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View Full Version : What is the blade tip speed on Scags?


tb8100
03-28-2008, 12:42 PM
I can't seem to find that spec anywhere. :confused:

Tagg
03-28-2008, 01:28 PM
Just RIGHT !!!

tb8100
03-28-2008, 01:41 PM
Just RIGHT !!!

well DUH. Everybody knows THAT.

topsites
03-28-2008, 01:44 PM
20,000 fps, give or take.

tb8100
03-28-2008, 01:50 PM
20,000 fps, give or take.

holy CRAP. Really??

So that's like, 120,000 feet per minute, right? 0_o

IA_James
03-28-2008, 01:55 PM
holy CRAP. Really??

So that's like, 120,000 feet per minute, right? 0_o

Fast enough to throw a pine cone the size of one of those small size footballs across a street and bounce off a Mustang, I know that.:nono:

newtostone
03-28-2008, 02:06 PM
Is it really 20k? i would love to know myslf i can never seem to find that information and when i ask a scag sales guy he acts like hes' never heard of what that is ;)

IA_James
03-28-2008, 02:21 PM
I think it's actually a little lower than 20k, more like 18-19k. I'm not sure how much faster it is than a home owner model. I think that's where you get the commercial machine jet engine sound when spooling the blades up vs. a home owner mower.

JimQ
03-28-2008, 02:34 PM
I just went out and measured one

Brand new Turf Tiger 61" Velocity Plus, 29hp Kawi

17,900 FPM

Like I said, it's a new unit. Never seen grass. It might pick up a few FPM as things break in.

ANSI limits blade tip speed to 19K FPM

Q

newtostone
03-28-2008, 02:42 PM
JimQ thanks for the insight!

tb8100
03-28-2008, 03:04 PM
I just went out and measured one

Brand new Turf Tiger 61" Velocity Plus, 29hp Kawi

17,900 FPM

Like I said, it's a new unit. Never seen grass. It might pick up a few FPM as things break in.

ANSI limits blade tip speed to 19K FPM

Q

Really? 17,900? I guess blade tip speed isn't everything. The Velocity+ is a fantastic deck. Exmarks and Toros are running 18400-18600 on their higher end models. Bad Boy, Encore, Wright, and a few others are right at that 19000fpm limit. I guess that's why the Scag discharges out larger clippings than some- fewer blade strikes per minute. Harder to bog a deck running a lower tip speed too. Interesting...

Thanks Jim!

tb8100
03-28-2008, 03:05 PM
How in the world do you measure that anyway??

BTW, what's the tip speed on that monster deck you were building?? :cool2:

JimQ
03-28-2008, 03:51 PM
How in the world do you measure that anyway??

BTW, what's the tip speed on that monster deck you were building?? :cool2:

You're right, blade tip speed isn't everything.

All you need to do to measure blade tip speed is measure spindle RPM then do a little math.

I use a photo-tachometer to measure spindle RPM.

You place a small piece of reflective tape on the blade drive sheave, fire up the deck, and point the photo-tach at it. It counts the pulses of reflected light and calculates RPM

Then the math part of it.

I'll use the numbers I just got from the Scag

Blade length = 21"
Spindle RPM = 3250

First you find the distance the blade tip travels every revolution. This is the circumference of the blade tip path.

21" x 3.1415... (pi) = 65.971"

then convert to feet

65.971"/12 = 5.497'

So the blade tip travels 5.497 feet every revolution

We know the blade is rotating at 3,250 RPM

5.497 ft * 3,250 RPM = 17,865 FPM


As far as the blade tip speed on that "Monster Deck"....well... that's top secret! :laugh:

I'll share more someday. I promise!

Take care! :waving:

Q

tb8100
03-28-2008, 05:03 PM
You're right, blade tip speed isn't everything.

All you need to do to measure blade tip speed is measure spindle RPM then do a little math.

I use a photo-tachometer to measure spindle RPM.

You place a small piece of reflective tape on the blade drive sheave, fire up the deck, and point the photo-tach at it. It counts the pulses of reflected light and calculates RPM

Then the math part of it.

I'll use the numbers I just got from the Scag

Blade length = 21"
Spindle RPM = 3250

First you find the distance the blade tip travels every revolution. This is the circumference of the blade tip path.

21" x 3.1415... (pi) = 65.971"
[quote]

wow, you know Pi to 4 places....that's more than me! I get to 3.14 and I get lost after that! :laugh:

[quote]
then convert to feet

65.971"/12 = 5.497'

So the blade tip travels 5.497 feet every revolution

We know the blade is rotating at 3,250 RPM

5.497 ft * 3,250 RPM = 17,865 FPM



Question: Is the spindle RPM the same as the engine or is it effectively geared down by different size pulleys on the spindle and PTO clutch? If so, shouldn't that engine be bumped up to 3650rpms? At least, that's how most manufacturers advertise their blade tip speed- 3650rpms...

As far as the blade tip speed on that "Monster Deck"....well... that's top secret! :laugh:

I'll share more someday. I promise!

Take care! :waving:

Q

:laugh: I figured you would say that but hey, it never hurts to ask! Later man-

Tim :waving:

skeet
03-28-2008, 05:09 PM
Fast enough to throw a pine cone the size of one of those small size footballs across a street and bounce off a Mustang, I know that.:nono:

:laugh: lmao...made my day!

JimQ
03-28-2008, 05:44 PM
Is the spindle RPM the same as the engine or is it effectively geared down by different size pulleys on the spindle and PTO clutch? If so, shouldn't that engine be bumped up to 3650rpms? At least, that's how most manufacturers advertise their blade tip speed- 3650rpms...

Nah, spindle RPM and engine RPM are independent of each other.

You're right. It all depends on the clutch sheave and the blade sheave diameters.

It just so happens that on a 61" deck (21" blade) that engine RPM and blade RPM are about the same to put the tip speed in the 18K-19K FPM range.

At the same engine RPM - (Most OEM's run around 3600RPM, give or take)
Larger decks will have a lower spindle RPM
Smaller decks will have a higher spindle RPM

For instance

A 3 blade 42" (deck 14.5" blade) would be spinning at 5000RPM to get a tip speed of 19K FPM

nograss
03-28-2008, 05:44 PM
My first requirement is that the tires go round and round.:weightlifter:

tacoma200
03-28-2008, 05:50 PM
Really? 17,900? I guess blade tip speed isn't everything. The Velocity+ is a fantastic deck. Exmarks and Toros are running 18400-18600 on their higher end models. Bad Boy, Encore, Wright, and a few others are right at that 19000 fpm limit. I guess that's why the Scag discharges out larger clippings than some- fewer blade strikes per minute. Harder to bog a deck running a lower tip speed too. Interesting...

Thanks Jim!

The Ultra Cut has quite a bit of internal baffles giving it a lot of lift so it recycles the clippings more than a deck with an open design such as the Velocity Plus or 7 Iron II decks. The larger chute openings also reduces lift on the Velocity Plus but spreads the clipping and reduces clumps. After running hundreds of hours on them and studying them that's my conclusion. The Velocity Plus deck relies on the open area in front of the blades to let the grass stand up while the Ultra Cut relies on lift to stand the grass up. Scag really had a good idea leaving the open area in front of the blades while some other company's didn't leave the room for the grass to stand up, great design overall for variety of working conditions (Velocity Plus).

tb8100
03-29-2008, 02:25 AM
Nah, spindle RPM and engine RPM are independent of each other.

You're right. It all depends on the clutch sheave and the blade sheave diameters.

It just so happens that on a 61" deck (21" blade) that engine RPM and blade RPM are about the same to put the tip speed in the 18K-19K FPM range.

At the same engine RPM - (Most OEM's run around 3600RPM, give or take)
Larger decks will have a lower spindle RPM
Smaller decks will have a higher spindle RPM

For instance

A 3 blade 42" (deck 14.5" blade) would be spinning at 5000RPM to get a tip speed of 19K FPM

Really? I thought most manufacturers used different size pulleys to maintain a high tip speed?

mag360
03-29-2008, 12:03 PM
Really? I thought most manufacturers used different size pulleys to maintain a high tip speed?

That's my understanding. Pulley diameter is the only variable between the motor and spindles.

TwistedSister
03-29-2008, 01:47 PM
20,000 fps, give or take.


WOW! 20,000 Feet Per Second...That's 13,636 MPH. I wonder how long the spindles last??? But serioulsy, I think he meant 20,000 FPM which is 227 MPH... about the same speed as most other commercial mowers. I think my Wright in about 18,500 FPM.

nosparkplugs
03-29-2008, 03:13 PM
After owning a Scag Tiger Cub 48" velocity deck 20hp Kohler, and using it on high end residential & commecial accounts. The velcoity deck works great for large area's not requiring a manicured look, it does produce a manicured cut, with double cutting, I was total satisfied with SCAG's quality of build:however even with the high blade tip speeds, I was double cutting, unless it equals a manicured look with minimal work, Fast BTS does not equal a manicured cut. The "spec sheet kings" don't always produce the best quality cut. There are just to many variables to just look at blade tip speeds.

tb8100
04-01-2008, 01:28 AM
Here's a response I got from Scag after I emailed them with this question (and also asked about blade overlap for the fun of it too):

Hi Tim,

For your reference, approximate blade tip speeds for Scag zero turn
riders...

Freedom Z:
--48" & 52" models: 17,000 fpm

Turf Tiger:
--52" models: 18,250
--61" models: 18,600
--72" models: 18,550

Tiger Cub & Wildcat:
--48" models: 18,650
--52" models: 18,500
--61" models: 18,700

Scag cutter decks have approximately 1" of blade overlap.

Thank you,

Tom Oechsner
Marketing Specialist
SCAG Power Equipment
www.scag.com

tacoma200
04-01-2008, 01:44 AM
Here's a response I got from Scag after I emailed them with this question (and also asked about blade overlap for the fun of it too):

Tom Oechsner at Scag has been very helpful anytime I've had a question or problem about Scag.

It's been a long time since I've seen it posted but but lowering your RPM's thus lowering tip speed has been a highly recommended technique for cutting very damp grass. I have used this method and found that it works in many situations. Especially with high lift blades you don't want all that lift when cutting wet grass.

tb8100
04-01-2008, 07:28 PM
Tom Oechsner at Scag has been very helpful anytime I've had a question or problem about Scag.

It's been a long time since I've seen it posted but but lowering your RPM's thus lowering tip speed has been a highly recommended technique for cutting very damp grass. I have used this method and found that it works in many situations. Especially with high lift blades you don't want all that lift when cutting wet grass.

Yeah, he's very helpful!

Mic_bug
04-01-2008, 09:25 PM
[QUOTE=JimQ;2236907]You're right, blade tip speed isn't everything.

All you need to do to measure blade tip speed is measure spindle RPM then do a little math.

I use a photo-tachometer to measure spindle RPM.

You place a small piece of reflective tape on the blade drive sheave, fire up the deck, and point the photo-tach at it. It counts the pulses of reflected light and calculates RPM

Then the math part of it.

I'll use the numbers I just got from the Scag

Blade length = 21"
Spindle RPM = 3250

First you find the distance the blade tip travels every revolution. This is the circumference of the blade tip path.

21" x 3.1415... (pi) = 65.971"
[quote]

wow, you know Pi to 4 places....that's more than me! I get to 3.14 and I get lost after that! :laugh:



Question: Is the spindle RPM the same as the engine or is it effectively geared down by different size pulleys on the spindle and PTO clutch? If so, shouldn't that engine be bumped up to 3650rpms? At least, that's how most manufacturers advertise their blade tip speed- 3650rpms...



:laugh: I figured you would say that but hey, it never hurts to ask! Later man-

Tim :waving:



3.14159265358979323846…:weightlifter::weightlifter:

tacoma200
04-01-2008, 09:40 PM
:waving:You should take pi out to the last digit for an accurate tip speed Mic Bug

cybervision
04-02-2008, 09:03 AM
Tom Oechsner at Scag has been very helpful anytime I've had a question or problem about Scag.

It's been a long time since I've seen it posted but but lowering your RPM's thus lowering tip speed has been a highly recommended technique for cutting very damp grass. I have used this method and found that it works in many situations. Especially with high lift blades you don't want all that lift when cutting wet grass.


I will have to keep this in mind. I have never thought to do this and I have wet condition most of the spring.

dave k
04-02-2008, 09:16 AM
The Ultra Cut has quite a bit of internal baffles giving it a lot of lift so it recycles the clippings more than a deck with an open design such as the Velocity Plus or 7 Iron II decks. The larger chute openings also reduces lift on the Velocity Plus but spreads the clipping and reduces clumps. After running hundreds of hours on them and studying them that's my conclusion. The Velocity Plus deck relies on the open area in front of the blades to let the grass stand up while the Ultra Cut relies on lift to stand the grass up. Scag really had a good idea leaving the open area in front of the blades while some other company's didn't leave the room for the grass to stand up, great design overall for variety of working conditions (Velocity Plus).
Tacoma
Do you think the UC would have less clogging or a better cut with a open design in front like the Scag?

tb8100
04-02-2008, 10:09 AM
Tacoma
Do you think the UC would have less clogging or a better cut with a open design in front like the Scag?

it would lose some of that vacuum, you could bet on that.

tacoma200
04-02-2008, 01:59 PM
Tacoma
Do you think the UC would have less clogging or a better cut with a open design in front like the Scag?

Yes it would probably clog less with an open design but then you loose the great lift/vacuum that makes the Ultra Cut leave a carpet like finish on a lawn and chop the clipping into small pieces that fall into the lawn. When it comes to a lawn that is fairly dry and not overgrown, a normal lawn in other words the Lazer Ultra Cut leave a much smoother cut. I don't want them to change anything about the Ultra Cut, when I get over grown lawns/wet lawns/biweekly I use the Scag though, its a workhorse. If everyone had their grass cut weekly here, or I lived in a higher income area with finely manicured lawns, I would use the Ultra Cut.

Both have their purpose and strong points.
Of course our grass is a lot different than what grows in most of GA.

tb8100
04-03-2008, 05:12 PM
Here's another message I got from Tom:


Tim,



STHM:

--52”: 17,500 fpm

--61”: 18,500

--72”: 19,500



Walk-Behinds:

--32” – 52”: 17,500 fpm

--61”: 18,500

--72”: 19,500



Thanks,

Tom Oechsner
Marketing Specialist
SCAG Power Equipment
www.scag.com

pugs
04-03-2008, 05:28 PM
STHM:

--52”: 17,500 fpm

--61”: 18,500

--72”: 19,500



Walk-Behinds:

--32” – 52”: 17,500 fpm

--61”: 18,500

--72”: 19,500

Looks like they got lazy on those models and just ran the same pulleys on all of the deck sizes.

tb8100
04-03-2008, 07:19 PM
Looks like they got lazy on those models and just ran the same pulleys on all of the deck sizes.

Hey, if it cuts right, why mess with it?

John Gamba
05-02-2008, 02:16 PM
Really? 17,900? I guess blade tip speed isn't everything. The Velocity+ is a fantastic deck. Exmarks and Toros are running 18400-18600 on their higher end models. Bad Boy, Encore, Wright, and a few others are right at that 19000fpm limit. I guess that's why the Scag discharges out larger clippings than some- fewer blade strikes per minute. Harder to bog a deck running a lower tip speed too. Interesting...

Thanks Jim!




They send out larger clippings because the front flow control baffle is farther forward then on the exmarks.Blade speed is only half of the equation.

John Gamba
05-02-2008, 02:19 PM
I don't want them to change anything about the Ultra Cut, .




Veritable blade speed on the UC will make that deck unbeatable in alot of conditions.

ProStreetCamaro
05-02-2008, 03:28 PM
Hey Tacoma have you ever looked at the underside of the x-factor gravely deck? It is wide open in the front like the velosity plus. There are no baffles at the front of the deck.


Looks almost exactly like this except its more straight across in the front.


http://www.scag.com/images/VDeckunderside475.jpg

John Gamba
05-02-2008, 04:34 PM
Hey Tacoma have you ever looked at the underside of the x-factor gravely deck? It is wide open in the front like the velosity plus. There are no baffles at the front of the deck.


Looks almost exactly like this except its more straight across in the front.


http://www.scag.com/images/VDeckunderside475.jpg


I think i'm going to order a Hydro scag with this deck next tuesday.

John Gamba
05-12-2008, 02:00 PM
Hey Tacoma have you ever looked at the underside of the x-factor gravely deck? It is wide open in the front like the velosity plus. There are no baffles at the front of the deck.


Looks almost exactly like this except its more straight across in the front.


http://www.scag.com/images/VDeckunderside475.jpg


Bought one:laugh::laugh::laugh: so far so good. more friday morning.:waving:

tacoma200
05-12-2008, 03:36 PM
Hey Tacoma have you ever looked at the underside of the x-factor gravely deck? It is wide open in the front like the velosity plus. There are no baffles at the front of the deck.


Looks almost exactly like this except its more straight across in the front.


http://www.scag.com/images/VDeckunderside475.jpg

No, send us one. Or a link to a picture. As far as I know Gravely is a good machine. I don't know why they are not one of the bigger sellers?:confused: