I’ve been messing around with hands free options for vacuglide for a while now, and I’m fairly happy with my current setup, which consists of a bungee cord attached to the top of the receiver, put through a suspended pulley, and then tied off to a point by my side.
In order to make your own you need some kind of clamp on your desk with an arm that rises up slightly higher than your stroke length, some way of attaching the bungee cord to the top of your receiver, and a pivot point to allow free travel of the cord. For the clamp I’ve used a camera tripod arm with multiple points of articulation, but after settling on a good height and spacing I now just use a 90 degree bent piece of all thread threaded into a nut in my desk.
For attaching the bungee cord I made a simple velcro ring, I imagine a velcro strap would work well enough, with 4 holes in it for wire that overlaps in an X at the top. I initially used string, but I prefer wire because it stays closer to the top of the receiver when sized correctly, which reduces the height your clamp has to be set at. I imagine you could 3D print something a little better, but I’ve been happy with this so I haven’t bothered fixing it. The bungee cord is just tied to the top of the X, below is a simplified diagram to better explain it.
At the top where the bungee contacts the arm, I’ve tried a few options. I’ve found that an enclosed small diameter rod is the best, you do have to thread the cord through every time, but it prevents the cord getting a little too crazy and working its way out of a simpler ridge. I’m using a 3mm chicago screw glued in place, ideally you want the cord to glide over the pivot using its stretchiness. And then finally you wrap the cord taut around a point off to the side. The cord should be reasonably taut through the whole range of movement, the stretch allows it to cycle down and remain central while coming back up. With low valve suction you may find pop-off an issue, there’s a sweet spot which can be adjusted by messing with how taut the cord is, too loose and it’ll veer off sideways while moving up, too tight and it’ll pull itself off. I use 3mm bungee cord, you’d probably be fine moving up but if you go much thinner it may not have enough stretch to compensate for the travel.
I have wondered if maybe a counterweight system would work too, but you get to a point where things work well enough and you stop iterating. Weighted rings around the receiver, quick adjustable cord tension, a secondary bungee cord going the opposite direction through the pulley to ensure straighter up and down movement have also been considered, but the goal for me is easy setup so I haven’t tried them. Now I just mount the arm to my desk, attach the velcro ring to the receiver, and I’m done. Taking everything apart is even easier.