ADJUSTING Three Point Hitch Mounted TANDEM DISC HARROWS

   / ADJUSTING Three Point Hitch Mounted TANDEM DISC HARROWS #1  

jeff9366

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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.
 
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   / ADJUSTING Three Point Hitch Mounted TANDEM DISC HARROWS #2  

ovrszd

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Wow. That's a lot of information regarding such a common tillage tool. :D
 
   / ADJUSTING Three Point Hitch Mounted TANDEM DISC HARROWS #3  

brasco426

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Yeah! What jeff9366 said. (Drops mic, walks off stage)! Great post I learned quite a bit being a newbie. Thank You
 
   / ADJUSTING Three Point Hitch Mounted TANDEM DISC HARROWS #4  

aarolar

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Excellent info, to add to the discussion at what tractor weight and hp would you consider a harrow to be a useful attachment?
 
   / ADJUSTING Three Point Hitch Mounted TANDEM DISC HARROWS
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jeff9366

jeff9366

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   / ADJUSTING Three Point Hitch Mounted TANDEM DISC HARROWS #6  

aarolar

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No I've got what I'm getting just trying to spur discussion.
 
   / ADJUSTING Three Point Hitch Mounted TANDEM DISC HARROWS
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jeff9366

jeff9366

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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.
 
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   / ADJUSTING Three Point Hitch Mounted TANDEM DISC HARROWS
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jeff9366

jeff9366

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^^^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.
 
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   / ADJUSTING Three Point Hitch Mounted TANDEM DISC HARROWS #9  

majorwager

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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......
 
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jeff9366

jeff9366

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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.
 

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