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Blade Tip Speed

#1

Ric

Ric

Wondering about the difference in Blade tip speed between the residential self propelled push mower and a commercial. Like the difference between the Toro Time master and the Turf master, or the toro 21" personal Pace. Anyone know or have any ideas?


#2

R

Rivets

Back to teaching mode.


All you need to know is the length of the blade and the RPM's of the motor.
Blade length multiplied by Pi. That gives you circumference. Now multiply that times your engines RPM's and divide by twelve.
If I'm not mistaken, the pulley that drives the blades should be the same size as the one on the crankshaft of most mowers. This gives your blade the same rpms as your motor. I could be wrong about that. Maybe some engineer on here could tell you more about that I don't know.

Example:
Blade length = 18"x Pi (3.14)=56.52
That gives you circumference.
Now all you have to do is multiply that by your RPM's (3650)

56.52 x 3650 = 206,298

Now divide that by 12 ie; 206,298/ 12= 17,191.5 ft/min
I think that's it.

The magic number that the industry used was 19,000 ft/min back around 2000, may have changed. To put it another way, blade tip speed will be between 175-215 mph depending on engine RPM's.


#3

M

mowerman05

just purchased a exmark 30 with a blade tip speed of approx 18500 fps


#4

Ric

Ric

mowerman05 said:
just purchased a exmark 30 with a blade tip speed of approx 18500 fps
Click to expand...

You just purchased the exmark 30" I just piked up the Toro Turfmaster today. :thumbsup: Toro Turfmaster 005.jpg


#5

lawn mower fanatic

lawn mower fanatic

mowerman05 said:
just purchased a exmark 30 with a blade tip speed of approx 18500 fps
Click to expand...

Ric said:
You just purchased the exmark 30" I just piked up the Toro Turfmaster today. :thumbsup: View attachment 12971
Click to expand...

Sweet! :thumbsup::thumbsup:


#6

wjjones

wjjones

Rivets said:
Back to teaching mode.


All you need to know is the length of the blade and the RPM's of the motor.
Blade length multiplied by Pi. That gives you circumference. Now multiply that times your engines RPM's and divide by twelve.
If I'm not mistaken, the pulley that drives the blades should be the same size as the one on the crankshaft of most mowers. This gives your blade the same rpms as your motor. I could be wrong about that. Maybe some engineer on here could tell you more about that I don't know.

Example:
Blade length = 18"x Pi (3.14)=56.52
That gives you circumference.
Now all you have to do is multiply that by your RPM's (3650)

56.52 x 3650 = 206,298

Now divide that by 12 ie; 206,298/ 12= 17,191.5 ft/min
I think that's it.

The magic number that the industry used was 19,000 ft/min back around 2000, may have changed. To put it another way, blade tip speed will be between 175-215 mph depending on engine RPM's.
Click to expand...



Thats what I have always heard 19,000 ft/min.


#7

midnite rider

midnite rider

wjjones said:
Thats what I have always heard 19,000 ft/min.
Click to expand...

That is 215.9 MPH. Boogety, Boogety!


#8

wjjones

wjjones

midnite rider said:
That is 215.9 MPH. Boogety, Boogety!
Click to expand...



Thats moving pretty quick.


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