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Auto reverse brakes issue

by argonaut » 23 Jun 2018, 22:00

OK ..... I gave up trying to fix this, had dozens of people provide suggestions. Replaced loads of spare parts, taken it into Indespension twice - still unresolved.

Instead I modified the Coupling so that the 'Brake actuating lever cannot move' i.e. the hydraulic coupling cannot move backwards.
I did this without touching the sliding tube, damper or seals.
Instead I drilled the frame such that a 12mm high tensile pin can be inserted immediately behind the 'S Pawl' (Brake actuating lever).


The white on pin is just primer I was pushing into the hole .... the red band is to make sure it goes in for correct insertion depth.
Not a through hole ... though both walls of the square section and 3/4 through the handbrake assembly plate .... didn't make it through hole as it would go though the swivel part of handbrake assembly, and was too close to grease nipple.

Sorry I can't post pics ... forum does not seem to want to accept links from FLIKR today


Insert pin for reversing up hill, remove and brakes function as normal.
https://flic.kr/p/JPrAtD

Image

https://flic.kr/p/276Fj9v
Image
Monterey 194fs with Monster MTK tower + water and SkySki = fun ...... towed by Kodiaq Edition
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by Bigplumbs » 24 Jun 2018, 05:57

Well done as suggested some time ago

May I ask how long that little job that you knew would work took as opposed to the time spent flogging that dead horse
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by argonaut » 24 Jun 2018, 09:20

Bigplumbs wrote:Well done as suggested some time ago

May I ask how long that little job that you knew would work took as opposed to the time spent flogging that dead horse



The time is not really relevant .... I could have done this mod on first day - there was no flogging of a dead horse, as you know from all the comments here, & on Ribnet - everyone was convinced its just a simple adjustment.
I wanted to diagnose the problem and fix the root cause, as a problem could impact other things.

If you get a noisy gearbox - you could put in handfull of sawdust so you don't hear it, but it does not fix the problem.

As it happens I have now taken a modern auto-reverse brakes and turned clock back 30 years to manual lock out brakes :( - but at least I have a work around.

I found articles by Bradley. Knott & AlKo that suggest they know this is an issue ..... and Indespension admitted fully it is a problem on trailers as they age.

My last thoughts are it is probably wear of the drums coupled with 'maybe' over drive from the coupling.
Neither 'wrong' but together take the 'limit of tolerance' outside that which allows the Autoreverse to trip .... for example I know the drums are at least 8mm larger diameter (maybe 10) .... that will take shoes out further, and teh angle it presses on autoreverse cams changes - maybe too much.

No way to prove without paying big money to change drums, and if its not them ... then a lot of wasted spend.


Add on - AlKo advise that they now fit auto adjust mechanisms to their brakes (like car drums used to be), I bet that is another complexity that will cause issues after a few dips in salt water.
The UK trailer industry should fit stainless disc brakes to marine trailers - the US do this, far better.
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by Bigplumbs » 25 Jun 2018, 05:58

Perhaps the 30 year old solution was always better than the modern approach

I was told once that NASA spent millions of dollars developing a pen that would work in zero gravity........The Russians just used a pencil

So how long did the fix take........... even though not relivent
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by argonaut » 25 Jun 2018, 08:29

Can't answer that ....
If you mean how long to drill a hole - minutes .... how long to figure out how to do this, where to do it, what diam, what part of mechanism to lock up - unknown was looking at it over days.
Loads of advice on making a bracket or rod to lock coupling .... became very complex, my neighbour who is a mechanical engineer ... spent some time looking at it, drew up a 3 part system, a bracket that went over main draw bar, a welded on brace that reached down to bottom of Actuating rod, and 2 lock-in pins & chains.

Yes it would have done it .... when I showed him my end solution he said 'OK .. that works as well' .... he did donate the 12mm high tensile pin.
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by Ianfs » 25 Jun 2018, 10:26

Shame its come to this, I fully understand why you wanted to get it sorted out correctly. It does seem like its a known fault with this system and as you said earlier, the new auto adjust system is looking for trouble with saltwater use. :shock:
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by betty boop » 02 Jul 2018, 21:24

bit late but found this tonight thought it may be useful for someone -

http://www.sbstrailers.com/PDF/SBS.PDF

PDF on brake adjustment and trailer maintenance etc.
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by argonaut » 02 Jul 2018, 23:46

It is a cut & paste ... of the AlKo document posted early on in this thread.
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by betty boop » 04 Jul 2018, 13:01

argonaut wrote:It is a cut & paste ... of the AlKo document posted early on in this thread.


no idea I didn't read it. was just trying to be informative etc.
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by Ianfs » 06 Jul 2018, 07:28

Maybe you've already done this but, I still suggest when you get some spare time, that you jack the trailer so wheels off the ground and try to compress the draw shaft in order that you can see when the brakes are being activated and potentially show the movement of all the contributing parts. By compressing it gradually bit by bit, you can go through each stage of braking and by turning the trailer wheels, all of them in turn to find the moment of braking this could give you more of an idea of what is actually happening. Also, when the brakes are fully engaged you should be able to turn the wheels backwards by hand. :)
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