My Saw Isn't Working Right????

[Ulma Doctor]

I get a bunch of strange happenings at the shop or in the field, this story is about just that...

I got a call on a Hollymatic Hi-Yield 16 Meat Cutting Saw, that was not turning on by the operator's description.

Upon arrival on site, i performed an initial inspection and gave the start button input to start the saw.
the 3 HP 3 phase motor turned, but the lower saw wheel was not turning...
Immediately i considered major belt slip or broken belting as the cause,
Boy was i wrong......


In 25 years of fixing broken things for money, i have never ran across this situation.
The shaft is 1" in diameter where it broke


A close up



Here's another look with the new shaft below



I was able to reassemble the saw with a new shaft/bearing assembly and get em' back to feedin' the masses.

Another day living the dream.

thanks for reading!

 

[Eddyde]

I had a ¾" shaft snap like that on a 2.5hp commercial swimming pool pump. I could never figure out why it failed other than some weird vibration from the impeller causing it to fatigue at that point?

 

[Ulma Doctor]

The original shaft was chromed steel, the new shaft is 304 stainless
maybe they changed materials due to other failures of this nature, but this is a relatively new thing on the factory's part.
up until about 5 yrs ago they were all chromed steel, but this is the first failure like this i ever came across,
I thought i seen it all.....

 

[brav65]

Harmonic vibration can be an extremely destructive force. It is amazing to see something so substantial fail due to a small force applied over a short duration but lots of cycles. I wish I knew more about metal fatigue from the scientific side rather than the scratch your head and wonder how that happened side. Thanks for sharing as usual Mike

 

[JimDawson]

It looks like what is missing there is a generous radius at the stress point, looks like a pretty sharp corner.

 

[coffmajt]

Fatigue usually starts from a stress riser, typically a 90 degree corner with no radius provided. Corrosion pits can also create stress risers, with the same high cycle fatigue failures as a result. My Marks Mechanical Engineers Handbook shows the potential for a 300 percent increase in stress at a sharp corner with little to no radius. Thanks for sharing. Jack

 

[mzayd3]

Reminds me of a shop I worked at that snapped a ~24" diameter roll on their roll former. I had never seen anything like it. I heard the replacement shaft was somewhere in the neighborhood of $70,000! They rolled rings for sections of pressure vessels with about a 9" wall thickness.


Sent from my iPhone using Tapatalk

 

[kd4gij]

Ha when I read the title and saw the pic I thought you where trying to cut metal on a meat saw Was going to say Da but then read the post.

 

[brino]

I once had the input shaft to the power steering pump on my truck shear off. The funny thing was that it sheared inside the pump. From all external appearances everything was fine, the serpentine belt was tight, the pulley was spinning. There was no easy place to measure pressure or flow.

So I set about to remove the pump, the belt was off and I spun the pulley by hand to get a better feel for resistance....there was none, and slight finger pressure pulled the pulley and a bunch of the shaft out of the housing......hmmm. On further dis-assembly the shaft had broke inside of the outer bearing keeping up appearances that nothing was amiss.

-brino

 

[rock_breaker]

That is why I seldom left the plant for lunch!
On one occasion I went to the local restaurant for lunch, 5 minute drive, had lunch and returned then noticed the crushing plant wasn't running. Investigation revealed the shaft holding the 10 grove 28 inch diameter 8 inch bore pulley had broken off just outside the supporting pillow block on the primary crusher. Fortunately there was a spare shaft and impact rotor (14 ton) about 1.5 days away. Express shipping was set up and an a 50 ton truck crane scheduled for the next 3 days. Torched the 60 1.25" bolts holding 30 ton hood on and was ready for the crane. Set the hood aside lifted the old rotor and broken shaft out of the pillow blocks and set it aside. New rotor arrived and started reassembly, work went on around the clock, pulled tension on the 10 belts 3rd day. Roped the area off pushed the start button on the 600 HP motor, filled empty rock silos then put safety guard on 2 days later. Normally the guards go on before restarting but we were minutes away from shutting the kiln down, an $8000.00 process at that time.
Took a long time to leave during lunch afterwards and even longer to relax and enjoy the meal.
Have a good day !
Ray