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Changing deck pulley to turn blades faster ?


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#31 UncleWillie OFFLINE  

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Posted March 14, 2017 - 08:56 PM

The problem with changing pulleys and running at a lower engine RPM would be the time you were in thick grass and raised the idle and things went past the manufacturers designed speeds and it all went to hell and someone got hurt. 

 

The engineers who designed them were not completely stupid. They say to run them WOT for a reason., 



#32 tater195 OFFLINE  

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Posted March 14, 2017 - 09:27 PM

Unless I missed something, that thread wasnt about running the engine at 30% speed, it was about overdriving the deck. There may be safety issues with doing that, but no argument that it will mow better due to mass, inertia and tip speed


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#33 DH1 OFFLINE  

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Posted March 15, 2017 - 01:25 AM

Sears tells me to run at full throttle when cutting with the deck for best results. I usually run at about 25-30% throttle. Would it make sense to do a pully swap to spin the blades faster? Has anyone else thought about this? I figure the time to act would be before the deck gets back under the tractor, probably april sometime.

 

Original Post 

 

No it does not make good safety sense.

Yes lots of people have thought of doing that. 

 

If it doesn't cut good/fast enough at 25-30% throttle then run it faster, Sears says to run it "full throttle when cutting"



#34 4tom OFFLINE  

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Posted March 15, 2017 - 06:20 AM

 I was under the impression that the higher blade speed was for the efficiency of the mulching blades. I would think the 50" deck that was available would add more load than a modest pulley change on the 42" deck. But enough, I will leave it be this year.



#35 LilysDad OFFLINE  

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Posted March 15, 2017 - 07:21 AM

  I see no mention in this discussion of the government mandated blade tip speed.

 

     I want to see someone get that deck going faster than the law allows and then hit one of your kids toys in the grass. You might put it through the window of your house. Or take out a passing car.

     I used to use a Gravely L w/ a big single blade head on it. You should have seen what it could do with a beer can or a rock!

 

PS - I just looked up a number. ANSI lists 19,000 ft. per min. as the max. speed at the blade tip. They have found that exceeding that speed can set up harmonics which can lead to the development of cracks which can cause blade failure.


Edited by LilysDad, March 15, 2017 - 07:33 AM.

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#36 UncleWillie OFFLINE  

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Posted March 15, 2017 - 07:31 AM

     I want to see someone get that deck going faster than the law allows and then hit one of your kids toys in the grass. You might put it through the window of your house. Or take out a passing car.

     I used to use a Gravely L w/ a big single blade head on it. You should have seen what it could do with a beer can or a rock!

A blade going at regular speed can fire a matchbox car through the side glass of a Chevy Astro van. It can also launch a 7/8 socket about 50 yards. Going faster you many have to have a weapons permit. 


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#37 LilysDad OFFLINE  

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Posted March 15, 2017 - 07:40 AM

Just cause it will go 3600 doesn't mean it has to.
 

 

Stiemmy, are you that guy​? You know the guy. The one going 45 in a 60 mph zone with 10 cars following him. Hmmm?



#38 larrybl OFFLINE  

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Posted March 15, 2017 - 07:51 AM

A blade going at regular speed can fire a matchbox car through the side glass of a Chevy Astro van. It can also launch a 7/8 socket about 50 yards. Going faster you many have to have a weapons permit. 

I wonder how you know? A dog's solid rubber ball toy can put a serious dent in a metal shed panel,


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#39 secondtry OFFLINE  

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Posted March 15, 2017 - 10:32 AM

     I want to see someone get that deck going faster than the law allows and then hit one of your kids toys in the grass. You might put it through the window of your house. Or take out a passing car.

     I used to use a Gravely L w/ a big single blade head on it. You should have seen what it could do with a beer can or a rock!

 

PS - I just looked up a number. ANSI lists 19,000 ft. per min. as the max. speed at the blade tip. They have found that exceeding that speed can set up harmonics which can lead to the development of cracks which can cause blade failure.

   Am I correct, that is about 215 mph. Don



#40 secondtry OFFLINE  

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Posted March 15, 2017 - 10:37 AM

  I remember a picture that circulated of an ankle with a piece of wire sticking through it. Don't remember if it was to justify blade tip speed limits or encourage protective clothing  DON. 



#41 WHdbJD ONLINE  

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Posted March 15, 2017 - 01:04 PM

Father-in-law had a blade on pushmower break,  1/2 of it buried itself in a hillside, the other 1/2

flew about 25 feet, thru both sides of metal shed and stuck in the side of a doghouse.

 

I don't know who was more scared, father-in-law or the dog !



#42 4tom OFFLINE  

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Posted March 15, 2017 - 01:10 PM

Just to clear up some details: tractor parts appear to be dated mid 90's to 01 assembled by someone else before I found it on craigslist. I have no tractor manual. Directions to run at full throttle came with the mulching blades. I have no PTO. The lawn is around 1/3 acre. I have never run the motor wide open. I have no tach, and don't know motor rpm. I do blow out the shroud after cutting every couple of times. I only cut every week or two, depending on the weather on my day off.

#43 tater195 OFFLINE  

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Posted March 15, 2017 - 01:21 PM

. The lawn is around 1/3 acre. I have never run the motor wide open.

That is your problem right there. You are using a sledge hammer to drive thumbtacks.



#44 stiemmy OFFLINE  

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Posted March 15, 2017 - 02:24 PM

Stiemmy, are you that guy​? You know the guy. The one going 45 in a 60 mph zone with 10 cars following him. Hmmm?


Nope, but thanks for asking;)

#45 stiemmy OFFLINE  

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Posted March 15, 2017 - 02:34 PM

That is why I stayed out of this as long as I could. I would like to hear from someone that is actually employed as an engineer on small engines, but I doubt we have any here. Anything posted prior on this is personal opinion and subject to debate. When in doubt, I go with manufacturers recommendation. I would like more info on that smokestack thing and what qualifies them as experts on this situation

I can't dissagree on the manufacturers recommendations, thats what they are there for. I was only in reference to the old engines of years gone by, and the types of engines those folks enjoy. I didn't reference anyone to being an expert, not do I claim to be. Just merely stating cooling, and oiling shouldn't be a problem at a lower speed. In my opinion.

As far as saftey, I wouldn't recommend it, but not my equipment as overspeed is very likely if forgotten about;)

Edited by stiemmy, March 15, 2017 - 02:48 PM.





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