I’m involved with the burgeoning Wellington Maker Group, a collective of people that like to create something from nothing in their spare time. As part of this group I’ve taken a 1/20th shareholding in our very own Makerbot Thing-o-matic and since I was part of the core group that assembled it, I’ve been lucky to get some early build time on it. At first I got involved with the whole thing just because it’s totally cool. I had no idea what I wanted to build. In the end I needn’t have worried as mother necessity gave birth to my invention.
Me, my brother, my brother-in-law and an old co-driver of mine all own the ubiquitous Logitech G25 to add realism to the online racing simulator we all play, rFactor. The G25 is a great wheel. It provides dynamic feedback which enhances game play well beyond any other controller on the market. The only downside, in the long run, is the wheel is a bit small. As such, I thought it’d be cool to get hold of a cheap aftermarket wheel and replace the original. Fortune had it I managed to pick up a used Momo racing wheel off of TradeMe for a mere $30 the same week the makerbot was built. Here was my project, to make it fit!
The standard name for a steering wheel adaptor is a boss, so what I was wanting to make was a Momo to G25 boss. The first step was to grab the parts, my vernier and open up Sketchup. It didn’t take long to get the basics together. The important things to note are that you only get once chance in Sketchup to change the accuracy of circles. You can see in the model image that the resolution of the circle is very low. More accurately it’s a 24 sided polygon. Turns out Sketchup can’t do true circles, just very high resolution polygons, so when you create a circle that is going to be large enough to have the shape noticeable, up the number of sides, 100+ would do nicely for what I was building but 24 doesn’t bother me at all.
Once the sketch was complete, I needed to get it into STL format. For that there is a SketchUp Plugin. You want to choose MM and then STL. Additionally, you will need to do a ctrl-A to select all (or equivalent in Mac or Linux) to select all of your object before running the export. You will now have an STL file which you will need to import into ReplicatorG.
At first I couldn’t work out why nothing showed up when I used the import function in ReplicatorG. The reason was because I hadn’t built the model around the origin in SketchUp, I had it floating out in space. To fix this use the ReplicatorG menu option of Move>Put on platform which should center your object. If everything has gone well, your item should be rendered in all its glory in the 3D box provided. You have some more options to flip it around if you’re worried about over hangs etc but for me now, everything was perfect.
The next step is to make some gcode. This is the machine language of CNC and what the makerbot thing-o-matic also speaks. Here is where, for me, some of the “magic” or mis-understood parts of the printing process come in. Bruce Hoult, another founding member of the WMG Makerbot group, had done the primary configuration of the bot, so I didn’t really have any problems with the print quality, as he had mostly sorted it. In fact he sent me a file that I needed to import that would enable all the correct options for the gcode rendering. Because each bot can be and will be configured differently, you need to render the gcode, or the bot instructions, specifically for your machine. You can think of the STL file as the common point of reference and the gcode as the specific instructions for your bot. With the appropriate settings I ran the gcode generation. It took a few minutes.
At this point, you are now technically ready to print. It took me about 4 false starts to get a print started properly. Seems there is no pre-warm code in the gcode I generated so I had to manually warm the extruder nozzle up myself using the control panel available in the top tool bar in ReplicatG. Our bot is set to extrude coloured PLA at 195C. After hitting run, the machine centered itself and began the predicted 2hrs30 print job. I couldn’t let it run completely unattended as I was having snagging issues from the PLA spool Bruce had printed but other that I had no problems at all.
It really was quite amazing to hold, what only a few hours earlier had simply been a concept, in my hands and the scary thing is that the next generation will take this ability for granted. Every school will have a 3D printer by the end of this decade and no doubt many homes too. For such a seemingly crude device (stacking hot plastic?!) the boss was strong, rigid and accurate.
Assembly was simple, I embedded the nuts into the designed recesses after cleaning them slightly with a craft knife (overhangs are the weakness of the extruder design). I then placed it on the G25 hub and used the original screws to attach it. The heads disappeared beautifully into the countersunk holes. Next I attached the wheel with my inch long screws which grabbed the nuts perfectly. No overhang through the boss at all means the design is very clean. I’d even managed to get the horn button recess correct and this slipped straight into the centre to give what I feel is a remarkably professional finish.
To top it off, the whole project was a success. The wheel feels great in the simulator and adds further realism to a great game. As with all successful projects they spur you on to the next so I’m hoping the sim will be getting some pedal and seat upgrades! But for now, I’m satisfied….
Whilst there potentially was some ability to make some money out of the project I decided since I’d had so much help in getting it up and running that I’d share the output. As such you can find my Momo to G25 boss on thingiverse and can print it out or play with the design to your heart’s content. Enjoy!