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what blade tip speed

#1

L

LandN

It seems that a lawnmower with a blade tip speed of 18,500 has the best cutting performance....so who sets 'that' number..the government?,the mower industry?.......is there a 'minimum' blade tip speed?.... has anyone compared the cutting performance performance of two near identical mowers with say a.. ...500(or so) tip speed difference to compare the cutting difference? just wondering here cause i'm 'still' researching the mower i want to get this spring and it is just short of the magic 18,500,actually it is 18,400fpm this mower has a price tag of 1,200.00 bucks so i want to cross my "T's and dot my "I's" i have to be 100% sure on this mower.thanks :biggrin:


#2

twall

twall

It's similar to the hp vs. torque discussion :wink:

The number you found is what a manufacturer found to get the best 'lift' (which also translates into 'blow' out the chute) based on how they designed their blades.

I'd think it's different for each manufacturer, depending on how they designed their blades.

As far as who sets the number, I guess Newton does....:laughing:


#3

L

LandN

i havent seen under the mower to see what type/kind of blade it has. i'm still checking out the top side yet:laughing: i hope i has a high lift blade on it or be able to buy one for it.


#4

twall

twall

Not to confuse you......

But, as critical as the blade is to cut - the deck design is equally as critical. Just putting new blades on won't for sure get you a "high lift" deck.

Most high lift decks have one common feature: a continuous lip that even extends under the chute, and a rolled under (as opposed to rolled out) lip. This sealed shroud causes a vaccum effect. That is what gives the potential for high-lift (or hi-vac, as we snapper fans call it). JD, on some models, also offers (and has offered) a true high-lift option.

Blades alone, although they can help a bit, won't give you the golf-course look you may be after.

That requires hi-vac.


#5

twall

twall

LandN said:
...... this mower has a price tag of 1,200.00 bucks so i want to cross my "T's and dot my "I's" i have to be 100% sure on this mower.......
Click to expand...


A measly 1200? :laughing: A snapper hi-vac rear engine rider without even an electric start will run you over 2g........

And JD??? Don't walk in unless you're pre-approved for a loan. :wink:


#6

K

KennyV

Blade tip speed makes a difference, especially as the blades get dull...

You can see the difference with any mower just slow down the engine RPM ... you will eventually cross the threshold of acceptable cut to not so acceptable ...

18,500 ft per min is 210 MPH and is a very good speed to cleanly clip grass ... even with a duller blade... :smile:KennyV


#7

JDgreen

JDgreen

LandN said:
It seems that a lawnmower with a blade tip speed of 18,500 has the best cutting performance....so who sets 'that' number..the government?,the mower industry?.......is there a 'minimum' blade tip speed?.... has anyone compared the cutting performance performance of two near identical mowers with say a.. ...500(or so) tip speed difference to compare the cutting difference? just wondering here cause i'm 'still' researching the mower i want to get this spring and it is just short of the magic 18,500,actually it is 18,400fpm this mower has a price tag of 1,200.00 bucks so i want to cross my "T's and dot my "I's" i have to be 100% sure on this mower.thanks :biggrin:
Click to expand...

Interesting and thought provoking thread...just checked the manual for my 60 inch 7-Iron deck, it states blade tip speed is 15948 fpm 2100 rpm, I usually mow at 2200 rpm which probably ups the fpm to 16,000. Can you tell us where you obtained the 18,500 figure, thanks.


#8

K

KennyV

I have seen the 18,500 blade tip speed as a suggested speed for blades up to 20 inch... as the blade gets longer than that the turbulence increases and causes additional problems... My largest deck runs a slightly lower BTS ... the 84 inch Land Pride running 3 blades 29 inches each, spin at 17,210 ft per min.
My 72 inch CTL with 3, a little over 24 inch blades, runs right at 19,000 fpm... In fine bladed grass I slow it down a bit for the 'perfect cut'.

So the 'Ideal' blade tip speed would appear to vary from grass to grass and blade length and deck design...

A 20 inch blade spun at 3,600 RPM is going to have right at 18,800 FPM... (that is going to be the average lawn mower)... Keep the blades sharp you could shed some RPM and still have a good cut... :smile:KennyV


#9

JDgreen

JDgreen

KennyV said:
I have seen the 18,500 blade tip speed as a suggested speed for blades up to 20 inch... as the blade gets longer than that the turbulence increases and causes additional problems... My largest deck runs a slightly lower BTS ... the 84 inch Land Pride running 3 blades 29 inches each, spin at 17,210 ft per min.
My 72 inch CTL with 3, a little over 24 inch blades, runs right at 19,000 fpm... In fine bladed grass I slow it down a bit for the 'perfect cut'.

So the 'Ideal' blade tip speed would appear to vary from grass to grass and blade length and deck design...

A 20 inch blade spun at 3,600 RPM is going to have right at 18,800 FPM... (that is going to be the average lawn mower)... Keep the blades sharp you could shed some RPM and still have a good cut... :smile:KennyV
Click to expand...

Good post, Kenny...:thumbsup: I do wonder though if any maker has ever sold a mower with a built in blade sharpener...I have an '89 vintage Craftsman chain saw with a built in sharpener...

Yeah, I am making this in jest, we will never have a built in sharpener on our mowers, would bve nice to have though.


#10

I

ILENGINE

The blade tip speed maximum is set by ansi standards at 19000. Lawnmowers blades are designed to withstand up to that speed and if exceeded the vibration harmonics can cause cracks to form leading to blade failure. So the longer a blade is the slower it has to turn.


#11

L

LandN

Hey guys thanks a bunch for the insight on my question of blade speed , i just got off of work so i couldn't get back to you all sooner,but i did read it all on my cell phone @lunch time.i will be more inclined now to purchase the mower now,just a few more things to check on it, thanks


#12

M

MASTERLAWNMAN

LandN said:
It seems that a lawnmower with a blade tip speed of 18,500 has the best cutting performance....so who sets 'that' number..the government?,the mower industry?.......is there a 'minimum' blade tip speed?.... has anyone compared the cutting performance performance of two near identical mowers with say a.. ...500(or so) tip speed difference to compare the cutting difference? just wondering here cause i'm 'still' researching the mower i want to get this spring and it is just short of the magic 18,500,actually it is 18,400fpm this mower has a price tag of 1,200.00 bucks so i want to cross my "T's and dot my "I's" i have to be 100% sure on this mower.thanks :biggrin:
Click to expand...

I have been told that the max speed is a Gov't mandated item from many years ago (30 PLUS).
Has to do with throwing blades and death.
Have ya ever seen a blade through a CBS block wall.
We use to play with the carbs on both chain saws and mowers to get max speed.
Worked at golf and polo fields for years (ONCE AGAIN 30 PLUS)
Worst thing created was the ethanol.
Only run boat gas, non/ethanol # 90 OR #91 or 103 race fuel since having to rebuild too many carbs

Great site.
Thanks,

signed,

the "MASTERLAWNMAN"


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