Blade drive/clutch question

[Gym123]

Sorry, hard to understand how "not worth removing" and "...vocabulary issues when the blade hits one and bends the crankshaft" should be in the same sentence. I get that roots and rocks aren't easy to remove, but hitting them? Not if I could avoid them. Use a string trimmer around them and go on with your day- beating the crap out of a mower isn't worth doing if it's avoidable.

 

[RevB]

My yard has exposed roots and some very large limestone rocks that are not worth the trouble to remove. As you already know, this causes some serious vocabulary issues when the blade hits one and bends the crankshaft. I have an old Toro Commercial deck with a Tecunseh engine on it right now. It works very well until I find a root or a rock. Usually I can avoid them, but sometimes we are gone to visit the grandchildren, and it always rains while we are gone, then the grass grows up over the little surprises, and that is when I bend the crankshaft. Some days you are the pigeon, some days the statue.

Anyway, I am playing with the idea of putting some kind of clutch arrangement on the end of the crankshaft, so that it might slip when it hits something that won't move. Problem with that is calibrating it so that it will slip when it hits a root, but not slip when it hits heavy grass or weeds. Maybe build a small belt drive like the Exmark 26.

We have a riding mower, but true to my user name, I can't see buying a riding mower and then a treadmill when I can simply walk behind the mower. BTW, my wife rides the mower. I get pretty scornful of those who have riding mowers that cost more than my first car, then spend wads more on exercise equipment, while the lot their house is on is 50x170.

Can anyone shed more light than heat on this? Thanks in advance

Yeah....remove the problems.

 

[kuldeepbaswal]

For a yard with exposed roots and limestone, the crankshaft-bending problem is really a blade-coupling problem. There are two practical paths to fix it without buying a new mower every other year:
1. Slip-clutch blade adapters. These sit between the crankshaft and the blade and act as a sacrificial torque-limiter — they slip when the blade hits something solid instead of transferring the impact straight up to the crankshaft. Search "shear hub blade adapter" or "slip-hub blade mount" for your engine spline. Around $40-60 from most small engine parts suppliers. Single best fix for impact damage on a fixed-shaft mower.
2. Belt-driven deck (what commercial walk-behinds use). A belt naturally slips a little when the blade gets hit hard. That's why commercial 21" walk-behinds (Toro Proline, Honda HRC) take rock strikes that would have killed a residential engine. If you find yourself replacing crankshafts more than once on a property, switching to a belt-driven deck pays for itself fast.
3. Higher blade tip clearance. Mowing at 4" instead of 2.5" raises the blade above most surface roots and small rocks. Most people set their deck too low for the conditions they actually have.
Other things that help on root-prone properties:

• Replace nylon "high lift" blades with low-lift mulching blades — less suction means less likelihood the blade pulls a rock into the path.
• Walk the mowing zone after long rain delays — 30 seconds of scouting beats a $200 crankshaft.
• Mark known rock hazards with cheap flagging stakes so you don't forget after months of growth.

If the Tecumseh is at end of life anyway, a commercial-grade replacement with a belt-driven deck and a shear hub is the long-term fix. I tested a handful of homeowner-and-pro options with durability data in this self-propelled mower comparison — the notes on which ones survive rough terrain are particularly relevant.

 

[RevB]

My yard has exposed roots and some very large limestone rocks that are not worth the trouble to remove. As you already know, this causes some serious vocabulary issues when the blade hits one and bends the crankshaft. I have an old Toro Commercial deck with a Tecunseh engine on it right now. It works very well until I find a root or a rock. Usually I can avoid them, but sometimes we are gone to visit the grandchildren, and it always rains while we are gone, then the grass grows up over the little surprises, and that is when I bend the crankshaft. Some days you are the pigeon, some days the statue.

Anyway, I am playing with the idea of putting some kind of clutch arrangement on the end of the crankshaft, so that it might slip when it hits something that won't move. Problem with that is calibrating it so that it will slip when it hits a root, but not slip when it hits heavy grass or weeds. Maybe build a small belt drive like the Exmark 26.

We have a riding mower, but true to my user name, I can't see buying a riding mower and then a treadmill when I can simply walk behind the mower. BTW, my wife rides the mower. I get pretty scornful of those who have riding mowers that cost more than my first car, then spend wads more on exercise equipment, while the lot their house is on is 50x170.

Can anyone shed more light than heat on this? Thanks in advance

Swing-back / Pivoting Blade Systems (most relevant match):

• MEG-MO blades: These use a central disc with short pivoting knives/tips that swing away from obstacles like rocks or debris. They are marketed to prevent bent blades and spindle damage. They work on various mower types (including zero-turns) and emphasize mulching. Users report they handle rough terrain better than standard blades, though cut quality can be more "bush-hog like" than premium finish. Available in the US with custom fitting.
• 
  
• Cutlass blades: Feature four removable/pivoting cutting tips per blade body that swing back on impact. The tips are quick-change (no tools needed for swaps/sharpening) and made of hardened steel. They are custom-sized and aim for durability in tougher conditions while maintaining a reasonable cut.
• There are also fixed strand weed whacker style but those would be a nightmare.....unless they were cable type. My guess is you're not looking for manicured.