Beautifully-Designed Tandem Tractor Built From MF-35s
Lon Jackson’s “MF-70” is composed of two 1961 MF-35s that look like they belong together. Before retiring, Jackson was a chief program engineer for Boeing’s Strategic Ballistic Missile Weapon System. The MF-70 combines his love of farming and his engineering expertise.
“I drove tractors like these starting at 7 years old,” says Jackson. “When I was 9, my dad bought a new 1955 Massey Harris Ferguson TO-35, which I still own and have restored.”
Jackson already had one MF-35 and found another to match. After extensive research, he created a design on paper that identified problems and solutions. The hand drawings were then entered into CAD files by a friend, Duane Davis. He did computer simulations to identify stress points and undesirable twisting. This led to further refinements, including thicker steel or added bracing.
Many of the major steel components were made by an area steel supply company. The CAD files were used to drive their plasma cutter. The trunion components and the articulation kingpin were fabricated by other vendors.
“Some of the cut steel pieces required further work to drill and tap holes, flatten large turn plates, mill grease grooves, smooth trunion bores, and so on,” says Jackson. “This work was done with the help of my friend Duane and his Bridgeport mill.
“The biggest challenge was the steering system,” says Jackson. “I started out wanting to retain as much of the original design as possible, with the power steering pump on the back tractor and the steering wheel column doing the work. However, neither was up to the task of driving the large cylinders needed to articulate the new tractor.”
Jackson ended up stripping out the steering systems along with the front axles and installing a Char-Lyn Orbitrol control unit. It provides manually-controlled hydraulic steering to the articulation pivot carrier that couples the MF-35s front to rear.
The carrier consists of two 18-in. dia., 1-in. thick steel control plates and incorporates a trunion design. A trunion is basically a shaft in eyelet mounts.
“It’s a very necessary component to allow the two halves to be able to twist up and down independently of each other without putting undue stress on the articulation joint,” explains Jackson.
An L-shaped bracket bolted to the differential on the forward tractor extends toward the following tractor. It houses two sets of eyelet mounts. Matching mounts on the underside of the lower control plate connect the two components with shafts. This provides the carrier with the ability to rock left and right over rough ground.
A matching round control plate is attached under the front end of the follow-tractor. When connected with a kingpin, the two plates provide the left/right pivot.
The lower plate has arms to either side with clevis mounts. Hydraulic cylinders mounted to the rear axles of the follow-tractor connect with these mounts to steer the MF-70.
Steering complications rose again as Jackson attempted to fit the orbit motor under the dash. He had to modify the dash sheet metal, throttle linkage, steering column, and steering wheel to make it work. New hydraulic hoses pulled hydraulic power from the lead tractor’s auxiliary outlet to the motor and then to the control cylinders. This left the rear tractor hydraulics to be used for the 3-pt. lift.
Aside from steering, other controls between the two tractors were linked mechanically. Jackson used custom levers added to the rear tractor with control cables to the OEM levers on the front tractor.
“The front tractor clutch is controlled via a lever mounted near the operator position on the rear tractor,” says Jackson. “This lever operates a master cylinder, which drives a slave cylinder on the front tractor, which via custom linkage activates the front tractor clutch.”
A tachometer mounted on the rear tractor lets Jackson monitor the engine on the front tractor. He has full control of forward, reverse, and all gears.
Contact: FARM SHOW Followup, Lon Jackson, 6484 NW Sisters Pl., Corvallis, Ore. 97330 (ph 541-738-0885; boxters986@comcast.net).
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Beautifully-Designed Tandem Tractor Built From MF-35’s AG WORLD Lon Jackson’s “MF-70” is composed of 2 1961 MF-35’s that look like they belong together Before retiring Jackson was a chief program engineer for Boeing’s Strategic Ballistic Missile Weapon System The MF-70 combines his love of farming and his engineering expertise “I drove tractors like these starting at 7 years old ” says Jackson “When I was 9 my dad bought a new 1955 Massey Harris Ferguson TO-35 which I still own and have restored ” Jackson already had one MF-35 and found another to match After extensive research he created a design on paper that identified problems and solutions The hand drawings were then entered into CAD files by a friend Duane Davis He did computer simulations to identify stress points and undesirable twisting This led to further refinements including thicker steel or added bracing Many of the major steel components were made by an area steel supply company The CAD files were used to drive their plasma cutter The trunion components and the articulation king pin were fabricated by other vendors “Some of the cut steel pieces required further work to drill and tap holes flatten large turn plates mill grease grooves smooth trunion bores and so on ” says Jackson “This work was done with help of my friend Duane and his Bridgeport mill “The biggest challenge was the steering system ” says Jackson “I started out wanting to retain as much of the original design as possible with the power steering pump on the back tractor and the steering wheel column doing the work However neither was up to the task of driving the large cylinders needed to articulate the new tractor ” Jackson ended up stripping out the steering systems along with the front axles and installing a Char-Lyn Orbitrol control unit It provides manually-controlled hydraulic steering to the articulation pivot carrier that couples the MF-35’s front to rear The carrier consists of two 18-in dia 1-in thick steel control plates and incorporates a trunion design A trunion is basically a shaft in eyelet mounts “It’s a very necessary component to allow the 2 halves to be able to twist up and down independently of each other without putting undue stress on the articulation joint ” explains Jackson An L-shaped bracket bolted to the differential on the forward tractor extends toward the following tractor It houses 2 sets of eyelet mounts Matching mounts on the underside of the lower control plate connect the 2 components with shafts This provides the carrier with the ability to rock left and right over rough ground A matching round control plate is attached under the front end of the follow-tractor When connected with a king pin the 2 plates provide the left/right pivot The lower plate has arms to either side with clevis mounts Hydraulic cylinders mounted to the rear axles of the follow-tractor connect with these mounts to steer the MF-70 Steering complications rose again as Jackson attempted to fit the orbit motor under the dash He had to modify the dash sheet metal throttle linkage steering column and steering wheel to make it work New hydraulic hoses pulled hydraulic power from the lead tractor’s auxiliary outlet to the motor and then to the control cylinders This left the rear tractor hydraulics to be used for the 3-pt lift Aside from steering other controls between the 2 tractors were linked mechanically Jackson used custom levers added to the rear tractor with control cables to the OEM levers on the front tractor “The front tractor clutch is controlled via a lever mounted near the operator position on the rear tractor ” says Jackson “This lever operates a master cylinder which drives a slave cylinder on the front tractor which via custom linkage activates the front tractor clutch ” A tachometer mounted on the rear tractor lets Jackson monitor the engine on the front tractor He has full control of forward reverse and all gears Contact: FARM SHOW Followup Lon Jackson 6484 NW Sisters Pl Corvallis Ore 97330 ph 541 738-0885; boxters986@comcast net
