Helical gear problems - Help

[gbritnell]

Tsutrina,
You are correct in what you stated. I guess what I tried to explain was 2 spur gears .50 wide have an instant contact of .50 whereas 2, 45 degree helical gears .50 wide will have an instant contact of much less. Yes as the 2 helical gears rotate each pair of teeth will mesh throughout the whole helical lead but the contact patch is much less.
gbritnell

 

[coulsea]

My first helical gear. of course i tried it on the wrong side of the spindle first hence the big chunk missing.

 

[TSutrina]

Tsutrina,
You are correct in what you stated. I guess what I tried to explain was 2 spur gears .50 wide have an instant contact of .50 whereas 2, 45 degree helical gears .50 wide will have an instant contact of much less. Yes as the 2 helical gears rotate each pair of teeth will mesh throughout the whole helical lead but the contact patch is much less.
gbritnell

Here is something to visualize. Think of the gear made up of thin pieces of metal foil like a motor lamination. The mating gear is also made this way and every piece of foil in one gear has a corresponding foil sheet in the other. Thus every pair is a thin spur gear. So what is true for a spur gear is true for each pair in the stack even if they foil pieces are skewed, off set by some tiny angle to create a helix gear. Just something to think about.

 

[nel2lar]

Tsutrina,
You are correct in what you stated. I guess what I tried to explain was 2 spur gears .50 wide have an instant contact of .50 whereas 2, 45 degree helical gears .50 wide will have an instant contact of much less. Yes as the 2 helical gears rotate each pair of teeth will mesh throughout the whole helical lead but the contact patch is much less.
gbritnell

gbritnell
I think you are looking at it wrongly. If you look at the tooth and measure the tooth, it will be more than the .5 of your material. The 45 degree will make it grow.
I'll be watching and most ot the time silent.
Nelson

 

[TSutrina]

gbritnell
I think you are looking at it wrongly. If you look at the tooth and measure the tooth, it will be more than the .5 of your material. The 45 degree will make it grow.
I'll be watching and most ot the time silent.
Nelson

Trigonometry will change the tooth cut when the two axis are not parallel. Image cutting a helix gear with a hobbing tool. It's proportions do not change, just altered by trigonometry. The pitch dimension is also altered by trig, everything changes by the sine and cosine multipliers. Thus the proportions stay the same. Tooth will not get thicker. Measuring between parallel faces the hob dimension is what you will get. To cut a spur gear the helix hobbing tool axis is place at an angle to the spur gear axis.