Hammermill or horizontal crusher?

Hello all,

I have recently run across this crusher for sale and i have been interested in one for a long time. Unfortunatly i do not have much info on it and was wondering if someone could give me info on what kind it is and what it is capable of before i go to look at it. I was sent these pictures i didnt take them and its 2 hours drive for me so i want to have some info before i go take it out and see if its worth buying.

Wouldn't any crusher have to have jaws? Seems to me it would have to be called a grinder. I assume for nothing harder than wood? But then I know nothing about it other than similarity to a feed grinder/hammermill.

Since there are no pics of the inside I'm basing this in what I can see. I believe what your looking at here is a hammer mill vs a crusher. There may be more types that I haven't seen but are basically three types of what are usually called crushers. The first is a jaw type and it has a moving plate and a fixed plate. The top of the moving plate is fixed on a pivoting joint (like one leg of a hinge) and the lower portion is on a movable toggle link that controls the length of stroke and allows you to adjust the dimention between the jaws. This dimension controls the size of material that gets through it. The secone type is a cone type. It's basically a cone shaped inner core turning within a cone shaped outer core. Typically the inner core is on an eccentric of sorts to the outer cone. The material is fed in from the top and as it flows between the cones the material going into it at the larger clearance between the cones gets crushed as it's drawn into the smaller clearance. That's an over simplification of the process but basically that's what happens. The third type if a roll crusher. Usually these have two rollers turning together in opposite directions to where material is drawn between them to be crushed. Usually one roller is fixed and the other spring loaded to prevent something oversized from jamming between them and causing damage. Depending on the material being crushed there are smooth drums, ribbed drums, testured drums, etc. Too you will see single roller crushers where a vertical roller rotates against a horizontal plate and the material gets caught and crushed between them. Technically these last machines are roll crushers of a sort but they are usually called mills.

Now depending on what you are trying to crush as to what type of crusher you need. The jaw type is best for larger pieces of material as well as hard material such as granite. That is why they are most often used as the primary crusher in rock quarries. The jaw takes the large pieces of shot rock from the face of the cut and crushes them down into smaller, more managable sized pieces. From the jaw the now smaller material then usually travels to one or more cone type crushers that crush the rock into progressively smaller pieces preparing it for a final screening to size. Depending on the hardness of the material roll crushers can also be used for this. Typically though they aren't used unless the material to be crushed is something softer like sandstone, etc. I've worked around alot of Martin Marietta's "rock" quarries in my life and have never seen a roll crusher in use in any of them due to the hardness of the rock being crushed. The one place I have seen one used was a jaw and roll combination used to break second hand brick into landscaping chips. In that case the roll was breaking the larger pieces that made it through the jaw into really small chips and then through a screen and either dumped on the pile or reciirculated back to the roll for another pass. Granted this setup started life as a mobile crusher for other material but it did an awsone job making brick chips too.

With all of that said what your looking at appears to have a single rotor in the middle of it. As such it should also have swinging hammers mounted around the OD of the rotor. Then at the bottom should be a screen that keeps material in the strike zone of the hammers until it's small enough to pass through. Basically the size holes in the screen determines the final size of the material passing through it therefore the size of the final product. If that is what your looking at then it is not considered a crusher but rather a hammer mill. Now depending on what your wanting to crush as to whether it will work for you or not. Typically a hammer mill is designed for softer material items such as stumps, scrap wood, etc. Don't get me wrong, it will handle softer rocky material as well but given the way it 'crushes' the material be prepared to see alot of wear to the hammers and screen in a relatively short amount of time if used for this. Given the feed setup of most hammer mills also, if you were to throw something hard into it the result is usually something broke on the machine if it jams as that beings everything to a screeching halt. If equipped with an overrunning clutch, etc the amount of damage can be minimized or possibly eliminated but if if is direct drive (which this appears to be) then you might as well expect something to break. Even worse is if the piece gets hit by a hammer and instead of breaking or getting bound up takes flight straight up. Both jaw and cone crushers are also known for doing that when something like a bucket tooth off a machine or an odd shapped piece of rock gets caught just right and 'squirted' out. In the case of a mill it'll be hit and knocked out just like hitting a ball with a bat. What ever it is that causes a piece to be thrown up like that, be it a 50 lb bucket tooth or 50 lb piece of hard rock, there are never enough places to hide until it hits the ground again. All you can do is find something solid over your head and pray....

Honestly I'm no crusher guru by any means but I have been around and worked on quite a few of them enough to know how and why they work, and at least a few things about them. I have been involved in making repairs to a few of them so I have a pretty good understanding of things to look for before buying. Hammer mills aren't that much different from the crushers in the things to look for either. I can say on the machine your looking at that the Allis Chalmers Engines were good engines for their time and from everything I've seen and heard over the years fairely reliable. I know the military used alot of them on their generators in years past. Dad used to work for an A/C dealer so he could tell you alot more about them than I could even begin to given the model or series number. As for the rest of the machine in the pics make sure the bearings on the rotor drum are in good shape,and make sure the hammers are relatively tight on their pins. Too look at the wear on the rotor, the hammers, and on the bottom screen. The hammer should have a face that when hung horizontal to the shaft is relatively flat. If they have been worn and built up that is fine as long as the proper material was used for the build up, the same goes for the wear surfaces on the rotor itself. As far as the screen goes, check the thickness of the material between the holes in obvious wear areas against the thickness of it in areas that don't get much wear. Too check the diameter of the holes in those same wear areas for ones obviously larger than others in the non wear areas. A worn screen alone can cost a pretty penny to replace and it is considered a wear part that will need periodic replacement. It's one of those pieces that's not a matter of if it has to be replaced but when.

Beyond that just look at the machine overall and make your call from there in so far as it's mechanical condition just as you would when looking at anything else. Like any older machine though one thing to do is to get the model and serial number off of the machine and insure parts are still available for it. Granted parts like the hammers can often be rebuilt when worn and screens can be replaced, but it's expensive to take care of even these routine repairs when parts are readily available but even more expensive when the parts have to be custom made. Any more questions please feel free to ask.