54" BAD BOY MZ Magnum (zero turn) Blade Replacement OEM Blades - Blades Slipping

[Peva]

Mechanical engineer driving manual transmission since 1975. Try me on the physics.

Fact: Idle speed activation of electric PTO shreds belts. Manufacturer says 2/3rd to full throttle when activating.

What the manufacturer says is not intuitive but real world experience supports their instruction. Yet you claim an aftermarket gadget makes it better? How? “Milliseconds” suggests slipping the expensive clutch rather than slightly less expensive belt. The manufacturer doesn’t seem to think this is necessary. Perhaps the blade drive is designed to absorb the shock of dumping the clutch? Motorcycles are designed to withstand dumping the clutch.

"Fact: Idle speed activation of electric PTO shreds belts. Manufacturer says 2/3rd to full throttle when activating."

While idle-speed shredding is counterintuitive, I don't doubt it. Likely some resonant frequency dynamics (as you said - within milliseconds) going on, which will vary with system design/dynamics - see one theory in next paragraph).

My original comment (post #20) was about a non-PTO blade engagement rider mower. I never would suggest blade engagement at engine idle (for one thing, that would stall some engines or at least it wouldn't recover very smoothly - perhaps that's what shreds some belts if it triggered the governor to suddenly go full throttle with PTO clutch/belt engagement friction having already achieved full static-friction engagement) with PTO or non-PTO system. With the old school rider that I had, what worked smoothly was engagement with engine at speed definitely above idle, but not near full speed - what I can safely call a "lower medium" speed. Idle engagement was jerky, and full engine speed engagement definitely destroyed the belts in short order.

As previously acknowledged, PTO/non-PTO - apples/oranges, and answer not necessarily the same for different examples of the same type.

Not arguing or disagreeing with anybody - just having a discussion.

 

[Freddie21]

I must have missed something, I thought this is a lawn mower forum? Not pc back to the future.

 

[Gord Baker]

First blade replacement. Went very smooth. Maybe too smooth.
Completed the installation, took the mower out for a test-drive, it was working great. About 5min the blades stopped turning.
Disengaged the blades with the cutoff switch, took it back into the garage, lifted it and checked the torque on blade bolts to ensure 110 ft lbs.
Torque was good.

• Started mower
• Engaged the blades (low speed)
• Belt squeal and smell
• Tightened front tension spring
• Started & engaged the blades (low speed) no squeal
• Test drove - engaged blades at full speed, squealing.
• Gave up on it before I took a hammer to it.

What could cause the belt to loosen when I never touched it while replacing the blades and the last time I ran the mower (before the blade change) it was fine?

What step did I miss when changing the blades that might cause the belt to loosen?

BTW - I never even touched the belt at all. All the work was performed under the deck the entire time.

I suspect one of the Spindles or bearings have seized up. Try turning each pulley by hand.
You have also likely overheated/burned the belt. Check Clutch operation as well. Does it engage?

 

[Freddie21]

WRONG FORUM

 

[Peva]

I must have missed something, I thought this is a lawn mower forum? Not pc back to the future.

A spammer that joined this morning. He posted in another thread too and has been reported from that thread.

In the future, that's what that "Report" button is for at the bottom of each post. Hit it in the post that is the SPAM post.

 

[Freddie21]

I have done that.