Permitted deflection of gear sets 1

[__G__]

Hi All,

I've been asked to provide some deflection limits of a large gear set in an industrial application. I have calculated the forces, but without going into extensive calculations on gear strength, I'm lookign for some general guidance on the deflection of the gears. I expect it should only be a few % of the height of the teeth (valley to tip) before you experience higher vibration, wear, stress and therefore shorter life.

Any suggestions?

 

[mfgenggear]

Op
AGMA has an extensive gear specifications.
I don't remember them all
I google this.
Ansi/agma 6101-f19
AGMA 927-F19
AGMA 911-B21
ANSI/AGMA 6000-C20

The analysis of gear box or gear train is very extensive.
Some but not all are
Torque and rpm in
Torque and rpm out.
Contact ratio
Contact stress
Contact wear
Beam strength (deflection)
Efficiency
Profile shift on pinion
Profile shift on gear
And it depends on the type of gears
The AGMA quality will effect all of above
The more precise al of above effect the above. But there is a cost vs Precision
And cost effective analysis.
The type and strength material properties
Will depend on the Contact stress, Torque
And rpm.

 

[Tmoose]

Like MFGENGGEAR said-
Contact stress
Contact wear
Beam strength (deflection)

...............

I think focussing on deflection with the goal of limiting it to "only be a few % of the height of the teeth" might be overlooking potentially serious problems elsewhere, especially if the rpm and tooth count will result in several million bending cycles in 10 fortnights.


BREAKAGE
"Breakage is the ultimate type of gear failure. Bending loads on gear teeth usually cause the highest stresses at the root
fillets and at the tooth profile/root fillet junctions. A gear tooth is a cantilever plate with tensile stresses on the contact side of
the tooth and compressive stresses on the opposite side. If the tensile stresses at the critical location are allowed to exceed
the endurance strength of the tooth material, fatigue cracks will eventually develop and with continued operation, will
ultimately progress to the point where the tooth will break away from the rim material."

https://www.rexnord.com/contentitems/techlibrary/documents/108-010_manual

..............

TBuelna said "Gears designed to these AGMA standards will always work."

https://www.eng-tips.com/viewthread.cfm?qid=248540

 

[mfgenggear]

I liked Terry very much, he is missed

 

[mfgenggear]

I like you too Tmoose salutations

 

[dgeesaman]

Really the only way I know how to assess this well is to perform an FEA-based contact analysis and incorporate the allowable assembly misalignment as well as deflections due to operating loads and thermal growth (if any).

If you're in a particular industry I expect the individual design groups will develop their own rules of thumb but I wouldn't expect those to be transferrable across all industrial power gear designs.

 

[mfgenggear]

There is expensive gear software that can analyze based on the design all attributes. But ultimately the gear manufacture will make it as designed.
The week component is the pinion gear.
It will obtain the most wear, and deflection. This is why profile shift
Is important. To strengthen the pinion