IH 781 / 881 Forage Harvesters

Classic Farm and Tractor Magazine – January/February 2017

By Kenneth Updike

In 1981, IH replaced its 720 and 830 forage harvesters with newer, updated models, the 781 and 881. These new forage harvesters were very similar to their older counterparts. Both the 781 and 881 had a long black stripe decal running the length of their tongue to identify them. In this story, the 781 and 881 may be referred to as the X81 chopper when a feature is not model specific.
Before you could chop forage, you had to feed it into the machine. On both the X81 choppers, IH fed the crop material into the chopper with four feed rolls. The first pair of rolls (top and bottom) was coarse toothed across their edges to aggressively grab and feed material. The second pair of rolls had a fine tooth roll on top and a smooth roll on the bottom. The pair of top feed rolls could “float” as dual springs on each side of the feeder house kept tension on them. This allowed the chopper to handle varying amounts of crop material and still help maintain a uniform length of cut. These feed rolls were driven by a 60 pound heavy link roller chain.
The length of cut was determined by the feed roll speed. Increasing or decreasing the speed of the feed rolls determined the length the forage material was cut. When you needed to change the feed roll speed, it was simple by just reversing one dual sprocket. The length of cut could be changed from 3/16ths inch to 5/16ths inch.
A smooth roll scraper bar was provided to keep the lower roll clean and not allow crop material to bunch and pile in front of the cutter head.
IH used dual electromagnetic clutches to start, stop or reverse the feed rolls. This was controlled by a toggle switch on the chopper control panel at the tractor. You could feed large volumes of crop material through the feed rolls by using this feature to prevent plugging of the chopper.
The 18 inch diameter high helix cutter head acted as a sharp pair of scissors, cutting material across the shear bar. The knives sliced the crop material instead of “chopping” it and this required less power.
An example of this was once again taken from my elementary school art class (I was told this art class stuff would pay off later in life and sure enough, they were right—it has!). A scissors cuts paper much easier than stabbing it with a knife. The helix cutter head on the IH X81 chopper acted like a scissors with the stationary shear bar having the forage material cut against it with a traveling contact point of cut.

Competitive brands used straight knives that “punched” through the forage material. They claimed that by using shorter sectional knives instead of longer helix/spiral knives, if damage to the chopper cutter head did occur, it could be easily and more cheaply fixed. This could be true, but how much foreign material (logs, fence posts, etcetera) were you putting into the chopper? The answer had better be ZERO! This method of cut used much more horsepower, provided a poor cut quality and wasted lots of fuel.
A set of 12 high helix knives smoothly sheared the crop material like a pair of sharp scissors. These knives were mounted on twin fabricated steel plates (three sets on the 781, four sets on the 881) to give superior knife rigidity and positive knife alignment for extra long cutter head life. The cutter head made 10,200 cuts per minute.
An extra long wearing shear bar was adjustable for wear, making it easy to maintain proper clearance between the shear bar and cutter head. The bar was also reversible for long life. When one edge wore out or became damaged, the bar could be reversed for renewed performance.
Whenever servicing a forage harvester, SAFETY FIRST was the golden rule. One should turn off the tractor’s PTO and wait for it to stop rotating before leaving the tractor. Serious injury and most likely death would occur if you did not heed these instructions. When using a jack to raise the machine, one should be sure to use the proper equipment (blocks, jack stands, etcetera) that were appropriate for secure and safe support of the unit being repaired.
IH X81 choppers were fitted with an IH exclusive Hydra-sharp cutter head knife rebeveling (sharpening) system. With this system, the cutter head knife could be re-sharpened in minutes. The circular grinding stone sharpened and rebeveled the cutter knife (even the ends) for complete, total edge sharpening. This unit was powered by the tractor’s hydraulic system so you could sharpen the cutter knives anywhere, any time without having to find an electrical power supply, as with competitive makes.
The unique centrifugal cleaning of the rotating sharpening stone prevented excessive buildup on the stone itself and provided an ever fresh abrasive surface. This unit was fully shielded for operator safety. One should ALWAYS follow the instructions provided in the owner’s manual when performing this service.
The feed roll and cutter head capacity depended on the material transport and blowing system to take the chopped forage away from the cutter and into the wagon/truck. If this system was undersized or underperforming, your chopper would run poorly or plug.
IH used a big 10 inch diameter cross auger that now had flighting 40 percent heavier than the previous 720-830 models on the X81 series. A heavy duty shear bolt hub auger drive kept the forage flowing to the blower.
Having the correct blower speed was an important feature in high capacity forage production. The 32 inch diameter blower on the IH X81 series choppers ran at a top speed of 8,378 feet per minute. This took the forage from the cross auger and sent it up the blower spout at more than 95 miles per hour!
The three paddles on the blower measured one quarter inch thick and were adjustable to compensate for wear individually. You could replace the paddles individually to not only extend paddle life, but to maintain maximum throwing capacity. The blower was offset to the left of the cutter head to give the chopper better balance. This design put the wagon directly behind the tractor to provide a straight line of draft. The inline pull of tractor blower-spout-wagon was especially important in rough or soft fields.
Many of the competitive makes did not offer this offset blower and they had to offset the wagon hitch point or rotate the spout. This made the wagon harder to pull in hilly or soft ground. The angle line of the blower made it harder to load wagons all the way to the back. The rear tow bar of the blower had a second hitching point on the right end to allow safer, easier movement of chopper and wagon and reduced overall width for highway transport.
The blower spout was controlled by an electric screw motor to rotate it. The deflector paddle was also controlled by a small electric winch motor. A replaceable steel spout liner was standard equipment. This liner reduced wear and extended spout life. Many competitive makes did not have a spout liner and when the spout wore through, an expensive repair was in store for you.
IH equipped the X81 choppers with an equal angle drawbar hitch. This was a drawbar extension that was designed to keep the u-joint angles equal at both ends of the telescoping implement driveline. This allowed operation around sharp curves without sacrificing performance or having u-joint chatter or damage. This equal angle system eliminated the hammering or chatter while turning and the driveline failures associated with it. This led to smooth power transmission to the chopper for better efficiency and longer driveline component life.
The 781 chopper was offered in either 540 or 1000 PTO RPM drive versions. The 540 RPM drive model will handle up to 95 PTO horsepower tractors. The 1000 RPM PTO would handle up to 140 PTO horsepower tractors. The 881 was built to run in 1000 RPM PTO speed only and would handle up to 190 PTO horsepower tractors.
Both the 781 and 881 were equipped with fully electric controls. No ropes, levers or cranks to struggle with while driving. The fingertip operated toggle switches controlled spout rotation, spout deflection and the feeder rolls. You could run you chopper from the comfort of your tractor cab with the windows SHUT! A fuse protected the control system from electric power overload. The control panel for the 781 and 881 was designed to fit into a special pocket built into the right hand console on the IH 86-30-50-60 and 2+2 model tractors. An attractive and easy to mount box was available for mounting in other tractor makes and models.
The list price of a basic 781 forage harvester was about $13,000. Compare that to the approximate price of a basic 881 forage harvester, which was $16,500. Both prices were from the early 1980s.
A number of options were offered for both models, including re-cutter screens ($118), blower spout extensions ($95) and an extra electric controls box ($179).
Of course, to use your harvester, you needed to attach a head to it. IH offered many head choices to fit a farm’s needs. For those who made “haylage” (chopped hay silage), IH offered a six foot wide hay pickup head for $1,715.
IH offered a two-row, row crop head that fit both the 781 and 881 and a three-row head that fit the 881 model only. The two row head listed for $2,780. The three-row head listed for $4,900. An optional power feeder (a vertical mounted feed roll drum on the head that assisted it in feeding material into the chopper) was an extra $213.
Both the two-row and three-row heads were adjustable for various row width settings. The two-row could be set for 28, 30, 32 and 34 inch narrow rows or 36, 38 and 40 inch wide rows. The three-row unit could be set for 28 to 32 inch wide rows. Both heads used cleated rubber gathering belts powered by plastic drive sprockets to carry the cut crop to the feeder rolls on the chopper (two belts per row). Twin, intermeshing steel cutoff discs cut the plant from its root. A tubular steel break over/push bar was standard equipment. This item knocked tall corn over to ensure that was fed evenly into the feed rolls of the chopper.
If you needed an ear corn snapper head, IH offered a two-row model to fit either chopper for $5,415. Some choppers needed to have axle extensions installed to achieve correct wheel spacing. If you needed these, they were available too at a cost of $45 each.
The 781 and 881 choppers, along with the hay pickup head, ear corn snapper and row crop unit heads, were all built by IH at its Hamilton, Ontario, Canada plant. In 1983, IH sold its hay equipment line to New Idea. The 781 and 881 choppers were then built for both IH (under contract) and New Idea dealers.
The IH 781 and 881 choppers were “cutting edge” forage tools for the farmer. They were still valuable assets to any forage growing farm. Both the 781 and 881 were dropped from production by Case IH in 1990.
Anyone who has ever had the experience of operating a pull type chopper can appreciate the skills that are needed to run one successfully.
I was “thrown to the lions” in my first experience in running a chopper. I was using a nicely worn IH 1486 (complete with oil leaks!) as my power unit. I was given a quick 100 yard demo run on how it worked and what to look for when running it. It looked pretty simple to me. Run the tractor wide open, don’t plug the chopper or run over/into anything.
My first wagon load was anything but great. While trying to watch and listen for everything, I wasn’t moving the spout from side to side to pack the corners of the wagon with silage to make it FULL! I got an earful about this and every wagon after that was a nice solid silage brick!
Some of your friends may be into motorcycles and such. A few may have a custom bike they ride. Once you have mastered the concepts of the chopper, you can make the claim that you belong to a “chopper gang” and you really DO know how to cut it!