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I've driven a number of cars with these and my last three have had them. I've never had any problems with them not working but anything with electrics ups the chances of failure; that said there is definitely a learning curve with the different systems and in the early stages an element of faith is needed. Oddly the only real advantage that I have found with them is with hill starts where it completely eliminates any chance of rolling back. For that it is very good but otherwise avant I completely agree with you on this and on starter buttons, space-saver or no spare wheels at all. Oh and electric tailgates. Two of our guys have these and by all accounts they're an initial novelty but then nothing but an unreliable curse.
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So how does one juggle EPB with clutch and accelerator on a hill start? And what is 'hill start assist'?
Is the EPB something originally aimed at the US market where everyone drives autos?
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You don't need to juggle it per se as you don't release it manually. Whether on a hill or on the flat, the handbrake will only release itself when there is enough power to move the car forward, at the point where you would feel the bite with a normal handbrake. If you are on a steep gradient or heavily loaded it will sense that more force will be required and will release at a different bite point. I've used it fully loaded in the Pyrenees and Lakes, it's been very good and I've not had a problem yet, though as I remarked above it is electrical so there's a greater chance of problems than with the purely mechanical device and when it does that will be a right pain.
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The motivation for electronic parking brakes was efficiency - an EPB applies more force than you can by pulling a handbrake lever.
On automatics, the EPB can apply itself when the car comes to a halt in stop-start traffic and release again as soon as the accelerator is applied, solving the "do I stay in drive" quandry discussed more than once here in the backroom.
It would seem to be an idea whose time hasnt' yet come, though...more R&D required...
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There's also the benefit of releasing cabin space by not having a lever between the seats, although that applies only if everyone gets the electric brake, not if it's only an option. Personally (and having tried only one of these devices, and only briefly) I remain sceptical: I'd rather be confident of controlling the car than have an extra box to store jelly babies in. My dentist would probably agree.
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I thought cars had to have a mechancially actuated parking brake to pass the MOT anyway, presumably this is not the case anymore, or was I sadly deluded in the first place?
FWIW the one car I drove with an electric handbrake ( Scenic Mk2) I really liked the idea & operation, but it did look like one more simple thing made complicated and hence less reliable in the process.
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>an EPB applies more force than you can by pulling a handbrake lever.
I can supply sufficient force to a handbrake lever to lock the rear wheels (as in a j turn) how much more force do you need?
I am all for technology in cars. The idea of hands free key cards and starter buttons is a natural progressive step as ALB, EBA, TC and stability control is to safety.
An electronic parking brake is just stupid tho. It serves no safety function, it adds no driving pleasure, it doesnt even have a wow factor. Just a "not sure if this is good or not" factor. I drove a scenic for a day with one. It worked perfectly well, but I didnt like it.
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TourVanMan TM < Ex RF >
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I could be wrong, but I think that the electric parking brake applies to all four wheels and applies considerably more force than a handbrake. I guess this would be advantage parked on a steep hill and/or under load and for safety when stopped at junctions or in stationary traffic. I don't think it's a big deal either way and I could easily live with or without but like starter buttons without comfort access, electric tail lifts etc. it is a solution to a problem that doesn't exist and one more thing to go wrong.
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One of the reasons (apart from cost) that I went for a Zetec C-Max rather than Ghia was to avoid the EPB that comes as standard on the Ghia.
It's a well known issue that the rear brakes on C-Max cars with EPB wear much quicker than the fronts.
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If the conventional mechanical handbrake fails the car can still be driven to a garage for a repair.
If epa fails, its an expensive callout etc.
I too thought a mechanical parking device was required for MOT ?
Its progress though, Advancing Backwards !
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There is manual release on the electric one. TBH if the conventional handbrake seizes, especially if it's a caliper rather than a cable problem, then most people are still going to be waiting for a callout.
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But drove a truck a few years ago that had a pneumatic or vacuum-operated handbrake, just a little lever sticking out from beside the seat that went on or off with a pleasant 'ch' sighing sound. Very powerful and easy to operate and didn't even look capable of not working.
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One thing intrigues me often - the electronics in cars fails so often, how does it work flawlessly on aeroplanes?
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One thing intrigues me often - the electronics in cars fails so often, how does it work flawlessly on aeroplanes?
It doesn't.
But it works much better. For a start, by automotive standards, 'no expense is spared' in manufacture. Then, and it's a big then, there are often one or two parallel backup systems. I suppose always when the system is 'safety-related'.
Why aren't the pilots and ex-pilots piling in with their actual knowledge, instead of leaving it to me to suppose things?
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>> One thing intrigues me often - the electronics in cars fails >> so often, how does it work flawlessly on aeroplanes? >> >> It doesn't. But it works much better. For a start, by automotive standards, 'no expense is spared' in manufacture. Then, and it's a big then, there are often one or two parallel backup systems. I suppose always when the system is 'safety-related'. Why aren't the pilots and ex-pilots piling in with their actual knowledge, instead of leaving it to me to suppose things?
>>
Depends on who the customer is.
About 8 years ago I worked for a company that made electronic assembles that went in planes, ships, subs etc.
Airbus, Boeing & Cessna asked for & got the best components money could buy with the best tolerance electrically, money wasn't an issue with these 3 they just wanted reliability.
Then we where asked to supply an electronic assemble for the Euro fighter or whatever its called now, they asked for cheap nasty parts that even Maplin customers would turn there noses up at, also they asked for 2 assembles per one aircraft, one was a back up just in case the first failed.
I remember seeing one of the Cessna units on heat / cool cycle testing, this testing would go on for days, it kept working up until they cranked the heat up way passed its design spec & the solder melted on the pcb's & the components dropped off.
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>>Depends on who the customer is.
I would say it depends more on the end use for the plane. For many reasons, including performance, the reliabilty requirements and redundancy strategy is different between a military and civil aeroplane. Which redundancy option you choose typically drops out of a statistical analysis of the likeliehood of various failure modes, based on the customer specification, the component MTTFs, and the loadings and configuration under scrutiny.
There isn't the same legal requirement to perform qualification testing for automotive parts - aerospace parts are typically subject to both development testing and qualification testing. Qual testing is done to industry wide standards, and the loadings are typically based on extremely pessimistic input data.
The requirements on aerospace software are also more onerous than most. For example, the instruction set is much reduced, and one bit being flipped by a cosmic ray or radiation particle isn't allowed to change the command being exceuted. To meet the reliability requirements determined by the statistical analysis, it is typical for high reliability electronic parts to be specified - these are really quite expensive, and in many cases, difficult to obtain. We have struggled obtaining parts as simple as diodes which would cost 50p in Maplin, and have eventually cost us £1000 each.
Material control, as described by Lee is also much tighter. Also more controlled are processes - these must be developed, qualified, and controlled - any change in even a tiny aspect of the material, component, or process can trigger the need for re-qualification.
Number_Cruncher
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Chatting to my local independent today he has asked the DoT how he is supposed to test electronic handbrakes; cannot be tested on the rollers as it locks before a reading is possible; cannot road test with a Tapley meter, not controllable therefore unsafe.
Advice he got was " do the best you can, we are thinking about it "
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apparently a creeping to the floor footbrake is also vosa acceptable on some late model (3 years old) cars
so someone told me on another forum
still find it unbelievable
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