…throttle, II.
What did you expect, a door? Do I look like Hodor to you??
Continuing with the adventure, I proceeded to mechanize the smöl piece that pulls the cable. The best spare metal I had around to do it was a small block of bronze, so I just went with it.
Drilling 1mm holes, even in easier material like this, is always unnerving:
Yeah, the M2 screw looks like it will hold properly.
In place:
Yeah, this photo was taken before the one on top of it, before rounding the peg.
Another issue I found was that the original inclined plane I had made seemed a bit too steep for the mechanism. At the time I was afraid that a shallower angle would result in the spring not being able to pull against the resistance of the rotary mechanism. After pondering a bit, I decided to make a less steep path, and also optimize the piece a bit, since this mechanism is only pull, and won’t require push of the slider:
And here, working absolutely beautifully:
The only momentary setback is that I only have at hand 0.6mm steel rope, but the PTFE sleeve is 1mm ID. That can introduce a huge amount of backlash that’s difficult to compensate, as you can see in the following video. Once I block the plunger of the brakes, the sleeve starts moving on it’s own to absorb the extra slack:
I did find a short piece of 0.8mm rope, and indeed works much better.
Forward jump a few weeks after that, when I received many materials I ordered for the real building of this.
- 18 & 25mm 304 stainless stock.
- 30mm titanium stock.
- 10mm thick teflon block.
- 0.5mm ID – 1mm OD – teflon tubing.
- 1mm ID – 2mm OD – closed loop spring bowden.
- 0.45mm braided steel rope.
In the meantime I was working on the Nixie-CAM, I also redesigned a bit of the pieces here and there, as I decided that altough for series production having a single body piece would be beneficial, for a single unit production I pretty much preferred to make the least amount of cuts/measurements, because of lazyness, of course. Also, turned the pretty pocket for tensioning into a simple slot, infinitely easier to machine.
With that, it was lathe time:
And drill:
Repeat with some different intermediate measures:
Get exciting pieces:
Add 4mm wide slots (non valid test piece in the image):
And cut the 45º ramps:
Because lazyness, I made the aluminium holders in the CNC:
After those processes:
Some teflon CNC machining:
By this time, I could no longer hold onto the bronze made push and puller, so that was the next step.
First, the puller, wich had to interact with the teflon ramp. It went from this:
To this:
I realized that it was NOT necessary for the set screw to be in front of the ramp, I could just drill through the whole piece and put it behind, freeing the travel lenght to the whole ramp. Win-win.
After that, I went back to the pad separator/pusher:
Taking measurements for the spring before machining down the metal block:
The teflon separator needs to be attached somehow to the metal pusher/retractor, and the “easiest” way was to make a dovetail joint…a 2mm wide dovetail joint in a 4mm wide piece…yes. XD
To be honest, the dovetail wasn’t as difficult as I thought it would be, as long as you do things calmly. The prong and small recess for a spring where CNC machined with a 1mm endmill at 24krpm. A bit unnerving, but it went well on the first try.
With all that done, they where ready for a test, even if some parts where still not finished:
1.- Thread the cable into the pad separator (double it on itself to not shear it easily with the M2 set screw):
2.- Cut excess teflon on puller side:
3.- Double thread the cable into the puller end and cut excess:
4.- Success!:
I’ll still have to dismantle it to put the counterweight-mass-nuts, and it’s missing the titanium covers (and change the 3D printed brake pads for metal ones, probably bronze too) but it is functional for a short test, wich I will do soon. Still, from the video on top, you can see what is going on.
The Electronic Mercenary 