If you go for air brakes only the spring brake chambers will sort your problem should the trailer come off as once the red line is broken the brakes will apply, as for the load sensing this is done at the moment down the multi pin ebs socket via air bag pressure, though if you leave this unplugged you will have full brake pressure all the time and as mentioned above the wheels could well lock up often, the other thing is the valve under the trailer will be 24 volt, just another thought after repairing many dump trailers and low loaders used behind fastrac type machines I get the feeling that the factory fitted compressors are poor and doubt if they are able to supply the quantity of air required for a 3 axle air suspension trailer that is fitted only with air brakes!
as you now know a drum braked trailer would be far easier to convert as its a simple job to add hydraulic bakes to a working air system! oh and as for copper grease on the calliper sliders I think you will find that out of the 2 sliders on each set up one is going to be a bronze type bush that’s sealed from the elements and gives little trouble and the other is a rubber type bush that’s open and allows grit and crap to corrode the slider pin ( a poor design even on road going trailers ) which is often the tight one!
yes parts are no problem but £300 wont go far when you start to replace pins and bushes on callipers!
just re read your last post and now see you are in a rush, if you start to move the trailer round before the air pressure is up you will not do the suspension any good due to the fact that the air bags are often slower to inflate than the spring brakes are at releasing, in short the whole idea is to complicated and far to many things are able to go wrong, I can only conclude that is why all farm dump and low loader trailers that I have worked on are fitted with springs and drums!
I think the op would be better starting again with an old tandem step frame semi low with no load sensing and drums with type 24s on ,it could be cheaper even at this stage .
Cant be done.How can you have a vehicle without air brakes controlling an air braked trailer.You need an air pulse from the foot valve to the modulator valve on the trailer to apply air to the chambers from the brake tank.
I thought I remembered hydraulic control of trailer vacuum brakes. So below from an early 1960s AEC Mercury workshop manual. The tractor does need to have full power hydraulic brakes, so the trailer can’t be towed by a little grey Fergie. Obviously a suitably sized and driven air compressor etc is needed along with reservoirs and a full trailer control air system. How to provide a secondary means of operation depends on how the tractor’s system itself works.
Bking:
Cant be done.How can you have a vehicle without air brakes controlling an air braked trailer.You need an air pulse from the foot valve to the modulator valve on the trailer to apply air to the chambers from the brake tank.
Is this a ■■■■ take?
Read it again, one of my tractors has air brakes. The other main tractor that doesn’t have air brakes will most likely be replaced next year, hence the dilemma whether to bother fitting dual air/hydraulic brakes to the trailer. Now probably just looking at how to have the best air only setup on the trailer.
I was expecting to have to fit a new load sensing valve, wasn’t expecting to be able to use the electronic one on there now.
I appreciate that the trailer I’m using isn’t the ideal starting point but it’s been done before, successfully. So I will be sticking with it!
I think what I need is a ‘combined relay emergency brake valve’. This would act as a regular brake valve and also provide a fail safe if the red line were to become detached. Then I assume the load sensing valve, T’d in to an airbag line, would be fitted before the yellow line gets to the brake valve rather than fitted on the output from the brake valve, if that makes sense. Would also have a hand operated dump valve for the tank to stop the brakes being left on whilst the trailer is stored.
cav551:
I thought I remembered hydraulic control of trailer vacuum brakes. So below from an early 1960s AEC Mercury workshop manual. The tractor does need to have full power hydraulic brakes, so the trailer can’t be towed by a little grey Fergie. Obviously a suitably sized and driven air compressor etc is needed along with reservoirs and a full trailer control air system. How to provide a secondary means of operation depends on how the tractor’s system itself works.
Erentek do actually sell a standalone unit to fit on the 3 point linkage of a tractor which uses the hydraulic pump and hydraulic brake system to generate the correct air supply to work air trailers, so the same sort of thing you describe. But I seem to remember they are over £2000, a lot of money for a big awkward thing that wouldn’t even get a lot of use!
Proved right in my assumptions. I thought that it all came down to how to do it on the cheap. I just pray that this isn’t the similar sounding trailer with plans for such an alteration that was sitting at Street Farm until a few months ago, because that means it is likely to pose a threat to my family.
cav551:
Proved right in my assumptions. I thought that it all came down to how to do it on the cheap. I just pray that this isn’t the similar sounding trailer with plans for such an alteration that was sitting at Street Farm until a few months ago, because that means it is likely to pose a threat to my family.
I’m not trying to do it ‘on the cheap’, I’m trying to avoid chucking money down the drain. Why would I spend £2000+ on a ■■■■■■■■■■ oil to air unit which would only be used for a year or so until the tractor is replaced? I may as well just use the trailer only with the air braked tractor for now. Air only wouldn’t be such a bad thing anyway, stops a lot of people from borrowing it
I’m not sure why you all have visions of a deathtrap held together with bale string and a braking system lashed up with whatever bits of things I can find lying around. I don’t have much understanding of HGV air systems so I came here for advice on what valves etc I would have to buy to install a suitable air system. I am talking new, quality components installed correctly, I fail to see how that differs to an ‘off the shelf’ trailer? I will admit that some things are suited to ‘bodging’, but safety critical items are not. Also, well the trailer is apart and has the floor off, now is the opportunity to do everything right first time.
Also if the prospect of this trailer worries you, I suggest you don’t go near any farms or farm equipment, a FWI investigation found that 25% of farm trailers had no brakes at all and only 40% of trailers had brakes that met minimum standards! There’s a nice thought for you all…
Not sure what the reference to Street Farm is about, this trailer was bought from a HGV disposal sale.
If you’re only having air you probably won’t need to do that much. Would need more info on what’s on there presently to advise though. You could still just fit the right electrics to the tow vehicle and leave as is.
Own Account Driver:
If you’re only having air you probably won’t need to do that much. Would need more info on what’s on there presently to advise though. You could still just fit the right electrics to the tow vehicle and leave as is.
I think for now I will work on the basis of air only with service chambers and an emergency relay valve. I can always add a hydraulic system at a later date without modifying the air system, looking unlikely though. I will have a look at what’s on the trailer currently, but it certainly seems over complicated! It would be nice to be able to leave it as it is, retaining the ABS/EBS and electronic load sensing by fitting the tractor with the necessary electrics but as air brakes are becoming more and more common on tractors, it makes sense to have it compatible with all of them. Thanks for your help and not just having a go at me for the sake of it!
Moose:
If you go for air brakes only the spring brake chambers will sort your problem should the trailer come off as once the red line is broken the brakes will apply, as for the load sensing this is done at the moment down the multi pin ebs socket via air bag pressure, though if you leave this unplugged you will have full brake pressure all the time and as mentioned above the wheels could well lock up often, the other thing is the valve under the trailer will be 24 volt, just another thought after repairing many dump trailers and low loaders used behind fastrac type machines I get the feeling that the factory fitted compressors are poor and doubt if they are able to supply the quantity of air required for a 3 axle air suspension trailer that is fitted only with air brakes!
as you now know a drum braked trailer would be far easier to convert as its a simple job to add hydraulic bakes to a working air system! oh and as for copper grease on the calliper sliders I think you will find that out of the 2 sliders on each set up one is going to be a bronze type bush that’s sealed from the elements and gives little trouble and the other is a rubber type bush that’s open and allows grit and crap to corrode the slider pin ( a poor design even on road going trailers ) which is often the tight one!
yes parts are no problem but £300 wont go far when you start to replace pins and bushes on callipers!
just re read your last post and now see you are in a rush, if you start to move the trailer round before the air pressure is up you will not do the suspension any good due to the fact that the air bags are often slower to inflate than the spring brakes are at releasing, in short the whole idea is to complicated and far to many things are able to go wrong, I can only conclude that is why all farm dump and low loader trailers that I have worked on are fitted with springs and drums!
So the spring brakes will stop a laden trailer if the red line comes off!!!
One hell of a set of springs.Spring brakes are park brakes not foundation brakes.
Foundation brakes (50% GVW) have to be applied if the air supply is lost.
Spring brakes only have to rate at 16%
Lose a red line off a laden 39000kg trailer and the brakes will lock out, no spring brake can get any where near that level of effort.
