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7117 48" mower deck vibration (resonance)


Papermaker

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Simplicity fans--

Over several years I've noticed that my mower deck occasionally breaks into vibration or resonates. Releasing the PTO stops the vibration as well as blade rotation, reengaging the PTO starts rotation and you can continue to mow normally but until the cutting load changes or ??? through varying grass and/or leave loads and the vibration starts. Once the vibration or resonance starts it continue regardless of load until the PTO is released. I've also noticed that many mower decks crack over time and wonder if the vibration is one of the causes.

While updating deck parts to newer blade clamping styles I've changed the shafts, shaft bearings, belt tensioner and spring and belts.

Any help is appreciated.

Thanks,

Papermaker

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5 hours ago, Papermaker said:

I've also noticed that many mower decks crack over time and wonder if the vibration is one of the causes.

I think every 48" deck I've ever owned that I purchased used, has always been cracked in front of the center spindle (700/7000 series & 900/7100/Sovereign series).  I however have not seen this in the 42" decks but I haven't owned as many of them.  Just my experience.  As far as your vibration goes, I would first ask if your blades were balanced but I see in your original post, you answered that question.  

5 hours ago, Papermaker said:

While updating deck parts to newer blade clamping styles I've changed the shafts, shaft bearings, belt tensioner and spring and belts.

Is your  deck the newer style with the shallow pockets or the older style with the deeper pockets?  Are you using the newer Gull Wing Blades or the older Straight Blades?

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Hi ShaunE--

Thanks for the detailed response.

I believe that I've got a later shallow mower deck, can you remind me of the things to look for to determine the deck type? I am using gull wing blades; I’ve got two sets and the vibration problem is present with both sets. Also, if blades or an individual blade balance was causing the deck vibration, I’m concerned about it would be present as a one/rev vibration whenever the blades are turning.

I've had several Sovereign/7117 48” deck tractors over the years and, going on memory, deck vibration or resonance has been present to some degree in all of them. The decks I've repaired were welded and the weld was ground flush to minimize stress risers. After the repair I used the tractor, with occasional vibration, until I moved on to a newer tractor. The 23 hp 7117 I have now is my forever tractor, so I went the extra mile and made what I hope is a forever deck repair. I flush welded the crack as I’ve done in the past and then made a boomerang shaped metal patch that spanned the crack, heat shaped it to fit the profile of the bottom of the deck and stitch welded it in place. The current repair is standing the test of time, no cracks are visible during annual inspections. Having said that, this repair hasn’t stopped the deck from breaking into vibration, so I guess that answers the vibration/crack question. Vibration is present on a sound deck, which probably It causes deck cracks.

Looking at the deck belt covers, there are a least two areas that limit the belt’s lateral movement which should reduce/stop resonance vibration. The right cover has a U-shaped belt guide that controls belt movement, looking at the guide it shows very little or no paint removal or wear. The left cover design also limits belt movement to the front of the deck. There’s a small indention positioned along the front of the cover, mine shows paint removal, evidence that the belt does move that far out. The guide and indention seem like they’d limit or prevent belt resonance vibration which, to my mind, leaves the belt tensioner as the source of the vibration problem. I’ve looked over the tensioner and don’t see much opportunity to improve the design. Maintenance wise It has new parts and is grease it annually.

Any insights you have are greatly appreciated!

--Papermaker

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23 minutes ago, Papermaker said:

can you remind me of the things to look for to determine the deck type?

Older, deep pocket, flat blade deck:

IMG_4462a.JPG.c5dbbb110379e007f9f35e02814f7b2b.JPG

 

Newer, shallow pocket, gull wing blade deck:

6273d94ff3363_48SimpDeck_0002.jpg.03eabff6329cc3f267f5ae1a2466f985.jpg

 

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Thanks for the photos PhanDad! Based on your photos I have a shallow deck. Have you experienced the vibration that I'm trying to stop?

--Papermaker 

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1 hour ago, Papermaker said:

Thanks for the photos PhanDad! Based on your photos I have a shallow deck. Have you experienced the vibration that I'm trying to stop?

--Papermaker 

I've ran many decks over the years and they all seem to vibrate some, more so as they age, but I've never experienced resonance.   

I've only had 2 of the shallow pocket decks, the 48" shown above and a 42" deck that came with the 7016H I picked up a few years back.  IMO, those decks are worse as far as vibration since the blade attachment "system" is inferior to the gull wing  design and leads to off center blade mounting.  

Here's a long post that illustrates the difference (about 2/3 down on page 1):

https://simpletractors.com/forums/topic/37879-spindle-repair-final-pictures-1690709-deck/

 

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On my 7117 vibration comes from the PTO belt idler pulley "dancing" when it runs.  It does this with OEM Simplicity belts and the tension adjusted in the green when the deck is lowered.  It has always done this but does not seem to hurt things other than a little wear on the idler pulley bracket pivot and the spring end.  

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10 hours ago, Tom45 said:

vibration comes from the PTO belt idler pulley "dancing" when it runs

Interesting!  Might indicate a pulley not symmetrical?

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