Air / hydraulic brake rams how to the work

[ih1455xl]

Just brought a step frame trailer on steel springs not got a tractor on air yet but planning on it so how do these work do they air in the tank to release when using hyd brakes and is it just a hyd ram threaded on the treaded rod coming out of the air brake actuator

 

[benny6910]

You will need to drain the air out of the tank to get the brakes to release if you want to use the oil rams.

 

[Mur Huwcun]

They’re a bit of black magic! Does not make sense! They are a fail safe and brakes come on if emergency line is pulled or ripped off but once tank is empty they return back releasing the brakes!!!

I think I’m right in saying that they’re a single line actuator and not twin therefore don’t have a spring applied parking brake

 

[ih1455xl]

I always thought there was a big spring inside so brakes on when no air pressure

 

[Mur Huwcun]

I always thought there was a big spring inside so brakes on when no air pressure

Yes on HGV ones but these are different.

This has geen up on here before, it’s the best explanation I’ve seen

https://cdn.aea.uk.com/2020/11/Look-Behind-You-Guide-pdf.pdf

 

[ih1455xl]

Yes on HGV ones but these are different.

This has geen up on here before, it’s the best explanation I’ve seen

https://cdn.aea.uk.com/2020/11/Look-Behind-You-Guide-pdf.pdf

That makes a lot more sense now I was wandering why I could move this step frame with no air it’s single line so next plan try and fit some short rams in between the air actuators

 

[milkloss]

I always thought there was a big spring inside so brakes on when no air pressure

only on the park brake of an hgv trailer. Service brakes (for braking during driving) have a spring to hold them off.

edit. The shunt button on an hgv trailer uses air from the tank to release the park brake to allow a non air vehicle to move them temporarily.

 

[Mur Huwcun]

That makes a lot more sense now I was wandering why I could move this step frame with no air it’s single line so next plan try and fit some short rams in between the air actuators

Or the slack adjusters have been backed off. Are the rods in or out of the chamber?

 

[Exfarmer]

Surely this type of air over hydraulic brake is the standard agricultural actuator which either uses air or hydraulic pressure to actuate , not to release as in lorry type braking.
That was how mine worked, but it was a few years back

 

[Mur Huwcun]

Surely this type of air over hydraulic brake is the standard agricultural actuator which either uses air or hydraulic pressure to actuate , not to release as in lorry type braking.
That was how mine worked, but it was a few years back

That’s how I see them aswell but they have a failsafe if red line is taken off but then when the air in the tank runs out.....

 

[FIL46]

Looks like if you have air on tractor, when brakes pressed the hole ram will push out of the black part applying the brakes, or if you are only hydraulic connect the hydraulic line to the tractor and the ram will push out only applying the brakes simple I think

 

[Two Tone]

Just brought a step frame trailer on steel springs not got a tractor on air yet but planning on it so how do these work do they air in the tank to release when using hyd brakes and is it just a hyd ram threaded on the treaded rod coming out of the air brake actuator

Trailers fitted with the type of brake actuator you show are used with either air or the hydraulic actuator, NEVER both at the same time.
The idea of the hydraulic rams is so that the trailer can be used, if the tractor pulling it doesn't have an external air brake system fitted.

When using the hydraulic brake system, there is usually a "Push to shunt" button you press to dump all the air out of the air actuators. If not, you can let all the air out of the tank, usually by pulling on the water drain valve until all the air is removed. Without doing so will not release the air brakes for you to move the trailer.

Once again, NEVER use both systems at the same time!

Air brakes are far superior, because they also incorporate a load sensor fitted to the trailer suspension that adjusts the sensitivity of the brakes, according to what the trailer load weight is. Thus saving the amount of braking and wear that the tractor pulling it has to exert on its own braking system.

 

[Zebbedee]

Most Ag trailers are fitted with single air actuators very often with a combined hyd actuation. Single air chambers (actuators) are just that ( one purpose) air supplied to chamber will apply brakes and springs in the drums release them again. When you remove the red line from tractor air then gets used from air tank on trailer to automatically supply air to chamber and applies brakes and this is your failsafe, however it is not a handbrake as when air tank loses pressure brakes will release again so modern hgv trailers use twin brake chambers. One side of chamber is as normal eg service brake but other half of chamber has a spring so with no air in system brakes are held on by spring in chamber attach the air lines to vehicle and release vehicle handbrake supplies air to spring side of chamber and releases the brakes then service side of chamber is allowed to work as normal.
Edit
I must stress that air or hydraulic neither are of any use if shoes and drums are not maintained correctly

 

[Andrew]

Unbolt the actuators already on the trailer and bolt on the ones shown in the OP.
To use on air, just plug the airlines in and wait for the tank to fill. When you disconnect the red line it should put the brakes on.
To use on on oil, drain all of the air out of the system, then use oil brakes as normal.

If the trailer has a shunt valve, you can use this to move the trailer short distances. But NOT on the road with oil brakes connected.
As said above, never use both systems at the same time.
Never use the air as a handbrake - when the air drains to nothing if will release the brakes.

The actuator you have shown is spring off, power on. The power is applied either via air pressure or hydraulic pressure. It is as you say a normal air on actuator, with a hydraulic ram in place of the threaded rod.

Another point to note - once fitted, you will probably find that the braking efficiency is far better with air than oil. The rules call for 50% braking efficiency on air over 40k, but only 25% on oil up to 40k. So manufacturers skimp on the size of the hydraulic ram to reduce cost.