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Mucking Machine "Finley"


Eimco 12B

Mucking machines   are small compressed air operated front end loaders designed for underground mining. Mucking machines were the first that were introduced in Bisbee mines in the late 1930’s to early 1940’s replacing hand mucking in the crosscuts and later into some stopes. In Bisbee the mucking machines were referred to as Finlay’s (in Bisbee pronounced “Finley”) no matter what brand or model with the exception of Cavo’s. The Finlay name comes from one of the inventors John Finlay who with Edwin Royle developed the first successful design. The Eimco 12B was the dominant mucking machine used underground in Bisbee. The other types of mucking machines used were the Eimco 21, Gardner Denver GD9, Atlas Copco Cavo 310 and 310L.   The basic operation of mucking machines is similar between types; the main differences are in the set-ups between drifts and stopes.


Filling a A car with Eimco 12 circa early 1940’s

      A typical drift setup for mucking with a Finlay is using either a canton or super switch installed with slide rails advancing to the face. Super switch or a canton switch is used to exchange full cars for empty cars. For quick loading the switch should be set back about 40 ft. from where the mucking is to take place. Super switches are to be used only when H cars are employed. Slide rails are rails that are laid down sideways, with the ball placed inside an upright rail. The side rails are then spiked down in a fashion that allows them to be sled forward with a bar or pick. The side rails are used to temporally extend the permanent rails to the face so mucking could be completed. The mine car to be loaded is usually connected directly to the Findlay so it can be towed. On occasion the mine car will be blocked into place and the Findlay will load a bucket and then back up to where the mine car is then load it. If loading E cars, a modified 12B is used that has a piece of metal welded on it to raise the rocker arm.  This modification keeps the bucket from catching on the lip of the E car. 

Loading cars with Canton switch

Loading cars with a super switch

     The Finlay is operated by a miner standing on a step located on the side of the machine.  In this position the operator could work the two controls, one for the bucket movement and the other regulates the Finlay’s travel. In mucking the operator will drive the Finlay into the muck pile with a lowered bucket until the machine stalls with the wheel still turning. The operator will crowd the bucket into the muck to fill it using a few quick jabs of the bucket control which causes the bucket to rise in the muck filling it.  The bucket when full will hold between 4 and 6 cubic feet with and could remove 30 cubic ft. per minute. The bucket is attached to a drive motor by a rocker pull chain located at the bottom center of the rocker arms.  When the bucket is full of muck the operator actuates the control for the drive motor, force is then exerted on the rockers arms. This force rolls the bucket rearward with such inertia that when the bucket hits the shock absorbing stops the muck is thrown from the bucket into the awaiting mine car. The Finlay will bounce and the front wheels will raise a couple of inches off the rail when the bucket hits the spring stops, this will also occur when the bucket is roughly let down raising the back wheels. The dumping of the bucket needs to be done in one smooth motion to keep from spilling muck on top of the Finlay.  While mucking, advance the center of the muck pile ahead of the sides this will keep the track clean. The muck pile will need to be kept sloped for safety. When finishing up the mucking do not drag the bucket against the face to keep from damaging the machine. Raw drift blast will fill from 26 to 32 H cars, timbered drift blast will fill 50 H cars.  All types of mucking machine are dangerous to use, the bouncing makes them easy to derail. Common accidents are operator getting pinned between rib and the machine, also the operator getting hit with the bucket.  


Finlay’s and Cavo’s were also used in cut and fill stopes.  A Finlay stopes will be on the level with a cross cut from the main drift entering it. Inside the stope a slusher will be set up to drag the muck to tracks that have a Finlay on them. The Finlay would then load the muck into cars which were taken out.

Cut amd Fill stope using a mucking machine

       The Cavo 310 is basically a rubber tired Finlay with a dump bed attached.  These were brought underground in Bisbee for use in the cut and fill stopes. The typical scenario is a open stope with good ground and little timber. The stope will have a pocket with a grizzly on it going to the level below. The Cavo will load its bed from a muck pile and then go and dump into the pocket. The operation of the Cavo is similar to Finlay’s. The mucking should be started on the right side first, this is the blind side of the Cavo and will prevent it from running over boulders which can cause the loader to turn over or throw the operator. The Cavo should be advanced into the muck pile with the bucket down, raise the bucket as the machine is moved forward filling the bucket. Then discharge the load into the Cavo’s dump bed and back the Cavo up a little so the bucket can be lowered to the ground. Repeat this until the dump bed is filled. Then the Cavo is backed up to the pocket and dumped. When mucking, avoid spinning the tires this causes tire damage. The operator needs to always control the Cavo from the platform this will prevent them from running over themselves. The operator will have to pay close attention to the bull hose (4”OD air hose) so it does not get run over.  The Cavo’s bounce is greater than Finlay’s because of the tires this makes them very dangerous to operate.


Diagram of Cavo 310 mucking a stope

Eimco 12, 12B and 21 mucking machine


12’s are the earliest version of Eimco products used in Bisbee and are sometimes referred to as 11’s. The 12 version that does not automatically reposition it’s self for a straight discharge of the muck into the car by the machine.( this was corrected in the 12b  version) By the 1960’s these machines had fallen into disuse were rarely used.  The 12B was the prevailing machine used underground mines worldwide until the introduction of the LHD. 12B’s are currently still in production with used ones still commanding between $4,000 and $6,000.  Bisbee only saw the use of a few 21’s because of large drift size need to operate them. They are still made today current prices of used models are $12,000 to $14,000.

Eimco 12B Specifications


  Year introduced                                        1938

   Weight                                                       4200 lbs

   Operating Air pressure                            60-125 PSI

   Air consumption                                       250 cubic ft


Eimco 21 Specifications


Bucket                                                        7.5-10 cubic ft

Weight                                                        7200 lbs

Diagram of  Emico 12b

Cover of Eimco 21 brochure   circa 1970’s

Gardner Denver GD9

 These machines were not popular, none of the current tour guides remember them in use. In other mining districts I have seen almost brand new ones abandoned while their worn out 12B’s are in use.

Diagram of GD 9 mucking machine.

Atlas Copco Cavo 310  & 310L

The 310 is most modern piece of mining equipment used underground in Bisbee. Introduced in Bisbee the 1970’s, a limited number were purchased and saw use  in  the boreholes at the Cole Mine.   They were continued to be used until the Bisbee mines were shut down. Rebuilt 310’s are currently available, as are parts.

Cavo 310 being used In the Cole mine

Cover of Cavo 310 brochure circa 1970’s-1980’s

  Cavo 310 specifications

Bucket         4.4 cubic ft

Dump bed capacity   35.3 cubic ft

Tramming speed at 85 psi    4.6 ft per second 

Tramming speed at 65 psi      3.3 ft per second

Working pressure Cavo 310   70-100 Psi

Working pressure Cavo 310L    60-70 PSI

Weight 6000 lbs

Wheel size 9.00 X 10” 12 ply

Tire pressure  55 psi

Wheel size alternative 8.25 X 10”. 10 ply

Tire pressure 65 psi

                              Other names for mucking machines                                                                      

Overshot shovel                                                                                                             

Overshot mucker                                                                                                                        

Overhead shovel                                                                                                                             

Rocker shovel  

Mine car loader                                                                                                                              

Mucking machine                                                 Used in Bisbee                                                    Mucker                                                                   Used in Bisbee                                                         Auto loader                                                                                                                                   Finlay                                                                       in Bisbee pronounced “Finley”


Julian Castillo  2010, pers. comm., 2 December 

Code of Safe Practice for Drift Mining July 1 ,1955, p34-45 Phelps Dodge Corporation

Code of Safe Practice for Mechanical loader March 17 1967, p1-19 Phelps Dodge Corporation

Code of Safe Practice for Operation of Cavo 310 Auto Loader April 11 1974, p1-23 Phelps Dodge Corporation

Eimco 12 & 21 Rockershovel Loaders Rail mounted Air powered loaders for Small and Medium Sized Headings, 2002 Eimco Elecon

Eimco 12B Rockershovel, Trident  S.A. circa 2009

The Eimco Rocker Shovel loader Model 12B Historic Mechanical Engineering Landmark September 4, 2000 p.1-11 ASME international

Henry Hernandez  2010 pers. comm.,  24 Dec

Loading Machine U.S. Patent 2,159,180  EB Royle, May 28 1937

Richard Graeme IV 2010, pers. comm., 8 February

Richard Graeme III  2010, pers. comm., 2 February

Pete Oiller 2010, pers. comm., 8 December

Vehicle Construction  U.S. Patent  3,393,759 D. Gustavsson, April 5 1968

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