MECHANICAL (DIESEL) EXCAVATOR
model design and text by Mike Stoodley.
photographs by Bruce Neilson.
This is a freelance model generally based on excavators seen in England during the 1930s and 1940s when steam was being replaced by diesel. The model also incorporates some of the features of the old Supermodel SML 19 ‘Meccano Steam Shovel’. It is virtually all Meccano apart from the realistic ‘to scale’ plastic tracks. The numbers in brackets ( ) refer to numbers on the figures.
The model has two means of operation. By hand, using hand wheels (3a) and (13) which drive down to and then through the E20 motor, and by electricity through the E20 motor. When electricity is driving the E20 motor, the hand wheels rotate automatically by being back driven.
Figure 1 Above – Rear of cab.
This shows the rear end plates with the electrical input terminals (A) for electric operation, and the two hand wheels for manually operating. Hand wheel (3a) controls the four basic movements; hoisting, luffing, swivelling and travelling via the E20 motor. Hand wheel (13) controls the bucket arms with Rack Strips and Pinions.
Figure 2 Above – Rear of body.
This shows the E20 motor power source (1a) with a 1/2“ Pinion (1) on the drive shaft engaging a 21/2“ Gearwheel (2) for reduction. The Collar (4a) controls the stop/start lever, while the Axle Rod (4) extends through to the driver’s cab. The Sprocket Chain drive (3) relates to manual control (See figures 1 and 3).
Figure 3 Above – Left side of cab.
This is where things get a bit more complex! The manual Sprocket Chain drive and 1” Gearwheel (3) drive the E20 motor Axle by engaging a 11/2“ Contrate Gearwheel (5) (See Fig. 4) on the motor axle.
The 1/2“ Pinion (13) drives manually the 57 tooth Gearwheel (14a) and the Axle Rod (14) which drives by Sprocket Chain (15) and 3/4“ Bevel Gears (16) (see Figure 4). The Gears (17) in turn operate the bucket arms adjustment by Rack Strips.
From the motor the final reduction gearing terminates in two 11/2“ Contrates (5) which engage long 3/4“ Pinions (6) which are fixed on sliding Rods (6a). The upper Axle Rod 6a carries 1/2“ Pinions (7) and (9) for hoisting and luffing. These motions are automatically braked by Worms (8) and (10).
The lower Axle Rod 6a carries two 3/4“ Pinions which engage 11/2“ Contrates for swivelling (11) and travelling (12)
Figure 4 Above – Winding Machinery.
Most of this view is self-explanatory showing the final drive to the hoisting drum (10a) which is visible. The luffing drum (8) is similarly driven. Swivelling is operated by Contrate (20) whose Rod also carries a 1/2“ Pinion. This engages a 31/2“ Gearwheel in a fixed position on the top of the base. Travelling is activated from Contrate (12) (figure 3) by Helical Gearing (18) by a vertical Axle Rod which goes down into the base of the model. (See Figure 5).
Figure 5 Above – Base with superstructure removed.
This shows an oblique overhead view of the base with one track removed. Following the Helical Gear drive (22) in the excavator’s body, Axle Rod (21) continues down below the swivel gear (23) , with a 1/2“ Pinion engaging a 11/2“ Contrate Gear. (See Fig 7 for on going transmission). The track boom show the jockey wheels (25), track adjustment wheel (26), main drive wheels and 11/2“ Contrate (27), and idler wheels (28).
Figure 6 Above – Base overhead view.
This is self explanatory simply being an overhead view of the spider-with-no-legs, being seven 1/2“ Pulleys evenly spaced in Curved Strips; the swivelling fixed 1/2“ Gearwheel and the trackless boom.
Figure 7 Above – Worms eye view of base.
This is an upside-down view of the underside of the base. Transmission to the drive wheels is routed through Contrate (29), Gears and Pinions (30) and Contrate (27). One of the two track-tension compression springs (31) is also visible, as well as the track adjusting wheel (26).
Limitations and Comments
1 – The completed model weighs in at 72 lb / 31 kg and is too heavy for the E20 motor and reduction gearing to actually drive it along the ground. So the model sits on a block of wood with the tracks just clear of the ground and the tracks ‘travel’ realistically.
2 – With the final Worm gear drive to the hoisting and luffing drums, these two motions are unrealistically slow (but powerful) due to the automatic braking systems via the Worm drives.
3 – The model breaks down into three modules, base, superstructure and boom / bucket. Over the last ten years each has been upgraded to give better actions and a more realistic look
4 – The top and side plates are easily removable to give visual and manual access to ‘the works’.
As with all other models, building this one has been jolly
good fun!
The track plates for this model are 'Flite Top flat
conveyor chain' manufactured in various sizes starting at 1", by the Regina
Group of Italy. The internet site address for this company is http://www.regina.it/flite.htm
and that will provide more details.
This chain is imported into New Zealand by Engineering Plastics Ltd, 42 Bennett
Street, P.O.Box 694, Palmerston North.
