cqaigy2
Super Member
Yes, it was the rust the confused me. I wonder how long it was cracked before it let go all the way?
Broke another wheel motor axle
- Thread starter MuncyBob
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agjones
Platinum Member
- Joined
- May 4, 2010
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- 618
- Location
- Jessup Mill, NC
- Tractor
- Rk55HC, Kubota kx040, power-trac 425d, Bobcat L23, Yanmar 401w, bx1880, IHI 30 and Fiori D40 dumpers, Magnatrac mh5000, Dew-eze ATM72LC Slope Mower, Terramite t6 4wd, DR Power brush mower
Your pictures are very revealing... This is a slow developing fatigue failure. Slow being relative to instant.
The crack appears to have started at the leading edge of the keyway. And while it could be a flaw in the metal, it's more likely fretting corrosion (link below) caused by vibration or slippage at the keyway. Basically the key was hammering the shaft... That's why it's so smooth from the origin to the point of instant failure when the cracked shaft could no longer bear the load. The rust indicates that the crack was slow to develop.
Different Types of Corrosion: Fretting Corrosion - Causes & Prevention. WebCorr Corrosion Consulting Services, Corrosion Short Courses and Corrosion Expert Witness. corrosion types, corrosion forms, pipe corrosion, generalized corrosion, pitting corr
See explanations of photo 6 here
Failure Analysis Of Machine Shafts - Maintenance Technology
It does not look like your brake pin rubbed inside the brake flange often, but there is one significant brake pin bend in the 'spider'. Note that where that bend is most defined happens to be directly over the keyway. Did the brake ever deploy while the machine was in motion?
The crack appears to have started at the leading edge of the keyway. And while it could be a flaw in the metal, it's more likely fretting corrosion (link below) caused by vibration or slippage at the keyway. Basically the key was hammering the shaft... That's why it's so smooth from the origin to the point of instant failure when the cracked shaft could no longer bear the load. The rust indicates that the crack was slow to develop.
Different Types of Corrosion: Fretting Corrosion - Causes & Prevention. WebCorr Corrosion Consulting Services, Corrosion Short Courses and Corrosion Expert Witness. corrosion types, corrosion forms, pipe corrosion, generalized corrosion, pitting corr
See explanations of photo 6 here
Failure Analysis Of Machine Shafts - Maintenance Technology
It does not look like your brake pin rubbed inside the brake flange often, but there is one significant brake pin bend in the 'spider'. Note that where that bend is most defined happens to be directly over the keyway. Did the brake ever deploy while the machine was in motion?
Impulse
Silver Member
So resurrecting an older thread here, but what exactly is a "tub failure". How does that fail?
On the 422 there is only 1 steering piston. The tub "failed" due to all the stress being put in that one area and the bracket that the cylinder is mounted to breaks away taking some of the tub with it. I had to have the bracket welded back on and then also some reinforcement welded into that area.
Impulse
Silver Member
That makes more sense. Thanks for the info.
Marks481
Platinum Member
- Joined
- May 29, 2005
- Messages
- 978
- Tractor
- Power Trac 422 (2005)
Contributing to that, there is a 1.5" diameter drain hole in the bottom right next to where the bracket is welded, which makes the tub floor more likely to flex, and a crack to propagate. Bad design.
