Gear basics - changing axis of rotation

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Discussion Overview

The discussion revolves around the mechanics of gear systems, specifically focusing on how to change the axis of rotation between gears that are not aligned at standard angles, such as 35 degrees. Participants explore various types of gears, including bevel and helical gears, and their applicability to non-standard angles of rotation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about possible configurations for connecting gears at an angle, mentioning bevel and helical gears.
  • Another participant suggests simply reversing the orientation of the driven gear.
  • It is noted that bevel gears are commonly associated with 90-degree angles but may also be used at other angles.
  • Questions arise regarding the use of helical gears at various angles, with some participants asserting they can only be used at parallel or cross-axis configurations.
  • One participant challenges the assertion that helical gears cannot be used at angles between parallel and 90 degrees, expressing uncertainty about the geometry involved.
  • Another participant provides examples of gear configurations that do not conform to standard angles, questioning the limitations of helical gears.
  • It is mentioned that helical gears can operate at any shaft angle, referencing external sources for clarification.
  • Participants discuss the range of angles for bevel and helical gears, noting that worm gears and spiral-bevel gears may also be applicable in certain configurations.

Areas of Agreement / Disagreement

Participants express differing views on the capabilities of helical gears, with some asserting they are limited to specific angles while others argue they can function at a wider range. The discussion remains unresolved regarding the exact limitations and configurations of these gears.

Contextual Notes

There are unresolved questions about the geometry of gear interactions, particularly concerning the conditions under which helical gears can operate effectively at various angles. Some participants express uncertainty about their claims and the underlying principles.

daring
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hi everyone! I'm sorry if this seems like a really easy question, but...

Suppose I have a device in which manually rotating gear A clockwise causes gear B to rotate clockwise. If gear A and gear B are at a weird angle to each other (say 35 degrees), what sort of intermediate parts could I use to achieve this rotation?

I've been reading about bevel gears and helical gears, but it seems like bevel gears are only used to change the axis of rotation by 90 degrees? I could be mistaken. Any thoughts on possible configurations are appreciated! Especially well-known configurations for this kind of thing.

(sorry if this seems really noobish! I'm actually a comp sci student with this newfound interest in mechanical engineering as of this summer.)
 
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Just have the driven gear turned around facing the opposite direction.
 
The axes don't have to be at 90 degrees, that's just probably the most common configuration.
 
Lsos said:
The axes don't have to be at 90 degrees, that's just probably the most common configuration.

oh cool! so bevel gears specifically can be used at random angles like 35? or other types?
 
daring said:
oh cool! so bevel gears specifically can be used at random angles like 35? or other types?

http://en.wikipedia.org/wiki/Bevel_gear" :

Beve_gear_schematic.png
 
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what about helical gears?
 
leborowski said:
what about helical gears?

What about them?
 
can they be used at random angles? 120 degrees?
 
I believe that Helical can only be used at angles similar to that of "Spur gears" (the one most commonly seen by younger kids, the basic one). Basically they can be parallel-axis or cross-axis.

parallel:
cross:
 
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  • #10
Ryumast3r said:
I believe that Helical can only be used at angles similar to that of "Spur gears" (the one most commonly seen by younger kids, the basic one). Basically they can be parallel-axis or cross-axis.

parallel:
cross:


I don't believe that is true. I cannot think of an exmple though. But if they work at 0 (or 180, whatever you choose to call it) and 90 I cannot believe they cannot work anywhere in between.
 
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  • #11
Averagesupernova said:
I don't believe that is true. I cannot think of an exmple though. But if they work at 0 (or 180, whatever you choose to call it) and 90 I cannot believe they cannot work anywhere in between.

Only parallel or cross axis. They cannot be used at any angle in between because they sum of their helix angles is always 90 degrees. I probably explained that wrong but it's something along those lines...it just has to do with the geometry.
 
  • #12
Gear1.jpg


Gear2.jpg


Gear3.jpg


The first two pix are of an oil pump gear and the camshaft that drives it. Notice that the teeth are not cut at the same angle. The last pic is of 2 identical oil pump gears meshed. They are not meshed at 90 degrees although it looks like it. It is difficult to get a pic that shows this. So, are you saying that although they mesh, and they are meshing at an angle that is niether 90 degree cross or parallel, there is some reason why one would not drive the other?
 
  • #13
I don't know. But, I want to take back what I said in post #11. I still don't think you can set them different than parallel or 90 degrees, but I just don't fully understand why (and indeed, if)...and don't have time to figure it out right now.
 
  • #14
Helical gear can be used at any shaft angle.

From http://www.roymech.co.uk/Useful_Tables/Drive/Helical_Gears.html" :

[PLAIN]http://www.roymech.co.uk/images9/gear_helical_3.gif
 
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  • #15
Bevel gears can be used at through a range of angles, but their shafts must be in the same plane. Helical gears can also be used through a range of angles, but the plane their shafts can be rotated in must be parallel planes. Worm gears can also be designed for use in a range of angles, their shaft alignments are restricted similarly to helical gears. There are also spiral-bevel gears (a combination of bevel and helical) and hypoid gears that can be used in a range of angles, their shaft alignments are not as restricted as for other types of gearing.
 

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