Holoprojector Servo and Astropixels Mount (MK4 Dome)

Version 1.2

• Added 2 new parts that are specific to mounting in the top “Pie” location. TopHoloFrameServo and TopHoloLockRing.

Intended Design/Use

I designed these parts for mounting MG90S servos and Astropixels to MrBaddeley's MK4 R2-D2 Dome. I wanted to feature moving Holoprojectors in my build and I also recently received a set of Astropixels which I think will be a popular option for other builders when lighting their R2 domes. So I set out to design parts that would bring it all together. I wanted to make a modular system so that adjustments or parts for other applications could be made without requiring a complete redesign of the foundational components. I also wanted to see if I could make it work without altering the original MainHoloA part.

I printed all of the parts with PETG except for the HoloServoHinge which requires a flexible filament like TPU.

If you haven't already, check out MrBaddeley's incredible droid work here:
https://www.patreon.com/mrbaddeley/posts

Information about Astropixels here:
https://r2djp.co.uk/category/electronics/astropixels/

I have tested this in both the front and rear Holoprojector locations. As of Version 1.2, there are 2 additional parts that can be used when mounting a Holoprojector to the top “Pie” panel. Instructions for those new parts can be found at the end.

I hope these help you!

Printable Parts

HoloFrameServo.stl
HoloPlateBracketTight.stl
HoloServoHinge.stl
HoloLEDPivot.stl
HoloLEDBarrel.stl
HoloLEDCage.stl
TopHoloFrameServo.stl
TopHoloLockRing.stl

Print Settings

0.2mm Layer Height
3 Perimeters
15% Infill
No supports required

Mounting Hardware

(Qty 2) - M3 x 6mm Socket Head Cap Screws

Assembly Instructions

Start by inserting the stock HoloFrameA part followed by MainHoloA into the hole in the dome. Ignore the clamps, they helped me take photos.

Place the new HoloFrameServo part on top of the previous parts. 8 different orientations are possible with the latest part (v1.1) simply by rotating it to fit your build. Make sure one of the rectangular alignment holes around the perimeter ends up positioned at 12 o'clock for things to lock in properly.

If using the optional new HoloSlideBracketTight part, first take note of which side has the small protruding tab that locks into the hole mentioned in the previous step. You need to make sure it's facing toward the hole (away from you in the photo above). Secure the previous parts by sliding it into the slots on either side of the Holoprojector. It's a tight fit, go slow and make sure that the tab seats into the hole creating a good lock. There will be a little bit of “play” or “wiggle room” when done, but it should feel pretty snug.

Next we place the servos into their mounting locations. Not the orientation before you proceed.

Before you install the servo mounting screws, check to make sure that their wires clear the underside of the HoloFrameServo part. You don't want the wires to be caught or pinched. I've also run the wires from the servo on the left of the picture above under the servo itself.

Secure the servos to HoloFrameServo using the small self-tapping screws that came with the servos. The holes in the printed part are not tapped, so go slow, and don't overtighten the screws. You may notice I've used some zip ties to help manage the cables - totally optional and up to you.

Next we assemble the flexible HoloServoHinge part (remember to print this in a flexible filament like TPU). Place the HoloServoHinge part such that the recessed areas for the servo horns face up. I find it's easier to press the horns in fully with it laying this way.

Press each servo horn into place being sure to check the orientation so that the splined holes are facing out or toward you as the photo above shows. It needs to be like this or they will not mesh with the servos.

Before attaching the flexible HoloServoHinge part, check that your servos are in their neutral position (the midpoint between their min/max rotation). Once verified, mount the HoloServoHinge part aligning the previously installed servo horns as seen in the photo above. This will ensure that you have the fullest range of motion.

Secure HoloServoHinge with the servo horn screws that came with your servos. These are short but there should be enough thread to get good engagement. Don't overtighten and try not to deform the flexible HoloServoHinge part too much as you tighten the screws.

Next, we assemble the parts that house the Astropixels PCB (light module) and act as the lever/pivot for moving the original MainHoloA part.

Above is a photo of an Astropixels PCB which you will need shortly.

Place the HoloLEDBarrel part such that the recess for the Astropixels PCB is down or away from you as in the photo above.

Place HoloLEDPivot on top of HoloLEDBarrel as seen in the photo above and make sure all the holes align.

Secure the parts to each other using the M3 x 6mm Screws. Note that the holes in HoloLEDBarrel are threaded but do not overtighten. Also note that the screw heads will not be flush when fully installed (as seen in photo).

Now place the Astropixels PCB into the side of HoloLEDBarrel that has the recess shaped like the PCB. Note that there is only 1 orientation that will work due to the pins needing to pass through the hole.

The Astropixels PCB should fit in with very little wiggle room. It should also sit flush with the printed part as seen in the photo above. Check before moving on.

The HoloLEDCage part features 2 locking tabs that match slots on the sides of HoloLEDBarrel. Be careful when aligning and pressing the HoloLEDCage into place. The tolerances are tight, but you should be able to press it on with a little force and will hear/feel a “click” when it is attached. This should mate against HoloLEDBarrel with no gaps and secure the Astropixels PCB into the assembly. If you ever need to remove HoloLEDCage, you can gently pry the tabs open a bit (using a tool if necessary).

The photo above shows how the assembled parts should look.

Insert the assembly into MainHoloA. It is intended to be a friction fit. It shouldn't spin or move freely.

Finally, press the HoloServoHinge onto the ball of HoloLEDPivot. It should only take light force, and should have more than adequate engagement to not come apart under normal servo load. The wires for the Astropixels can also be attached through the rectangular hole in HoloLEDPivot. At this point ensure that HoloMainA and HoloLEDPivot are flush with each other as seen in the photo above.

Top “Pie” Location

Start by inserting the original TopHoloFrameA part into the original HoloPie part and take note of the orientation of the curved cut in the TopHoloFrameA piece. It should be aligned as shown by the orange arrow in the image above.

Insert MainHoloA through the previous parts (shown above with the internal parts from previous steps already installed). Place TopHoloFrameServo over MainHoloA and once again make sure the curved cuts all align as indicated by the orange arrow.

The following steps require the TopHoloLockRing shown above. It is designed to hold the previous parts together and replaces the original HoloLockRing part. It still features a small locking “tab” on one side and the overall “C” shape allows it to be installed around the larger TopHolloFrameServo part. It's a bit tricky, so try and read/follow along.

Insert one end of the TopHoloLockRing into one of the retaining channels. I like to start with the one indicated by the orange arrow in the photo above. Just get it started and make sure it's in the channel. The other end of the TopHoloLockRing will be out/above the opposite retaining channel as indicated by the green arrow above. This is fine for now.

Rotate TopHoloLockRing clockwise to feed it through the first retaining channel (orange arrow in photo) until the opposite open end of the “C” clears the opposite retaining channel.

You should be able to get the other end of TopHoloLockRing into the second channel as indicated by the orange arrow above. You may need to carefully bend it a bit to get it started.

The orientation of all parts as seen in the photo above should allow for easy installation into the dome. This should give you the most clearance. Rotate the TopHoloLockRing and TopHoloFrame Servo parts until everything lines up. Also ensure that the small locking tab of TopHoloLockRing is fully seated/engaged with the matching hole in TopHoloFrameServo.

You can now install the servos and other components as described in the assembly instructions for the front/rear Holoprojectors earlier in this document.

Notes

Version 1.1

• HoloFrameServo now has 8 holes at 45 degree increments for the locking bracket that allow more flexibility in orientation when installing. 
• HoloFrameServo height was increased by 1mm to allow the bottom of the servos to clear the lower ledge of the dome in some orientations.
• HoloLEDPivot height was increased by 1mm to match the servo height adjustment.

Version 1.0

• Initial release

* For personal use only
* Not for sale