Broken mower bolt.

[Woodworks]

Shaft looks fine. It's an old Stiga Multiclip Pro that's been a good solid machine.

 

What's crank protection?

[IVECOKID]

Shaft looks fine. It's an old Stiga Multiclip Pro that's been a good solid machine.

 

What's crank protection?

 

Crank protection example ,Hayter lawn mower blades slips round if it hits a solid object ie BRICK ,its not fixed solid by locacting pins but just the main centre bolt .

 

Ste

[Woodworks]

Ah gotcha. When I got it someone had stuffed 2 bolts through the holes in the sides of the flange onto the blade. Only took one encounter with a rock for me to think this was a bad idea and now it just use the center bolt to hold the blade. If it smacks a rock it can spin.

[IVECOKID]

Ah gotcha. When I got it someone had stuffed 2 bolts through the holes in the sides of the flange onto the blade. Only took one encounter with a rock for me to think this was a bad idea and now it just use the center bolt to hold the blade. If it smacks a rock it can spin.

 

Each make of mower have there own design ,Hayter blade is under tension when bolted up to a disc ,some machines have locating pins like your photo which means it locks in place but should shear pins or forced over them ,not too sure with that make , I may be corrected at some point.

 

Ste

[GardenKit]

Glad to see you got the broken bolt out OK Beau.

 

It broke because at some time it has been overtightened. You can see in the picture that the bolt is slightly tapered towards the break, this shows that it had stretched when over torqued.

 

It may have stayed intact until the impact damage that sheared off the two drive pegs on the blade boss. The blade could then have self tightened a little more under impact and broken.

 

Equally well, with the drive pegs missing the blade could have spun anti-clockwise under deceleration and loosened the bolt.

 

The pegs are designed to shear under impact and prevent the crank from bending. Broken bosses MUST be replaced as soon as the pegs are broken for safety reasons.

 

The correct torque is 40NM.

 

Barrie.

 

By the way Beau, the electric height adjuster for the Villa will be sent to Mr D tomorrow.

[IVECOKID]

Glad to see you got the broken bolt out OK Beau.

 

It broke because at some time it has been overtightened. You can see in the picture that the bolt is slightly tapered towards the break, this shows that it had stretched when over torqued.

 

It may have stayed intact until the impact damage that sheared off the two drive pegs on the blade boss. The blade could then have self tightened a little more under impact and broken.

 

Equally well, with the drive pegs missing the blade could have spun anti-clockwise under deceleration and loosened the bolt.

 

The pegs are designed to shear under impact and prevent the crank from bending. Broken bosses MUST be replaced as soon as the pegs are broken for safety reasons.

 

The correct torque is 40NM.

 

 

 

Ste

[Woodworks]

Glad to see you got the broken bolt out OK Beau.

 

It broke because at some time it has been overtightened. You can see in the picture that the bolt is slightly tapered towards the break, this shows that it had stretched when over torqued.

 

It may have stayed intact until the impact damage that sheared off the two drive pegs on the blade boss. The blade could then have self tightened a little more under impact and broken.

 

Equally well, with the drive pegs missing the blade could have spun anti-clockwise under deceleration and loosened the bolt.

 

The pegs are designed to shear under impact and prevent the crank from bending. Broken bosses MUST be replaced as soon as the pegs are broken for safety reasons.

 

The correct torque is 40NM.

 

Barrie.

 

By the way Beau, the electric height adjuster for the Villa will be sent to Mr D tomorrow.

 

Thanks Barry

[Woodworks]

Been thinking about this

 

Garden Kit you say "Broken bosses MUST be replaced as soon as the pegs are broken for safety reasons."

 

I was just going to pop in a new bolt as the last one has done me around five years and it came to me without bosses but suspect they had been broken in it's previous life.

 

Reality is this mower gets used for rough work and WILL hit stones. With just a bolt the blade just slips without any breakage. New bosses means more load before breaking them and more expense.

[GardenKit]

The problem with that Beau, is that the blade can spin and become loose. The pegs are there for a reason.

 

I would never send a mower out with a broken boss, but do see plenty come in with broken pegs but the blade is still tight and the owner is blissfully unaware.

 

I also get them come in with a loose blade and broken pegs following impact.

 

There are others (and later Stiga's) which have pegless bosses but the blade has friction washers each side and is clamped tight. As you said, these are better because they just slip.

Yours, without the pegs is just a metal to metal contact.

[Woodworks]

Can I get a pegless boss for an old machine?

Sounds ideal for the use we give it.