Modèles réduits d'engins de travaux publics et de grues.

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"The aluminum collection".

THE CATERPILLAR 785 TRUCK,

scale: 1/15 th.

LThe plans are the result of the usual process: the measurement of dimensional dimensions on the real machine.

Note that here we are in front of the largest machine studied, therefore the largest model

to reproduce from the Caterpillar collection.

Personal impression at the time of the odds reading:

"Facing a" monster "more than 6 meters in width, more than 5 meters in height,

11 meter long and fitted with 3 meter diameter tires.

Make a statement of dimensional dimensions over a period of 7 days,

execute the most precise plans possible, undoubtedly remains the hardest job

and which most often generates a mixture of tension and stress ...! "

LThe construction of this model is also made of aluminum glued with epoxy glue

for high stresses (reinforced by pegging) and cyanoacrylate glue

for low stresses ".

Production: from February 1998 to May 2003,

totaling: 2750 hours.

The real machine ...

... and its PDF.

Extract from dimensional measurements at the surface mine

de Mercoirol (la Grand-Combe, Gard) 1998/1999.

White helmet, blue jacket ...

... safety boots ...

... the author at work!

The model.

The chassis.

Construction of the chassis.

All the parts constituting the frame are traced, cut and folded by hand because it is necessary to respect very precise profiles and dimensions. All cut from 0.5 mm aluminum sheet. The multiple fixings are obtained by gluing (epoxy glue), after having been reinforced by internal screws, installed before the application of the glue, in order to obtain more resistant seals for the different assemblies of the parts.

The body.

It is also made of aluminum sheet 0.5 mm thick and shaped by hand.

It mainly consists of ten removable elements (including the cab), using M1 and M1.6 studs.

Exploded view of the elements

bodywork.

First removable covers.

Second removable cover.

Cabin.

Skirt (left side).

Second platform

with her skirt (right side).

Grille.

The transmission.

SOn the model, the mechanical components which constitute the transmission are present and may be functional. But the option chosen for this model is to stay in a "static" register; it is a choice in relation to the finish aspect of this model.Indeed, we can easily imagine that it can deteriorate very quickly,

at least on this type of construction and finish,knowing all theconstraints

what canundergopublic works machine, especially small.

The kinematics.

She is made of :

- a 12-volt automobile heating fan electric motor drives the rear axle via a telescopic shaft between two cardan joints.

- a gearbox in the ratio: 1/1 and an epicyclic gear at the entrance of the rear axle to the ratio: 3.5 / 1. Some components, such as the universal joints and the toothed crown are made "in house", (molding).

- the rear axle includes a bevel gear in the ratio: 3/1 with differential.

- the kinematic chain ends with a double reduction with an epicyclic train in each hub, with a ratio of: 3.5 / 1 per train.

12 V electric traction motor.

Double reduction with planetary gear

in each rear hub.

Functional organs.

Steering cylinders and bucket.

They are of personal design.

As for the D8K, the option chosen for their operation is pneumatic energy,

this choice is related to the finishing aspect of the model.

Steering cylinder.

Telescopic bucket cylinders

two-stage and double-acting.

The suspension cylinders.

Front suspension cylinder and steering system.

Rear suspension cylinder.

The tires.

They are molded "house" as follows:

1) plaster cast of a drilled drum, all at dimensions slightly higher than the final tire.

2) machining of the different shapes (internal curve, external chamfer).

3) drawing of the different sculptures on its radial surface.

4) carving, one after another and by hand of these sculptures.

5) finishing: soft sanding and painting to benefit from a non-porous surface Once the model is finished, we move on to the construction of the mold.

6) making a circular formwork with a diameter greater than the plaster model.

7) positioning of the plaster model inside the formwork, slightly raised and resting on three studs.

8) immersion up to its radial axis, in a liquid elastomer.

9) after polymerization, total immersion of the plaster model in the same elastomer. Pre-lubrication is desirable to prevent the two materials from bonding together.

10) demoulding at all. Two hollow flexible elastomer half-shells are then obtained and the plaster model is recovered which is intact.

11) hand pouring of a product of your choice in each of the flexible half shells.

12) demoulding of the half-tires which are then glued radially together and machined to remove excess glue. A hollow tire is thus obtained with, in its center, a starting point on both sides.