The secret is in this gear, in the pic it's the one with the peg that stops it turning. The top half has 4 more teeth than the bottom half. Because the flying pinion HAS to mesh with both gears, the left gear is advanced 4 teeth during the bottom half of the rotation.

I originally printed the gears as 14.5PA but found that the teeth were too fine for the printer. Just like 3-d printed holes come out under-sized the teeth were slightly crowding into the gaps. I got over this by increasing the PA to 25 degrees which made the teeth more triangle-shaped, and printing the gears on a raft to raise them off the heated bed somewhat. Later I increased the PA of the bottom half teeth of the split gear even further to 30 degrees, to aid the meshing of the pinion over the mis-matched tooth size.

The actual cutting action is caused by the two end-pivots being off-set by 1mm so as the workpiece 'speeds up' it also moves towards the cutter,

Edited By Pete Rimmer on 11/12/2019 11:06:56

Here's a link to the video of me working the model. Sorry about the white balance, it looked fine on my phone, only came out too white when I converted it for sharing.

Balzer Reliever

ARG, looks like dropbox has ruined the quality. I'll have to fix it later.

Edited By Pete Rimmer on 11/12/2019 14:11:22

You're right about it would need careful timing Brian. I just used the orientation of the gear in the patent and though the motion is not perfect it's good enough to be indicative of the operation.

I never found any evidence of a real working one. It does have some limitations, such as it will only produce 15-tooth cutters unless you find another combination of gears that will work out to different number of tooth advancement whilst being close enough to a similar diameter that the meshing can be fudged by profile-shifting. I haven't looked at it closely but what little I have done suggest that there can't be too many options. The Eureka machine on the othr hand is very easy to change the tooth count, plus it doesn't suffer the problem of meshing mis-matched gears.

I'm afraid not. I found online converters but have no way to test the output file so I'm loathe to just run it through the converter and share it.

Perhaps one of the other members can help? I don't mind adding the STL to the file list if someone tests it first. 'm sure that many other people would prefer that too.

Thanks Steve. With your permission I'll add the file to the Thingiverse page.

I'll also install designspark, as it will run on my old 32bit Dell, so thanks again.

Edited By Pete Rimmer on 17/12/2019 00:02:28