didier godefroy

looking to model a set of beveled gears in solidworks

Question by didier godefroy

I know there are many youtube and other tutos about modeling gears, even beveled gears, but I need to do a configuration that hasn't been treated and I need the proper method that is suitable for manufacturing those gears, not just some quick simple mockup for visual only. I need to model the proper curves for the teeth, so the gears can be manufactured properly and work for real.
The reason this hasn't been treated yet is that what I need to do is a bit unusual. See the attached visuals. A big plate/gear 500mm outer diameter with a lip on its perimeter and the gear teeth would be on the inner side under that lip, with a small perpendicular bevel gear driving that big plate from below.

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4 Answers

didier godefroy
Answered on 18 Aug, 2015 03:23 PM

I didn't get into the details of module, pressure angle and the likes, but this mostly remains open and mostly would be driven by the size of the parts.
I would prefer a pressure angle of 15degrees, mostly because those parts are plastic, they would be subject to manufacturing variations and low tolerance, the positioning for the parts is likely to be a bit shaky, so a low pressure angle should make the gears less sensitive to this. As far as module is concerned, this affects the number of teeth, and since the small gear is so small, the choice of number of teeth will be more driven by the small gear diameter.

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didier godefroy
Answered on 18 Aug, 2015 04:54 PM

Solidworks' toolbox stuff is for ready made standard parts available for purchase somewhere. What I am doing is totally custom and there is no chance any toolbox part of from anywhere else would be suitable. First the pinion has little chance de be found as needed, then the big gear cannot be found anywhere because it's a complex part with many other functions with lots of features on it, plastic injected. I need to apply gearing teeth to that big gear plate on its internal face on its lip, and drive it with a small pinion that needs to match that exactly.
What I am making can't be made from standard stuff.
Those attached drawings were the simplest to show only the relevant stuff and the real part is quite a lot more complex. Actually the big gear isn't really a gear and it doesn't even have any axle. I just need to put proper gear teeth on it with a suitable pinion driving it, and both gears axes are colinear, although the gear faces must be beveled.
Not a simple task, and that is why I posted the question.

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didier godefroy
Answered on 18 Aug, 2015 07:40 PM

Alright then, to be more specific. I'm attaching a visual of the large plate that must be given gear teeth below.
That round plate does not have an axle nor a central area. It's supported on its outer edges on rollers. That plate is meant to be horizontal only, and a small motor with a 4mm axle to drive it, with a small beveled pinion. I only have about 10-11mm of room to put that pinion there on the inside of the outer lip, because there are other things below that plate that are close to the outer edge.
As I showed on those simpler visuals, the position of the pinion is such that its axis is co-linear with the big plate's axis. Only the inner edge of the big plate needs to be beveled, like the beveled pinion, so it's a beveled gear set, but with an axis going in the same direction.
I hope I'm clear enough. Maybe I can draw something else to explain if need be.
The gear ratio should be in the 60-65 range, and I think the small pinion should be fine with 16-18 teeth.
The big plate has an outer diameter of 500mm and its outer lip a thickness of 4mm. I would give the teeth a face width of about 4mm on each gear.
All this rotates very slowly, with the motor axle rotating at some 12rpm typically.
I'm adding one more visual to this. It's a zoomed detailed view of the large plate in cut view, without all the complex features for all the other stuff, as it's too heavy for my machine to manipulate easily.
That outer lip has a 10mm height on the outside edge. That edge and most others are drafted a bit for proper injection molding.
Those parts are to be made of ABS.
As I mentioned, I prefer to give the gears a 15deg pressure angle. Whatever else to be derived from all the dimensions and constraints.

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didier godefroy
Answered on 18 Aug, 2015 08:28 PM

I made one more simplified drawing to get a closeup cut out view of the relevant area where the gears mesh.
This should clarify the goal, with the placement of the pinion in regards to the large plate's outer lip.
This is just a rough placement. There are no gears drawn yet, and some dimensions need to be tweaked for the pinion.
This is an unusual setup for bevel gears, and certainly not something that geartrax spits out easily. I still can't see how geartrax could even do this at all.

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