ZT52HD DECK VIBRATION FIX

[Cphillips82]

While not being a Gravely, I had a similar sort of thing happen with a Dixie Chopper.
The Idlers went so I replaced them with a pair of similar size because the owner did not want to fork out $ 176 for genuine pulleys.
The tensioning pulley was smaller then the original by about 1/2" , not much on a very long belt.
Don't know why but even when I tightened the spring a few turns, the belt slapped around like one of the pulleys was oval.
I wondered if the pulley was not made correctly & the bearing was not concentric with the working face so I fitted a bigger pulley because that was all I had on hand and the belt ran smooth as silk, so we left it like that.
The suspect pulley went onto a Z master for a commercial customer to keep him on the road, worked fine so is still on there.

So it might be nothing more than a bad combination of pulley sizes , belt tensions & springs.

Yeah I think you may very well be right, its just strange that some owners dont have the noise but many do. So inconsistencies at the factory with placement or parts? IDK

 

[Cphillips82]

Just a reminder to anyone reading this if you have the same issue COMPLAIN TO GRAVELY SUPPORT ABOUT IT!

 

[gravelyzthd52]

My dealer came to my house today to check out the noise from my deck. After looking at a bunch of different things we may have figured out what is causing the noise on my mower. There is part of the lift arms on the front of the deck that are connected between two brackets on the deck housing. When he wedged a long metal nail set between the linkage and the deck brackets the noise stoped. When he took the nail set out it would be ok for a few seconds but then start up again. He took some pictures of the brackets and is going contact Gravely on Monday to see what they say about it. It really was interesting because when he wedged that in there there was no noise at all, just the beautiful sound of mower blades spinning at high RPM’s. I really hope this is the problem and they can come up with some fix for it.

In the pictures of both right and left side you can see where the rod is touching the bracket on one side. Would be interesting to see if someone else can make the noise stop by wedging something between the rod and the bracket on left side of the deck (if you are sitting on the mower). I will let everyone know what he hears back from Gravely.


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[gravelyzthd52]

Here are the pictures from my last post. They didn’t attach for some reason and I can’t edit it.

 

[Cphillips82]

Thanks for posting that info. Mine is currently at my dealers being looked at so I will call them first thing Monday to have them try that and to read your post. Perhaps installing some kind of rubber insert in there or even a spray on rubber like Flexseal?

 

[bertsmobile1]

Vibrations and resonances are weird things and a speciality field all of their own.
Deck pulley sizes are determined by pluging in loads, tensions power demands into equations that the belt makers provide.
Thus it is easy to come up with little things like a pulley mounting hole at a length on a tensioning arm that is a length that will cause resonance between the spring & the belt.
Then you get slight differences between the production prototypes and the actual production line output.
Cost structures prohibit the old days system of testing each & every one off the line and this problem could be something that requires a set amount of wear to happen before it is triggered.

Unfortunately your pictures did not seem to work.
Can you repost them or put them into a photo hosting app ?

 

[Cphillips82]

I rewatched your youtube videos and that is definitely the same noise as mine so I’m pretty pumped that you may have figured it out!

 

[gravelyzthd52]

Vibrations and resonances are weird things and a speciality field all of their own.
Deck pulley sizes are determined by pluging in loads, tensions power demands into equations that the belt makers provide.
Thus it is easy to come up with little things like a pulley mounting hole at a length on a tensioning arm that is a length that will cause resonance between the spring & the belt.
Then you get slight differences between the production prototypes and the actual production line output.
Cost structures prohibit the old days system of testing each & every one off the line and this problem could be something that requires a set amount of wear to happen before it is triggered.

Unfortunately your pictures did not seem to work.
Can you repost them or put them into a photo hosting app ?

I reposted them in a separate post above because I couldn’t edit it to fix the pictures.

 

[bertsmobile1]

Thanks for that.
Now I got a handle on it
So looks like s heavy rubber sleeve on that shaft so it can move a little & not bang on the mountings looks to be an answer to the symptoms .
Now to tackle the cause.

 

[gravelyzthd52]

I took a video this morning demonstrating what my dealer found yesterday while checking out my deck. I would be interested to see if other people with this issue can reproduce what I did in the video. Will send to my dealer so he can show Gravely. You can see in the video when push the round part in the noise stops instantly.

https://youtu.be/TWIK9W_LoLI