Long Addendum Teeth Profile
Long Addendum Teeth Profile
(OP)
Hello All,
We came by the knowledge of some competitor companies (agricultural tractor transmissions) use high addendum gear profiles like 1.35xM. Even the gears are have high numbers of teeths, the tips are very small unlike the normal profile.
I could not understand the benefits of such so-called high depth teeth and was looking for articles about it but could not find a good source. Does any of you familiar with such profile gears? Do you know the advantages of such profiles? Do they give better tooth root strength or flank safety?
Best regards
We came by the knowledge of some competitor companies (agricultural tractor transmissions) use high addendum gear profiles like 1.35xM. Even the gears are have high numbers of teeths, the tips are very small unlike the normal profile.
I could not understand the benefits of such so-called high depth teeth and was looking for articles about it but could not find a good source. Does any of you familiar with such profile gears? Do you know the advantages of such profiles? Do they give better tooth root strength or flank safety?
Best regards
RE: Long Addendum Teeth Profile
Don't know the reason this particular type of gear geometry was used for your tractor transmission.
RE: Long Addendum Teeth Profile
Also, why does the bending strength decrease?
RE: Long Addendum Teeth Profile
it's not a good scenario, thus profile shift + at the pinion teeth to
increase pinion tooth bending ratio, - profile shift at the gear.
to have proper tooth contact.
good attributes are the following
contact ratio 1.5 + depending the loads.
contact stress
high tooth bending stress ratio
there is a good video to help with under standing the above
AGMA tooth stress
https://www.youtube.com/watch?v=VaUsmBspl58
The gears of the competitors might be an issue, but not enough data
to really make a proper answer.
Follow proper design factors.
scuffing or scoring also must be considered.
RE: Long Addendum Teeth Profile
if the number of low number of teeth , under cut will result
and again cause week tooth bending ratio.
if the pressure angle is to high apexing of the teeth will result.
this is not good. a good gear program would be
on that calculates all of the previous post and the above.
RE: Long Addendum Teeth Profile
Both high addendum and long addendum (a positive profile shift) decrease the top land width.
The bending strength decreases as the addendum gets higher because the meshing forces that act at the tip of the tooth are further away from the tooth's base; a force acting further and further away from the critical section creates more and more bending stress in it.
RE: Long Addendum Teeth Profile
Now that I have a little understanding of it, I speculate that even if the gears are not case-carburized or otherwise hardened, decreasing the land width still increases the chance of failure. At the start of the mesh, all of the force is at the tip, where the cross-section taking the load is the least. Shear and bending stress at that point might be enough to cause a failure even if the bending stress at the root is safe.
mfgenggear, that is a long video, but a good one.
RE: Long Addendum Teeth Profile
some times it's unavoidable to have tooth tips that are on the thin side.
when this does happen do not carburize the tooth tips and end faces to minimize
the effect as spigor stated.
a good program will calculate the tooth tips land width.
example of that, is tooth tips are .070 inches, case depth is .030.
unavoidable thru case hardening will happen.
this is why it is important not only for stress loads, but for geometry
to pick the correct Module or diametral Pitch, and pressure angle.
when I process parts my personnel written programs looks for this.