ADJUSTING Three Point Hitch Mounted TANDEM DISC HARROWS

[jeff9366]

If you are considering the acquisition of a Disc Harrow, first read this LINK covering Disc Harrow selection:

LINK: Disc Harrow Selection For 18-45 Horsepower Tractors (Revision 2b)



The Three Point Hitch mounted Tandem Disc Harrow is a secondary tillage implement. The Disc Harrow is a form of tiller, most efficient mixing and smoothing soil in long runs, i.e. fields. The goals in harrowing are mixed soil and a smooth bed behind the implement.

Primary tillage implements are mostly plows: most often traditional Moldboard Plows, less often Disc Plows (which are NOT Disc Harrows). The primary purpose of plowing is to invert the upper 6" to 8" of soil, bringing nutrients to the surface, burying sod, weeds and the remains of previous crops; encouraging decomposition. Plow goals are distinct from Tandem Disc Harrow goals.

Other primary tillage implements are Offset Discs, and Chisel Plows. Primary tillage implements should break sod in a single pass.

Light tractor implements pressed into service for sod breaking include Subsoilers, Middle Busters, (aka Potato Plows) and Field Cultivators. None flip/turn/invert sod like a plow.

ADJUSTING THREE POINT HITCH MOUNTED, BOX FRAME, TANDEM DISC HARROWS
Version 1​

Convention: I call Disc Harrow 'discs', "pans".

INITIAL ADJUSTMENT OF A NEW TANDEM DISC HARROW​

When you take delivery of a new Tandem Disc Harrow from a common carrier, you will receive it mal-adjusted. To save space Disc Harrows are shipped with the gangs collapsed inward, to minimize shipping width.

So, to start, mount the Disc Harrow on your tractor's Three Point Hitch, raise the implement with your hydraulic control to float all pans above the ground, PLACE BLOCKS TO SUPPORT HARROW BOX FRAME SO FRAME CANNOT DROP, loosen gang hangers, usually U-bolts, and slide the gangs out/wider along the frame. Usually, thumb pressure will suffice. As the paint ages and dust accumulates, spray lube helps overcome stickiness and a soft-blow mallet helps overcome inertia.

FRONT GANGS, which are the CUTTING GANGS, throw soil OUT, and should be fairly close together. You do not want an untilled center strip between the left/right front gangs. Neither do you want the inside pans of the two gangs to collide when tractor bucks over rough ground.

(Very large Disc Harrows sometimes have an optional Middle Buster shank, center mounted after the front gang, to disturb soil between two front gangs.)

REAR GANGS, which are SMOOTHING GANGS, throw soil IN, are set wider apart. Rule of thumb for initial spacing between rear gangs: Diameter of rear pans, less two inches. So a rear gang with 18" pans should be trial-set with 16" space between the inner pans on the right and left rear gangs. The rear gangs collect soil. The widest point on an operating Disc Harrow will be rear collecting and smoothing gangs.

Level Disc Harrow left-to-right, adjustment via 3-Pt. (threaded) right Lifting Rod.

FIELD ADJUSTMENT OF THE TANDEM DISC HARROW​

The FRONT GANGS are the CUTTING GANGS. Increasing pan angles and increasing weight/pressure on the front gang will increase front gang's ability to cut. Draft force resistance to the tractor increases as pan angles increase.

To increase pan angles, slacken retainers and move gangs on center pivot to increase 'V' angle/angle of attack. As either front or rear gangs are adjusted more aggressively, its working width decreases.

To increase weight/pressure on front gangs, shorten the Top Link, which raises the rear of the Disc Harrow, shifting weight from the rear gangs to the front gangs. (Some rear gang weight is transferred to the Disc Harrow front gang, some weight is transferred to the tractor's front and rear tires through the 3-Pt Lower Links, increasing traction.) It is possible to shorten the Top Link until the rear gangs are lifted entirely above the soil. However, start with a weight distribution of around 55% front, 45% rear.

Output of the front gangs is input to the rear, smoothing gangs. So if front gangs are set very aggressively the input received by the rear smoothing gangs will be large lumps and the output bed behind the implement will be less than smooth.


The REAR GANGS are SMOOTHING GANGS. Start with the rear pans set two increments less aggressively than the front pans. Shortening 3-Pt. Top Link decreases weight on the rear gang. As the rear gang is a long distance from the 3-Pt., a half-turn adjustment of the Top Link will make a difference. Modify angle of attack of rear gangs as necessary. If you have "outrigger" furrows trailing the outboard pans of the rear gang, slightly lift entire Disc Harrow, perhaps one inch, with hydraulic control.

Too much rear pan angle will cause too much 'return' soil to be thrown in the center, leaving a low swell in the field. This is aggravated if the rear gang hangers are set too narrow. The rear gangs should collect from a wider swath than the front gangs, as the center space between the rear gangs is wider. The widest point on the implement should be the outer dimension of the rear gangs.

The goal in harrowing is a smooth bed behind the implement.

For good soil mixing a Disc Harrow must be pulled at brisk speed, so soil is thrown in and out vigorously. Pulled too slowly, soil falls off the pans and does not mix. Pulling a Disc Harrow as wide, or wider than tractor tire width, aggressively adjusted, will remind you to engage tractor 4-WD.

REASONS TO CHANGE DISC HARROW ADJUSTMENT IN THE FIELD.

More Aggressive
​

Crop residue or field has not been broken or soil is hard: Adjusting the front/rear gangs to more aggressive settings may increase pan penetration, however tilled ground will be relatively rough. Increasing gang angles will make the Disc Harrow pull harder so tractor may require a lower gear. (Typical wild game food plot scenario.)

Less Aggressive​

With each pass of the Disc Harrow tilled ground is softer, so tractor and pans sink deeper, increasing draft force. Tractor may stall out or not be able to pull Disc Harrow at 4-5 mph, to mix soil. Decreasing front/rear gang angles will decrease draft force, allowing tractor to pull Disc Harrow faster and leaving a smoother finish, to a certain degree. Lifting the entire implement via hydraulic control will decrease draft force on tractor.

During second pass lengthen Top Link to shift weight 40% front gang, 60% rear gang, increasing implement float.

If you decide to make multiple passes, steer tractor at 45 degree angles, preferred to 90 degree angles, on successive passes. (Because of bias angle on Disc Harrow pans.)

Do not over till.

 

[ovrszd]

Wow. That's a lot of information regarding such a common tillage tool.

 

[brasco426]

Yeah! What jeff9366 said. (Drops mic, walks off stage)! Great post I learned quite a bit being a newbie. Thank You

 

[aarolar]

Excellent info, to add to the discussion at what tractor weight and hp would you consider a harrow to be a useful attachment?

 

[jeff9366]

Excellent info, to add to the discussion at what tractor weight and hp would you consider a harrow to be a useful attachment?

Thank you. Too many local variables to answer. Read the selection LINK and make a decision based on your conditions.

If you are considering the acquisition of a Disc Harrow, read this LINK covering Disc Harrow selection:

LINK: http://www.tractorbynet.com/forums/attachments/308251-disc-harrow-selection-18-45-a.html?highlight=

 

[aarolar]

No I've got what I'm getting just trying to spur discussion.

 

[jeff9366]

I regret is not being more informed when buying my tractor, back blade and disc harrow. Implements are both Land Pride. The back blade is fine. I only use it for snow removal. However the disc is a total piece of crap. It mounds the soil to the middle of the disc and then I have a %^&%% of a time getting the field leveled out again. I used it once and it's been sitting in the barn since.

The disc works OK as far as discing up the dirt. The problem is; it moves dirt to the center of the disc in windrow fashion. Then a pain to level out again.

As your Disc is cutting to expectation, your center mound problem is result of imperfect gang adjustments.

1) The rear gangs throw soil inward. Too closely spaced rear gangs create the objectionable windrow. The faster you Disc, the greater the quantity of dirt thrown inward, creating the center windrow.

You need to space your rear gangs farther apart. Rear gangs should be spaced a little less than pan diameter apart. If you have 20" pans, trial space rear gangs 18" apart. Spacing a little less than pan diameter will ameliorate or eliminate center windrow.

Moving gangs farther apart usually requires loosening several U-bolts then sliding gang assemblies outward on the frame. Lubricating frame, a mallet and sometimes a dowel to "encourage" friction/dust break and movement may assist.

2) Decreasing the gang angle of rear gangs will also decrease center collection. Rear smoothing gangs should first be adjusted two increments less aggressively than front cutting gangs. Trial other increments.

 

[jeff9366]

^^^Would it help to add weight to the disc?

I've seen a lot of really old ones that are used seasonally around here with added weight... one has concrete to add weight.

The front gangs on a Disc Harrow are the cutting gangs.

The rear gangs on a Disc Harrow are the smoothing gangs.

When I have witnessed weight added to a Disc Harrow it is on the back, although weight is needed on the front to increase soil penetration by the cutting pans. (Difficult to weight the front because of Three Point Hitch tower.)

The technique to make a marginally effective, unweighted Disc Harrow cut marginally better is to shorten the Top Link until the rear gangs are barely touching the ground. Almost all rear gang weight is then transferred to the front, cutting gangs. Output will be rough. A second pass with front and rear gangs in approximately equal soil contact is necessary to produce a reasonably smooth bed behind the implement.

Occasionally I have seen rear weighted Discs with the Top Link shortened, WHICH STRESSES THE TOP LINK AND BOX FRAME BEYOND DESIGN PARAMETERS. Top Link is the most likely component to fail but frame welds may let go too. (The last Kubota Top Link I purchased was $212.)

Disc after a soaking rain when soil is soft.

Do not supplementally weight a Disc Harrow. Sell the one you have that is too light and buy one with larger diameter pans which will be effective.



Tandem Disc Harrows are SECONDARY TILLAGE implements. If you need a disc type implement for PRIMARY TILLAGE research Offset Discs and Disc Plows. A Disc Plow is not a form of harrow; it is a type of plow.

 

[majorwager]

Wow, and that is just volume One, might be a ten volume set?

Likey to be available through, Books on Tape, must be careful if there is a slight chance of plagiarism, original material copywritten? Lawyers scrambling in the background......

 

[jeff9366]

So we have about a 3 acre field that is currently a mixture of grass and weeks that we mow at 3.5 high. Problem is itç—´ a old tobacco field that still has some of the ridges left in place from the previous owner. They are not terrible but enough we need to mow slow or it makes you sick going over them. So my plan is to spray round up next weekend then by end of month start disking and breaking up the soil like in a X pattern or going against the ridges.

What is the best implement to smooth and even everything back out? Once done I will use a cultipacker to smooth and press the dirt then spread new grass seed.

A week after you spray, mow as short as possible: "scalp."

Few with Disc Harrows adjust them after putting them to use. If you first process the field two or three times (depending on the weight bearing on each of your disc pans) to loosen ridges, then adjust gang angles less aggressively in increments, the disc may meet your needs solo.

Shorter Top Link = more weight on front gangs.

More weight on front disc gangs throws dirt OUT. Use on ridges. PHOTO


Longer Top Link = more weight on rear gangs.

More weight on rear/wider disc gangs gathers dirt in. Straddle the swales.

The faster you disc the more dirt is moved.

As the field is smoothed, adjust hydraulic Position Control so disc is in lighter contact with the soil.

Your last past should be a moderate speed, pans sunk 2" to 3" in soil, front gang adjusted moderately, rear gang adjusted less aggressively than front gang, but not "straight", weight distribution about equal between front and rear.


Before you seed I highly recommend a <$10.00 soil test and soil amendment per test result(s). You need to inform testing agency what variety of grass you intend to plant for optimum amendment results.

 

[BAP]

I hope that isn’t a finished harrowing job, because around here we would consider that a poor job. A good job shouldn’t any ridges or any valleys.

 

[jeff9366]

I hope that isn’t a finished harrowing job, because around here we would consider that a poor job. A good job shouldn’t any ridges or any valleys.

No, it is not. Just an illustration of how wide front gangs toss soil when Disc Harrow is pulled at a brisk pace.

 

[jeff9366]

Bought a Woods 5' Disc for the L3800
Purpose was to clean up some bottom land.
Only wants to go in 6 to 8 inches... thinking I need to add some weight for better performance?
Never been around or used a Disc... it does seem a little light compared to some I have seen.
There are several adjustments to angle... have it set in the middle.

The Woods Disc Harrow model number would be useful.


First, shorten your Top Link, that will shift more weight from the rear, smoothing gangs to the front, cutting gangs. Start with 60% front, 40% rear. [You can shorten Top Link until rear gangs are near clear of the soil.]

Second, increase the angle of attack for your front gangs. With increased angle of attack, increased cutting will occur; unfortunately draft force resistance also increases.

Generally speaking you want front gangs set to give the degree of cut/penetration desired.

The rear gangs should be set less aggressively than the front gangs; just aggressively enough to provide smooth bed behind the implement.

How aggressive the front gangs are set determines input to rear, smoothing gangs.

A Disc Harrow with 9" spacing between pans will cut significantly more aggressively than a Disc Harrow with 7" spacing. A Disc Harrow with 7" spacing between pans will leave a significantly smoother bed behind the implement.

A Disc Harrow with 18" diameter pans can penetrate only around 6" deep in best conditions before pan hubs limit penetration.

If you have "outrigger" furrows trailing from the outer pans, rear gang, raise the entire Disc Harrow one inch with your hydraulic Position Control lever then tweak the Top Link if necessary.

I regularly view ridiculous photos of weighted Disc Harrows. If you cannot achieve penetration desired through gang angle adjustment you need a Tandem Disc Harrow with larger diameter pans or, if you have a light tractor, a PTO-powered roto-tiller.

 

[jeff9366]

Going to be broadcasting 1.5 tons of mixed seeds: cowpeas, pigeon peas, canavalia, moringa and castor bean.
The large plot, which is currently cow pasture will be prepared with subsoiler, 5 bottom plow, and disc harrow.

Would a second pass with the disc harrow be good enough to plant (partially bury) these mostly bean-sized seeds? Or would they maybe go too deep?

If you adjust the gang angles on your Disc Harrow to relatively minor angles, the DH will bury seeds less deep.

If you adjust your Top Link so 40% of the weight is on the front gangs, which throw dirt out and will leave seed on the surface, and 60% of weight on the rear gangs, which gather dirt in, covering the seeds, you should be good with bean size seeds, assuming you subsequently have 3/4" or more rain per week.
(Rear gang is wider than front gang.) (Longer Top Link transfers more DH weight to the rear gang.)

In addition, use the Three Point Hitch hydraulic position control to just set the DH pans just into the soil surface.



Smaller seeds often require sunlight to germinate. Covered, small seed germination declines. Small seeds are best pressed into the surface of the soil, uncovered, with a Cultipacker. PHOTOS

MORE: https://www.tractorbynet.com/forums...ing-three-point-hitch-mounted.html?highlight=

 

[jeff9366]

​

CREDIT: - pmbutter - March 18, 2019

"There is a lot of contradictory information about choosing optimal paired holes to pin tractor/inboard end of the top link to the tractor.

The top hole gives the least elevation change of the tail wheel, but better maintains parallelism with the ground.

An earth turning plow ought to be in one of the upper holes, so it remains at a proper working angle, regardless of its depth.

The bottom hole provides the greatest elevation change of the "tail wheel" of my "implement", but it also the greatest angular change relative to the plane of the ground.

The bottom hole is best for something like a landscape rake where you might want to lift it up and out of the way, perhaps with a little more angle so trash drops off the tines."



RELEVENT VIDEO:

I will experiment with connecting the inboard pin of the Top Link to each of the four paired, vertically stacked mounting holes on my L3560.

For Disc Harrow smoothing it would seem the top holes might even harrow pressure of all pans in contact with the soil.

For Disc Harrow cutting/penetration it may be connection at the bottom holes, combined with a shortened Top Link, will shift weight to the forward cutting pans in an interesting way.

I have to experiment......

 

[jeff9366]

Creating raised garden beds with a Disc Harrow:

LD1 - 7/24/2022​

Do you have a 3PH disc? A 6 or 7' disc?

We use a disc to create garden beds for sweet potatoes.

1) The front disc gangs/pans throw dirt outward.

2) With a level disc you get a level field.

3) The rear gangs pull dirt toward the middle of the disc.

Set the rear disc gangs/pans as aggressive as you can. Lengthen the toplink all the way to let the rear gang dig in and keep the front gang out of the dirt.

With the front gangs kept out of the dirt and the rear ones pulling dirt in, you get hills/rows.

I use the same gathering-in adjustment to fill the dead furrow after moldboard-plowing the field.