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This is not entirely a 3D printing question, but closely related since I want to print parts for a prototype.

The problem : I need to create a mechanism with 2 parallel shafts, at some distance apart, rotating in the same direction, either clock- or anticlock-wise.

The distance (> 1m) makes it impractical to set a chain of gears between the shafts, so my approach is to have a third shaft at 90 degrees with bevel gears; the driving motor will attach to this third shaft.

Not being a mechanical engineer, I tried to understand a bit more about bevel gears, and found out there are straight, spiral and other types. For printing I came across a very good OpenSCAD script that creates bevel gears with angled teeth.

bevel gears with angled teeth

So here's the 1st question : for any type of bevel gear except the straight ones, does the geometry of the teeth impact on the direction of rotation ?

Since I don't want different rotation speeds on the parallel shafts, and there is no constraint of the rotation speed of the third, my plan is to create gears with identical sizes.

2nd question : Should I use larger or smaller gears ? What's the impact of the number of teeth on the gear operation for the bevel gears ?

And last, but not least, any hints, comments or suggestions on printing the gears is appreciated.

Thank you all in advance.

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    $\begingroup$ Hi Stefanu, welcome to 3D Printing.SE! Unfortunately the question has nothing to do with 3D printing and as such will likely be closed. This would be a question to ask at Engineering.SE. Note, you could do it way more simple using a belt and pulleys! That is how I coupled the 2 Z lead screws of one of my 3D printers. $\endgroup$ – 0scar May 21 '19 at 9:28
  • $\begingroup$ Thanks for the tip; before posting, I looked for a more appropriate place to ask, but I finally posted here because I am also looking for printing tips for the gears. $\endgroup$ – stefanu May 21 '19 at 9:40
  • $\begingroup$ As for the belt and pulleys, I was afraid it may cause tension problems and vibrations may cause the belt to slip or even come off the driving wheel. That's why I was looking into bevel gears. $\endgroup$ – stefanu May 21 '19 at 9:46
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    $\begingroup$ @0scar I would say that questions about designing gears suitable for 3D-printing is highly on-topic, and should not be discouraged. Perhaps the OP needs to re-focus his question, and also split it up into several questions -- one topic per question. $\endgroup$ – Mick May 21 '19 at 10:30
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    $\begingroup$ @Mick, indeed and I certainly agree, good point to notice! But all questions address gear design, the final only states that it should be printable. It would be better to first find out what type of transmission is best (ask at Engineering) and then ask here if it is feasible to print. Otherwise, the options are just too many. $\endgroup$ – 0scar May 21 '19 at 11:32

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