Rock Crusher

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Rock Crusher

There is nothing unusual about loggers needed rock and lots of it close to the job. This is profoundly the case in Western Oregon where rainfall is high. Sometimes you attempt the do it yourself solution as we did here with this 18x36 primary crusher. While the photos are not particularly helpful in understanding the art of making big rocks into small rocks, a description should help. The crusher here is called a primary crusher. In major commercial operations a primary crusher will be followed by secondary crushers to make the rock even smaller.

For example if fine gravel for asphalt pavement is being made, the rock coming out of the primary might be fed into a cone crusher, and from there into a 'roll crusher'. These names are very descriptive of how the crushers work. A cone crusher works sort of like an orange juicer. The central rotating cone spins and the outer shell is tapered so the gap between the two is narrower at the bottom than at the top. the rock is poured in the top and can't get out until it is small enough to fit out the crack between the turning cone and the shell at the bottom.

Similarly a roll crusher is about what you would expect from the name--- big flat steel wheels, and a stream of rock is poured between them. IT works well with fairly small rock being made even smaller.

As is common, the primary crusher is a 'jaw crusher'. That is one of the oldest types and is quite efficient. A jaw crusher has is a V shaped box (18 x 36) being the dimensions of the box--- implying that nominally you can get a rock in it up to about 18". IN simplified description, there is a stationary jaw and a moving one. Just think of one side of the V moving closer to the other side of the V and then back again. The bottom of the V is not quite closed so as the jaw moves closer and then further away from the stationary jaw, the rocks slide further and further down in the crotch and then get squashed until they can fall out the bottom. The moving jaw is moved back and forth because the top of it is on an eccentric shaft with a couple of massive flywheels to assure that the crushing stroke is completed. Besides the crusher itself you need two other major components. You need an Apron feeder. This is typically a box that you dump the rock to be crushed into, and it has some sort of a conveyor that can be controlled that lets you manage the amount of rock going into the crusher.

then on the bottom you need a way to move the rock away from underneath the crusher as it falls out the bottom. If you have a steep enough hill or set up the crusher high enough you can set up a slide and get the rock to slide into a pile or bunker, but it now is more common to have an underbelt as shown here that catches the rock and moves it to a pile -- or if a secondary crusher were in use---delivers it to the secondary crusher. In the operation here we were starting with rock about 12" or so and had the jaws spaced for the output was less than 3 inches. You can shim the moving jaw to create any sized gap you want at the bottom and thus make different sized rock, but making small rock in a jaw crusher really slows production.

Jaw crushers come in all sizes. You just need one with an opening as big as the biggest rock you want to feet into it. With enough money even 40 x 60 crushers can be bought. When you break rock loose in a quarry, a variety of geological conditions, and the manner in which you dig it loose affect the size of the rock you get. Then you have to get a crusher big enough----although you can sort out 'oversize' using a rock sorter called a grizzly which is usually a sloping steel grate--- Rocks small enough to fit through the grate do so and those 'oversize' slide down the grating to the oversize pile.

This particular crusher was powered by an old D-8 motor, actually a D-13000 a model number patterned after its displacement---about 1300 cu. in. The engine was capable of about 100 hp and probably weighed 5,000 lbs or more. It had probably twice the power needed for this crusher as jaw crushers don't need a lot of power (compared to cones or Rolls). The true reason for selecting an old Cat motor was that they turn slowly. That engine at full throttle turned at 900 RPM. It was belt driven to the jaw, and since the jaw needs to turn very slowly, the belt speed reduction was much easier manage.

The crushing unit itself you can't seen in these photos as it is a big iron boxy structure with two giant flywheels on it behind the engine. The rock is dumped in a hopper in the back of the equipment and was fed out of the hopper with a moving chain belt (sometimes a shaking floor is used) which controls the speed that the rock is dropped into the crusher. The rock drops in the crusher and when it is finally small enough falls out the bottom onto the belt that you can see.

They crusher we had here was quite old as crushers go--dating back to the 1920's. It was a Llewellen sold by Howard Cooper of Portland, a long time, but now defunct heavy equipment dealer. The feature that dated it was the fact that it had babbitt bearings whereas all the newer crushers have roller bearings. Roller bearings are far more expensive and will work at much higher speeds, but the Babbit bearings are relatively cheap and you can make them yourself as we did on occasion. Indeed in the early machine age babbitt was sort of standard for bearings.


Indeed until about 1940, babbitt was pretty much an industry standard of bearings. It is a blend of tin, antimony and lead which is quite soft and silvery in color. Because it is soft it will turn against a hard steel shaft without wearing it. Like any lead compound it has a fairly low melting point so you have to be careful and lubricate is sufficiently so that it doesn't get hot enough to melt. the main shaft in this crusher was about 4" in diameter and the main support bearings where around 18" long. we had one fail so we had to repour it. Generally speaking, you make a babbitt bearing by getting some babbitt (it comes in bars) and melting it in a cast iron pot using a blow torch or a propane torch. Once the babbitt is liquid you simply pour it in a mold and let it cool out. The make a special ladle for the pouring. It is a spoon with a divider in it with the connection between the sides at the bottom of the spoon. This way the scum that forms on top of the molten metal will be held back. We did a 'pour in place' using the shaft and the casing for the mold. Since our bearing was so large we had to round up a fairly large pot and melt up around 20 lbs of babbitt.

Once the pour was made and cooled out the job still wasn't done. Then you have to work the bearing in. For this you need some 'Engineers blue' which is an oily mixture based on "Prussian blue" the same basic chemistry that used to be in blueprints. You smear this on the bearing, assemble it and turn the shaft some. It will be forced off the high spots and accumulate in the low spots. You then get in the bearing with a bearing scraper which looks like an inside out spoon and scrape the high spots down, and continue the process until the shaft fits the bearing perfectly or at least perfectly enough. The problem is that the if the shaft is just sitting on a few high spots the pressure will be too much and it will overheat. Consequently the running in process involves bluing, scraping, lubricating, running, checking to see if it is heating too much, and then bluing, scraping, and running until you can get the bearing so it will run without getting excessively hot, as you don't want to melt things down. It is a tedious process and took me most of a day of this before I got the bearing to 'go'.

Once it would run at a slow speed with lots of lubrication heating excessively, I was able to power run it in and after a few hours of turning then it set itself and after that it never even got warm to the touch. Alas, I think the art of pouring a babbitt bearing and turning it in is a lost art, but technically it is not particularly difficult.


The other thing you see in one of the photos is a UD-14 powered electric generator sitting on a trailer. This crusher setup had 2 electric motors on it---one for the feed conveyor and one for the apron feeder. There was no electric power around. It is kind of interesting on its own. It was a navy surplus 30kw 3 phase generator with a UD-14 engine. This is the stationary engine version of a TD-14 engine used in well -- International Harvester TD-14 dozers. It was vintage WWII, and the unique thing about that family of IH engines is that they started on gas and then converted to diesel, but unlike the Caterpillars of the era that had a pony engine, these did not. they had a 3rd valve in the cylinder controlled by a big lever on the side of the engine. The spark plug was hidden behind the valve. When you cranked the valve open, then this lowered the compression and exposed the spark plug so the engine could start as a gas engine. Then once it was running and warmed up a little you closed the valve and opened the diesel throttle. She would then catch on diesel and you were ready to go to work. Sort of creative but IH used this on many of their dozers for many years. It was a historic trademark feature of IH dozers and not a bad one. The engine itself was a relatively low speed engine (1200 rpm on the generator) -- fast compared to the Cats which were 900 RPM on the generator application, but certainly slow compared to the Allis Chalmers that used Detroit Diesel automotive engines until they bought Buda in the 1950's.

We don't normally think of IH as being a player in big diesel engines but in the middle of the 20th century when they were making a serious play in the construction machinery market they very much made their own engines. In the early 1980's IH nearly went broke and spun off the construction machinery division to Dresser and now it has all but vanished, but I grew up thinking there were very much 3 viable choices of bull dozers, Red ones (IH), Orange ones (AC), and Yellow ones (Cat). Then Yellow overwhelmed, and it has only been in recent years than any construction equipment maker has dared to paint their equipment any color except yellow.

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