ZT52HD DECK VIBRATION FIX

[cpurvis]

If you call Ariens/Gravely first, I suspect they're going to ask if you've talked to your dealer.

So you might as well talk to the dealer first.

 

[coder]

Does anybody have the belt tension spec for the Apex 52 ( same as HD 52) PTO belt? Is it something like 1/2" deflection @12 lbs pressure perpendicular to the belt?
It would be even better if they had different tensioner springs to swap out to adjust the tension. My feeling is that the belt is simply not
tensioned correctly.

 

[bullet bob]

Coder. With all due respect sir, I think you need to have a nice long talk with your dealer. This should be your first step.....

 

[coder]

Guys, after going to 2 dealers last fall and finding no solution for the deck vibrations (harmonics) I finally got my 52 HD out and decided to fix it on my own. After looking over it was obvious it was related to the tensioner. If you look at the way the arm was designed the pivot point gives the idler pulley twice as much mechanical advantage over the spring. I ended up machining a new arm with pivot point that is twice distance giving the spring the mechanical advantage. The vibrations are about the same however the horrible noise is now gone! The spring vibrates half as much as it used to. If you guys are interested I can post a picture of what I did.

Effectively, by replacing the tensioner arm with one with a different mechanical advantage, you have just increased the tension on the belt, right?
Was there a calculation involved to estimate the amount of tension increase or did you just eyeball it? Or maybe you have a belt tension gauge, and you used it to dial in the optimum belt tension?
IMHO the same effect could be achieved by increasing the tension some other way.

For example, the easiest and most obvious way would be replacing the belt with a slightly shorter belt. I have successfully done this on my old JD powerflow drive belt, where I had a similar issue. Of course the belt there was way too loose and floppy.

The current Ariens PTO belt is nominal 98.5", and other aftermarket belts are available in 98, 97, or 96" lengths. Actually, my local tractor supply house carries various sizes, so I could go through a few, measuring the resulting tension, until I experimentally determine where I need to be. Probably pick up a few different sizes, until I get to the tension I want and just return the ones I did not need.

Effectively the tensioner pulley/arm just would not push quite as deep into the belt, and the spring would be stretched a bit more, increasing the overall belt tension. Of course the degree of shortening vs the resulting tension increase is kind of trial and error, unless we measure the result. We would not want to "over-tension" and cause trouble with the spindles and pulleys, right?
Another possibility is to replace the tensioner spring with something heavier (if one is available) or ( shudder) maybe an adjustable one?

I have just opened a case with Gravely, and in due course I will ask them about the belt tension. I am curious to find out about their "anti vibration kit", and any other suggestions they may have.

What say you all?

 

[coder]

Coder. With all due respect sir, I think you need to have a nice long talk with your dealer. This should be your first step.....

You are right.. I am just dragging my feet. I expect they will tell me "They all do that, it is normal",
and I am not looking forward to hearing that. How many of you heard that answer?
(I know it is stupid, but let's see how far I get with Ariens.
At the very least Ariens will answer my explicit questions, such as what is the belt tension supposed to be, or
whether they have a kit to deal with this. Supposed to be a well-known issue.).

I am reading that the allowed deflection is 1/64" for every inch of span, and this particulate belt
segment has a long span. This is at 10 or 12 LBS pressure to create a deflection.

I have also asked them about the max air restriction of the Kawi Fr691 engine
(I am in the process of putting a filter minder on it).

Ariens got back to me and recommended putting on a "shorter belt", remarking that the vibration does not
effect cut quality. Cut quality is fine, my concern is that the excessive vibration will lead to
premature wear of various deck parts. No mention of any "anti-vibration kit".

They did not say anything about how much shorter, or what the belt tension should be.
Sounds like they are encouraging me to run with scissors. Mediocre!

I made a mistake of assuming that spending 7k ( with the bagger)
would buy me something that works well without any issue. Live and learn, I guess.

 

[coder]

Ariens got back to me and recommended putting on a "shorter belt", remarking that the vibration does not
effect cut quality. Cut quality is fine, my concern is that the excessive vibration will lead to
premature wear of various deck parts. No mention of any "anti-vibration kit".

They told me the vibration issue is known to them. They recommended to put on a PTO belt 1" to 1.5" shorter than what it came with.
Sorry, said they, they do not have such belt. And of course I have to pay for it...

Pretty lame. I am using it as it is for now, hoping that it will "wear in".
The length of the belt is unclear. Parts diagram says 98.5", Ariens say 102" . I have to take it off and measure it.
The plan is to measure, find an aftermarket belt 1": shorter, balance my blades and see what happens.

 

[coder]

BTW just put a Donaldson housing on my FR691. Since it has a threaded hole for a filter minder already, I put a JD filter minder on it which measures the highest restriction
that occurs during operation in the range of 0-8" water column.

Did mow with it, and it measured < 1" restriction. So as far as I can tell, putting a cylindrical filter (and the safety inner filter) on this engine does not cause high air restriction,
like some folks asserted it would. Based in this, it seems to me that the myth that a cylindrical filter/ housing combo would cause the engine to run rich (or having any other
negative consequence) is busted.

I believe the only way an air filter can cause an engine to run rich is by causing an air intake restriction. I do not see any other mechanism.
If the filter is unable to deliver the air volume the engine needs, that will also manifest as increased air restriction.

Needless to say a high end cylindrical filter set and housing is superior to the tiny OEM filter in every other way.
E.g..: Air filtration quality, longevity, and operational robustness (by virtue of having a secondary, safety filter)

I am willing to reconsider my point based on a rational argument, am I missing anything?

 

[coder]

Just to be clear, the air volume delivery capability can be stated as: The air box and filter(s) are able to pass through X CFM air, while causing no more than Y
inch ( water column) air flow restriction at the engine air inlet. The "air restriction" caused by a new air filter is not a fixed value.
It is an air restriction curve, plotted against the air volume. This plot shows a non-linear function. (Source: Donaldson filter collateral)

But in this case, we are not trying to estimate the restriction, we are measuring it directly under actual operating conditions.
And we have seen the measurement, and it is good.

PS. If you are interested in the max air volume pulled by the Kawi FR691, I calculated it using Donaldson's formula with these inputs:
CID = 44.3 RPM: 3600 VE: 90% Air volume at max RPM is: 41.5 cfm.

The Volumetric Efficiency maybe less, but that would just drop the air volume needed further. At 80% VE it would only pull 36.9 cfm)
The Donaldson/Kawi cylindrical filter + safety combo is rated at 86 cfm @ < 8" (water column) nominally,
but we can see that the actual measurement shows a max restriction way lower than 8".

 

[bullet bob]

What'd he say????

 

[cpurvis]

What'd he say????

(in a raised voice) HE SAID THAT THE DONALDSON DUAL-ELEMENT AIR FILTER SYSTEM IS THE CAT'S MEOW.