Why are lawn tractors so slow?

[boggen]

see attached picture.


#1's = blade tip speed stays the same, but...
A = slower MPH = less blades of grass cut per rotation of blade.
B = faster MPH = more blades of grass need to be cut per rotation of blade.

#2's belts, and friction / heat they get.
A = belt folds back and forth, and actually twists. belt really does heat up a lot. every wiggled a wire back and forth till it broke into 2 pieces? ((assumption pulley on mower is upward vertical position.))
B = ((assumption pulley on mower is laying horizontal )) belt still needs to be bent back and forth, and twist some.
C = 3 separate belts going to say a hydraulic motor with 3 pulleys on the end of it.
D = hydraulic motor per each blade. all heat / friction is put into the hyd oil and carried away.
other words = the more a belt heats up, the more likely it is to stretch. more stretching = more slipping on pulleys = additional heat.

#3's needing to pull grass up into the blades due to being flatten / ran over before blades get to the grass.
A = riding lawn mower. wider / thicker front tires. and in that more grass is flatten.
B = zero turn mower, caster wheels on front = smaller wheels / tires. that do not flatten grass as much.
overall it takes power to suck and draw blades of grass up into the blades.
other words = blade shape can determined how much suction there is to draw grass up into the blades to be cut. the more suction power there is, the more likely the mower HP is needed to get the blade to spin. and keep it spinning at wanted RPM's

#4's = weight distribution. over drive wheels.
A = riding mower, engine weight for most part over front wheels, while human weight is over rear wheels.
B = zero turn mower, engine weight and human weight kinda balance themselves of the rear drive wheels.

#5's = more of attempt to show a kids "tetter tottor" of #4's
other words = traction, more weight on drive wheels more likely you get more traction vs spinning wheels.

==============
torque and RPMS, and getting the power transferred to the blades constantly, and to tire err making sure you have traction...

i would say riding mowers = not as efficient as a zero turn mower. when comparing cutting grass...
riding lawn mowers = flatten / smash more grass into the ground before blades get to it, belts heat up and slip more, less weight over 2WD rear tires for traction.
zero turns = sharper turns / quicker turns, able to keep eye on were you are driving vs last path (not moving eyes back and forth like on a riding mower)

 

[Turbys_1700]

I mow a 7+ acre lawn.
My Wheel Horse garden tractor is rough riding and I wouldn't want to try to mow our entire lawn with it, it would likely take an entire day to mow the lawn.
My 35 HP compact tractor with an 84" finish mower rides better, but trying to mow over 5-6 MPH gets really rough. (takes just over 3 hours to mow the lawn)
I can mow the same lawn with a 35 HP Hustler Super Z zero turn w/ 72" deck in 2 hours. With the flex forks, suspension seat and 7-8 PSI tire pressure the ride is MUCH better than the tractors.
The rough areas I have to slow down, but much of our lawn I can mow at full speed (13-14 MPH).
With the better ride ,better maneuverability and much higher mowing speeds, my Super Z zero turn will mow circles around the tractors.

I can concur. If I try to mow too fast with my tractor and RFM the ride quality and quality of cut suffers. I hope to get a zero turn in the near future.

 

[savageactor7]

Pretty sure it's the sub-surface of a prepared lawn that allows a zero turn (ZT) to cut at a higher speed.

Our lawn is recovered farm land that gives you the appearance of being very flat...but it's not. Even with reduced tire pressure an adult can't cut at full speed...too hard on the body.

I bet those ZT's we see running at speed are on lawns that were york-raked not too long ago.

 

[ovrszd]

I did a little more research and I'm probably not 100% on track on the blade tip speed explanation. Apparently there is a national standard that limits mower tip speeds to 19,000 fpm on commercial equipment and a little less on residential equipment. Our compact tractors, ZTRs and high end garden tractors probably have a 10 to 15% edge on the smaller machines which would probably improve the cut but not allow for a huge difference in mowing speed.

Kenny, I too did some research. Never knew blade tip speed was such a technical issue.

It appears there are regulated limitations on such things. Who would have guessed.

I also don't know how much difference it would make and can't seem to find any reliable opinions on that. Here's some data I copied concerning John Deere Garden Tractor decks that seems reliable.

48inch Blade tip speed 16,956ft/min
54inch Blade tip speed 17,143ft/min
60inch Blade tip speed 16,500ft/min
62inch Blade tip speed 17,131ft/min
Those are Based @ 3,600RPM


So, if it's not blade tip speed, then what is the explanation for the claim that Zero Turn mowers can mow at a faster ground speed than a similar deck on a Garden Tractor?? I'm very interested to hear a valid theory in that regard??

 

[ovrszd]

Pretty sure it's the sub-surface of a prepared lawn that allows a zero turn (ZT) to cut at a higher speed.

Our lawn is recovered farm land that gives you the appearance of being very flat...but it's not. Even with reduced tire pressure an adult can't cut at full speed...too hard on the body.

I bet those ZT's we see running at speed are on lawns that were york-raked not too long ago.

I totally agree with you. My lawn is mostly recovered pasture. You ain't mowing it at full speed regardless of what type mower you have.

 

[art]

We sell four brands of zero turns and one thing that I have found out, many don't cut well once they are past 5 mph!!! They do talk of 10 mph speed but at that they maybe cut 50% of the grass and they do throw grass out the shoot but the quality of cut goes as the speed increases.

To see how you are doing drop 2 by 4 on edge after cutting then move back about 15' and see if you have a clean line or a bunch of whiskers sticking up. It should be a finite line, otherwise rev the engine up, or slow down! Look at the grass, if it is split ends then you have dull blades.

 

[MossRoad]

 

[ovrszd]

We sell four brands of zero turns and one thing that I have found out, many don't cut well once they are past 5 mph!!! They do talk of 10 mph speed but at that they maybe cut 50% of the grass and they do throw grass out the shoot but the quality of cut goes as the speed increases.

To see how you are doing drop 2 by 4 on edge after cutting then move back about 15' and see if you have a clean line or a bunch of whiskers sticking up. It should be a finite line, otherwise rev the engine up, or slow down! Look at the grass, if it is split ends then you have dull blades.

Good tips Art.

The older I get the more detail oriented I am. Also, being retired, I'm not rushed for time. I am now more interested in what my yard looks like the day after it's mowed than I am about how long it took me to do it.

 

[LD1]

Speed and quality are changed by MANY factors

If you mow every 3 or 4 days and are only taking an inch off the top, full speed gets a good cut.

If you are like me and mow every 8 or 9 days and have to take 3 or 4" off the top, quality suffers up near the 10MPH range as it starts leaving little stripes of uncut grass between the blades. But just a tad slower, maybe 6-8MPH it still cuts nice with sharp blades

Grass type also effect the cut. Thin and flimsey stuff like kentucky bluegrass dont cut worth a darn IMO. The bigger fatter stiffer blades cut lots better. There are a few areas in my yard that have a high percentage of bluegrass. It kinda lays down more than the rest, so it appears to not be as tall. But that stuff is thick and you can hear the motor working harder to get through it

And keeping blades sharp makes a world of difference in any type grass

 

[ovrszd]

Speed and quality are changed by MANY factors

If you mow every 3 or 4 days and are only taking an inch off the top, full speed gets a good cut.

If you are like me and mow every 8 or 9 days and have to take 3 or 4" off the top, quality suffers up near the 10MPH range as it starts leaving little stripes of uncut grass between the blades. But just a tad slower, maybe 6-8MPH it still cuts nice with sharp blades

Grass type also effect the cut. Thin and flimsey stuff like kentucky bluegrass dont cut worth a darn IMO. The bigger fatter stiffer blades cut lots better. There are a few areas in my yard that have a high percentage of bluegrass. It kinda lays down more than the rest, so it appears to not be as tall. But that stuff is thick and you can hear the motor working harder to get through it

And keeping blades sharp makes a world of difference in any type grass

My yard has every variable imaginable since it's primarily pasture. I try to mow every 4-5 days so I don't have clippings laying around.

This Spring I switched blades. That has done more for the quality of my cut, tidiness of the clippings and increased speed than anything else I've ever tried. They are called "Predator 2" blades. Cost $45 for a set of three to fit my 62" deck.