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What do you say happened here?


Coytee

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This is a 540 PTO shaft off my tractor.  Tractor is an International 1066 with dual shafts.  Upper shaft is 1000 rpm, this one is 540.

 

Yesterday, noticed it wasn't working.  Started digging into it and found this.

 

Clearly I have to get this fixed...but am scratching my head on how a piece of steel that's around 1.375" (1 3/8) inches thick simply snaps.

 

PTO end.jpg

PTO side.jpg

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  I've seen things break on machines....  Walked away scratching my head. 

 

fwiw

it looks like there was a crack in the shaft, guessing by the shiny spot of the top of the break, in pic #1

The "polished" spot might indicate movement at that place.

 

 

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Not being a metalurgist nor engineer (but according to my wife I AM a PITA!!)

 

Anyway, I was thinking that the 3/4 section of it is maybe bad steel and the only thing holding it was the shiny part which sheared recently, therefore is shiny.

 

(Trying to use my McGyver skills)

 

:ph34r:

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I don't know.  I have not yet pulled the PTO unit from the tractor.  I was working on removing the speed increaser (15' hydraulic rotary cutter so it has a VERY heavy speed increaser hanging off the PTO to jump the RPM's from 540 to approximately 2,160.  It's a 4X increaser)

 

Was all I could do to lift the speed increaser single handedly....but....I'm persistent and it's off.  When I got it off, I saw this hanging on the input side of it where this pulled out of the tractor.

 

That's where I am now.  I'm told the PTO unit is also VERY heavy so I need to get some help or create something where I can hang it around my neck like I did with the increaser and use my legs to hoist it.  Still working on that part.

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26 minutes ago, Coytee said:

Not being a metalurgist nor engineer (but according to my wife I AM a PITA!!)

 

Anyway, I was thinking that the 3/4 section of it is maybe bad steel and the only thing holding it was the shiny part which sheared recently, therefore is shiny.

 

Agree.  B)

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I think what happened is, It broke. :mad:

 

But really I have never seen one of those break, I would have thought the gear on the other end would have had a better chance of breaking. Hope you don't find any other problems as you take it apart deeper, that may be the cheaper part to replace compared to what's inside.

 

You seem to have the strangest luck at times, things happen that should never.

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1 hour ago, Coytee said:

This is a 540 PTO shaft off my tractor.  Tractor is an International 1066 with dual shafts.  Upper shaft is 1000 rpm, this one is 540.

 

Yesterday, noticed it wasn't working.  Started digging into it and found this.

 

Clearly I have to get this fixed...but am scratching my head on how a piece of steel that's around 1.375" (1 3/8) inches thick simply snaps.

 

PTO end.jpg

PTO side.jpg


That is the way hardened steel breaks! Brittly! SNAP! 😞

John Kuthe...

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I do sometimes tend to push things.  "IF I can cut a 1" sapling with this, how about 2"???  how about a 14" mature walnut tree?!!!"

 

Ok, I'm kidding on the walnut tree.  I do however tend to push things and things happen when I go to far.


Thing is...  I've only got maybe 2 actual hours of mowing time on this thing.  I'd hate to think it's that fragile.  Besides, the mower has an integral bypass (hydraulic bypass) valve in it for when it gets into something too deep, the bypass opens (is supposed to) and prevent damage to the pump on the mower.

 

I'm still shrugging my shoulders but, I DO like your succinct assessment....  "it broke"

 

:emotion-21:

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So, you mechanical type...  think this through with me.

 

PTO is rotating at 540 RPM's.  It's connected to a 4x speed multiplier hanging on the PTO so now the speed is 2,160.

 

I'm guessing you have more speed but less power (?)

BUT...  if you whacked the blades on an immovable object, then the shock from the blades would travel through the mower back to the speed increaser which would be a speed reducer in reverse....  so whacking something would give you 4 times the impact on the PTO verses 1/4 the impact.

 

Reasonable or am I backwards?

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That's the way all tech breaks. It goes from working, working, working.......to BROKE!! Faster if you push your tech! I know,m as a kid I used to take the little electric motors and connect them to a train transformer and rev them so hard and fast they would burn up and THEN STOP!

Things rarely if ever break in reverse! Like a dead light bulb never just spontaneously starts working again! 

John Kuthe...

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1 minute ago, JohnKuthe said:

Like a dead light bulb never just spontaneously starts working again

 

So what I'm hearing is, I can break the bulb to get to the inside and while it's plugged in, stick my tongue on the leads and all will be fine.

 

Excellent!!!

 

(and Dtel was wondering why things happen to me!)

 

:huh:

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5 minutes ago, Coytee said:

So, you mechanical type...  think this through with me.

 

PTO is rotating at 540 RPM's.  It's connected to a 4x speed multiplier hanging on the PTO so now the speed is 2,160.

 

I'm guessing you have more speed but less power (?)

BUT...  if you whacked the blades on an immovable object, then the shock from the blades would travel through the mower back to the speed increaser which would be a speed reducer in reverse....  so whacking something would give you 4 times the impact on the PTO verses 1/4 the impact.

 

Reasonable or am I backwards?


I'll bet impact represented mathematically by the Dirac Delta function may go 2,4,8,16! Is FOUR times the impact power, maybe! I'm an Electrical Engineer not Mechanical!

And I've bent the drive shaft of electric lawn mowers by hitting the blade against a flagstone! Oops! Electric motor didn't last very long after that!

John Kuthe...

John Kuthe...

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I thought most of those mowers had a clutch or shear pin built in to prevent things like this from happening. 

 

The pto shaft looks like it was fine, the shiny part may be the last piece to break making that slightly rounded shiny design? I have broken some things like a tractor tie rod end, and after looking at them in one case you could see where it was cracked previously and even rusted and eventually the rest broke which left a look similar to the clean broken part of yours.

Good luck when you look inside, hope it's just the shaft. 

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No clutch on this mower (at least, not one between the mower & tractor).  The mower is supposed to have an integral pressure relief valve that will release if you get tied up in something.  From what I've read, the mower will audibly sound different when it's doing this.

 

I'll never know, but I'm hoping it's simply something that happened prior in life and just now letting itself be known.  Since I have so few hours of actually using the mower (only bought it last fall and spent a couple months getting the shifter fixed so during that time, it certainly wasn't getting any use.  

 

I'm just surprised to see something like that snap....  then again, the 1066 is rated at something like 125 HP (don't recall if that's PTO or drawbar, either way, it's a stout machine)

 

 

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The little tributaries or veins may be cold shuts in the forging process.  Then again, it could have happened in the twist.  Forged input and output shafts usually don't break smooth like that, so I would guess air voids or cold shuts from those void lines.   Either way, it was still strong to last this long, just finally let go.

 

 

 Taking a second look,  there are a few wear lines from the shaft riding on the housing.  It may have scored it enough, that it snapped right on the edge of one, which would explain that complete straight break.

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My take is if there was a shear pin in that shaft it would be breaking about once a week, every time you hit a rock. My grandfather had a six foot blade attachment mounted on the back of his tractor operated by the power take off and every time he mowed the pasture he would break the shaft on a rock. Many, many many times. Then he retired. Got rid of the mower. The rocks won.

JJK

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