The A2 crusher is mounted on cast iron wheels. It was last on active duty in the early 1990s at Markku Hokkanen’s farm in Keuruu.
There, it was used alongside a tractor to crush piles of stone collected from the farm’s fields. “I think we crushed a total of 700–800 cubic meters of stone with the A2. The crusher’s 22-by-28-centimeter jaw could take chunks the size of a human head, and the jaw crushed a trailer load of stone into rubble in a couple of hours,” Markku Hokkanen says.
“You had to be careful to keep the crusher’s speed at a maximum of 300 rounds per minute. If the speed was any faster, the working power was completely lost. You also couldn’t go near the crusher, as the jaw could shoot pieces of stone up into the sky.”
Markku Hokkanen shows the size to which the Lokomo A2 was able to crush head-sized chunks of stone.
Crusher technology from 1858
Keijo Viilo, Research Director at Metso Minerals, knows well the origins of the technology employed in the Lokomo A2 jaw crusher.
“The crusher is known for its double toggle technology, developed and patented by the American Eli Whitney Blake, working in New Haven, Connecticut. He won a two-mile road contract from the city and thought that it must be possible to develop a mechanized device to produce the crushed aggregate, earlier made manually with a sledge hammer.”
“Blake designed a device where the crushing motion was implemented with the help of a fixed and a moving jaw, an eccentric shaft, six different joints and two toggle plates, supported in a cast iron frame,” Viilo explains.
“In a Blake crusher, the pressing motion used for crushing is in the right direction, which saves wearing parts. Drawbacks include a heavy and complex structure and stones jumping upward.”
One of the drawbacks of the Blake-type Lokomo A2 crusher, presented here by research director Keijo Viilo, is the small stroke at the top of the jaw.
Lokomo designed its own Blake crusher model in the early 1920s
The first Blake-type crusher was designed on Lokomo’s drawing board in Tampere at the beginning of the 1920s. A total of four crushers of different sizes were created in the series, some of which were delivered mounted on cast iron wheels.
In a crusher catalog of the time, the A2 model was described to be well suited for smallish building sites and road construction, where a lightweight machine that is easy to transport was needed. Already in August 1921, Lokomo arranged a crushing demonstration for the press and customers at its factory.
Lokomo manufactured Blake-type crushers until 1953. After that, they were taken over by jaw crushers equipped with one toggle plate, on which the current C series equipment is also based.
Attempts to crush aluminum in addition to stone
The Lokomo A2 crusher was probably dispatched from the factory to Finnish crushing sites in the 1920s. At the end of its career, a junkyard in Eura acquired it for crushing aluminum cylinder heads.
However, the A2 was not designed for crushing metal, which is why the junkyard sold the crusher to Markku Hokkanen in Keuruu, Central Finland.
The cleaned-up and painted Lokomo A2 is now on display together with three other historical crushers, representing Metso’s first steps in the technological development of mobile crushing equipment.
On January 12, the A2 arrived back to Metso’s Tampere factory, from where it was dispatched in the 1920s.