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Rubery Owen three line air system

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Question please to those with knowledge of the Rubery Owen brake system ,our stores trailer has air over hydraulic on the front axle and air / linkage to the rear, there is three line air on the drawbar , service and emergency either side of the towing point and coming centrally from the drawbar the third line which I assume is parking brake. Does this operate the front axle , rear or both on application? Any advise welcomed to assist thanks.

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  • 1 year later...

Back in time the ford transcontinental era tractor units had 3 air lines red blue yellow as the norm I believe the blue was back up to the yellow so in theory if you put a variable air supply down the blue breaks should work as if using the yellow.

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Dear All,


The reason why I suggested a ref book is that the subject is complicated AND it is easy to get in trouble. Not least because it is easy for the authorities to check!


For instance, if you look at back of Bedford MK / MJ you will see a black brake hose permanently fixed to the vehicle pugged into the 'blue' socket. It is called, I think, the bridge. Its purpose is if a two line braked vehicle / trailer is connected rather than a three line one, the air will come out of the aux socket, through the black hose, and then via a double check valve out through the service yellow palm coupling. The result is that if you operate the aux hand control valve in the cab, the trailer brakes will still be applied as well as the vehicle brakes, (even with a two line trailer).


If you are towing a two line trailer with a three line towing vehicle it is important to consider what the blue aux line is doing!




With a two or three line air braked trailer, the brakes should apply automatically if the trailer should break away and this is effectively a legal requirement. To test this function fully charge the trailers air tanks. Turn off the shut off valve on the red line and then disconnect the red line palm coupling. The trailer brakes should immediately come on fully. If they do not you MUST rectify the fault. Since the driver can test this functionality at any time, you cannot claim that you did not know fault existed.



Next steps.


I have an air brake ref book and will see if there is anything that I can usefully scan.



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Thanks John, your comments all being correct , getting back to my original question and perhaps expanding more, I am trying to understand the braking system on our trailer as installed but seized so unable for me to practically test. The third line looks capped off beneath the drawbar , this is the same on others I have studied ( so is that that auxiliary line ? )

that aside does the parking brake operate both axles or only one ?

a Rubery Owen manual would be the answer!

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Evening Pete, thanks for that , so I know now what should happen but there must be seizure or foul play in certain valves/ lines, even though we have tried to clean out the system. ( sounds more like an old Scammell than a trailer doesn't it !! )

so warmer evenings and a dose of enthusiasm req'd to move forward .

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