if i wanted to build a jaw crusher...

   / if i wanted to build a jaw crusher... #31  
I too grew up with a gravel operation. The use of a jaw was to crush the larger rock 12" plus, into about a 3-4". That product was fed into a roll crusher.

Using a jaw will require strong iron, as there is a significant impact. I remember when a particularly hard rock would enter the jaw there was a lot of banging. Jaw surfaces are also curved. As it was mentioned the rotating movement is in a manner to feed the rock into the jaw, but occasionally and hard rock, would fall in and be squeezed back out, propelling into the air.

The roll crusher is less stressful as the material is fed and into a small space between 2 rotating rollers, vs being banged together.

I would explore the roller idea before the jaw if I could as i think there will be less maintainaince .

In any case..good luck with your interesting project.
 
   / if i wanted to build a jaw crusher... #33  
opps...I see that someone bumped it and I got caught.

It is an interesting subject, but only for those where gravel is expensive. Here its cheap enough to buy..its delivery that costs.
 
   / if i wanted to build a jaw crusher... #34  
I remember seeing a rotary hammer rock crusher that was pulled behind a potato harvester. It pulverized the rocks to sand size pieces before they were discharged back to the field. Don't remember the design details.

Simlar crushers/pulverizers are used to pulverize coal in a power plants.
Coal mixed with flue gases (no oxygen there) enter axialy from sides and is crushed. Since the crusher also works as a blower pulverized coal is blown upward. The bigger pieces have to much energy to make a turn around a baffle installed in the duct and are bounced back to the mill. Small and light pieces (powder) make the turn and are blown to the burner.
 
   / if i wanted to build a jaw crusher... #35  
There are models available from the UK, a small one that weighs around 740kg with an opening of roughly 16" x 6.5" that runs off either donor vehicle hydraulics (roughly 5-6TPH), a power pack or a 3PL system + a larger version with a jaw opening of roughly 20" x 10" weighing approx 1650kg - again as a stand alone unit run from a donor vehicles hydraulics or as a standard 3PL system (roughly 14-15TPH).

Both can handle rebar, stone, blocks, bricks, flint, kerbstone etc...
 
   / if i wanted to build a jaw crusher... #37  
I want to build one as well. I have access to flywheels and cranks from large one-lung gas engines and am trying to piece one together from those. The jaw plates I figure can be bought at any industrial/excavation supply place. By using existing plates they then can be replaced, saving manufacturing each time they wear out.

I used to run an old Pioneer, and the prospect of building one is apealing. Keep us up to date if you get a prototype built.
 
   / if i wanted to build a jaw crusher...
  • Thread Starter
#38  
Been thinking of this since 2008, but I am planning to actually start the build next winter: this winter i am busy moving my workshop from my birth farm barn to the new place i rent next to my appartment. It would give me more time to work on my own projects, instead of servicing and repairing the stuff on the farm..

I read a lot of thesis and scriptions of science engineers around the world, from Germany, UK, to India. These students all tend to simplify the load to laboratory conditions, but it does get me up to date with the rock fracture mechanisms: point loaded rocks dont fail by comrpession, they fail because the pulverised material beneath the contact area acts somewhat like a fluid, it transfers the compressive force to the sides, causing the rock to split because its tensile stress is exceeded. Crushing a concrete ball with a 20n/mm compressive strength and 300mm diameter requires only 18 ton, because the tensile strength is 1/10th to 1/15th of the compressive strength. However in the real world we dont crush round balls, in Holland we hardly have natural rock so it will crush concrete slabs and kerbstones, which may contact the jaw on all 10 ribs if it is a square piece of concrete.

the point where i'm getting stuck is how ten vertical ribs of the crusher, would create a rock fracture perpendicular to the jaw ribs... Even if the rock doesnt break, the crusher with 10 ribs of 20mm wide, and a 30mm throw, would push 82mm of the rib into the rock, resulting in a 34 ton load in 20N/mm2 hard concrete (standard industry floors are 15 N/mm2)

Can anyone point me in the right direction ? I would rather use knowledge already there, than to overbuild and then find the real load by holding the bearings on by shearbolts, to get an idea of real world load conditions, so i can calculate how big the safety margin on the design strength actually is.
http://ethesis.nitrkl.ac.in/1483/1/...nalysis_of_Swing_Jaw_Plate_of_Jaw_Crusher.pdf
 
   / if i wanted to build a jaw crusher...
  • Thread Starter
#40  
Maybe someone has access to a 15x24 or 13x20 inch jaw crusher and can measure the shaft diameter for me ? It would at least be a starting point for me. I would use the highest grade of shaft (CrMo4V) anyways, as 99% of the crushers use shafts of equivalent material.

Another thing i'm running into is bearings: i want to avoid roller bearings due to price and complication of design: Its not a mining operation, it just has to run a few days in the year.

SKF plain bushings dont cut it: they have high load capacities and sufficient slide speeds, but the online calculator deducts 80% of the capacity for operating near the slide speed limit, so there isnt much left. using wide bearings means bigger distance between shaft loadpoints, means more bend force means thicker shaft, means more bearing slide speed...

Old crushers used Babbitt bearings. What is the modern equivalent of a Babbitt bearing, RG7 bearing bronze, or RG12 ?
 
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