Gears

Hi,

One way of doing it is to create a parametric model that adjust accordingly to the parameters you enter in the table.

hi there,

I have already created a parametric model of the gears. :)

I f you did it right, the model should update automatically to reflect the new sizes.

Which is the gear ratio you want to obtain?

Hi there;

From the gear ratios mentioned below i have calculated the number of teeth

as you can see there is a big diffrence in the number of teeth and from the photo above you can see that there is a very big size between the gears. i know they will not all be the exact same size but the first and second gears are huge and i was seeing if there was a way to make them smaller while keeping the ratio.

Conventional gear ratios follow from the relative (pitch) diameters which also Correspond to the number of teeth. This provides a rolling contact and a constant speed. The only way around this is to have tooth engagement that is no longer purely rolling, but also has sliding contact, and is thus slightly irregular in velocity. An exaggerated, simple example would be a Geneva Wheel. A more subtle example can be seen on my YouTube channel, by searching, “Unmatched Tooth Spacing”.

If you’re willing to have sliding contact and irregular output velocity (with a regular input velocity), then anything is possible.

The physical size of each gear is determined by, tooth size (module) and required number of teeth in gear wheel. When, in a gear set, some of these gears are not required to mesh together by using different tooth modules through the gearbox the required physical sizes of the gears can be changed, so possibly you may be able to re-design to a more compact overall size, by using a different module for different gear pairs. Consideration though, has to be taken of what tooth modules you can use, as the beam strength of teeth is a factor in choosing a suitable module for a set of gears transmitting required power and torque. I have attached an image and gear train details for a teaching aid I have designed. In this case the design will not work unless this use of different tooth size/module is not used. You may possibly make your design more compact by using different tooth size/module in different places.

Hi lawrie,

i have breifly looked into the bending stress of gears and looking into the lewis equations however what ever I could find was in AMGA however I require it to be in metric. I have previously created a discussion in my group and have provided an example where I have tried to convert the units to metric but this didn't produce the correct answer.

https://grabcad.com/groups/cars-and-automotive-design/discussions/bending-stress-in-gears

If you take a look you could help me figure out what I have done wrong. in the thread I have provided my reasearch source.

Also i understand that each gear doesn't need to have the same module only the the gears that are meshed together need the same module.

this is the method that i have used to calculate the number of teeth from the distance between shafts.

• Define a center distance
• using these two formulas simultaneously

(1) a=1/2•(d1+d2)

(2) i=d2/d1

i = Gear ratio

d1 = ref. Ø gear 1

d2 = ref. Ø gear 2

• With the calculated ref. Ø you can achieve the number of teeth by defining a module. using the formula

Z = ref. Ø/module

I could work out the number of teeth for both both gears in each set. Therfore each gear set i could use a diffrent module to adjust the size of each gear therfore i could make it a more compact design.

I am new to the use of the formula for bending stress and I hade gotten fed up with the lewis formula since it wasn't producing a realistic value and i was not able to solve what i was doing wrong. Therfore if you would be so kind in explaining what I have done wrong and how it would link with the module choice for diffrent gear applications.

regards

Yohann