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newblade
06-06-2005, 07:09 PM
I used doubles today for the first time ever. I was impressed with the cutting ability but it didn't look like it did as good a job as the singles? I also noticed bogging down on the motor a little more. I have a 22hp kohler on a 60" exmark. I took them back off due to quality. Anyone else ever have any problems using doubles?

packerbacker
06-06-2005, 07:28 PM
I used doubles today for the first time ever. I was impressed with the cutting ability but it didn't look like it did as good a job as the singles? I also noticed bogging down on the motor a little more. I have a 22hp kohler on a 60" exmark. I took them back off due to quality. Anyone else ever have any problems using doubles?





Doubles will take some of the power away. Its going to have to work harder with 2X the weight on it. But a 22HP should be more the enough to run it.

eshreve1234
06-06-2005, 07:56 PM
I used to run doubles on my HD 75(gators under high-lifts). I bought some Meg-Mos and now use them exclusively. I have found they do stay sharper longer, and they strain my motor less than doubles, but more than a single blade. Striping has also improved over a single blade, and is the same as a double blade set up. I do recommend the Meg-Mos to people, all the claims are true, except the wet grass and not scraping a deck.

Doc Pete
06-06-2005, 08:19 PM
Doubles will take some of the power away. Its going to have to work harder with 2X the weight on it. But a 22HP should be more the enough to run it.

First, weight has nothing to do with it, once it's spinning. I have 25 hp on my 54" machine and it's "just enough" power to run highlift doubles .22hp on a 60" machine is underpowered......Whatever other problems you may have, the first is you don't have enough power to run them properly.

packerbacker
06-06-2005, 08:22 PM
First, weight has nothing to do with it, once it's spinning. I have 25 hp on my 54" machine and it's "just enough" power to run highlift doubles .22hp on a 60" machine is underpowered......Whatever other problems you may have, the first is you don't have enough power to run them properly.






Coorect me if Im wrong but doesnt the motor run the pulleys which in turn run the belts which in turn run the spindles which in turn make the blades go?

If your running double blades your increasing the workload of everything else.

Lawn-Scapes
06-06-2005, 08:31 PM
When I ran a 25hp Lazer I felt it was just enough to run doubles. I think 22hp would be just a little too under powered.

packerbacker
06-06-2005, 08:42 PM
When I ran a 25hp Lazer I felt it was just enough to run doubles. I think 22hp would be just a little too under powered.




We used to run them on 48 Exmarks with 17 HPs. It sounded like a helicoptor and you couldnt use a sulky but it did ok.

MMLawn
06-06-2005, 08:54 PM
22HP is really not even enough power for a 60" deck, then add the doubles and that is your problem. I am really quite shocked that they even offered a 60" (esp if it is a ZTR and not a WB) with just a 22 as the smallest I had seen on a 60" was a 23HP and I don't care for that one either as I think you need at least 25HP on a 60"

grass-scapes
06-06-2005, 11:16 PM
Coorect me if Im wrong but doesnt the motor run the pulleys which in turn run the belts which in turn run the spindles which in turn make the blades go?

If your running double blades your increasing the workload of everything else.
Momentum....Thats the magic word. It takes more power to get it spinning than to keep it spinning. BUT, when the blade contacts grass, it loses its momentum and needs the power of the engine to bring it back up to speed, so, if you werent cutting grass, you wouldn't need all that power except when you first started the blades. Since you don't need a ride on blower, you don't have enough power.

DennisF
06-07-2005, 12:08 AM
It's a simple physics problem. More blades means more weight. More weight requires more HP to keep it moving.

packerbacker
06-07-2005, 12:09 AM
It's a simple physics problem. More blades means more weight. More weight requires more HP to keep it moving.






Thanks. I thought I was going crazy for a second :dizzy:

Doc Pete
06-07-2005, 12:28 AM
Thanks. I thought I was going crazy for a second :dizzy:

Well, if you believe that is your problem, ya, I'd say you're crazy. It ain't the weight.......

dvmcmrhp52
06-07-2005, 12:42 AM
Well, if you believe that is your problem, ya, I'd say you're crazy. It ain't the weight.......




Quite simply put, yes it is the weight as well as the added lift of two blades versus one creating the need for more horsepower to overcome the force of air versus blade and the weight of those blades.

Add ten blades, do you think it won't need more grunt to turn those blades?

txlawnking
06-07-2005, 01:11 AM
I had the same problem on my 52" machine with a 22 hp engine.. If I went real slow ( @ 3/4 of my normal wide open pace ), the cut was beautiful with doubles ( both hi lifts ).
Running one Hi-lift with one Raptor Mulcher really did help though, as the Mulch blades created less areodynamic drag, yet still exposed the grass to more cutting edges.. You might try that deal and see if it works for you.

Doc Pete
06-07-2005, 08:17 AM
Quite simply put, yes it is the weight as well as the added lift of two blades versus one creating the need for more horsepower to overcome the force of air versus blade and the weight of those blades.
Add ten blades, do you think it won't need more grunt to turn those blades?


"A body in motion tends to stay in motion"....Read your physics book. It's not the weight, however, it is the drag of the blades.
"Quite simply", that should be obvious.......

packerbacker
06-07-2005, 08:31 AM
Well, if you believe that is your problem, ya, I'd say you're crazy. It ain't the weight.......





Well apparently Im not the only one who thinks that attaching more weight to the mower will make it work harder thus decreasing the power.

CWG
06-07-2005, 08:41 AM
Funny post!
Albert is not amuzed! :D
http://www.nip.upd.edu.ph/photonics/news/aeinstein/einstein07.jpg

TLS
06-07-2005, 09:08 AM
As Pete said, its not the weight (your clutch will see this though), it's the aerodynamic drag that multiple lift foils create.

22hp isn't enough for doubles.

I have 27hp and it isn't enough most times.

Remember, a Lazer with mule drive isn't as efficient with regard to its transfer of power through the belts.

naturescape
06-07-2005, 09:48 AM
Try the Exmark LOW LIFT blade under a gator blade. That really helps to reduce drag, it might just do the trick for you. You'll probably have to order the blades.

betterlawn
06-07-2005, 10:28 AM
You guys can argue about anything. Its physics (again). Weight is not the issue. Once you get a 10000lb flywheel spinning it takes very little to keep it spinning. Adding a 10lb weight to 500lb mower is not going to really make much of difference.

Unless your cutting grass with it of course. What takes up double the power is the fact that you've doubled your cutting surfaces and you're cutting twice as much grass (**). I'd be surprised if the aerodynamic forces were even signficant. If that was the case you'd be loading the engine significantly sitting on the driveway. That said, yes you will probably "double" that portion of the power requirement while the blades are spinning, but I would hope that an unloaded blade doesn't suck up more than a few HP.

** I realize that your not really cutting twice as much grass as both blades are hitting the "same" pieces of grass, but you get my point. Some freshman engineering student want to analyze the cutting forces to shear a blade of grass?

Power only matters if your operating at the edge of your torque/speed curve. If your operating in the proper range for your equipment, your speed should be constant and it shouldn't matter.

Take two mowers, fill them each with .25 Gallon of gas, run one with double and one with single blades sitting in the driveway. See how long it takes to run out of gas on each. That's your "waste" HP comparison right there. That's a lot cheaper than mounting a $2K torquemeter on the spindle... Of course, I doubt anybody really cares that much...

RobH
06-07-2005, 10:49 AM
I started running doubles this season on my Scag 17hp 48" hydro w/b. I haven't noticed any loss of power in cutting.

I am running gators over stock high lift blades. I think the cut is very good, however, I am still finding myself double cutting up here in the Northeast. We have had plenty of rain and I am cutting very thick lawns.

I hear a lot of guys here preach about the Megmo blades. I'm thinking of trying them out, but they look to be rather expensive. However, they may be worth it. I don't believe I have read anybody having a bad experience using them.

Pro-Scapes
06-07-2005, 10:58 AM
22hp on a 60 is underpowered to begin with.

you definatly wont be cutting at a productive speed with the increased drag. When I had a 61" 25 kohler it was barley adequate in medium grass with doubles. More cutting surface is going to equal more drag. Your going to bog down. Your going to go through belts faster and probably a little more wear on your clutch. So far im just happy with the cut of my toro atomics. Going to go with gators soon.

Im surprised you dont bog 22hp down with singles if you cut near full width in decent grass.

Doc Pete
06-07-2005, 01:09 PM
Well apparently Im not the only one who thinks that attaching more weight to the mower will make it work harder thus decreasing the power.

OK.... here's the deal.... YES, weight does make a difference.. BUT........ the "difference" is:Insignificant

dvmcmrhp52
06-07-2005, 06:02 PM
OK.... here's the deal.... YES, weight does make a difference.. BUT........ the "difference" is:Insignificant




I believe you said it has NOTHING to do with it.


Reread my post boys................
There is no insignificance when speaking of 22 horsepower doing that much work.
Quote all the theory you like, the real world proves itself different from theory on a daily basis.
I've spent enough time in my life proving that to engineers who have the same thought process.

packerbacker
06-07-2005, 06:09 PM
I believe you said it has NOTHING to do with it.


Reread my post boys................
There is no insignificance when speaking of 22 horsepower doing that much work.
Quote all the theory you like, the real world proves itself different from theory on a daily basis.
I've spent enough time in my life proving that to engineers who have the same thought process.





Thats what Im saying. If you are adding something like double blades to the mower you are making everything else work harder and that includes the engine.

txlawnking
06-07-2005, 06:11 PM
:rolleyes: Someone flunked physics! :dizzy: As I noted earlier, When I ran doubles on my 52" machine, the added aerodynamic drag bogged the engine. But the WEIGHT also added a signifigant load as well.

It is harder to start, keep in motion, and stop something with more weight. Period.

Dave is spot on. When I went to engage my blades, with the doubles, it bogged the engine much more when you would engage the clutch than it did with just the regular single blades..

betterlawn
06-07-2005, 06:27 PM
[QUOTE=txlawnking]:rolleyes: Someone flunked physics! :dizzy:
It is harder to start, keep in motion, and stop something with more weight. Period.

QUOTE]

Yeah someone did. Sorry man, I just can't let this one go.

Harder to start, YES
Harder to stop, YES
Harder to keep in motion, NO. That's not physics, thats sixth grade science...

If the aerodynamic forces are bogging you down sitting in your driveway, than its a wonder you aren't lifting off the ground like a little hovercraft.

I'd bet my paycheck that its the additional cutting/mulching thats requiring extra power.

Engineers don't know everything - but this is not an opinion, its friggin' Newtons laws...

packerbacker
06-07-2005, 06:33 PM
[QUOTE=txlawnking]:rolleyes: Someone flunked physics! :dizzy:
It is harder to start, keep in motion, and stop something with more weight. Period.

QUOTE]

Yeah someone did. Sorry man, I just can't let this one go.

Harder to start, YES
Harder to stop, YES
Harder to keep in motion, NO. That's not physics, thats sixth grade science...

If the aerodynamic forces are bogging you down sitting in your driveway, than its a wonder you aren't lifting off the ground like a little hovercraft.

I'd bet my paycheck that its the additional cutting/mulching thats requiring extra power.

Engineers don't know everything - but this is not an opinion, its friggin' Newtons laws...







Either way its harder work on the engine and thats what some of us are disagreeing about.

dvmcmrhp52
06-07-2005, 06:43 PM
[QUOTE=txlawnking]:rolleyes: Someone flunked physics! :dizzy:
It is harder to start, keep in motion, and stop something with more weight. Period.

QUOTE]

Yeah someone did. Sorry man, I just can't let this one go.

Harder to start, YES
Harder to stop, YES
Harder to keep in motion, NO. That's not physics, thats sixth grade science...

Anything with more weight is harder to keep in motion,to say otherwise is silly. By your logic a turbine on a hydro plant will be kept spinning as easily as a tire on a car. Not true.

If the aerodynamic forces are bogging you down sitting in your driveway, than its a wonder you aren't lifting off the ground like a little hovercraft.

The "lift" of the blades has a definite impact on horsepower. There is no arguing that point.

I'd bet my paycheck that its the additional cutting/mulching thats requiring extra power.

This of course is part of the equation, but you can run a mower with doubles and not do any cutting with the blades and there is a noticeable drain of power just to move the machine forward in comparison to a machine without doubles. That power is being used up somewhere.........

Engineers don't know everything - but this is not an opinion, its friggin' Newtons laws...

Newtons law says it will take LESS power to keep a body in motion, it doesn't say it requires no power.

dvmcmrhp52
06-07-2005, 06:44 PM
[QUOTE=betterlawn]







Either way its harder work on the engine and thats what some of us are disagreeing about.




Enough said.

all ferris
06-07-2005, 06:46 PM
Once an object is set in motion it will tend to stay in motion untill another force acts upon it. The force that is trying to stop the blades from turning is:
1. the grass you are cuting
2. wind resistance caused by the lifts on the blades.
3. mass.

So the more of these forces you add the more power (force) the engine will have to generate to overcome the above mentioned.
Remeber the energy is NEVER lost. It is just transfered to something else (i.e. heat)
If you don't believe me just watch how much more fuel you burn when you use doubles.

Doc Pete
06-07-2005, 08:04 PM
I believe you said it has NOTHING to do with it.


Now, let's see..... Do you really believe I said nothing, or do you just think you believe I said nothing????

dvmcmrhp52
06-07-2005, 08:08 PM
[QUOTE=Doc Pete]First, weight has nothing to do with it, QUOTE]



I don't believe I missed anything.

Doc Pete
06-07-2005, 08:22 PM
[QUOTE=Doc Pete]First, weight has nothing to do with it, QUOTE]


I don't believe I missed anything.


Wait minute!! :dizzy: Are you actually continuing this???? ;) No....... Your kidding, right??? You can't be really carrying on, you just can't, that would be just too funny for words.....

Man...... Hello????? :o ...... the boat left the dock a while back, and the reason it's getting smaller is because it's moving away, not because it's shrinking........

WoodBrothersLC
06-07-2005, 09:05 PM
We were set on running doubles for early spring, but when we tried them on our 23HP Stander, you could definately tell a major difference from the moment the spindles slowly started up. I personally wouldn't ever run doubles on any of our machines after how much of a dissappointment doubles really were.

dvmcmrhp52
06-07-2005, 09:15 PM
[QUOTE=dvmcmrhp52]


Wait minute!! :dizzy: Are you actually continuing this???? ;) No....... Your kidding, right??? You can't be really carrying on, you just can't, that would be just too funny for words.....

Man...... Hello????? :o ...... the boat left the dock a while back, and the reason it's getting smaller is because it's moving away, not because it's shrinking........




Correct, and you missed the boat.

Doc Pete
06-07-2005, 09:32 PM
We were set on running doubles for early spring, but when we tried them on our 23HP Stander, you could definately tell a major difference from the moment the spindles slowly started up. I personally wouldn't ever run doubles on any of our machines after how much of a dissappointment doubles really were.

Sorry to here that. Maybe it's your machine and not the blades........Frankly, most of us love Doubles, and they can do things singles could never do.

This is my machine at 9 mph with doubles, not bagged, either.
This is an SWB 25hp/54" (walkbehind) with bullrider velky.

TLS
06-07-2005, 10:00 PM
Doubles will drag the RPM's down (close to 200rpm) just sitting on the driveway compared to singles.

I'm running DC's X-blades currently.

Lawn-Scapes
06-07-2005, 10:35 PM
Tommy.. How do you like the X blades?

After I finally received the correct size blades for my mower.. I cut with them for a couple of days. I decided I liked regular doubles better.

TLS
06-07-2005, 11:22 PM
Tom,

I have yet to form an opinion.

I'm running the X blade with a OEM notched foil Lazer blade. It really works the engine, but today I cut a bi-weekly 3 acre site from 8-9" down to 3-1/4" with not ONE stringer, one plantain, or one weed poking it's ugly head back up. Clippings were being dispersed a good 20 feet.

Problem is, I'll need to put my anti-blowout baffle back on if I continue to use these. My foot plate was 3" thick full of grass!

I'd like to try the DC flat blade, but was told that they were not yet available. Maybe I'll just cut the lift wings off a set of blades?

It's been so long since I've run doubles, but these seem to really run smooth (balanced) and didn't have the noise that regular doubles have.

Lawn-Scapes
06-07-2005, 11:32 PM
My experience was a little different. I had more stringers and the clippings didn't disperse as well as regular doubles. However.. the stripes were more enhanced with the X blades.......

TLS
06-07-2005, 11:36 PM
Were you using the flat blade or a stock DC blade with the X's?

Also, blades will perform differently with these two very different decks.

newblade
06-07-2005, 11:38 PM
What does the x blade look like?

Lawn-Scapes
06-07-2005, 11:41 PM
I was using the standard high lift blade. The flat blade was not available when I purchased the X blade. It was released and then for some reason it was recalled.

I'll have to try some other blades....

Lawn-Scapes
06-07-2005, 11:45 PM
Looks like this......

The second blade fits into the recessed area and forms an X

grass-scapes
06-08-2005, 08:36 AM
[QUOTE=betterlawn]

Well, I DIDN'T fail physics. and I AM an engineer. Like I said, its the grass that does some of the slowing down of the blades, Air resistance that does some of the slowing down, and the actual drag created by the pistons, lifters, etc of the engine. There are many forces acting against the NATURAL motion of the blades to keep spinning. Thats why, in a vaccuum environment, something will keep spinning when no other forces are acting against it. Gravity alone is a big factor in stopping your blades from spinning. There is resistance, I agree, but its not as much the added weight as it is drag. Why argue over the particulars. Doubles will not work in this case.

Doc Pete
06-08-2005, 12:34 PM
I started running doubles this season on my Scag 17hp 48" hydro w/b. I haven't noticed any loss of power in cutting.

I am running gators over stock high lift blades. I think the cut is very good, however, I am still finding myself double cutting up here in the Northeast. We have had plenty of rain and I am cutting very thick lawns.

I hear a lot of guys here preach about the Megmo blades. I'm thinking of trying them out, but they look to be rather expensive. However, they may be worth it. I don't believe I have read anybody having a bad experience using them.

I'm in the Northeast, too. I'm running custom doubles and rest assured, nothing will make cutting 8 inches of wet grass look good. :rolleyes:
Doubles can fix a lot of problem, but nothing fixes wet, thick grass, other than double cutting and better dispersion.....

Forget the Megmo's for your machine. You won't be able to turn them fast enough to make you happy with the cut. They eat HP because of the high sail.

One thing, get rid of the gators, they make thick lawns worse. I'd run another pair of stock highlift blades. You don't to chop the grass more, you want to blow it out more and disperse the clippings. Gators do the opposite. They have less lift and chop more.... That's no good for your situation.

Pete

Dashunde
06-08-2005, 05:58 PM
I read all of this comedy, and there are a few things to note.

1. Aerodynamically.... mower blades do not create lift.
They are not airfoils and they do not adhere to Bernoulli's Theory, nor to the Venturi Theory.
Bernoulli's Theory basically means that the air traveling across the long chord of a airfoil must travel faster than the air on the other side... where velocity increases, pressure decreases causing lift, thrust, or vacuum depending on the intended design.
The design and shape of mower blades create far far too much turbulence to maintain any sort of true lift.
Mower blades beat the air (and grass) into submission and out the chute. When the air is beat out of the chute, there is a vacuum created under the deck, the vacuum in the deck is what makes the grass stand up, not the blades directly.

In order to move the cut grass out of the chute the blades must be shaped as they are. They are intended to push (sling) grass, not create "lift".

If your in doubt about what I am saying, compare your mower chute air velocity/volume to your blower - the blower uses a true airfoil and 1/10th of the power to create much more velocity.

The average Cessna would not reach 20kts using a large prop-sized mower blade, let alone reach a flying speed.


2. The extra mass of the 2nd set of blades is insignificant with the exception of start-up and bog-down.
After being bogged down the extra blade weight will take a bit longer to recover the lost RPM's.
If your cutting thick grass the slow RPM recovery will be seen as greatly under-powered.


3. Frictional Drag - Here is your biggest enemy when running double blades.
It is almost self explanatory. Even though the 2nd set of blades is not truly cutting twice as much as a single set, it is nonetheless cutting something.
If the 2nd set is cutting just 1/4 of what the original single blades cut by themselves there is a tremendous amount of power being used.
And again... plain ol' Frictional Drag - even if the 2nd set of blades where cutting nothing at all they are still spinning around in there contacting and pushing air and mulch material.

dvmcmrhp52
06-08-2005, 07:20 PM
Doubles will drag the RPM's down (close to 200rpm) just sitting on the driveway compared to singles.
.

Mr. Daschunde,
Do you believe this is a lie?^


(Quote from daschunde)
2. The extra mass of the 2nd set of blades is insignificant with the exception of start-up and bog-down.
After being bogged down the extra blade weight will take a bit longer to recover the lost RPM's.
If your cutting thick grass the slow RPM recovery will be seen as greatly under-powered.
(end quote)


Really?

Doc Pete
06-08-2005, 10:41 PM
Really?

Could you just tell us how many different types, sizes and blade shapes you've done all your testing on..... Or, are we listening to theory???

I've made and tested 5 different styles of blades (sails), three different lengths, and 2 different sail angles for one machine. And you?????

TLS
06-08-2005, 10:48 PM
1. Aerodynamically.... mower blades do not create lift.
They are not airfoils and they do not adhere to Bernoulli's Theory, nor to the Venturi Theory.

I'm going to have to disagree with you on this.

They certainly DO create lift.

dvmcmrhp52
06-08-2005, 10:49 PM
Could you just tell us how many different types, sizes and blade shapes you've done all your testing on..... Or, are we listening to theory???

I've made and tested 5 different styles of blades (sails), three different lengths, and 2 different sail angles for one machine. And you?????


Enough.
Have a nice evening, part time pete.

dvmcmrhp52
06-08-2005, 10:51 PM
I'm going to have to disagree with you on this.

They certainly DO create lift.




Give it up Tom, they just want to continue to try to impress.
Reality speaks for itself.

Nuff said on this issue.

scout_pete
06-08-2005, 11:59 PM
I noticed my truck starting to bog down on hills a little more when I trailer two mowers that both carry doubles. :dizzy:

Doc Pete
06-09-2005, 12:09 AM
Give it up Tom, they just want to continue to try to impress.
Reality speaks for itself.

Nuff said on this issue.

Ah, the great kids game. If you can't win, quit.
Hmmmmm, What's the problem now?? Tommy is wrong. Mower blades don't create "lift". Gees, first you split hairs over the small amount the weight of blades suck up Horsepower, now you think blades create lift, because the result of a "vacuuming effect". You can't have "lift" without an "angle of attack".

Doc Pete
06-09-2005, 12:13 AM
I noticed my truck starting to bog down on hills a little more when I trailer two mowers that both carry doubles. :dizzy:

Hold on there. Tell the truth, you stopped at BurgerKing and had 4 "double" bacon cheeseburgers. With all the weight of "THOSE DOUBLES" is the real reason why the truck was starting to bog :D :D :D :D

tshank
06-09-2005, 01:46 AM
2 high lifts will drop rpm's 'bout 150 or more. Bogs easily. High lift with flat blade drops rpm's 'bout 50. Doesn't bog nearly as bad. Doesn't matter if the flat blade is .207 or .250 as far as rpm's go. Tried light flats w/3" high lifts, rpm's dropped the same as w/2 1/2" high lifts. Didn't seem to bog any worse.
Cut quality? On a Dixie, I think you could tie a brick to the end of a string and it would still cut the same.

All I know is what I read in the paper.

Dashunde
06-09-2005, 02:34 AM
Mr. Daschunde,
Do you believe this is a lie?^


(Quote from daschunde)
2. The extra mass of the 2nd set of blades is insignificant with the exception of start-up and bog-down.
After being bogged down the extra blade weight will take a bit longer to recover the lost RPM's.
If your cutting thick grass the slow RPM recovery will be seen as greatly under-powered.
(end quote)


Really?


No... it's true. But keep in mind that a 200 rpm drop where the normal rev's are in the 3500 rpm range is about a 6% loss.
The rpm loss is not caused by the mass of the blades.
It is caused by the turbulent drag of the very un-aerodynamic 2nd set of blades.

Dashunde
06-09-2005, 03:43 AM
I'm going to have to disagree with you on this.

They certainly DO create lift.

Yes.. The effect it has on the grass IS to lift it up, but this is a byproduct of the blades secondary function, which is to push all air and debris out of the deck, causing a vacuum which lifts the grass as the edge of the deck passes over.

The blades themselves do not create direct aerodynamic "lift". They are not airfoils. They are not even close to the proper shape to create lift.
If you got your blade spun up to a normal tip speed* of 18,000fpm out in the open, without the deck, it would produce only a slight breeze... now on the other hand, that same blade will be producing a good deal of radial airflow, ie.. air being pushed away from the tips, due to their shape.
This is how the blade performs its secondary function... throwing grass out of the chute.
*With an industry average of 18,000fpm your blade tips are moving at a relatively slow 205mph. Your average airplane prop, which truly is a lift-producing airfoil, has a tip speed that nudges up to the speed of sound, around 635mph on a standard day at sea level. Occasionally you'll hear a plane pass over head that is making an unusually loud brap sort of noise. That pilot has allowed his prop tips to slightly exceed the speed of sound, and what you are hearing are little sonic booms.
My point is that a mower blade is spinning far to slow to produce a significant amount of lift.

Some of you might be thinking about the Angle of Attack (AoA) created by the flipped up trailing edge of the blade...
AoA is a producer of ram lift. And ram lift is very inefficient.
In a real aircraft ram lift produces only 8-15% of the functional lift of an asymmetrical airfoil (wing).
As AoA increases so does drag and turbulence, at an almost exponential rate.
This is the very same turbulent airflow that pitches the grass out of the chute.
AoA is very useful on control surfaces (rudder, elevator, ailerons), but not for true controlled boundary layer lift.
The average AoA of a jet in cruise is about 5-7 deg nose up.

packerbacker
06-09-2005, 08:29 AM
Im surprised all you scientists mow grass for a living :rolleyes:

heavenlydeere
06-09-2005, 10:15 AM
the test subject: 04 jd 777 60'' 27hp 3900rpm.
1. installed standards over highlifts
2.loss of power
3.better cut with single highlift
4.installed single highlift
5.end of story

Doc Pete
06-09-2005, 12:45 PM
the test subject: 04 jd 777 60'' 27hp 3900rpm.
1. installed standards over highlifts
2.loss of power
3.better cut with single highlift
4.installed single highlift
5.end of story

And that's fine. We need to keep in mind different companies have difference size sails. Hustler offers a 30 degree standard and 42 degree highlift sail. Now, I'm using another highlift blade and it's sail is 60 degrees. For sure, I can't spin 2 of these 60 degree blades. I'm using one 42 degree and one 60 degree blade, as my best combo.
This is why many guy's don't like Megmo's, the sail is just too high and requires too much HP to drive them.

Meg-Mo
06-09-2005, 04:03 PM
The left on the MEG MO blades do the best for the most customer but the lift can be reduce very easy. Cut a small amount off the lift like 1/4" at point to nothing in 1" and that will change the lift a lot.

naturescape
06-10-2005, 05:00 PM
The left on the MEG MO blades do the best for the most customer but the lift can be reduce very easy. Cut a small amount off the lift like 1/4" at point to nothing in 1" and that will change the lift a lot.

Nicely said, LOL. How do you sell anything?