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Any tips for identifying slightly out of balance /bent spindles ?

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#1 humpy OFFLINE  

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Posted February 03, 2018 - 07:05 AM



Had a previous post about a too loose cutter belt, causing the belt to "flap" excessively. Have minimized this a fair bit  with a smaller belt  and resulting  tighter tension , but it still is flapping more than it should. I couldn't test with a genuine MTD belt as advised by the forum  as they were out of stock and it would be a week+ wait to order in.


First time really using/testing  this mower as bought it with a  destroyed transmission belt pulley which i replaced.

The person who i bought it off had run over some polypipe that had tangled in the blades enough to cause the main drive tensioner  spring to also snap.


I checked the blades are in balance,,, and have  spun the the cutter pulleys  by hand when still in the deck when the belt was off. -- they appear to be  in alignment . and even  when running  the engine using the cutter and blades engaged  also appear to rotate  evenly , but of course  the shafts may be just  be out of whack a tiny bit, just enough to cause this flapping.?


I also ran the  engine and cutter deck with the blades removed to triple check the blades were not the problem, and  the amount of flapping stayed the same, so the blades can at least be ignored.


Was thinking of taking off the spindles off the deck  and checking for alignment  / bent bolts etc.?.  however, wondering if there are any tips  other than sitting them on a table and spinning them by hand and watching for any wobbles etc to track down what the issue is, especially as if it IS  a out of whack spindle, it would appears  be a very minor amount and quite hard to detect.( well it has been so far!)..

Spindles here in Australia are around $150 each!, so swapping in a new one just as a test would be a bit pricey unfortunately :(..


Many thanks



Edited by humpy, February 03, 2018 - 07:06 AM.

#2 shorty ONLINE  



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Posted February 03, 2018 - 07:18 AM

I have left the blades on the spindles and spun by hand to check them. Just fast enough to see if there is any wobble. Not always foolproof, but in your case, if it is enough to cause the bouncing of the belt. You would be able to see it.
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#3 MiCarl ONLINE  

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Posted February 03, 2018 - 08:18 AM

I believe belt systems are pretty forgiving.  Like shorty, I'd expect any spindle/sheave problem that caused the belt to misbehave to be quite obvious.


One thing to look for when turning the spindles and idlers is a damaged sheave that changes width as it turns.  That could also cause problems.

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#4 larrybl ONLINE  


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Posted February 03, 2018 - 10:36 AM

As I just finished repairing a deck, I also spun each by hand to check the smoothness. One method that I have used was to power the deck with an electric drill, which would give you more speed to check things.

Please be cautious if you do this.

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#5 chieffan OFFLINE  

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Posted February 03, 2018 - 11:45 AM

As had been stated, a damaged or bent pulley can make a belt bounce.  Had a tractor with belt drive to the tranny.  Clutch pedal would bounce constantly. Found one of the universal hub/pulley  combo at the tranny drive.  The hub was a bit loose in the pulley and welded off center a few thousandths.  Another place to check on the deck pulleys. 


Would a stronger tension spring help? 

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#6 jms180 ONLINE  



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Posted February 03, 2018 - 11:57 AM

one way to check is with deck on is to measure the tip of blades from front to back and rotate and check left to right. Park the mower on a flat surface and measure from the tip of blade down to the flat surface then rotate and measure the other end of blade. Measurements should be same for both blade tips. Hope the makes for understanding.

Edited by jms180, February 03, 2018 - 12:11 PM.

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#7 secondtry OFFLINE  

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Posted February 03, 2018 - 02:03 PM

   One good way to check for wobble is with a triangular welding magnet. Stick it to the deck next to the pulley and turn the shaft while watching the gap. If that doesn't make the problem obvious you need to look somewhere else. I have gone as fare as to stick a random piece of steal  (nut, socket what ever) to the leg of the magnet that is parallel to the shaft to minimize the gap. Don   

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#8 EricFromPa ONLINE  



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Posted February 03, 2018 - 07:39 PM

Are the belt guides installed on the deck And the PTO? If either one of those is not installed the belt will jump around. Some mowers the belt jumps around a bit anyway. If the deck hangers and/or pins are worn it will also cause the belt to jump around and the belt will fit loose.

#9 Alc ONLINE  



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Posted February 04, 2018 - 06:17 AM

You mentioned that the po hit something hard enough to snap the tension spring . If you have stamped pulleys could one of them have gotten the "V" spread out in one spot causing the belt to ride lower in the groove each time it came around ? 

#10 humpy OFFLINE  

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Posted February 04, 2018 - 06:24 PM

thanks for all the help...

it looks like one pulley may have a bit of a wobble compared to the other....

will try and grab a replacement pulley asap and retest