tempestvr

December Blog - Sneak peek at SR6 Alpha

Added 2020-12-22 16:48:37 +0000 UTC

Hi Guys,

It’s time for a bit of show and tell on the SR6 design I have been working on recently, which I plan to get out before Christmas. There’s still time!

Over the last couple of months I have managed to get a prototype 6-axis stroker design working with a special set of “breadboard” components. This was essentially a base and a set of brackets that allowed me to move the servo mounting positions around to try out different configurations.

My aim this month has been to turn this arrangement into a set of parts that you guys could easily assemble for yourselves - SR6 Alpha. I'll get the STLs and software for this out in the next few days. The eventual end point, of course, is a set of build plans just like the OSR2, but that won't be this month as I am running out of time!

It’s worth saying at this point that I don’t intend SR6 as a replacement for OSR2. It’s a parallel, more advanced version of the same concept. Both machines use TCode and therefore both can be driven by exactly the same apps and plugins.

The concept I have had for SR-6 from the beginning was to replace the OSR2’s main arms with two triangles, each controlled by a pairs of servos. These four servos are the main driving force behind SR6, and can thrust and roll the receiver, just like the OSR2. Unlike OSR2 they can also move the receiver forward and backward, and in theory a bit of twist.

This arrangement works very well, and as it turned out these four servos in their brackets went straight down onto the breadboard base and I never actually had to move them again.

Six degrees of freedom requires six servos, so SR6 needed to have two more servos. Arranging these to get the kind of movement control I wanted has been the most challenging part of designing the SR6.

The approach I have taken is to have the 5th and 6th servos act like the pitcher servo on the OSR2+. I tried several configurations but the trick turned out to be to arrange the servos facing inward, with the linkages angled diagonally outward. In this configuration moving these together has the effect of pitching the receiver, and moving them in opposite directions will move the receiver from side to side.

Now that I have a configuration that works, my aim has been to come up with the simplest possible design for you guys to build.

OSR2 was designed with this philosophy and in its simplest form it’s actually just 6 3D printed parts. SR6 is quite a bit more complicated, with a total of 16 3D printed parts.

I recommend that anybody who wants to build an SR6, especially the Alpha release, try their hand on an OSR2 first!

The receiver has been relatively straightforward. Essentially it’s the same as the basic OSR2 receiver, but with four contact points instead of just three. In fact for the prototype I literally used a mirrored version of the OSR2 receiver. I have since produced a purpose-designed SR6 receiver for the alpha-release.

Something that I will definitely be adding in the future is a twist receiver for SR6. The twist that the main arms can produce is very small and not worth implementing in my opinion.

The arms and links I will be releasing in the Alpha release are pretty basic and derived from the OSR2 pitcher and support arm. They seem to work well enough though.

Finally there’s the base. Mounting six servos in a 3D printed component is a bit more challenging than just two, especially as the whole arrangement needs to be very stiff for the concept to work. There’s also not a huge amount of space inside the box with all six servos in position.

The arrangement I have gone with for this Alpha release is a two-part fully closed box that all six servos are screwed into. The Romeo and power supply are mounted in a removable tray, which is inserted into the lower section. This might turn out to be a bit too cramped and clumsy and need re-visiting, but it seems to work okay for now.

I’ve still got some work to do on the software side of things, but I think the hardware is pretty much there now. So this is what I intend to release to you in the next day or so. Stay tuned!

Merry Christmas!

Tempest

Finally, here’s a rough parts list: