austin man
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| posted on 12/4/14 at 05:34 PM |
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trailer rebuild
I have just replaced all of the suspwension units on my trailer with 1300 kg indespension units previous units were fubbared an only one axle had
breaks these were hydraulic? The new units use cables instead ? Due to this I have made a lever arrangement to pull the brake on whe the towing hitch
pushes in, my concer is that when the hitch is connected to the brake sytstem it wont push in so doesnt appear to apply the brakes if I pus on the
hitch. The only thing I can think of is that there is a mechanism for reversing without appyling the brakes if so could the be the reason??
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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owelly
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| posted on 12/4/14 at 05:39 PM |
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I'm a bit confused by what you've written but if you've used proper auto-reverse trailer brakes, as fitted to most modern
trailer/caravan hubs, the brakes won't engage when you reverse the trailer as the mechanism in the drums sort of collapses when the drum turns
backwards.
http://www.ppcmag.co.uk
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austin man
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| posted on 12/4/14 at 06:00 PM |
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Its difficult to explain really if the hitch is not connected to the brake system it can be pushed inlike a shock absorber when I connect it to the
8mm rod that pulls the brake the hitch does not push in. Is this because I am effecrively reversing the trailer by pushing it and forward inertia
isnt being applied?
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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jacko
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| posted on 12/4/14 at 06:01 PM |
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What is the hitch like is it like the type with a big spring in ? or is it like whats on a alco caravan chassis ?
do you have a photo Mate 
Graham
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owelly
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| posted on 12/4/14 at 06:02 PM |
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What sort of hitch is it? We need piccies perhaps!
http://www.ppcmag.co.uk
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austin man
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| posted on 12/4/14 at 06:14 PM |
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Its a Bradley one which previously operated a master cylinder by way of a pushrod I am now using the rod to connect to lever producing a pulling
motion I do think ther will be a big spring in there thr are also 2 grease nipples on it. Will tray ang get pictures
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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jacko
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| posted on 12/4/14 at 08:40 PM |
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http://www.lsengineers.co.uk/bradley-d40-50mm-ball-hitch-coupling.html
Is it like this ?
If so it has a plate that swings over to stop the brakes coming on when reversing
There is a big spring inside it to damp the pushing effect by the weight of the trailer / load
Graham
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SteveWalker
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| posted on 12/4/14 at 09:13 PM |
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Probably just that the force needed to push the brake mechanism is more than you can apply by hand - from my recollection with a caravan, the lever
was pushed by the hitch only two or three inches from its pivot, whereas applying the handbrake used a lever nearly two feet long operating on the
same pivot and push point.
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austin man
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| posted on 12/4/14 at 09:35 PM |
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Yes like that jacko even without the plat swung over the hitch wont depress so I think its possible something in the brake drums that stops the
braking when reversing
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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austin man
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| posted on 13/4/14 at 09:38 PM |
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this is what I am working with
 
Description
 
Description
all help appreciated,
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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adithorp
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| posted on 14/4/14 at 07:54 AM |
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Without the hitch attached, how much/far does the brake rod pull? If thats adjusted so it has littlle play, then the hitch can't move any
distance. Maybe you need more leverage at your relay lever (looks 1:1 at the moment) to allow it to work better but pushing by hand is rarely enough
force to operate the brakes.
The reversing mechanism means that as the shoes contact the drums the rotational force on the shoes forces them down ramps at the end brackets and
releases the brake shoe from the drum. Going forward doesn't have that effect. It doesn't block/stop the movement of the cable so you
should still feel the movement.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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austin man
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| posted on 14/4/14 at 08:39 PM |
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quote:
Originally posted by adithorp
Without the hitch attached, how much/far does the brake rod pull? If thats adjusted so it has littlle play, then the hitch can't move any
distance. Maybe you need more leverage at your relay lever (looks 1:1 at the moment) to allow it to work better but pushing by hand is rarely enough
force to operate the brakes.
The reversing mechanism means that as the shoes contact the drums the rotational force on the shoes forces them down ramps at the end brackets and
releases the brake shoe from the drum. Going forward doesn't have that effect. It doesn't block/stop the movement of the cable so you
should still feel the movement.
what would you recommend as the ratio on the lever
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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adithorp
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| posted on 14/4/14 at 10:13 PM |
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Not the foggiest!  Sorry thats not very helpful... even if true.
I could have a measure of the lever lengths on mine tomorrow which should give a clue as to whats normal. It might be 1:1 for all I know.
If you had a handbrake you'd know how far the rod pulls and then work out a leverage to give that movement from say 1/2 or 2/3 the hitch max
movement... maybe?
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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