wiggs
Member Since: 03 Sep 2006
Location: Manchester
Posts: 14368
  
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Good idea ..but then you wont get them nice power point presentation slides 
I have PM 'd Martin about the docs  as it would be good for everyone ( well almost everyone  ) G4 Gone ...but not forgotten
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 8th Oct 2008 2:14 pm |
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Harlequin
Member Since: 29 Mar 2007
Location: Hornsea, East Yorkshire
Posts: 231
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Here's another slant on the EPB. My D3 is 18 months old and has done just over 28k miles. Until recently, I hadn't had a problem with the brake until - a few days ago - it started to 'clunk' as it reached the end of its travel when being applied. It didn't do it every time - just now and again. Anyway - I though that it wasn't that serious and I would mention it when I put the Disco in for service.
Last Thursday, I am in the middle of a very busy junction in the middle of Hull - right hand filter at traffic lights. Applied the brake - waited for the lights - they change to green - and off I go. Except I didn't.
The brake had locked up solid and wouldn't release no matter how many times I flicked the switch. Tried driving off - including in low ratio and the car wouldn't budge an inch.
So there am I talking to LRA on the phone with traffic blasting their horns and forcing their way past me -it was pretty horrendous.
Anyway, whilst I am talking and flicking the brake switch up and down - lo and behold, it clears - and I am off again.
When I get back to the office and ring my favourite dealer, I am told that it's probably an adjustment issue and that LR wouldn't cover stripping down the brake unless a service is done at the same time because they would argue that the service was nearly due and therefore it was a service issue. Whilst I wasn't too chuffed with this explanation, I accepted it because the dealer has always provided excellent service (and value) in the past.
Service now done - brake seems to be OK - but very disconcerting when it happened. I was taught to be cautious.
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| 8th Oct 2008 4:35 pm |
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colinm
Member Since: 06 Oct 2008
Location: Derbyshire
Posts: 47
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From what I have seen so far the actuator has a force sensor to allow it to modulate the cable tension but it has no position sensing so is not able to detect a cable adjustment problem. If you disconnected one of the cables it would seemingly actuate in the apply direction and keep running until the nut/threaded rod (that do the pulling) reach the mechanical limit and stall the motor. My experience of rod and nut servos (for radio control applications - don't ask!  ) is that having hit the mechanical stop like that it's not guaranteed that reversing the servo will unlock it as the inertia of the motor can really lock the thing up tight. The documentation actually warns technicians from operating the unit with a cable disconnected as it can damage it.
I wonder if the noise you were hearing was the actuator starting to reach its limits of travel and that it finally got to the point where it could lock itself up.
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| 8th Oct 2008 6:47 pm |
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10forcash
Member Since: 09 Jun 2005
Location: Ubique
Posts: 16534
 
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There's a spring clutch unit between the motor and the splined drive - thats what causes the noise...
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| 8th Oct 2008 9:23 pm |
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colinm
Member Since: 06 Oct 2008
Location: Derbyshire
Posts: 47
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Quote:There's a spring clutch unit between the motor and the splined drive - thats what causes the noise...
Interesting - I can find no mention of it in any of the documentation. Have you any more details of it?
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| 8th Oct 2008 10:32 pm |
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NJF
Member Since: 05 Oct 2007
Location: Gone
Posts: 2466
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TFC wrote:There's a spring clutch unit between the motor and the splined drive
I haven't a clue what that means. He's a boffin. Not a single mention of a thingummywhatchumaflip. 
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| 8th Oct 2008 10:38 pm |
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10forcash
Member Since: 09 Jun 2005
Location: Ubique
Posts: 16534
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Its part of the EPB gearbox (item 6) between the motor & splined drive
Logically, there has to be a clutch to prevent motor stall and overheat in the event of over-extending the PB cables prior to force threshold being reached
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| 8th Oct 2008 10:54 pm |
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10forcash
Member Since: 09 Jun 2005
Location: Ubique
Posts: 16534
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wiggs wrote:... as it would be good for everyone ( well almost everyone )
James May wrote: cock 
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| 8th Oct 2008 10:58 pm |
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colinm
Member Since: 06 Oct 2008
Location: Derbyshire
Posts: 47
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10forcash wrote:Its part of the EPB gearbox (item 6) between the motor & splined drive
Logically, there has to be a clutch to prevent motor stall and overheat in the event of over-extending the PB cables prior to force threshold being reached
Well, it would be extremely easy to do both the torque limitation and overheating protection electronically by motor current monitoring/control (electric window-lifters all work this way). The high pitched scream could originate from the PWM bridge drive to the motor. Unfortunately a slipping clutch does not guarantee that you will not get the threaded drive hung up at one end especially as such clutches tend to become 'handed' after some use and this applies even for a ball-screw drive as per NC routers etc.
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| 8th Oct 2008 11:12 pm |
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NJF
Member Since: 05 Oct 2007
Location: Gone
Posts: 2466
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OK, that's enough. Does anyone on the site speak English? 
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| 8th Oct 2008 11:20 pm |
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wiggs
Member Since: 03 Sep 2006
Location: Manchester
Posts: 14368
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10forcash wrote:
James May wrote: cock
And yes your are being one !!!
"**coming soon! Fire pump maintenance!!** No idea what i'm doing but I can talk a good job!"
Oh very mature  G4 Gone ...but not forgotten
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| 8th Oct 2008 11:28 pm |
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colinm
Member Since: 06 Oct 2008
Location: Derbyshire
Posts: 47
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NJF wrote:OK, that's enough. Does anyone on the site speak English?
Being in Luxembourg I would have thought you would be into linguistic diversity 
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| 9th Oct 2008 10:50 am |
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