dadohead
Gold Member
Hi,
Background: Here is a project I started about 2 years ago. Since I retired (2016) I've wanted to build a rotary cutter that addressed the issues I find in the typical single spindle cutter. For years now I mow about 4 acres of field and the ditches to my lane. I mow about 3x year; sometimes cutting 24" grass to 4" hoc. I mow with a JD 2520 (20hp pto) and a Frontier 5' cutter (I've tried others too). I retired from Deere after 25 years of designing tractors and finish mowers.
The problem: The problem with the single spindle cutter is cut quality; it just doesn't pickup tire tracks! The Frontier RC2060 runs CCW. The tractor pushes the grass forward in the tracks and mashes it down. The LH side of the cutter back sweeps the tire track and cuts well. The RH side aligns the forward sweep of the blade to the tire track and cuts very poorly. After several days, the RH tire track stands back up almost uncut. To combat this, minimal overlap is applied when cutting (essentially keeping the RH tires OUT of the high grass). I only cut about 2 1/2' of a 5' cutter to get acceptable cut quality. Drives me crazy!
The concept: twin spindle cutter, conventional CCW rotation, offset spindles, with mower shifted to the right so BOTH blades back-sweep the tire tracks! Given that I only have a 20hp PTO tractor, a priority was given to power reduction as well. With the tire tracks being mechanically swept up, a lower tip speed could be used as well as a medium lift blade. Impact cutting starts at about 12000fpm tip speed (going lower just "combs" the grass). I targeted this mower at 13,500fpm. 1" rake was designed in so the cut material would release and not recirculate saving power.
The build: I started by purchasing a used, beatup KeenKutter 3pt finish mower. It was junk! I did save the gear box and mounting. Trinkets were cut off of the deck and scrapped. Sheet steel was added to the rear of the mower.
You can see the yellow outline of the original 72" mower. What made this concept possible for me was that Fred Cain (small manufacturer in KY) makes a 3' CCW rotary cutter. I bought 2 of his 3' stump jumpers, blade sets, and assorted parts. He threw in 2 stripped out OMNI gear boxes (just like the one from my KeenKutter). I cut the gear box off of these, annealed the spindles, machined the base castings... they became the mower spindles! I used 1/4" plywood templates to guide my plasma cutter to shape the housing. I needed 2 driven sheaves with a specific diameter and offset to make it all work.
In another life, I was a wood patternmaker at Caterpillar. It's been 40 years since I've turned a pattern but i remember how! Two sheaves were cast in nodular iron at a nearby foundry. They were machined in my shop to receive 2- HB kevlar belts.
Just like we used to design finish mowers, I started with no baffles underneath.... and just like every conventional rotation 2 spindle mower I've ever seen: the front spindle wanted to hand off all of its discharge to the back spindle! Baffles were needed. I started adding baffled using cardboard and duct tape and testing until the cutter started to behave. Then the baffles were reproduced in steel.
Bumper guards and chains were added at the end. How does it work???
Testing: Ok... I LOVE this thing! My 20hp tractor handles the 6' cutter just like it was my old 5' but with better cut quality!
One note: with the mower shifted to the right (to back-sweep tire tracks) you gain a 1 foot bonus trim section on the right of the tractor! Huge improvement. Time to cut the field is half of what used to be. I hired the kid across the road (just out of film school) to shoot some video last year. It was the first mow of the season so the field was tall and extra wimpy.(tough to cut well).
Somebody needs to make this design. What do you think?
Background: Here is a project I started about 2 years ago. Since I retired (2016) I've wanted to build a rotary cutter that addressed the issues I find in the typical single spindle cutter. For years now I mow about 4 acres of field and the ditches to my lane. I mow about 3x year; sometimes cutting 24" grass to 4" hoc. I mow with a JD 2520 (20hp pto) and a Frontier 5' cutter (I've tried others too). I retired from Deere after 25 years of designing tractors and finish mowers.
The problem: The problem with the single spindle cutter is cut quality; it just doesn't pickup tire tracks! The Frontier RC2060 runs CCW. The tractor pushes the grass forward in the tracks and mashes it down. The LH side of the cutter back sweeps the tire track and cuts well. The RH side aligns the forward sweep of the blade to the tire track and cuts very poorly. After several days, the RH tire track stands back up almost uncut. To combat this, minimal overlap is applied when cutting (essentially keeping the RH tires OUT of the high grass). I only cut about 2 1/2' of a 5' cutter to get acceptable cut quality. Drives me crazy!
The concept: twin spindle cutter, conventional CCW rotation, offset spindles, with mower shifted to the right so BOTH blades back-sweep the tire tracks! Given that I only have a 20hp PTO tractor, a priority was given to power reduction as well. With the tire tracks being mechanically swept up, a lower tip speed could be used as well as a medium lift blade. Impact cutting starts at about 12000fpm tip speed (going lower just "combs" the grass). I targeted this mower at 13,500fpm. 1" rake was designed in so the cut material would release and not recirculate saving power.
The build: I started by purchasing a used, beatup KeenKutter 3pt finish mower. It was junk! I did save the gear box and mounting. Trinkets were cut off of the deck and scrapped. Sheet steel was added to the rear of the mower.
You can see the yellow outline of the original 72" mower. What made this concept possible for me was that Fred Cain (small manufacturer in KY) makes a 3' CCW rotary cutter. I bought 2 of his 3' stump jumpers, blade sets, and assorted parts. He threw in 2 stripped out OMNI gear boxes (just like the one from my KeenKutter). I cut the gear box off of these, annealed the spindles, machined the base castings... they became the mower spindles! I used 1/4" plywood templates to guide my plasma cutter to shape the housing. I needed 2 driven sheaves with a specific diameter and offset to make it all work.
In another life, I was a wood patternmaker at Caterpillar. It's been 40 years since I've turned a pattern but i remember how! Two sheaves were cast in nodular iron at a nearby foundry. They were machined in my shop to receive 2- HB kevlar belts.
Just like we used to design finish mowers, I started with no baffles underneath.... and just like every conventional rotation 2 spindle mower I've ever seen: the front spindle wanted to hand off all of its discharge to the back spindle! Baffles were needed. I started adding baffled using cardboard and duct tape and testing until the cutter started to behave. Then the baffles were reproduced in steel.
Bumper guards and chains were added at the end. How does it work???
Testing: Ok... I LOVE this thing! My 20hp tractor handles the 6' cutter just like it was my old 5' but with better cut quality!
One note: with the mower shifted to the right (to back-sweep tire tracks) you gain a 1 foot bonus trim section on the right of the tractor! Huge improvement. Time to cut the field is half of what used to be. I hired the kid across the road (just out of film school) to shoot some video last year. It was the first mow of the season so the field was tall and extra wimpy.(tough to cut well).
Somebody needs to make this design. What do you think?
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