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OT optimal cutting speed and feed rate for lawn mower blades?

A lot of people working as mower deck engineers........shouldn't be. Buy a better mower, that deck is to short. That Bolens is a 'lawn tractor' designed to cut 2" off of a lawn and nothing taller if you want a quality cut. The best cutting mowers I've ever had were the 3 wheel Scags with the 6" tall decks. Nice finishing cut quality even in 6-8" tall grass with near brush hogging ability in grass up to 12" as well. The tall design eliminates clogging and the grass can stand up better. I started out with a Craftsman lawn tractor, 18hp Onan, really shallow deck, tried many things to get it to cut better, POS. Gave up and bought a well used Scag. Now I have a 61" diesel Grasshopper zero turn which is OK, but does not cut as well as either Scag did. The "wrecking crew" lawn service that cuts the property next door has zero turn Kubota's. They look more like 4 wheelers as the pack of them zoom around the property at high speeds and WOT. I'm waiting for a mid-air collision between those goof balls.

I also notice quite a difference between fresh sharpened blades and blades with even 15 cutting hrs on them as far as cut quality. They still look and feel reasonably sharp, but they don't cut as cleanly.
 
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Yeah, not that simple when you're running a big deck in high and/or somewhat wet grass. I'll take all the help I can get at that point. Tilting the deck down in front does help, and quite a bit. It ain't about looking pretty or not.
I guess I was trying to make a machinist joke about not having a circular cutter trammed. I better keep my day job. I am a lousy comedian :).
 
This thread makes me think that I am not crazy for wanting to build the lightest, best pushmower ever. Like they made before safety attachments that make the machine heavy and hard to use only better. I have an old Ariens that doesn't want to die and would like to replace it with a new uber version. Likely will not happen but I like the idea.
 
Darn..I missed the joke.
But here is a mower joke;

Saturday morning I got up early, quietly dressed, made my lunch, and slipped quietly into the garage. The grass needed cutting but I thought it better to go fishing. I hooked up the boat to the van and proceeded to back out into a torrential downpour. The wind was blowing 50 mph, so I pulled back into the garage, turned on the radio, and discovered that the weather would be bad all day.

I went back into the house, quietly undressed, and slipped back into bed. I cuddled up to my wife's back; now with a different anticipation, and whispered, "The weather out there is terrible."

My loving wife of 5 years replied, "And, can you believe my stupid husband is out fishing in that rickety old boat on a day like this.?"
 
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Where can I find the source for that info? I am not trying to be rude, I would just really like to know the details behind that. If that standard does exist, whoever wrote it has already been down the road I am heading, I would like to study their research.
Apparently it is an ANSI spec.


I have no idea when I got that number stuck in my head but it was a long long time ago.
 
Apparently it is an ANSI spec.


I have no idea when I got that number stuck in my head but it was a long long time ago.

Good find! The article has a link to a .pdf of the ANSI spec https://www.google.com/url?q=https:...868846912025&usg=AOvVaw1GCf1bShLPjEyiF767MLyz

The testing requirements are interesting but here is the specific verbiage in question:

Screenshot_20230919-025033_Samsung Notes.jpg

Again, great find Gearclash, thank you for sharing!
 
While you may want to decrease your mowing time by increasing the blade and ground speed rates it seems most companies design their machines to give the best quality results when operating in the 5-mph range. Above that speed the profile of the air flow under the deck changes significantly enough to interrupt the flow of the grass to the discharge chute. The tumbling grass then forms clumps reducing the blade performance.

JD has tried over the years to improve airflow by adding a flexible rubber strip on the front of their larger decks. The rubber strip allows the blades to create more of a vacuum to raise bent over grass and keep it vertical allowing the blades to make a cleaner cut. This system works fine if you're only cutting grass. However, if you have leaf cover the strip has a tendency to push the litter ahead of the mower rather than let it slide under the deck and get chopped up with the grass clippings.

A few years ago, there were several adds on TV touting the fast-mowing speeds of several name brand machines. If you looked closely the operators were all but bouncing off the seats on what appeared to be a level well maintained lawn without noticeable bumps or holes. About the only suspension on any of the machines was the spring action of the seat and the flexibility of the tires. I have 2 garden tractors that can be used for mowing the JD445 has a top speed of 8 mph, and the Case 224 has a top speed of 12 mph. The Case is all but impossible to control when attempting to go full throttle on anything but a paved road.

If you really want to get the job done in a hurry the best machine for the job would be the one in the link below. It has a 4-cylinder 999cc motorcycle engine that turns up to 13,000 rpm and puts out 200 hp. In 2019 itset a world record speed of 150.99 mph in Dresden Germany.

 
Actually, the best way to design a deck so that it can cut with higher quality and increased ground speed is to add more and smaller blades! A smaller blade spins higher RPM to get equal tip speed. Higher RPM at the same ground speed equals: less "feed per tooth." I always wondered why they didn't make a 5 blade deck for something like a 72". Probably just too expensive.
 
I used to tell new machinists the difference between climb and conventional mowing. The grass will get re-cut when climb mowing, but will be out of the way for conventional. When mowing leaves, a climb technique would blow leaves in a direction that would be easier to gather when done.
 
That exception for blade tip speed is interesting. I always assumed that tip speed limits were a blade material tensile limit factor. The way that exception is worded makes it sound as though it is more of an expelled particle speed factor.
 
Likely it would be best to grin a little greater angle..and take a couple of swipes with a file, so to take away any soft edge from overheating the edge..the very thin edge gets hotter than the rest of the grind area.
 
I have a simple suggestion:

Sell the Bolens! Then it's someone else's problem.

And cut your grass with the John Deere.

Then pop a top and have a cool one with no worries.
I've been mowing it all with the JD for nearly 10 years. It takes nearly 3.5 hours, 48" deck is too small. Although the Bolens leaves a less than desirable finish, it has knocked an hour off of the total time.

I am confident that increasing the blade speed, replacing the running gear with a well designed caster system and doing away with the integral chute portion of the deck will provide results that I can be content with.

It really is a nice little garden tractor, whoever had it before me took very good care of it. It has plenty of power and uses less than half of the fuel that the JD consumes. JD = 5 gallons of gasoline to mow the yard. Bolens = 2 1/4 gallons of diesel for the same task.

For what I paid for the Bolens, I really have no reason to complain. I'd like to get a 60" Hustler but I cannot justify the price, considering that the only thing it's good for is mowing grass.

This experiment is more fun anyway. It doesn't take much time to fab up a good wheel kit and swap out a few pulleys. So far I get the feeling that most riding mowers stay around 16k SFM to ensure that they are well under the maximum limit and also pass the projectile test.

While we can all speculate, none of us actually know what the results will be from a drastic increase in blade tip speed. I intend to fu€k around and find out 😁.
 
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When I was a kid the school mowers had giant bat wings with multiple reel mowers. None of these weed whip designs. I think they were not powered just friction drive. My father always insisted reel mowers gave a cleaner cut. All the golf course greens mowers are reel.
Bill D
this one looks to be pto driven.
 

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I've been mowing it all with the JD for nearly 10 years. It takes nearly 3.5 hours, 48" deck is too small. Although the Bolens leaves a less than desirable finish, it has knocked an hour off of the total time.

I am confident that increasing the blade speed, replacing the running gear with a well designed caster system and doing away with the integral chute portion of the deck will provide results that I can be content with.

It really is a nice little garden tractor, whoever had it before me took very good care of it. It has plenty of power and uses less than half of the fuel that the JD consumes. JD = 5 gallons of gasoline to mow the yard. Bolens = 2 1/4 gallons of diesel for the same task.

For what I paid for the Bolens, I really have no reason to complain. I'd like to get a 60" Hustler but I cannot justify the price, considering that the only thing it's good for is mowing grass.

This experiment is more fun anyway. It doesn't take much time to fab up a good wheel kit and swap out a few pulleys. So far I get the feeling that most riding mowers stay around 16k SFM to ensure that they are well under the maximum limit and also pass the projectile test.

While we can all speculate, none of us actually know what the results will be from a drastic increase in blade tip speed. I intend to fu€k around and find out 😁.
What model JD are you using? I use a 445 all wheel steer. It has a 22 hp water cooled 2 cylinder engine. It came standard with a 60 inch mower, but I had to downsize to a 48 inch model to get between the trees. Sometimes the grass gets a good 6 inches long but it has no problem powering through. There aren’t any rocks or debris ion the ground so I can keep the blades razor sharp. They usually get sharpened once or twice a year depending on how many times I have to mow. On wet years it’s every 4 days. On drier years it can be as long as 2 weeks between mowings.

Over the years we’ve taken down nearly 30 trees. I’ve considered getting a 60 inch deck but doubt it would save much time due to the shape of the yard and the placement of the remaining trees

It takes about an hour to mow and weed eat along the fences. Add another half an hour when I edge the drive and walks
 
When I was a kid the school mowers had giant bat wings with multiple reel mowers. None of these weed whip designs. I think they were not powered just friction drive. My father always insisted reel mowers gave a cleaner cut. All the golf course greens mowers are reel.
Bill D
this one looks to be pto driven.
The reel mowers have largely been replaced by rotary mowers even on the greens. The reels did a fine job as long as there weren't rocks or debris on the fairways. They had a tendency to jam when hitting sticks, and chip either the reel or the bar if they caught a rock the wrong way.

They were also a real PITA to sharpen. My uncle had a small engine shop and sharpened reel mowers for several golf courses. Every year a few blades were ruined when someone ran over the edge of a cart path the wrong way or got something caught between the reel and the bar. Some models could just have the blade replaced while others needed to have the entire reel replaced. As rotary mowers became more popular reel mower parts became harder to find and more expensive.

From time to time, I still see a gang reel mower working at a high-end golf club, but most often places use rotary mowers due to cost concerns.
 








 
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