Draft control at the top link

[Meg]

This message is a reply to an archived post by DavidP, South Wales on May 06, 2019 at 10:53:14.
The >Hi David,
I've been working away on the back of the 135 and have reached the top of the lift cover.
Read everything about the draft control spring I can find but still not sure how it works. I want to replace the boot and judging from the rest of the tractor I'll probably end up replacing the whole assy. I understand why it was developed but not how it does it. Although it's in the lift cover it doesn't appear to be hydraulic , people mention that it senses changes in the soil but it was invented a long time before sensors. Mine has a fair degree of play back and forth, the boot is shot and the allen screw is rusted beyond hope. It has a cat 1 pin as standard for the top link but badly worn, as I intend using her on a daily basis I want to make sure she's as work ready as poss. Sorry if I sound really thick but this one puzzles me.
Thanks
Lloyd

 

[DavidP, South Wales]

Hello Lloyd, hope you haven't been blown or washed away by this bit of bad weather that we are having at the moment.
Once understood the principle of the Draft and Position Control is quite simple. If you have a plough mounted on the three-point linkage and you lift it from the ground the weight of the plough rear of the lift arm balls will cause a tension force in the top link and consequently into the internal hydraulic linkage. When a plough enters the ground the resistance created by the soil will try to lift the rear of the plough. This cannot happen due to the top link which now has a compression force within it. When ploughing for example adjustment of the Draft quadrant lever will either cause the plough to work deeper or at less depth. Moving the Draft lever forward will allow the plough to go deeper and vice-versa. When you move the Draft lever you are changing the 'balance' of the internal linkage.

Think of the hydraulic system as a perfectly balanced see-saw. If you add or subtract weight on one side you must do the same to the other to maintain the balance. When the Draft lever is set to plough at a certain depth any changes in the ground conditions will 'upset' the balance. If you hit a patch of heavier soil the compression force in the top link will increase slightly. The internal linkage will 'sense' a change and tell the pump control lever to move into the pumping position briefly. This will have the effect of raising the plough slightly and reducing the compression force in the top link to the loading previously selected. If the heavy patch continues then the system will remain at that height and make it easier for the tractor to maintain it's forward speed. When you come to the end of the heavy patch the compression force in the top link will reduce either to the previous setting or below it. The linkage now tells the pump lever to place the pump control valve into the 'discharge' position briefly. This allows the plough to go deeper to a previous setting. Clearly if forward motion slows significantly then it will be necessary to raise the Draft lever and consequently the plough to allow forward movement to resume.

If you should encounter a boulder or other large object an emergency response occurs in the shape of an immediate rapid lift of the plough to clear the object. The word 'sensor' is a little too modern for the Ferguson System but 'sensing' is correct in that the system is continually 'reading' the loads placed on the top link and instantly automatically responds to any change when required. This would be far quicker than the driver might be able to.

If you have end-float in the top link/rocker mechanism it is essential that this is removed and any worn parts replaced. Significant end float will prevent the three point linkage lifting. You won't need anything as heavy as a plough for this to happen. I have had tractors in for repair in the past where they would not pick up something as relatively light as a Haybob. The wear present places the pump lever towards the 'neutral' position when the Position Control lever tells the system to lift.

It is important to slacken the locking allen screw if you can. If the control spring nut is badly rusted and seized in the cover don't waste time trying to undo it. It is far quicker to drill it through on both sides to weaken it and then carefully using a punch close the nut in to loosen it in the cover. Don't hit it too hard as it is possible to crack the cover at the 6 o'clock position.

When you have removed the CS assembly come back and I'll talk you through the next stage.

DavidP, South Wales

 

[Meg]

Thank you David. That answer should be archived as compulsory reading.Spent hours yesterday trying to explain other posts with part answers to myself but now I am there orthereabouts. I want to understand things before I try to repair, restore or replace in the hope that I do a better job that works, is safe and is more satisfying. I even managed to explain the basics to my wife who is very patient but I find it helps me to work through these "problems" . I watched Lance at Bundy Bear (Youtube) tackling the similar setup on a 35 which will help with the removal. I think it will be a case of drilling out the allen screw and/or your suggestion for the locking nut removal. I'm taking pics on the ipad before I start each section to help me with the partial rebuild , costed the back end at around ?1100 for parts so far, included new tyres, rims, brake assemblies etc. Once I've drained the transmission I can check the filter, the pto selector feels positive and the hub bearing and diff and diff lock move smoothly. Fingers crossed. A full rebuild/overhaul of the hydraulic pump will have to wait for next winter unless something else happens. The gears feel fine as does the clutch. The electrics are shot and the steering needs a lot of attention. Engine starts and runs, no smoke, knocking or scary noises. Water pump and hoses need replacing plus front tyres.
Will look at an engine rebuild next winter if she lasts the summer of reasonably gentle use.
Many thanks your comprehensive answer.
We are lucky here with weather, one or two trees down, most of our land is fairly steep so no flooding. Could be much worse.
Take care
Lloyd.

 

[DavidP, South Wales]

Hello, further to your reply;hope your wife understood the basic operation of the Ferguson system. I actually emailed my reply to my wife in the hope that it would help her to understand our passion for things MF!!!!!! As a farmer's daughter I think she needs to know about these things!!!!!!! Somebody might ask her to explain it one day!!!!!!
I spent some time with one of my customers this morning stripping part of his MF35 gearbox. Having read your email I recalled that he has a set of front and rear wheels for sale in Bridgend. I've just spoken to him he tells me that the rear centres are about a year old and likewise the front wheel rims. If you should be interested they could be a cheaper alternative to new. The front tyres are about 1/2 worn but are showing their age in some places. The rears would do for the time being. What other items are you thinking to replace?
If you would care to give me a call my number is 07772 236 583
Regards
DavidP

 

[Meg]

Hi David
The rear centres I have are useable but pitted, the rims on the rear are "see through lace". The front tyres, the left has less tread than a racing slick but the right isn't too bad. They all hold air but that's about the only good point. I've tried 'brass rubbing' the rears to read the size and make ,it looks like Ved ???????? Industrial Tyres but the size has long since perished.
I would love to save some of my hard saved budget and wondered what sort of price and location. We're just outside Cardigan and I have a Navara pickup if I could get them in the back, or take the top off our IWT small livestock trailer. In addition I need complete new brake assemblies, inner seals, square mudguards, hand brake,seat hinge and pins, top link draft control assy, top link, lower links , nuts and bolts and odds and ends to complete the back end and get her mobile. When I've rebuilt the back then I'll look at the engine, steering and wiring.
I've heard a mixture of ratings for the well known suppliers, some dodgy foreign knockoffs etc, wondered who you might favour?
I wondered if the top lift cover needs removing to connect the draft control spring assy to the draft control beneath?
I'm still looking for the UK full service manual, the I & T shop manual is not really enough.
Thanks for your patience.
Lloyd.

 

[DavidP, South Wales]

Hello, will get back to you tomorrow. The likely tyres that you have are from Netherlands manufacturer Vredestein. Not in the class of Goodyear or Michelin but well respected.
DavidP

 

[DavidP, South Wales]

Hello, I will try and take some photos if you have an email address that you can send me. They would go in a Navarra but easier to load into a trailer that has a floor ramp. If the backplates are badly rusted you don't have much choice other than renew. Inner hub seals are easy to replace once you have the half-shafts out. Shafts should be shimmed correctly afterwards. There is no need to remove the cover to access any part of the control spring
. I buy from Bepco,Agriline and Sparex. Generally all parts are satisfactory but some sheet metal items can require fitting. The difference in metal thickness can be considerable. If you are looking fo a manual try Big Stew on ebay. I have bought quite a few from him.
Regards
DavidP