Hybrid Rotary Cutter Proof of Concept

[jmc]

I'd bet Deere was sorry to see you retire!

 

[350c]

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.

View attachment 3717293
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.

View attachment 3717294

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.

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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!

View attachment 3717986
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?

Great work and great idea; good luck with future progress in marketing. On a related matter, I question why trail- or pull-type rotary cutters are not readily available, if at all, for SCUTs and CUTs -- in my experience, the vibration from a rotary cutter is not transferred to the tractor nearly as much through a drawbar as through a 3-point hitch. That vibration cannot be good on a tractor, especially on smaller tractors. The flex hitches help some, but the vibration is still transferred more. Since you worked for JD, is there a reason for not having more, or at least SOME, choices in pull-type mowers for smaller tractors?

 

[Runner]

I would think tow-behind mowers would be much harder on the U-joints than three point mounted models. For that reason alone, I would stick with the three point model, unless I really needed tow-behind because of the size.

 

[dieselscout80]

Thx so much!

A few questions:

• It appears to be a 2 spindle, CCW rotation?
• Does the LH stripe align with the LH tractor tire?
• Where does the LH mower spindle align with the stripe? Dead center? Right? Left?
• Just curious. Your mower looks symmetrical (not staggered). How do the 2 blade paths cross to assure complete cutting?

The mower appears to be centered with tractor. If your mower can shift, it would be most effective to move the mower to the right some so the LH spindle can back-sweep the tire track.

It’s 3 spindles (114” cut) and the stripe is from the left tire to the far left side.

 

[dieselscout80]

I would think tow-behind mowers would be much harder on the U-joints than three point mounted models. For that reason alone, I would stick with the three point model, unless I really needed tow-behind because of the size.

I love my pull behind mower it doesn’t bounce around like a three point does with a cutting height of 6” to 8”, so the ride is better. I do wish it was a batwing so the deck followed the terrain better.

Backing into fence corners it not as easy and lifting a 9.5’ mower would be difficult for my tractor. I outline my pastures with my flail mower and a fence trimmer.

 

[shooterdon]

Very impressed with your skill and execution.

I cannot fabricate so must buy whatever I need to get the job done.

I would buy a fail mower and not wait for the grass to get 24" high. I doubt you need more than 20 PTO HP for cutting grass at a 48" mow width. The flail will not leave those windrows either.

Sorry, but those windrows are not acceptable.

 

[5030]

Very nice but not marketable because the cost to make it commercially would be prohibitive. Not many people would pay the added cost when much cheaper alternatives are available and if that ground was mine, I'd be cutting, raling and bailing it....lol

 

[dadohead]

It’s 3 spindles (114” cut) and the stripe is from the left tire to the far left side.

Ok, looked up Woods C114-1: 3 spindle, CW conventional rotation, staggered spindles.

From videos I see on YT, the LH tire track hits the left spindle at about 10:00-11:00.... that's the forward sweep on this CW blade. Anytime a tire track aligns with forward sweep it spells trouble!

So, what to do... sharp blades, WOT (wide open throttle), slower ground speed, lower HOC, and most effective: shift mower left to put tire track 12:00 or more on LH spindle (BACK SWEEP IT!). Hopefully won't screw up RH spindle cut.

A ring baffle may help... exactly like radiator fans: close to the blade helps (3/8- 1/2" radially) and just into the wing region axially. In Experimental, I'd have the guys weld more wing on a blade too (welder needs to KNOW what they're doing! Pre-heat 5150 etc). Wing: 30 deg for better lift / 45 deg wings = less lift and THROWS grass further. Welcome to the club!

 

[dadohead]

Very nice but not marketable because the cost to make it commercially would be prohibitive. Not many people would pay the added cost when much cheaper alternatives are available and if that ground was mine, I'd be cutting, raling and bailing it....lol

Lol... you always have an opinion Flip!

Disagree... similar build costs as 3pt finish mower. One less spindle / blade set, less 4 gauge wheels / mounting. Add: more steel / weld time. Had this discussion with Woods.

Target BIG volume 1000/BX tractor owners.... sell mowers. You know what they say about opinions though... ;>)

 

[dadohead]

I would buy a fail mower and not wait for the grass to get 24" high. I doubt you need more than 20 PTO HP for cutting grass at a 48" mow width. The flail will not leave those windrows either.

Sorry, but those windrows are not acceptable.

Smart. But I'm an old rotary guy who's not smart! Would not trade the 72" WOC with 1 foot right side trim for 48" flail.

Yes, the windrows after cutting 24" are there... after a week or so they are not. I can live with it. Remember, this is a first shot. If I was at Deere, I would have started with a carrier rig that held the mounting and drive. Fiberglass deck shells would be made to insert in. After the cut was behaving, ALL KINDS of work would go into the discharge (deck shapes, baffles, etc) to spread it out better. I don't have those resources anymore. That's why I want somebody to make it... they'll do it better!

Implement companies are small. They cant spend resources then just "get on base".... they need "home runs". This might not go anywhere.... I tried. Sure love reading all your comments!

 

[dieselscout80]

Ok, looked up Woods C114-1: 3 spindle, CW conventional rotation, staggered spindles.

From videos I see on YT, the LH tire track hits the left spindle at about 10:00-11:00.... that's the forward sweep on this CW blade. Anytime a tire track aligns with forward sweep it spells trouble!

So, what to do... sharp blades, WOT (wide open throttle), slower ground speed, lower HOC, and most effective: shift mower left to put tire track 12:00 or more on LH spindle (BACK SWEEP IT!). Hopefully won't screw up RH spindle cut.

A ring baffle may help... exactly like radiator fans: close to the blade helps (3/8- 1/2" radially) and just into the wing region axially. In Experimental, I'd have the guys weld more wing on a blade too (welder needs to KNOW what they're doing! Pre-heat 5150 etc). Wing: 30 deg for better lift / 45 deg wings = less lift and THROWS grass further. Welcome to the club!

Thanks

I’m going to need a bit of translation.

What does these mean:
1. “just into the wing region axially” mean?

2. “pre-heat 5150”

 

[dadohead]

1. Axially: in the direction of the fan axis. Bring the height of the rings just into the blade wing height to create maximum lift... more is not better (leaves more blade exposed for cutting too). Note the ring heights on my initial post.
2. Most blades are made of either 10B38 or 5150 steel and hardened to the HRC 38 range. They are difficult to weld safely. Many won't do it. I've had several blades welded by expert welders. They preheated the parts before welding. Not for amateurs like me!

 

[dadohead]

Since you worked for JD, is there a reason for not having more, or at least SOME, choices in pull-type mowers for smaller tractors?

Cost. Pull-type mowers require at least 2 rear wheels and external hydraulics to operate the lift. Since their driveshafts operate in 3d space, expensive CV joints must replace the cheaper cardan joints found in 3pt mounted mower driveshafts.

 

[Little Red Tractor]

That is an exceptionally well-done project. You certainly put all your acquired skills to work on it and it came out great.

I'll guess that most of us share your frustrations with single spindle cutters. They just don't give good cut quality unless you do a LOT of overlapping. Great, great job.

 

[Runner]

2. Most blades are made of either 10B38 or 5150 steel and hardened to the HRC 38 range. They are difficult to weld safely. Many won't do it. I've had several blades welded by expert welders. They preheated the parts before welding. Not for amateurs like me!

I was wondering about the blades on your cutter which seem to have high-lift ears welded onto them. Did you experiment with different heights/shapes of "ears", and did you do the welding on them?

 

[dieselscout80]

Woods makes three types of blades for the C114 straight, twisted and high fin. I have the high fin (lift) blades.

I have thought about adding more to the fin to increase lift.

Would you recommend adding the baffle first or increasing the blade fin/wing?

 

[dadohead]

I was wondering about the blades on your cutter which seem to have high-lift ears welded onto them. Did you experiment with different heights/shapes of "ears", and did you do the welding on them?

Yes, I had wings welded on. The stock Fred Cain 3' blades I started with were very low lift... just a small 'tip up' for a wing. Initial testing proved the concept very quickly as the tire tracks were back-swept nicely. The forward-sweep region (usually the weakest part of the cut) was pretty bad. As I mentioned before, the front blade was handing off all of its discharge to the rear and completely disturbing the cut as well.

Ring baffles came first. They separated the chambers and got the material flowing efficiently. The rings also add lift. The cut improved but the forward-sweep was still weak (right side of each blade on my CCW mower). The guy I used at Deere is now retired but still welded the wings onto my blades. The cut improved significantly.... a forward-sweep stripe is still present though.

After living with the mower though, there was NO CHANCE of ever going back to the single spindle... I wanted best cutting/safest blade for the long run. I contacted Haven Steel, maker of the Fred Caiin blades (and every other swing blade made) and had them make new blades. They are sized like the Fred Cain blade with a wing profile following our best JD blade... that's what I'm currently running.

In taller grass, a forward-sweep stripe is still there. It is a "hump" shape, not the ragged/uncut stripe my Frontier would produce if you cut full width. It is acceptable to me though. This is 20" cut to 4":

I'm finding that the job goes so much faster now that I'm mowing more often. The look improves as well.

 

[dadohead]

Would you recommend adding the baffle first or increasing the blade fin/wing?

Woods knows what they're doing. With 3 lifts already available, I would assume their high lift would be as good as you could get. I wouldn't weld on them.

First thing I would try is to shift the mower left to put the tire track to the back-sweep of the blade. The mower tongue is probably adjustable to shift the mower position. That would be VERY effective. If not, fab a ring baffle and tack it to the LH chamber. Be mindful of how your mower discharges though: side discharge? Rear? The baffle must allow somewhere for the material to discharge. Hope this helps!

 

[BnRidge]

I wanted best cutting/safest blade for the long run. I contacted Haven Steel, maker of the Fred Caiin blades (and every other swing blade made) and had them make new blades. They are sized like the Fred Cain blade with a wing profile following our best JD blade... that's what I'm currently running.

Every deck seems to require a different type of blade. I worked for a blade manufacturer. There were a couple of tests we did that simulated running across a stake, like a surveyor stake, or a fence post in the case of a forage harvester, yet the blades afterward needed to still function, and without breaking. There were instances of broken blades - one was on I94 near the Milwaukee veterans cemetery, where they were mowing the lots. A broken blade went across the highway and through the windshield of a car. I was going to say welding on them sounds like a quick r&d thing to get it done, but then you went out and had some made.

 

[D&D]

Yes, I had wings welded on. The stock Fred Cain 3' blades I started with were very low lift... just a small 'tip up' for a wing. Initial testing proved the concept very quickly as the tire tracks were back-swept nicely. The forward-sweep region (usually the weakest part of the cut) was pretty bad. As I mentioned before, the front blade was handing off all of its discharge to the rear and completely disturbing the cut as well.

Ring baffles came first. They separated the chambers and got the material flowing efficiently. The rings also add lift. The cut improved but the forward-sweep was still weak (right side of each blade on my CCW mower). The guy I used at Deere is now retired but still welded the wings onto my blades. The cut improved significantly.... a forward-sweep stripe is still present though.

After living with the mower though, there was NO CHANCE of ever going back to the single spindle... I wanted best cutting/safest blade for the long run. I contacted Haven Steel, maker of the Fred Caiin blades (and every other swing blade made) and had them make new blades. They are sized like the Fred Cain blade with a wing profile following our best JD blade... that's what I'm currently running.

In taller grass, a forward-sweep stripe is still there. It is a "hump" shape, not the ragged/uncut stripe my Frontier would produce if you cut full width. It is acceptable to me though. This is 20" cut to 4":

View attachment 3752433

I'm finding that the job goes so much faster now that I'm mowing more often. The look improves as well.

Ok, I'm convinced. Please ship my free demo unit (in Kioti Orange) with account funding for fuel and wear parts. We will provide future evaluation and testing of performance on a variety of east coast lawn and pasture grasses.