CREATION OF THE CHASSIS (I)

The leaders of the chassis creation process are the Swedish team and the French team with the help of the Croatian team.

One of the objectives of the DEMETER project is the creation of a Mine detection Rover. The following short presentation outlines the design of the Rover´s chassis, in order to produce a chassis that corresponds to the needs of a dedicated all-terrain mine detection vehicle.

 

The first steps we took was to study a commercially available chassis model of a Leopard II from the Torro brand, which are very robust vehicles that function adequately on all types of terrain. The commercially available chassis became our development test model.

 

studying the chassis
studying the chassis

Once the engineering of our test model had been studied, Alexandre Catala automation teacher and his colleague David Pugnet and Damien Barbe  began to design sketches for the creation of a new chassis.

chassis cad designing
chassis cad designing

The students participated very actively in the process and it helped them to put into practice all the CAD knowledge learned so far in a real project. In addition, this project is an excellent exercise to improve your English language skills.

 

cad designing workgroup
cad designing workgroup

First we chose to create an aluminium frame by a plate folding and adjustment technique. Regarding the fixing points for the side wheels, we have decided to carry them out using CNC machining.

 

                                                                side view of the rover with wheels and suspensions

One of the most complex parts of designing and machining is the suspension, which is based on torsion bars. The design and machining of the suspension system required all the expertise and knowledge of both teachers and students.

 

 

    Wheels and suspensions

Torsion bar

 

Below is a video explaining the technical operation of the rover:

When the different study phases were completed, we designed and visualised the new rover on 3D software, so that its design could involve as many students as possible from our school.

 

3D Overall drawing

3D Wheel support

 

When the 3D model was finished we started manufacturing the chassis by bending sheet metal. Damien Barbe aeronautical structure teacher , guided his students until the realization of the first frame. Numerous skills were acquired: drawing reading, cutting sheets, plotting, machining, bending and adjusting the sheets together.


3D rover model on the screen

Adjusting the aluminium plates

 

At the same time, we asked for highly motivated machining teachers to work on the project. Olivier Couzy, Mathieu Soucasse and Laurent Massoulard (machining teacher) worked with their students on the programs as well as the machining of the rover’s wheel supports.

First wheel support machining

The machining work of the different parts of the rover allowed the involvement of many students, always with a lot of motivation because the final object is concrete.

First wheel support before demoulding

                                                                        Final result ready to be assembled

To allow the wheels to be assembled and guided to the torsion bars, we also had to machine a bearing shell. This intricate part was machined with a CNC turning and milling machine. Students were able to learn many machining skills.

Bearing shell machining on turning machine by a student

The machining students also machined parts called “ball bearing support” for guiding and maintaining the track. Then the industrial maintenance students carried out the assembly operations. During these activities all these students were able to develop several skills, reading drawing, machining with a CNC turning machine, plotting, drilling, tapping and fitting.

                                                                   Ball bearing support after CNC machining

Industrial maintenance students during a tapping operation on the ball bearing supports

Wheel support and ball bearing support assembled on the frame

SOLVING A TECHNICAL PROBLEM WITH OUR DESIGN

During the assembly of the parts related to the wheels and the suspensions we noticed design errors. Indeed a bad position of an suspension abutment prevents us from adjusting the wheel cranck to the bearing shell. Therefore no wheel can be mounted.

To solve this problem Alexandre CATALA and François Tollite (mechanic and drawing teacher) decided to modify the position of this abutment in order to allow this possible adjustment. The students of these teachers had to carry out all the measurements in order to know exactly the modifications to be made with great precision. For this activity the students worked on skills on understanding mechanical connections, reading 2D and 3D drawings and measuring with precision tools.

 Support whell drawing before modification

 Support whell drawing after modification

SOLVING AN OTHER TECHNICAL PROBLEM ABOUT FRAME DRILLING

We encountered another technical problem when drilling the frame through the drilling of the support whell. By only using the drill bit it is impossible to guide it and obtain perfect concentricity between the both parts.

To solve this problem we decided to make a drill barrel to guide the drill bit during machining in order to obtain perfect concentricity.

To design this new maintenance object, Patrice SUIN (teacher of physical and mathematical sciences) also invested in this project had the idea to design this object for our students using a drawing design software that only uses the mathematical rules to make the design (GéoGébra).

Drill barrel drawing made by industrial maintenance students with 3D AND 2D mathematical design software

Students using Géogébra sofware to design drill barrel under the supervision of Patrice SUIN. During this activity, these students were able to work on many geometry skills. Place a point, draw parallel, perpendicular lines, place and draw a circle.

Then the students used their drawing made on géogébra to design the drill barrel on a 3D design software (solidworks) then the drill barrel was printed with the 3D printer.

Drill barrel drawing designed with Solidworks 3D

The drill bit guided by the drill barrel. Ready for drilling !

Some explanations about the drill barrel by an industrial maintenance student

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