator, thee engine started and the ebrake released... this was an automatic (with rear view CCTV for what that's worth since the perceptions in it were completely different to the views in the mirrors).

I really wasn't that keen on either idea. I like to be in control.
With a mechanical handbrake working through the rear brake assembly, you have a very tactile feedback and you can then feel for roll back or forward as you release the footbrake.
You will also know immediately of the cable snaps...and you will get a feel for how well it behaves as any other changes are likely to be progressive.
An electonic brake will either work or not work... so what's the failure mode? fail in position? fail and apply fail and release?

I suspect that the more such features are added, the lazier and less "switched on" the driver becomes ... a recent study reports that drivers using cruise control are significantly more likely to have accidents than drivers without....

JMW

http://www.ViscoAnalyser.com