# Internal bevel gearing, possible? Generator scripts?

I’ve been pondering a concept to 3D print which would use a combination of an internal spur gear (where a small normal involute spur gear interlocks with internalised teeth on a bigger spur-like involute gear) with a bevel gear, which switches angle of the shaft (by 90 degrees in the situations I’m thinking of). But I’m not sure if it is mathematically possible to get proper involute teeth to exist for this geometry. I’ve drawn up a diagram of the reference cones of such a gear system (see the attached picture), and I wonder if when real teeth are put on the cone surfaces they could ever run or would trying to combine bevel cones with an internal gar make the teeth jam? I have looked around online for the concept but seen nothing particularly about this combination of a bevel and internal gear, search terms for “internal bevel gear” bring up plenty about internal spur or external bevel gears, but nothing about combining the two.

I also wonder if anyone can suggest how I might calculate, if this design is possible, what the involute curve would be so I can model it by creating a equation surface/line in blender (methods fo any CAD software would translate across fine)? Would I start with the usual involute surve equation? I wondered whether any online calculators can generate an involute curve for this type of gear (I’ve found good ones which can for internal spur gears OR external bevels)? Or what sort of geometric procedure I might work through in CAD software to convert an internal gear profile or bevel gear profile to form an internal bevel?

Thanks

Infraviolet: But I'm not sure if it is mathematically possible to get proper involute teeth to exist for this geometry.

I think it's very unlikely that people here will be able to help with that - it has nothing to do with programming an Arduino.

I suggest you enquire of some of the CNC or 3D printing forums - for example the REPRAP Forum.

Another possible source of info would be a Forum dedicated to the CAD/CAM software you are using to design the part.

...R

Its not possible with standard teeth, as the inside of one gear meshs with the outside of the other and vice versa, causing speed disparities across to tooth. Normally the lines of contact all project back to the point the axles would meet. Standard bevel gears have inside-to-inside and outside-to-outside contact.

Why can't you just use standard bevel?

Its traditional to use peg and slot or peg-and-peg gears for 90 degree turns, BTW, such as windmills and such like (although this is also because they are easier to make without specialized tooling.)

Thanks for the tips.