Digital Tachometer for Harley Davidson Sportster (Part 12 - Housing design and brackets)02 Mar 2017 - 0 Comments
Following list will summarize the parts included on the housing and bracket assembly for the speedometer and tachometer:
1-Dual gauge bracket (ref#: 67338-97) (seen on Part5)
2-Gauge cover and glass from an old analog speedometer: In order to avoid humidity issues I will reuse the gauge cover from an old analog speedometer bought some time ago to get some ideas for this project.
3-3D printed housing:
Following design has been done with FreeCAD v0.15. According wiquipedia, FreeCAD is a parametric CAD 3D design tool. It is opensource (GPL and LGPL license) and focused in mechanical engineering, industrial engineering and architecture. It is available for Ubuntu by typing the following command:
It can not be compared with other professional CAD tools, but FreeCAD offers enough resources to allow the design of complex models. The housing, as you will see, is quite simple and as beeing my first 3D printed design I feel quite satisfied. The design can be summarized in 5 steps:
3.1- Exterior part: In workbench “Part Design”, we will create a sketch on the X-Z and will draw the shape of the housing. Afterwards, with the option revolve, we will be able to revolve 360º in order to have the basic housing shape.
3.2- Base for the screws: In order to hold the housing to the bracket, a rear cover will be needed. In order to do this, 4 cilyndrical shapes will be added to the base as material reinforcement. Creating a new sketch in the top base face, we will draw 4 circumferences and afterwards we will extrude them 6mm in the +Z direction.
3.3- Switch hole: Same as before, we create a new sketch in the top base face and draw a circumference and afterwards we execute the pocket operation in order to create the hole (-Z).
3.4- Bracket “horns” and wire holes: As we said at the beginning, this bracket has a special “horns” used to center and fix the speedo and tachometer units. We will need to create an orifice in the housing to allow these shapes to fix the unit and at the same time to allow the harness to go inside and connect with the PCB. This time, we create a new sketch on the bottom base face and then we perform a pocket upwards (+Z).
3.5- PCB placing stands: In order to place the PCB inside the housing we will create interior side stands. To do so, first we will create a new sketch in a parallel X-Y plane 15 and 27 mm over the top base face. Afterwards, we can extrude 3mm in +Z direction in both sketches.
3.6- STL File: This is the file we will have to send to the 3D printing company of your choosing. Basically, once the design is finsihed, it is needed to glue all the extruded parts. To do so, go to workbench “Part” and in the toolbar go to Part > Boolean > Union. Once this is done, we have finished our part. Now we have to export it as .STL by going to File > Export and then selecting the Mesh Formats (.stl) format.
| FreeCAD v0.15 File
STL for 3D file
Why did I not use the old analog speedometer housing?
2 main reasons:
1- General dimensions were not appropriate for fixing the housing to the bracket or the PCB to the housing.
2- I wanted to try 3D printing :D
Finally, here you have the 3D printed housing.