*Whilst this post is based around the CNH Terraglide 1 system the principle is the same for all hydraulic suspensions and the discussion is open for various machines.*
I have heard from many people that the latest Terraglide on the newer 4B tractors works very well but I think its fair to say that the original setup never worked as well as we would have liked. I wrote a post on here last year on how to fit cab air suspension to New Holland tractors https://thefarmingforum.co.uk/index...sion-upgrade-for-new-holland-tractors.299452/ Since then I have been playing around getting my front suspension to work better on my T6.160.
I was fortunate enough to get my hands on a genuine New Holland dual accumulator upgrade kit. This made quite a difference but I have been told by several people that changing the pressures improves the ride. The problem has been what to change the pressures too?
I did quite a bit of research on various forums and the internet and it all got quite confusing as some say they found improvements with higher pressures and some believe lowering pressures makes the ride softer. As I didn't find the answers I was looking for I decided to search further afield and to the inventors of Hydro pneumatic suspension, Citroen. Citroen have been using this system since the 50's and allowing other manufactures such as Rolls Royce to use the technology before it found its way into the construction and agricultural fields. I went onto a Citroen car forum and found all the same arguments for whether to use higher or lower accumulator pressures that I was finding for tractor suspension. I then had a breakthrough by finding a very clever Citroën engineer from the Netherlands who made the whole tuning processes very clear. He said the best way to make the ride smoother is to change the valving. This is easily done on a Citroen as the valve is a simple disc type check valve at the base of the accumulator. Bigger orifice for a smooth ride, small orifice for a firmer sporty ride, but bigger accumulators at the correct pressure can also achieve a smoother ride. The valve chest on tractor front suspension is quite a complex and expensive item so I thought that was best left alone leaving the solution to increase the hydraulic damping volume in the system...
As the gas and oil pressure within a hydraulic accumulator will always be equal they work at their best efficiency when the chamber is 50% oil and 50% compressed gas which kind of makes sense. The tricky part is what pressure to pre-charge the accumulator in order to achieve this. There is quite a complex scientific equation to work this out but as we are using an inert gas (nitrogen) and we forget about thermal expansion we can simply say that the pressure of the gas doubles when the chamber size is halved. Or in simple terms the pre-charge pressure is half that of the oil pressure in the hydraulic system.
The next step was to find out what pressure was inside the hydraulic system of the front suspension at varying loads so a remote gauge was connected to the system.
I measured the front axle weight on a weigh bridge and took systems pressures at varying loads to give a full spectrum of what the suspension had to cope with which are as follows.
No front loader drill on back - axle weight 830kgs - system pressure 23bar
No front loader nothing on back - axle weight 2780kgs - system pressure 60bar
Front loader fitted nothing on back - axle weight 3460kgs - system pressure 85bar
Front loader fitted with grab nothing on back - axle weight 4420kgs - system pressure 105bar
Two silage bales on loader nothing on back - axle weight 5250kgs - system pressure 145bar
As you can see it is a lot for one accumulator to cope with. This was the point where everything started to make sense. The dual accumulator kit had given an excellent ride when running with an implement on the back or driving around with the loader on the front and even better with a grab on the loader but if the loader came off the ride became harsher again. The two accumulators fitted to my tractor were pre-charged to 15 bar and 60 bar meaning the system had a lack of damping at 60bar hydraulic pressure. Suggesting a 30 bar accumulator would give a smooth ride for an empty tractor. As the tractor spends most of its life with the loader on I decided to keep the 60bar accumulator and add an additional 30 bar accumulator. This then in theory covers me for the very wide range of front axle loads my tractor experiences.
There is now a total of 3 litres of accumulators damping the suspension which is almost too much as you can see the axle self levelling on loader work sometimes, but the ride is now incredible. You can see the axle moving absorbing the bumps no matter what weight is fitted to the front of the tractor. Even hitting plough furrows with 20psi in the front tyres you cant feel anything until the rear axle passes over it. The damping control from the Terraglide valve block is very good at controlling bounce on the road and the extra capacity from the accumulators provides very smooth stable control for road work .
I hope this Knowledge I have gained will help others set their tractors up to ride as well as mine. I know there are a few of us already playing around with accumulator pressures and I feel I have started a post where lots of useful information can be shared here. So on that note can I suggest we keep this post for useful questions and answers on the subject rather than individuals opinions on various types of tractor suspension. There are lots of reasons why manufactures don't do this to start with including cost, reliability, servicing, safety etc, etc. not to mention everything engineering can be improved!
I have heard from many people that the latest Terraglide on the newer 4B tractors works very well but I think its fair to say that the original setup never worked as well as we would have liked. I wrote a post on here last year on how to fit cab air suspension to New Holland tractors https://thefarmingforum.co.uk/index...sion-upgrade-for-new-holland-tractors.299452/ Since then I have been playing around getting my front suspension to work better on my T6.160.
I was fortunate enough to get my hands on a genuine New Holland dual accumulator upgrade kit. This made quite a difference but I have been told by several people that changing the pressures improves the ride. The problem has been what to change the pressures too?
I did quite a bit of research on various forums and the internet and it all got quite confusing as some say they found improvements with higher pressures and some believe lowering pressures makes the ride softer. As I didn't find the answers I was looking for I decided to search further afield and to the inventors of Hydro pneumatic suspension, Citroen. Citroen have been using this system since the 50's and allowing other manufactures such as Rolls Royce to use the technology before it found its way into the construction and agricultural fields. I went onto a Citroen car forum and found all the same arguments for whether to use higher or lower accumulator pressures that I was finding for tractor suspension. I then had a breakthrough by finding a very clever Citroën engineer from the Netherlands who made the whole tuning processes very clear. He said the best way to make the ride smoother is to change the valving. This is easily done on a Citroen as the valve is a simple disc type check valve at the base of the accumulator. Bigger orifice for a smooth ride, small orifice for a firmer sporty ride, but bigger accumulators at the correct pressure can also achieve a smoother ride. The valve chest on tractor front suspension is quite a complex and expensive item so I thought that was best left alone leaving the solution to increase the hydraulic damping volume in the system...
As the gas and oil pressure within a hydraulic accumulator will always be equal they work at their best efficiency when the chamber is 50% oil and 50% compressed gas which kind of makes sense. The tricky part is what pressure to pre-charge the accumulator in order to achieve this. There is quite a complex scientific equation to work this out but as we are using an inert gas (nitrogen) and we forget about thermal expansion we can simply say that the pressure of the gas doubles when the chamber size is halved. Or in simple terms the pre-charge pressure is half that of the oil pressure in the hydraulic system.
The next step was to find out what pressure was inside the hydraulic system of the front suspension at varying loads so a remote gauge was connected to the system.
I measured the front axle weight on a weigh bridge and took systems pressures at varying loads to give a full spectrum of what the suspension had to cope with which are as follows.
No front loader drill on back - axle weight 830kgs - system pressure 23bar
No front loader nothing on back - axle weight 2780kgs - system pressure 60bar
Front loader fitted nothing on back - axle weight 3460kgs - system pressure 85bar
Front loader fitted with grab nothing on back - axle weight 4420kgs - system pressure 105bar
Two silage bales on loader nothing on back - axle weight 5250kgs - system pressure 145bar
As you can see it is a lot for one accumulator to cope with. This was the point where everything started to make sense. The dual accumulator kit had given an excellent ride when running with an implement on the back or driving around with the loader on the front and even better with a grab on the loader but if the loader came off the ride became harsher again. The two accumulators fitted to my tractor were pre-charged to 15 bar and 60 bar meaning the system had a lack of damping at 60bar hydraulic pressure. Suggesting a 30 bar accumulator would give a smooth ride for an empty tractor. As the tractor spends most of its life with the loader on I decided to keep the 60bar accumulator and add an additional 30 bar accumulator. This then in theory covers me for the very wide range of front axle loads my tractor experiences.
There is now a total of 3 litres of accumulators damping the suspension which is almost too much as you can see the axle self levelling on loader work sometimes, but the ride is now incredible. You can see the axle moving absorbing the bumps no matter what weight is fitted to the front of the tractor. Even hitting plough furrows with 20psi in the front tyres you cant feel anything until the rear axle passes over it. The damping control from the Terraglide valve block is very good at controlling bounce on the road and the extra capacity from the accumulators provides very smooth stable control for road work .
I hope this Knowledge I have gained will help others set their tractors up to ride as well as mine. I know there are a few of us already playing around with accumulator pressures and I feel I have started a post where lots of useful information can be shared here. So on that note can I suggest we keep this post for useful questions and answers on the subject rather than individuals opinions on various types of tractor suspension. There are lots of reasons why manufactures don't do this to start with including cost, reliability, servicing, safety etc, etc. not to mention everything engineering can be improved!
