Rubber tube Slingbow++ Arms for the Adderini

cults3d

After designing the first XL arms for the Adderini I did somewhat of a "loop" design for the Baraba which allows you to combine a self produced bow string with Theratube of your choice. This was following the design of Alex76 (https://www.thingiverse.com/thing:5318878) but I didn't like that it required so many screws and is rather complex to print. Applying the "tube" design for mounting the loops to either Adderini or the Baraba seemed much more logical to me. I consider the "loop" approach as well as the shorter slingbow arms somewhere in between the original Adderini arms with Theraband and my other XL arms using only one tube. In regard to tube length I can not really give you a good hint. Alex76 states 20 cm for each side (with a bit shorter arms) and from my previous experiments with single tubes and the longer XL slingbow arms of mine I also went for 10-12 cm Theratube silver. Keep in mind that double tube means double draw weight in general. The slingbow++ arms a somewhat shorter than the XL arms which reduces the torque on the arms themself as well as the Adderini but I would rather start with may be 18 cm per each side if you use Theratube Silver or some stronger rubber tubes from Ali Express. Those little plastic balls in the end of the Tube make adjusting pretty easy. Use some common sense. I broke two XL arms being printed in PETG with 100% infill simply because I thought to myself "Hmmmmm....this could also work for Theraband Gold". You have be warned :-) Of course as every rubber, the tubes will wear out after a decent amount of shots. You can see the degration at any contact area of the tube (e.g. holes through the slingbow arms or where the tube touches the bowstring). If any "cracks" start appearing or the rubber looks strange simply mount a new piece of tube. You should also pay attention to the holes in the slingbow arms as well as their borders. Use fine sandpaper to smooth out any print artifacts. Applying some "grease" which is suitable for rubber in this area (silicon grease should work) will not hurt either, I guess. For standard use (as described above) I guess PLA will we always sufficient if you use a decent wall thickness and somewhat reasonable infill (e.g. 1.6-2 mm / 30-40% infill). If unsure, use a more robust filament such as PETG. For PLA I found eSun PLA+ being pretty reliable.