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aac's DIY RAC link project


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Intro 1.0
Following on my review of the IDO Fast SF:  my Helmet Build Project.
One of the first things I definitely wanted to try where the RAC Arms.

This is a concept of Ops Core where the headset bracket is attached to the back of the ARC rail  (Accessories Rail Connector) instead of at the top. Like with the COMTAC rail mounts, this frees up the upper part of the ARC rail for other accessories such as lamps.


2.0 AXL Advanced
The Ops Core RAC headset is quite an expensive item with its $1300, and many LE and military units still use the COMTAC.

AXL advanced from Texas developed something inventive, the RAC link
This is an adapter with which you can connect your (old) COMTAC to the ARC arms.


The AXL RAC link consists of Tegris loops which hook behind the “ears” of the COMTAC , and are held together by a central post, which can also rotate in the RAC arms.
a complete RAC link kit (ARC arms included) cost $215, thats $1085 less than a full RAC headset !
Below some photo's of the AXL RAC link spotted in the wild.
rac link collage3.png (3.35MiB)
rac link collage2.png (2.59MiB)

3.0 GeGe Store
This construction also greatly stimulated my DIY urge, it appeared that ARC arm replicas can be found on Ali express,(quite cheap) 
I found mine at GeGe Store, quite an interesting store by the way. Where I already got some items from like my Ronin Task Force belt, Kagwerks S7 Case, and Crye Pads

Make sure you take a look at GeGeStore anyhow 


4.0 Tegris
Tegris, is a kind of Carbon fiber filled PE , it was bit more difficult to find, there are no CN repro's of it AFAIK,
When I sant an email to the manufacturer Milliken , they turned out to be very helpful and almost immediately offered to send me some samples, a pleasant surprise.
Tegris is a very solid, tough, strong, woven thermoplastic, and exist in many colors and thickness, (expressed in layers)

5.0 Reversed Engineering
And for the rest it became DIY, recently I also entered the digital metal-age (CNC, Solid Edge drawing etc..) 
I started by drawing the central clover-shaped post, with only some Google images as reference, ruler, calculator, and Solid Edge.


6.0 CNC Machining
When I finally had my sketches ready, I could start making a CNC program, and finally mill the parts of the central clamp. 
I chose to mill these from aluminum instead of plastic (like the real AXL), because I find it a bit more editable for small, tight details, and also stronger.



7.0 Assembly
Adjusting to the RAC arms took a bit of Dremel work in the end before it would run smoothly enough.


And then it was time to get my old , COMTAC II (Ztac) , and to “reverse-engineer” the Tegris loops. First I made a template from plastic sheet, to determine the correct center distances, and then draw the Tegris loops on the Solid Edge, and cut them on the CNC cutter.


With all the parts collected now, I could now start assembling everything.   


Pulling the Tegris loops over the studs of the clamp was quite a struggle, but in the end these came to be super tight, once again, Tegris turns out to be a really strong, tough material.


Here the Earpro's are finally attached to the RAC arms, and the cable of the Comtac neatly routed in the attachments provided for that purpose on the RAC arms


8.0 The End Result
Last step, slide the RAC arms into the ARC rail until it snaps into the slots.
here's the result on my FAST SF


The whole assembly looks very good IMHO, and also fits well, the RAC arms can be set in 3 positions, by pulling them open. When you pull far enough they lock into a certain position, the spring pressure is quite strong, and the clicks are not very clearly felt, when you press the black button at the bottom the arms spring back into the closed position, which happens with sufficient force

1. Closed position the cups are pressed against the ears
2. Ventilation position: the ear cups stay in front of the ears and an airflow can pass
3. Stow position: now you can rotate the arms, and Comtac on the back of the helmet.
This is quite fiddly, with some practice it works a bit better, but still…     

It also means that your headset is now always attached to your helmet, and can only be used like that, plus always the extra weight on your head and neck, it seems to me that this set-up is best suited for DA configurations.

Be sure to check out my full RAC Link photo album here








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