1 Introduction
2 In-situ underwater restoration
3 Brushless angle cleaning brush
The device is designed for the preliminary phase of the process of conservation and restoration of cultural heritage,
namely the cleaning operations that allows a first removal of impurities and sediments from artefact. Specifically, the
quick release chuck can fit various types of brushes in terms of shapes and material. In addition, the device can be
used as an angular grinder by installing a traditional disc blade, along with the adapter, on the M14x2 chuck.
In the angle-brush configuration, a 1750 W brushless motor allows a no-load speed of 1000 / 1500 RPM. This two
particular speeds have been chosen after cleaning test on a specifically designed test rig. Speeds can be selected by
means of a 3d-printed magnetic switch placed in an easily accessible position on the tool side. An identical switch
enables to turn on and off the device. Brushes, also developed during MaTaCoS project, differ in size, materials and
bristle configuration. In particular, a set of radial brushes, made of tampico fiber, nylon and abrasive nylons, has been
developed. As a result of rig and in-situ tests, the diameter of certain brushes has been reduced from standard 120
mm (40 mm length bristles) to 80 mm (20 mm length bristles) in order to reduce bristles bending due to water drag. A
stainless steel 3d-printed quick release chuck allows a fast brush installation and switching, removing the need of key
of other tools at once, to the benefit of underwater ease of use. Along with the set of traditional radial brushes, an
innovative 3d-printed tube brush has been designed, fitted with a screw conveyor shape element that allows the
removal of small particles from narrow cavities.
In the angle-grinder configuration a 2600 W brushless motor, fitted in the same device’s aluminium body, lets a
spindle speed of 10000 RPM. Using a standard adaptor for the M14 spindle, a 110 mm cutting disc can be installed. In
both configurations, brushless motors are powered by an 18 V, 2 Ah Lithium-ion battery pack that ensures an
autonomy of 30 – 90 min. Operators can hold the device with one hand directly on the cylindrical motor case and, to
ensure a more precise control of the tool during underwater operations, use a second knurled aluminium handle on
the device side. A removable stainless steel cover protects operator’s hand during cutting operations.
Furthermore, the stainless steel 3d-printed quick-release chuck can be used to install, along with an add-on bracket, a
frontal cup brush suction device. The tool is designed to clean a larger area compared to the one of radial brushes,
while the suction mechanism keeps the contact between brush and surface and, simultaneously, improves operator’s
visibility by vacuum away durst and particles through a flexible hose. The suction is generated by a centrifugal pump
to whom the frontal cup is connected. The pump impeller is moved by the chuck and has been designed fallowing A. J.
Stepanoff one-dimensional design method [X] for a radial flow pump: starting with spindle speed, water flow (i.e. 60
m3 /h) and prevalence (i.e. 10 m) and considered motor power and torque and blade material yield strength, velocity
triangles at impeller inlet and outlet had been defined and therefore established blades profile and volute cross
sections.
Two different battery pack have been developed: the first one cable-connected with the device, the second one
integrated directly on the tool main body, by means of a quick release connector. Specifically, cable connected battery
case allows a lighter, handier and more compact device. On the other side, battery pack must be attached to
operator’s belt by means of a stainless steel carabiner using the battery’s eyebolt. The integrated battery pack, on the
other hand, fits restorers’ need of a simple one-hand battery replacement: by sliding the 3d-printed stainless steel
sleeve, operator can indeed release the flat battery pack and replace it without any further action on the sleeve itself.
The device’s body is made of anodized 6 series aluminium alloy, manufactured by means of a 3-axis and a 5-axis Cnc
milling machines. The same technology has been used for battery packs and knurled handle manufacturing. Moreover,
for components such as spindle assembly, quick release chuck and integrated battery pack sleeves has been used a
hybrid manufacturing process in which 3d-printed parts, made through Direct Metal Laser Sintering (DMLS), have
been post-processed with Cnc machining to achieve higher accuracy and smoother surface finish. For this purpose,
specific expansion clamps had been produced my means of nylon 3d-printer.
4 Brushless hammer drill
If the angle brush is an excellent solution for a quick rough removal of not too tough accumulation of microorganisms
such as algae and molluscs, in presence of dense and strong encrustations is much more effective the use of hammers
and chisels. In order to go further the traditionally carried by hand cleaning operation, letting a higher cleaning speed
rate and, at the same time, reducing the physical effort needed, a brushless hammer drill has been designed.
Furthermore, thanks to its 3 operating modes, the tool can be used also to core concrete samples of submerged
structures such as dams or harbour piers.
Hearth of the device is a piston moved by a wobble bearing whose rotation produces reciprocating motion of the
piston itself, compressing the air inside the working chamber in the spindle cylinder. Thus generated air pressure
propels a steel striker towards the anvil in the cylinder front end, resulting in a stress wave through the device bit. To
power the hammer mechanism, after several rig test, has been selected a 3100 W brushless motor that allows an
impact rate of 0 – 6200 bpm with an impact energy of 3,2 Joule and a spindle speed of 0 – 1400 RPM. In addition,
motor torque allows to core standard 100 mm diameter concrete samples. A 18 V, 2 Ah Li-ion battery pack powers the
brushless motor and, by means of an underwater pluggable electrical connector, can be replaced during underwater
operation.
Hammer mechanism is placed in a waterproof anodized 6 series aluminium case. By means of a selector knob placed
on the left side of the device body is possible to switch between the three modes of operation: hammer-drill, drillonly, and chisel-only. This feature, along with the SDS-plus chuck, makes the device extemely suitable for a wide range
of application, from artefacts restoration to underwater structures maintence.
5 Electric mortar gun
A specific powertool for consolidation phase has been eventually developed. The device aims to facilitate the
structural repair and strengthening, by means of injection of specifically designed mortar, of stone and masonry
artefacts whose deterioration may be accelerated after removal of encrustations due to water erosion. The demand
of a handy, light-weight device has been met by developing a compact, cordless hand-held tool.
The instrument consists mainly in an anodized aluminium waterproof body containing the electric motor along with
gearbox reducer, battery and electronic components. Masonry is stored in a 0,5 L anodized aluminium cylinder
screwed to the thread connector placed on the device’s front end. The material consolidator is compressed in the
cylinder by means of a piston head moved by a stainless steel rack. Rack’s pinion is driven by a dc brushed motor that,
by means of a 215:1 reduction ratio planetary gearbox, provides 225 kg pushing force to easily extrude even dense
compound mortar. Rack speed can be continuously adjusted from 0 to 6 mm/s by means of a knurled knob housed on
the left side con the device body whereas extrusion is performed by means of a magnetic switch trigger placed on the
ergonomic handle. Several nozzles have been designed to accommodate restorers’ needs. Nozzles differ in exit cross
section’s dimension and shape whereas converging angle has been kept around 12° to facilitate mortar flow sliding.
The waterproof aluminium case contains an 18 V, 1 Ah Lithium-ion battery pack. Thanks to an underwater pluggable
electrical connector linked directly to the battery, the device can be recharged without removing battery case.
Handle shape and dimensions match Pheasant S. and Haslegrave M.C. [X] guidelines for hand tool ergonomics.
Specifically, handle ensure a high grip with the operator’s hand and a proper hand grip-forearm angle so that, when
the tool is in use, wrist remains as close as possible to the its neutral position in which strength of grip is greatest,
preventing incidence of work-related disorders.
When a mortar cartridge is finished, it can be replaced by means of a release mechanism that allows to manually
withdraw the piston head pulling back the rack end by means of a plastic handle. Rack withdraw is possible due to a
spring button placed on the right aluminium case. Pushing this button allows a steel pin to withdraw letting the last
planetary reduction stage ring gear at idle then leaving rack pinion free to rotate.
Tool main body consists of a Cnc milled aluminium plate that supports engine gearbox and transmission shaft. A 5-axix
Cnc milling machine has also been used to manufacture the nylon ergonomic handle and aluminium side cases.
Furthermore, wide use of 3d-print has been made for production of small complex shape parts such as rack sliding
guides, electronic components support frame and switch trigger.
6 Test
7 Conclusions