Disc Harrows: Tandem vs. Offset.

[Glowplug]

For all intents and purposes they are the same disk. One disk is offset and one is tandem, both are 3ph disks. Which disk works the best, digging deepest, leaving the ground the smoothest, etc?

That is the million dollar question and the real question of the thread.

 

[California]

I have a couple of related questions:

• Assuming the same width, is there a difference in horsepower needed?
  
• Is either better for discing off to the side? (For an orchard it is important to keep the tractor as far as possible from the foliage.)

 

[JoeinTX]

"JoeinTX, if the offset were to weigh 23% more than the tandem, then which disk would perform best? If they weighed the same, then which type performs best?...."


If the offset were 23% heavier, then it would work better than the lighter tandem if they weighed the same and had the same disc spacing. The converse if the tandem were the heavier.

"Here's a question for anybody that might have an answer. You have two 8' disks, both weigh 1000lbs each, both have 22" notched blades, both have the same angle on the blades. For all intents and purposes they are the same disk. One disk is offset and one is tandem, both are 3ph disks. Which disk works the best, digging deepest, leaving the ground the smoothest, etc?..."


Assuming the two are identical in all aspects other than the arrangement of the disc gangs..........I don't see any difference in them from what I've experienced. Same weight, disc spacing......the same amount of down force is being exerted per disc.....same ground pressure....just using a slightly different pattern for turning the ground and flipping it back.
With any disc it's going to be about ground pressure-two 8' plows (tandem or offset) but one with 6 discs per gang and the other with 8 discs per gang and the former is going to be a better true plow penetrating the soil and turning it over while the latter is going to be a better preparation tool busting clods and cutting plant growth better regardless of disc type.

On top of these two types, a company called Diamond Disc Plows produced a third variation on the disc plow.......taking the common "X" style arrangement of tandem discs and reversing it having the disc gangs is a "<>" arrangement. It was only a gimmick and did nothing to effect the performance of the same basic tool. They are no longer in business from what I can research.

Look at some of the various discs produced for severe duty by Fleco or Rome or others........the common theme is greater weight on fewer discs for maximum penetration be they in a tandem or offset configuration.


In short, what do you want? Do you need a ground turner or a ground preparer? For the first, the greatest weight on the discs and for the latter the more discs per given weight is best.


Same everything......number of discs....spacing...weight......no real differences.

 

[MtnViewRanch]

So maybe the only real difference is strength? Since it seams like the primary till disks are mostly offset style, do they build them like that because it is more cost effective and stronger? There has to be a reason for having the two different types of disks. One more question, if you have 2 of the same disk, one is 3ph and one is a pull disk, which one works the best? We always think that a pull disk works better, but if the disks were actually the same except hook up, would one type be any better than the other?

More questions to ponder.

 

[Glowplug]

So maybe the only real difference is strength? Since it seams like the primary till disks are mostly offset style, do they build them like that because it is more cost effective and stronger? There has to be a reason for having the two different types of disks. One more question, if you have 2 of the same disk, one is 3ph and one is a pull disk, which one works the best? We always think that a pull disk works better, but if the disks were actually the same except hook up, would one type be any better than the other?

More questions to ponder.

I don't know the answers to your questions obviously, since I am the original poster. But maybe offset disks, in their configuration, tend to be more "aggressive" and more often used as primary tillage tools. I don't know. I think the reason people tend to think of pull-type disks working better than lift-type simply has to do with weight and not the actual hook-up. I could be wrong though. It WOULD be an interesting controlled experiment to have identical disks in terms of weight, size, number of disks, etc. and have one set up as an offset and one in tandem and then each of these as either a pull type or lift type and then measure objectively how much soil disturbance they can accomplish in identical conditions. I really wouldn't be too surprised if all four actually produced nearly identical results. Sounds like a good science project! Anyone out there want to loan me the money to buy four disks? I'll be glad to do the experiment and put this to rest once and for all!!

 

[MtnViewRanch]

I don't know the answers to your questions obviously, since I am the original poster. But maybe offset disks, in their configuration, tend to be more "aggressive" and more often used as primary tillage tools. I don't know. I think the reason people tend to think of pull-type disks working better than lift-type simply has to do with weight and not the actual hook-up. I could be wrong though. It WOULD be an interesting controlled experiment to have identical disks in terms of weight, size, number of disks, etc. and have one set up as an offset and one in tandem and then each of these as either a pull type or lift type and then measure objectively how much soil disturbance they can accomplish in identical conditions. I really wouldn't be too surprised if all four actually produced nearly identical results. Sounds like a good science project! Anyone out there want to loan me the money to buy four disks? I'll be glad to do the experiment and put this to rest once and for all!!

I'm sure that you, uh, any TBNer would be happy to perform this experiment with donated $$$$ or equipment and be able to keep 1 of said experiment disk for there trouble.

 

[gonzalesmachine]

The diffence between the two types of discs harrows is that an offset disc will allow deeper penetration but it is harder to keep the soil level and the opposite is true for tandem discs. In a tandem disc the longitudinal force exerted by the disc blade is offset by the longitudinal force exerted by another disc blade on the oppisite side. This causes the disc harrow to tend to want to float. With an offset disc the tendency for the harrow to float is decreased due to no oppisite disc blade.

 

[FredH]

I use a 72" King kutter disk on my property , ( basically its a " NO BRAINER " brush / weed hog . In other words , me being a dumb truck driver does not like to think when I comes home and do my chores . So rather than put the 5' brush hog on to mow down both sides of our driveway , ( each side 25' x 800' ) , I put the disk on and only have to figure out how to drive straight ) .

In in the area of Southern Oregon that I live in , the soil is pretty much a clay type , soaks up alot of water in winter and you could build a house out of it in the summer , once you cut it out of the ground . Not sure of the actual weight of disk ,( 500# plus ) , But I added a piece of 3"x 12" I-beam towards the back , ( right over the top of second gang ) . Then on top of that I strapped a used 40 gallon galvanized water tank that was laying around from when we changed our well system . Although I have completely filled the tank and disked with it , I usually only run it about 1/2 full as the driveway is downhill . Going down is not a problem , but coming back up I need to have the FEL loaded with rock to keep the front end down , otherwise have to lift disk which kinds of defeats the purpose .

Pulling it behind my 5 year old TC30 , I can bury the disk up to the gang axles by dropping the 3 point all the way , which is pretty close to the same depth that any tiller cuts .

I compared it to my neighbors tiller in another thread here .

http://www.tractorbynet.com/forums/attachments/113240-help-me-justify-tiller.html

Take Care

Fred H.

 

[jeff9366]

I think the reason people tend to think of pull-type disks working better than lift-type simply has to do with weight and not the actual hook-up. I could be wrong though.

It would be an interesting experiment to have identical disks in terms of weight, size, number of disks, etc. and have one a pull type, the second a lift type and then measure objectively how much soil disturbance each accomplishes in identical conditions.

Harry Ferguson's three point hitch made the tractor practical. Three point hitch mounted implements transfer weight to the rear wheels through the Lower Links and to the front wheels through the Top Link, improving tractor traction.

Before Ferguson, tractor weights were expressed in TONS. Many were on tracks. Tractors were hugely expensive.

Practically all offset discs are towed. Towed implements do not transfer weight to the tractor, all the implement weight bears on the soil, increasing penetration. {{ Unless the towed implement is partially supported by transport wheels.}} Draft force is higher. Tractor traction is less, so a relatively heavier, four wheel drive tractor is necessary. Strain on the implement is higher, therefore offset discs are built heavier than three point mounted tandem discs.

{{ Downside to TOWED: greater potential for soil compaction.}}

edit: (( I have never heard of a towed Tandem Disc Harrow appropriate for 18-40 horsepower compact utility tractors. ))

For the same reasons, towed Cultipackers compact soil more effectively than three point hitch mounted Cultipackers.

 

[Poopdeck Pappy]

. . .
{{ Downside to TOWED: greater potential for soil compaction.}}

Why would that be? I have plowed many, many hours with a pull-type offset disc (a big one) and soil compaction was never a concern or problem.

The biggest downside to an offset disc is that you can only turn one direction when pulling it. Well, you CAN turn right but only in a big, gentle arc. And, even doing that, it's easy to get cocky and turn a little too sharp to the right and find the frame of the disc harrow climbing up the right rear tire. And then, if it doesn't climb all the way up on top of you and kill you or tear up your tractor, you get to go home and change your underwear. Don't ask me how I know.

( I have never heard of a towed Tandem Disc Harrow. ))

There are lots of them out there. I've seen pull-type tandems as small as 6' or 8', but most of them are in a size/weight class that would not lend itself to being mounted on a 3 point hitch. Some are wide enough to have gangs that fold up for transport (and you can also fold them up and plow with only the center section when you want to sacrifice width to really concentrate weight on a small area).

Here are just a few of them I found on the local Craigslist:

CASE 18 Foot Disc Plow

Disc/Plow, seeder, cultipacker, chain harrow

Large Disc for Sale