Flat washers..to withstand shock or vibration

plow hand

Well-known Member
I run a rock crusher at work and a chute that I have
bolted on it will snap the 5/8 grade 8 bolts is there a
tough impact washer available...thanks
 
Yes. I would use heavy Belleville Washers are for that purpose. I would use the heaviest thickness I could find (google them) and use 3 washers under each bolt head. Stacked cup down cup up cup down. I would also tighten the fastner untill almost all the cup was out of the washers, and no tighter. I would use locktite on the nuts to prevent unscrewing. Jim
 
Try your nearest Cat dealer,their lock washers are flat and their bolts are great.
 
Hello plow hand,

Your problem is not the bolts, although you can get higher grades if you need them, but your washers. They most be soft. When they get crushed the bolt gets loose and will fail. You need to get grade 8 washers, they are super thick. I would also recommend same grade locking nuts if used, and lock tite. Also the bolt hole has to be the size of the bolt, and the shoulder part of the bolt should go through, which means no threads in the hole,

Guido.
 
Is this a factory installed chute?

Just wondering if some design change needs to be made.

It is possible once the bolts are made strong enough, the problem may transfer to the next weakest link, like stress cracking the chute or breaking what the chute is bolted to.

Just a thought...
 
Who built the crusher and what do they suggest. They built the machine and sure would have someone who can help with any problem you would have with their machine. When i was working and we had a problem with any machine always went to the manufacture for help.
 
Another idea which I have seen used is to place a spacer on the outside of the bolt and use a longer bolt. When you torque a bolt, you are counting on the stretch of the fastener to maintain tension. The shorter the bolt is means it will yield to shock load and fatigue sooner. A 5/8 bolt may require an additional inch or two spacer. Using a harder grade bolt some times is not the correct answer when dealing with stress failure as they will snap, rather than stretch and return to the proper tension.

Check out some final drive components made by the heavy equipment manufactures and you will see the application of longer bolts and spacers to overcome shock loads on fasteners.

Beagle
 
Just wondering, if you are snapping off bolts, are the holes out of round? If so, drill them out and install larger bolts.

You can get flat washers that are about 3x thicker than normal one. There are a few places in town that sell bolts for industrial use. That's where I go when I need special bolts and washers.
 
Would have to see the application but is it possible to put a liner in the chute? I worked in a stone quarry and we lined all of our chutes with hardened steel. 1/2" thick up to 3/4, depending on the size of rock. We then used 5/8 plow bolts with the nuts and washers on the outside of the chute. Burnt a hole with torch and then tapered the hole so the tapered plow bolt head would recess into the liner. Had to burn holes in the chute to bolt on the liner. We then welded around the head of the bolt with a pretty heavy bead. Welded bead was harder than the head of the bolt. Once the liner wore out we torched off the nut and washer on the outside, removed liner and installed new one. Saved a lot of wear on the chutes and kept us from building new chutes. Most liners would last a few years depending on how much rock went over it and what size.
 
With a rock crusher you may have a fatigue problem with the bolts themselves. You may want to look into a proper structural bolt with hardened washers and properly tension the bolts (turn of the nut method or use indicating washers). Developing tension in the bolts helps reduce the fatigue. The other option, if it is a fatigue issue, is go to a softer, more ductile bolt.

The connection configuration also may come into play (are the bolts in tension or shear).

Your friendly local mechanical or structural engineer should be able to help you with this issue.

bjb
Structural Engineer
 

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