Dual Blades on Finish Mower

   / Dual Blades on Finish Mower #1  

TractorGuy

Elite Member
Joined
Sep 15, 2013
Messages
4,611
Location
N. FL
Tractor
John Deere 4310 CUT, Ford New Holland 575E Industrial Backhoe, John Deere F725 Front Mount Mower
I've been wanting the try out the dual blade idea on my finish mower for some time. My current blades didn't really need sharpening but I touched them up while they were off. I sharpened an old set and put them on top of the better blades. I tack welded them together to keep them square if I hit something.

The tractor is a 3 range hydro and the mower is a 6' Agmate. I usually have to run about half speed in the mid range for a decent cut. With the double blades I was able to get about the same quality cut at full speed in mid range. I can only run full speed over about 2/3 of my property but that should cut mowing time down a bit.

I eventually plan to make some blades using disc mower blades. Not sure if I will do it using bars or a round plate. I would prefer a round plate. You can get a dozen replacement blades for about $20 with those. Not sure how long they last compared to regular blades so that will be another experiment.

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   / Dual Blades on Finish Mower #2  
I'm looking forward to seeing your disc blade approach.

 
   / Dual Blades on Finish Mower #3  
Did you bend those dual blades so they both cut at the same height?
 
   / Dual Blades on Finish Mower
  • Thread Starter
#4  
Did you bend those dual blades so they both cut at the same height?
No I just stacked and tacked. I didn't bother to check for evenness. Identical blades would only be a 1/4" different but these are two different brands so they may have a different offset.

The top blades are original and the bottom blades are Caroni.

After mowing the whole field I wasn't as impressed as I was to begin with. I did push it as fast as possible to test results. I am finding some areas with uncut strips so I will probably have to slow tractor speed next time if I let the grass get that tall.
 
   / Dual Blades on Finish Mower #5  
Check out Meg-mo blades. They are too expensive for me. If too expensive for you — this might be a good design for you to copy and fabricate your own.
 
   / Dual Blades on Finish Mower #6  
You tried running the tractor at higher than the rated pto rpm right?
 
   / Dual Blades on Finish Mower
  • Thread Starter
#7  
You tried running the tractor at higher than the rated pto rpm right?
A little but not by much. I usually try to run it at the next mark beyond the PTO mark on the tach.

It tends to drop RPMs as I mow and I have to keep bumping the throttle up. I need to look into adjusting the tension on the throttle.

Ideally you want to increase blade speed but most PTO finish mower boxes don't spin the blades like a quality zero turn would. I installed a larger pulley to increase blade speed a little but I would like to spin them much higher.

The double blades DO put more stress on the engine in high grass. You can feel and hear the engine working harder. This grass was overgrown and thick. I was laying a pretty good mat of hay down.
 
   / Dual Blades on Finish Mower #8  
I cannot see the belt configuration in your pics. But if you mean you put larger pulleys above each blade, that would decrease blade speed.
 
   / Dual Blades on Finish Mower #9  
I cannot see the belt configuration in your pics. But if you mean you put larger pulleys above each blade, that would decrease blade speed.
Since he said a larger pulley and NOT larger pulleys....I took that to mean the drive pulley and not the spindle pulleys. So that WOULD increase blade speed.

I too have messed around with double blades.....and different deck designs react differently. I see yours is a rear discharge.

There is no doubt in my mind that double the number of cutting edges HAS to be an improvement to cut quality. But....I am not sure about double the air flow with twice as many high lift blades. If you try to "lift" more air than can easily be discharged out the back....the air has to go somewhere. And what I have found is that it tends to bounce off the deck and blow down and out all sides. Which is the opposite effect of what you want to"suck" the grass up. Too much airflow/turbulence isnt a good thing.I have found that dropping one or both sets of blades to a low-lift type does alot better. Currently I have a set of standard lifts paired with gators (muching blades done have nearly as much lift) and it is about as good as it can get in terms of cut quality, clipping distribution, etc

What do the clippings look like? Do they look chopped up finer than before?
 
   / Dual Blades on Finish Mower #10  
I did the same thing; went from 2 single bars to 2 crossed bars, doubling the blades.
My deck is bigger though. 1/2 ton and 9-1/2' wide.

I figured the only reason not to was if there wasn't enough torque available to do the extra work.
The deck maker says 20hp, and my tractor has 85Hp, so there's some spare.
Anyway, I now mow about 1-1/2x higher wheel speed. it saves about an hour each time I mow the grass.
I also use the deck as a brush cutter for the outer fields and it does bog down a little in high pto gear but it works ok.
 

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