[arobwk]

I came across a web recommend (re a particular manufacturer's 2-gang offset disc harrow) about allowing 2" overall sideways slack/movement in the 3 Point Link setup when working a disc harrow.  In other words, to set the 3PL lift-arm stabilisers a bit loose.  Any general thoughts/experience please? 
(Accepted that settings for one brand/particular harrow might not suit another brand/harrow and that a bit of experimentation will be required)

[stufe35]

This is good advice, to allow some articulation between the tractor and the discs as you drive across the field to allow for slight steerage movements as you correct your line.

Otherwise you can induce massive loads in the stabiliser chains that they were never designed to take.  Ie the disc Harrow will be trying to stop your tractor turning, and all this force will be through one of the chains.

[arobwk]

Thanks for comment/confirmation Stufe'.  I will allow a decent amount of sideways slack on the 3PL for the next work-out (with gradual incremental tests) AND take extra care on the lift and turn manoeuvres, especially on the final across-slope harrowing!

[oor wullie]

I tend not to use stabiliser chains with my discs.  As Stu says the forces on the chains can be huge for equipment that is in the ground (certainly don't use chains on a plough) and I don't feel any problem with harrows moving about a bit.  The check chains on my tractor are sufficient to stop anything hitting the tyres.

[stufe35]

I agree, just really needed if sway is excessive when travelling down the road, or to prevent excessive swing as you turn on the headland.

[arobwk]

It wasn't hot and sunny in Cornwall today - couldn't see through mist more than 50 yards!  Soil was bit claggy (my dog brought good part of the fields home with her), but I wanted to experiment so did short stint.  Only gave harrow a bit of sideways slack on the 3PL today, coupled with extra length on top link - much better!  Ref oor w's input, I'll try a bit more slack next time.  Also thinking to try out using a chain as replacement for rigid top-link. 

Now then, what exactly does the term "headland" refer to?  (Some time back, I tried various search phrases for a ploughing definition, with nary an inkling!) 

In passing, neighbour dropped off his old 3-section zig-zag (9' or so) for me to try out: I shall be very interested to find out how many sections my 35HP tractor can manage.

[stufe35]

Do not replace your top link with a chain, it defeats the whole point of how a 3 point linkage works, and is dangerous in that your tractor could rear up.  Although admittedly this is unlikely with discs, more a plough.

The headlands are the bit at either end of the field where you turn around.

What sort of tractor is it ?

[arobwk]

Stufe' – Thank you kindly for the headlands explanation. 
Tractor is alpine-type Agromehanika AGT 835 TS (35 HP) which is 4WD and with 2/3 of it’s 1 tonne-ish weight over front axle.  Latter detail offered in view of your advice re chain top-link - and I hear you loud and clear on that point and fully acknowledge the need for caution – again, TY.  However,  I see it like this: 
The risk of a rear-ward flip exists with any pulled implement that could snag on, say, an immovable object.  If a harrow is a towed variant (i.e. not 3PL mounted) the risk of going into a rear-ward flip scenario would be, I assess, no different (assuming mounted as low as possible).   Using a chain as the top-link on my 3PL-mounted harrow would make it more akin to using a towed harrow, but still with the ability to lift it.  Therefore, while fully accepting that a rigid top-link provides extra protection against catostrophic consequences, a chain top-link would not increase the risk of a back-flip occurring compared to using a towed harrow on a draw-bar.  (If that assessment is wrong, I shall be most grateful to hear.) 
Finally, I would add that I would not consider using a chain top-link routinely, but I have some pronounced across-slope dips (along the line of removed stone-walls) that defy a good, even harrowing with my existing set up.  Eventually, the dips will get smoothed out!  I wouldn't dare consider a chain top link on something like a topper!

[stufe35]

Read this. 


https://en.m.wikipedia.org/wiki/Three-point_hitch

The top link is an essential part of a triangle which transfers the weight onto the back wheels of your tractor to give it more traction.

It can also stop you flipping over backwards.

The only time you would use a chain for a top link is on a trailed implement like a topper to allow it to follow the contours of the ground.
Soil engaging implements ( other than light implements like harrows ) ought to be used with a solid top link.

Does your tractor have depth (or draught) control ?

[arobwk]

I think I know what you mean Stufe' and, no, I don't have depth/draft control.  To be clear though:  3PL hydraulic control lever has only 3 positions: up, "neutral", down.  Lever stays in down/lowered position (without returning to neutral position automatically) which equals 3PL/implement float.  If I manually put lever in "neutral" position, after lowering 3PL/implement, I sort of thought that would lock the height of 3PL/implement, but, if I'm using box grader as a bull-dozer, I note that the 3PL will ride up if encounters resistance from what-ever I'm trying to bull-doze so I guess "neutral" doesn't mean rigidly locked under all circumstances!
I'm still in learning mode with the harrow, but if I want to reduce it's natural draft I draw it into the ground and then, while tractor stationary, give control lever a stab to raise harrow slightly and then slowly pull away.  Also, if I feel un-due drag while in motion, I will do same, i.e. give the lever a quick stab (up) to raise the harrow slightly.  Much concentration required!! 
P.S.  Thanks for link - been there already though and just about every web-site on tractor safety!!

[arobwk]

The only time you would use a chain for a top link is on a trailed implement like a topper to allow it to follow the contours of the ground.

Please forgive a junior's retort to his senior, but I have to say that I'm not too sure that a chain top-link would be good on a topper - too easy for the topper to flip forwards (rather than the tractor backwards).  Something I came across during my searches on chain top-links.

[stufe35]

Hi,

If you look at the links below you will see the point where the top link attaches is linked to a chain, fibre strap, or flexible wire, so that the A frame can rotate allowing the machine to follow ground contours. Giving the same effect as a chain top link.  This is a fairly normal arrangement on a topper as you can see.

The front of the topper should be supported by holding the hydraulic arms at the correct height, ie with the skids of the topper just above the ground. This will stop the chance of rotation you are thinking about.

Hope this helps.

Regards

http://www.ebay.co.uk/itm/Grass-Topper-Field-Topper-Pasture-Topper-For-Tractor-9-Topper-Major-Yr-2008-/311699607269?hash=item4892be8ee5:g:Up8AAOSw4shX3AgQ

http://www.ebay.co.uk/itm/Cutlass-8ft-Finishing-Mower-Topper-Tractor-Mounted-650-VAT-/322254614449?hash=item4b07df2fb1:g:7S4AAOSw8oFX0Yd4

http://www.ebay.co.uk/itm/Fleming-6ft-topper-mower-pasture-topper-/201667347969?hash=item2ef44f8601:g:DNoAAOSwxg5X1u23

[arobwk]

Ah ... yes ... I get it!  I'll replace the harrow's rigid support tube, between its top-link posts and rear end, with a chain.  Unfortunately I do not know what my 1.3m harrow weighs as it is not as-advertised on Siromer site.  As-advertised it would be 300kg, but mine has 14 discs rather than 16 and then disc size is 18" rather than 16".  Email to Siromer beckons as I wouldn't want a chain link to break under tension, especially if it should break at the far end with 1 mtr plus of chain wizzing through the air in my direction!
Thanks Stufe' - your advice very much appreciated.  Regards.
 

[stufe35]

  I'll replace the harrow's rigid support tube, between its top-link posts and rear end, with a chain. .
 

Why ?

If you want to allow your discs to articulate over the humps you describe, just use a chain for a top link ...it will have the same effect and is far simpler than replacing your stays.

For normal use though your discs will be more effective when held in a horizontal plane by the action of a rigid top link.

[arobwk]

Admittedly, a chain top-link would be easier, but, having considered the implement images you pointed me to, I like the fact that I would still be able to crank a rigid top-link in for extra rear-end ground-clearance when transporting the harrow - my AGT/harrow combo doesn't offer much of that!  Alternatively, for transportation, I could of course lower the harrow with the rear gang over a pallet or something so that it tips forward thereby slackening the chain to allow it to be shortened, but that means more faff. 

Again thanks for input. I shall experiment.