ADJUSTING Three Point Hitch Mounted TANDEM DISC HARROWS

[jeff9366]

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

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

ADJUSTING THREE POINT HITCH MOUNTED, BOX FRAME, TANDEM DISC HARROWS ~ BETA EDITION ~
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There is not much information in the Tractorbynet.com archive regarding adjustment of Box Frame Tandem Disc Harrows. The information in the archive is scattered and can be difficult to access.

I solicit contributions from the readership. This content may be most valuable to new Disc Harrow owners, who have the implement mounted for the first time and are wondering: What do I do now? I look forward to learning too.

I foresee three sub-topics.

1. The three means by which gang angles are adjusted on most Tandem Disc Harrows: clamp plates (80%), levers (varied) (17%) and screws (3%).

2. Cutting Adjustments: Gang Angles adjustment, Gang Hanger adjustment, Top Link adjustments, "widths" explained.

3. Related: (non-adjustable) Pan Spacing, tractor 4-WD Vs 2-WD, rigid Top Link vs Hydraulink, Position Control, QIV (Quarter Inching Valve), Draft Control

I own a Howse 16/18" Disc Harrow, 9" pan spacing, 587 pounds, purchased new. Howse purchased to pull behind Kubota 'B' series tractor-loader, tractor since sold. <eventually pictures> I am close to purchasing a Montroe Tufline Disc Harrow, around 900 pounds; I am dithering between two Tufline 'TH' models. Replacement Tufline will have lever gang angle adjustment. Tufline will be pulled by my Kubota L3560.

I also pull a Frontier Disc Harrow with 24" pans behind a JD 5301 with two wheel drive, for a neighbor. I need to record particulars on this combination. <eventually pictures>

Convention: I call Disc Harrow 'discs' ~pans~.

If you take delivery of a new Tandem Disc Harrow from a common carrier, you will probably receive it completely out of adjustment. To save shipping space and shipping costs, Disc Harrows are shipped with the gangs pushed inward, toward each other, to minimize shipping width. So, to start with, mount the Disc Harrow on your tractor's Three Point Hitch, raise the DH to raise all pans off the ground, PLACE BLOCKS TO SUPPORT HARROW SO IT CANNOT DROP, loosen gang hangers, almost always U-bolts, and slide the gangs out along the frame. Usually, thumb pressure will suffice. As the paint ages and dust accumulates, a soft-blow mallet helps overcome inertia and stickiness.

The front gangs, which throw soil OUT, should be fairly close together. You do not want to leave an untilled strip between the left/right front gangs, neither do you want the inside pans of either front gang to contact when tractor is bucking over rough ground. (Very large Disc Harrows sometimes have an optional Middle Buster shank, mounted after the front gang to disturb soil between two front gangs.)

Rear gangs, which throw soil IN, should be wider apart, in order to collect soil tossed wide my front gangs. As I do not know the size of your DH, I cannot recommend a finite distance, but outer pans should be pretty close to outer frame. <eventual pictures>

The Disc Harrow is considered a secondary tillage implement. (It is a form of tiller, performing the same job as a PTO operated roto-tiller, but designed to till log rows.) Primary tillage implements are primarily plows: traditional Moldboard Plows, Disc Plows (which are NOT Disc Harrows), Offset Discs and Chisel Plows. Primary tillage implements should be able to break sod in a single pass. Disc Harrows will not break sod unless the pans are at least 20" in diameter and bear on the soil with at least 50 pounds per pan; even so a Disc Harrow with 20" or 22" diameter pans will require multiple passes to disrupt sod and is not likely to kill pasture grass roots for two or three years.

When plowing was the primary function of tractors, Disc Harrows were used in the Spring to knock down 12"-14"-16" waves in fields, from the bottom of one furrow, to the top of the ridge formed from soil previously in the furrow. After Disc Harrowing, field would be rippled but lower, the soil would be mixed and spring weeds disrupted. Today, in the age of no-till agriculture using Roundup and GMO seeds, Disc Harrows are used in the field to disrupt crop residue. Disc Harrow are also used for wild game food plot preparation and maintaining firebreaks.

The two front Disc Harrow gangs, left/right, support the cutting pans. Angle of adjustment of gangs and therefore pans, is achieved by removing lock pins and moving front gang pivot, at the center, forward or back along the center box frame. Increasing the "V" angle on the front gang increases soil disruption and throws soil OUT. Usually there are four, sometimes five angle adjustment holes. (Really, four is enough.) As the gang angle is increased, pans adjusted cross-wide to tractor direction, the resistance load on the tractor, called Draft Force, increases too. Generally, smaller, lighter Disc Harrows are adjusted more aggressively than heavier Disc Harrows, to compensate for having less weight bearing on each pan.

Another means to increase front pan cutting force is to shorten the Three Point Hitch Top Link.
Shortening the Top Link shifts implement weight from the rear gang to the front gang. (picture) With the Top Link geometry on my tractor it is possible to lift the rear gang completely free of the soil, so all the rear gang weight shifts forward. (Some of the rear gang weight is transferred to the Disc Harrow front gang, some weight is transferred to the tractor's rear tires through the 3-Pt Lower Links, increasing traction.) As the front gang is adjusted more aggressively, its working width decreases.

The two rear gangs are for smoothing and throwing soil IN, toward the center of the Disc Harrow. Rear gangs are usually adjusted less aggressively, "straighter" than the front gangs. The working width of the rear gang, therefore, is slightly wider than the working width of the front gang, allowing rear gang to collect soil from a wider area than the front gang, to throw soil inward. (picture). The "straighter" rear gangs bisect front gang furrows, smoothing the row. The outside pan on each rear gang, tend to create an unwanted, deeper furrows. Outer pan furrows are ameliorated by adjusting rear gang straighter and by shortening the 3-Pt. Top Link, which decreases weight on the rear gang. As the rear gang is a long way back from the 3-Pt., a half-turn adjustment of the Top Link will make a difference.

For good soil mixing a Disc Harrow must be pulled at brisk speed, so soil is tossed in and out vigorously. (picture) Pulled too slow, 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.






(Light tractor implements that are pressed into service for sod breaking include Subsoilers, Middle Busters, aka Potato Plows, and Field Cultivators. None flip/turn sod like a true plow. Nor do Chisel plows flip/turn sod but being very heavy Chisel plows are placed in the primary tillage category.)

http://www.lsuagcenter.com/NR/rdonl...45263BDD8/11557/pub2917tractorimplements1.pdf



TO BE CONTINUED

 

[jeff9366]

It is possible to pull a Disc Harrow too fast. Too fast causes the front gang to rise/floats and stops cutting. Four to five mph is speed range for best soil mixing.

Too much front gang angle will cause the pans to stop rotating, so they skitter along the soil surface, rather than penetrate. Skittering occurs when soil is hard.

If the Top Link is adjusted very short, so most weight is on the front gang, and the front gang is set very aggressively, the outer front pans will cut more than the inner front pans because of frame droop. (Frame is suspended from the Top Link attached to the front-center of the Disc Harrow.) This produces an uneven result and is hard on the frame. For an even result you want 55% weight on front gangs, 45% weight (+/-) on rear gangs. You also want Disc gangs level left-to-right, adjustment by the threaded Lifting Rod , connected to right side Lower Link.

Too much rear gang 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 cut 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. (photo)

REASONS TO ADJUST A DISC HARROW 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 you may require a lower gear. (Typical wild game food plot scenario.)


Increasing gang angle will be only marginally effective if your Disc Harrow is too light, i.e. less than 18" pan diameter. If you have a really heavy Disc Harrow, say 24" diameter pans, it will cut through most vegetation.

Shorten Top Link so additional weight is shifted to front, cutting gangs.

Changing soil conditions within a field.

Disc one or two days after a good rain, when ground has softened. Do not disc wet soil; it will dry adobe brick.




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.

Lengthen Top Link to shift weight 40% front gang, 60% rear gang, increasing float.

If you decide to make multiple passes, steer tractor at 45 degree angles, preferred to 90 degree angles, on successive passes. Do not over till.

Use passive settings to thinly cover seed. Not as good as rolling in seed. Equal to using a drag to cover seed. (wild game food plots) Pray for rain.




CHANGING GANG ANGLE ADJUSTMENTS; Clamp Plates, Levers, Screws


PASTURE RENOVATION USING DISC HARROW - POSSIBLE? PRACTICAL?

Pasture renovation keeps much of existing turf living, while treating compacted pasture to improve water movement, aeration and fertilizer penetration. Pasture renovation includes overseeding after treatment.

The primo tool for pasture renovation is the (expensive) K&M Hay King Renovator.

K&M Mfg. Product 3

Can a Disc Harrow be adjusted to accomplish pasture renovation? This question comes up occasionally on this site, but no one seems to have actually accomplished it.

Following is speculation on my part:

Wait for ideal soil moisture. (Hooved animals compact soil more than anything else.)

Adjust front gangs aggressively. Shorten Top Link so most implement weight transfers to front gangs. Disc once, then once or twice at 45 degree angles.
Sod should now be scrubbed 3" - 4" deep, shallow enough not to kill pasture grass roots which grow 6" to 9" deep. (in Florida)

Adjust front gangs to 'straight', passive. Leave Top Link short. Disc again, once.
Will front pans penetrate to 5" in order to improve water movement, aeration and fertilizer penetration? I do not know.

Will concavity of pans (float) prevent pan penetration? If "straight" pans penetrate 5", will concavity of pans leave fissures in disced field?

Pans are sold with a range of concavity. Eighteen inch diameter pans, for instance, vary from 1-1/8" concavity to 2-1/4" concavity. Twenty-two inch diameter pans vary from 2-1/2" concavity to 4" concavity.




TO BE CONTINUED.

 

[jeff9366]

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If you take delivery of a new Tandem Disc Harrow from a common carrier, you will probably receive it completely out of adjustment. To save shipping space and shipping costs, Disc Harrows are shipped with the gangs pushed inward, toward each other, to minimize shipping width.

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Rear gangs, which throw soil IN, should be wider apart, in order to collect soil tossed wide my front gangs. As I do not know the size of your DH, I cannot recommend a finite distance.

A good dimension to use when making initial SPREAD adjustment of REAR gangs is pan diameter less two inches.

ie: For 18" pans, set initial rear gang spread at 16".

ie: For 22" pans, set initial rear gang spread at 20", etc.