AGMA 11 VS AGMA 9 Specification / What's the real word differerance 1

[Stuntee]

Hi there, I have a question regarding a project im working on. I have a proffesionaly designed set of planetery gears which were designed to AGMA 11 spec.
The sun is splined on a SAE 24-48P,36T, 30*
The ring is a 63T,
My question is how much and what knind of real world difference will AGMA 9 make VS the specified AGMA 11 on these gears.
My manufacture can not provide higher than AGMA 9 on the internal spline of the sun gear and the internal teeth on the ring gear. But can achive AGMA 11 on the Planets and the teeth of the SUN gear.
Any insight would be greatly apriciated.

 

[israelkk]

It is directly affect the minimum and maximum backlash and center distance tolerance added to involute and lead errors if it is important. it will also affect gear noise, gear life, scoring, etc.

 

[tbuelna]

Stuntee,

I can't provide you a meaningful answer because the description of your gearset and operating environment is lacking some critical details.

As israelkk noted, the difference between a class 9 and class 11 gear is mostly based on allowable tolerance limits for things like involute and face profile, lead, indexing, etc.

If you have high pitch line velocities in your mesh or heavy loads, the difference in quality class between 9 and 11 can have a significant effect on dynamic tooth loads, tooth contact stresses, vibration and noise. Dynamic tooth loads or edge loading conditions can easily increase the bending and contact stresses in the gear by a factor of 2 or more over a simple gear load calculation that does not consider these effects.

And of course, regardless of how precise your gear teeth are, if your mounting structures, gear structures, and bearings have misalignments or inadequate stiffness under load, then that higher quality gear mesh is meaningless.

Consider this: at quality class 9 or higher, your gear tooth tolerances are measured in increments of ten-thousandths of an inch. If your gear shaft or housing has deflections under load of just 5 or 10 thousandths (ie. 10 times the gear tooth tolerance) at the mesh, what good is a gear tooth held to a few ten-thousandths accuracy?

Good luck with your gears. And if you want to provide some more detailed information, maybe I can be more helpful.

Terry

 

[Stuntee]

Thanks Terry and Isralekk for the great information. I would like to go a bit more in depth with this is if possible. I understand what you mean about the housing and bearings Terry. From what I can gather from your comments there would be a differance in the ten-thousands on the teeth of the ring gear from agma 11 to 9. Correct! The planets can be done to agma 11 and same with the sun.
What additional information could I provide to you Terry to find out a bit more specifics about the increased backlash and lowered strength of the ring gear and corresponding planets if the ring gear is ground to agma 9. Assuming we factor out the housing variables ect. Is it possible to figure out how much strength would be lost ect?

 

[mfgenggear]

Stuntee

what is the actual reason for not being able to hold AGMA 11 gear. Is there no clearance behind the ring gear or is it because the vender can not grind Internal gears?
Is there access though the gear

My company grinds AGMA class 11 ring gears with no problems. I am sure many others Vendors that can also grind Internal gears with no issues. Aslo it may be, it can be CNC power gear Honed. Send out some more quotes.

where are you located?

 

[tbuelna]

Stuntee,

It's not a "loss in strength" per say between a class 9 & 11 gear. More correctly, it's that you must apply a knockdown factor to your TCA calculations for the geometry and index errors that increase with lower quality classes.

For example, increased face profile errors (crown and lead errors) will naturally increase the tendency towards edge loading along the line of contact. This means higher Hertz stresses for a given PL force.

Increased involute profile and T-T index errors can cause higher dynamic tooth loads. At high PL velocities, dynamic loads can easily be double static tooth loads, for contact or bending.

As a rule of thumb, helical gears tend to be less affected by dynamic loading issues than spur gears. This is due to the greater number of teeth in contact across the face of a helical mesh at any given instant (face contact ratio).

Generally, backlash will have little impact on tooth strength or load capacity.

It is not so difficult to accurately grind large ring gears to class 11. The difficulty arises when you remove the ring gear from its grinding fixture and attempt to inspect it to class 11 tolerances, after it springs out of round.

Hope that helps.
Terry

 

[mfgenggear]

Terry

True but the ring gear is ground & inspected in the restrained condition.

however I have been able to make rings round within .001 or less by using Gleason quench die & grinding in the free state.

 

[Stuntee]

Mfgenggear and Terry
I am located in Canada, i have invented / come up with idea using a planet gear assembly for motorcycle use. I hope to have it on the market in the next couple of months.I am not an engineer and am haveing the gears made in Asia due to cost. If I had them made in North America my idea would be dead due to price.

The problem is the manufacturer, on ID gears / splines they can only achive agma 9.

So I have a decision to make, weather to go for this or not. That is why I thought of asking here and hopefully getting some answers from people much smarter than me.
From what I can gather from the info you all provided there will deffinatly be reduced strength due to tooth loading or orherwise. I just don't know how much 10%? - 25%? 50%? I k ow it's a loaded question, there are so many variables. I just don't know what to do.

Thanks for all your help thus far and Marry Christmas!