ZT deck belt frayed.

[RalphVa]

I have a new Cub Cadet ZT2 54" zero turn. It has about 8 hours on it. The deck belt came off of the center spindle pulley twice. I'm pretty sure that I did something wrong the first time; either shut the engine off with the PTO engaged or starting with it engaged. Not sure. Put it back on and mowed a lot with no problems. The second time I have no idea what happened but again it came off of the center spindle pulley. Put it back on and it has not come off again since then. Everything is perfect. But, both times I continued to mow for a moment after it came off because it was still driving the outboard spindles so I did not notice immediately. So the original belt was very frayed.

When I did the recommended 5 hour maintenance I went ahead and replaced the deck belt. I got a cheap $20 belt. (The Cub Cadet replacement belt is $60-$80 dollars). So for the last 3 hours of use time it has performed perfectly. Mows great. No unusual noises. But, I looked under there today and the new belt is frayed. Mostly on the lower (closer to the ground) edge of the belt but some on the upper edge as well. The contact surfaces of the belt look fine. I cannot see any obvious alignment issues with the various pulleys. Several pulleys have belt retainers on them. I'd heard of issues with those being bent and contacting belts but mine are straight with no clearance issues.

The mower is new so I can take it back to the dealer. But that's a 30-40 minute trip plus time without the mower and would rather not if I don't have to. Again, it is performing perfectly.

So I have two questions: 1) Are there simple things I should look for (this is my first ZT or riding mower of any kind). 2) Is it possible that a $20 belt is just going to fray at the edges.

Any help appreicated.

Get a Ryobi or Ego or even a Gravely, and they will not have any belts. No gear box either. No gas. No oil.

 

[N80]

Get a Ryobi or Ego or even a Gravely, and they will not have any belts. No gear box either. No gas. No oil.

No thanks. Not against electric but none of those would be up to the job I have.

 

[N80]

Here is a screen shot of close up of the video with medium throttle PTO engagement. You can see that the belt is well outside of the edges of the center pulley. It never looked like it would come off but when engaged at full throttle it did not jump nearly as far off the pulley as at medium throttle. I may try a video at low throttle next weekend to see what that looks like.

 

[tomplum]

If you do well with engaging the deck at WOT, all's well. If not, it wouldn't difficult to fashion a guide at the center pulley. Might also do better with a bit more tension.This is a perfect example when dealing with a belt that jumps, to think of the belt being pushed through the pulley complex rather than being drawn through.

 

[Richard001]

Great investigation work.

I have no doubt that the tensioner pulley, the one with the spring, is that the spring fully extended.

You may also want to video record the action of the tensioner pulley.

 

[tomplum]

I think sometimes on these larger decks, they build a greater range of motion in the tension spring to accommodate the longer belt and added guide pulleys. So a longer spring fits the bill to keep a more even tension. I didn't see the build model on this, but these usually have a metal "J" hook for the deck end of the spring like some others use. What is nice about them is it is quick and easy to pop another hole in the housing to put an extra inch or so of tension or better align the pull of the spring on the tensioner. I think the OP's hypothesis is correct that the belt hopped the center spindle pulley when things went south. I've looked at similar decks that seem to have a lot of slap after that pulley and the MFR parked a guide pulley directly on the input side of that pulley in an attempt to control the belt travel. So then they spec'd a hard start to control the belt. Combine that with the extra positioning pulleys that direct the belt back to and from the PTO clutch on a ZTR and there is a lot going on.

 

[N80]

There is indeed a lot going on and the first half a second or so looks like utter chaos. The whole deck jumps up. The tensioning spring/pulley bounces back and forth a long time before settling down. For anyone who is curious it is very easy to do. Just get someone to sit on the mower and do the engagement while you use 'slo-mo' on your cell phone. I did it with the mower on my trailer to minimize blowing/thrown debris. A clean patch of driveway would work just as well. It is an amazing thing to see.

I don't know if any Z turns have it, but I love the hydraulic PTO clutch on my manual Kubota L4400. I can move that lever so slow and smooth my rotary cutter starts up without any movement of the mower deck at all. Smooth as butter. Quiet as a mouse.

 

[RandyT]

I would love to have the option of slow engagement on my Kioti. More like the electric clutch on your Z turn. Electric over hydraulic can be just as violent as a plain electric PTO on a mower. And it may not be as violent as it sounds, but where the rotor starts turning and the blades clank back trying to catch up it sounds awful.

 

[N80]

So far the new belt has about 3.5 hours on it and it looks fine.