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Bevel gears bearings preload

AlexO

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Sep 12, 2004
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I decided today to replace the bevel gears in my MAHO700 just for the fun of it. Each gear has two bearings on the lines of 6014/5/5/7. Pretty big. I took them off today and they don't feel quite right. My question is what sort of preload figure would be reasonable for each bearing pair on each gear, in pounds/Kg/tons etc ? And should I adjust the preload greased or dry ( oil ) ?
 
BTW:
Shaft drive BMW motorcycles have about that size of bearing in the final drive hypoid bevel gear. Preload was set with shim plate and I think spec called for something like 0,1mm preload.
 
Many industrial bevel gear setups (not final drive for a car or motorbike) don't use any preload....just capture the bearings at net or so.
Set the free play relatively close on the gear set ...the normal thrust generated via the gears will provide all the preload you need...
Just need to be sure there is no axial play with each set.

Cheers Ross
 
Many industrial bevel gear setups (not final drive for a car or motorbike) don't use any preload....just capture the bearings at net or so.
Set the free play relatively close on the gear set ...the normal thrust generated via the gears will provide all the preload you need...
Just need to be sure there is no axial play with each set.

Cheers Ross

Thanks Ross. Is there anything really wrong if I set the gears slightly on the tight ( low backlash ) side ? I don't trust the pack of shims is from these specific gears and I know absolutely nothing about gears. Less than zero. Gears scare me.
 
Are they plain bevel gears or helical? Helical requires a bit more planning. You have to worry about preload, blacklash, and tooth engagement pattern.
 
When setting bevels with little or no information, the mesh is as important as (if not more) than the bearing preload.
I find ''feel'' for the mesh and blue on the gear teeth give best results.
 
Are they plain bevel gears or helical? Helical requires a bit more planning. You have to worry about preload, blacklash, and tooth engagement pattern.

They look curved. :) And please, don't scare me....
 
When setting bevels with little or no information, the mesh is as important as (if not more) than the bearing preload.
I find ''feel'' for the mesh and blue on the gear teeth give best results.

Gears have short shafts supported by deep groove bearings at short distance. They will need some preload or they'll wobble. It seems ( ??? ) for that size bearing around 50Kg preload it's what's needed.
 
You're on the right path. If it were me, I might set the bearings for something like 5in-lbs rolling resistance (pre-load), and .004" backlash. Then shim both gears as needed to get the contact pattern centered. It can be very time consuming.
 
I agree with "Sami"...Not sure i see any real difference in setting straight cut bevel gears or spiral bevels......The both need to have a good mesh pattern (oval pattern mid tooth both power and coast side) and run freely.
As to backlash...in my experience keeping that to minimum.(.003-.004").., test by feel (rattle) and be sure to test through several revolutions of the gear set to be sure there are no tight spots....
Gears can run with almost zero clearance depending on speed and power requirements....but they won't tolerate binding....

Cheers Ross
 
I agree with "Sammy"...Not sure i see any real difference in setting straight cut bevel gears or spiral bevels......The both need to have a good mesh pattern (oval pattern mid tooth both power and coast side) and run freely.
As to backlash...in my experience keeping that to minimum.(.003-.004").., test by feel (rattle) and be sure to test through several revolutions of the gear set to be sure there are no tight spots....
Gears can run with almost zero clearance depending on speed and power requirements....but they won't tolerate binding....

Cheers Ross

Problem with these gears with the matching (?) shims is that the tooth pattern is perfect ( as far as I can see ) and they feel nice running CW ( in reverse ) and rattly running CCW ( normal ). I was thinking I did not have enough stiffness in the shafts/bearings.
 
Problem with these gears with the matching (?) shims is that the tooth pattern is perfect ( as far as I can see ) and they feel nice running CW ( in reverse ) and rattly running CCW ( normal ). I was thinking I did not have enough stiffness in the shafts/bearings.

Have you blued the teeth to see the contact pattern.
 
Not blued but yellow greased. :) Pattern seems good : right in the middle and almost as long as the tooth. What clearance should I start with ? 2-3 thou ?

That's about right for starters, go with AlfaGTA's suggestions and you won't be far out.

Re the rattle one way and not the other, ...that is probably down to ordinary wear and tear, and trying to take ''too much'' of it out by shimming etc etc is asking for trouble.

FWIW yellow grease is nowhere near as good as engineers blue, ...if you can't get blue use artists oil colours (or at a pinch your wife / girlfriends lipstick) ......and apply it VERY thinly, ........thick blue tells too many lies.
 
That's about right for starters, go with AlfaGTA's suggestions and you won't be far out.

Re the rattle one way and not the other, ...that is probably down to ordinary wear and tear, and trying to take ''too much'' of it out by shimming etc etc is asking for trouble.

FWIW yellow grease is nowhere near as good as engineers blue, ...if you can't get blue use artists oil colours (or at a pinch your wife / girlfriends lipstick) ......and apply it VERY thinly, ........thick blue tells too many lies.

Thanks. I'll go with what you're saying guys. Thanks a lot.
 
If your gears have a lot of time on them and have mated with a good pattern,do not attempt to take up any backlash from wear.You will put the gears on the unworn edges of the gear faces and depending on the load can cause noise or even breakage.
Backlash does not cause problems unless the gears are worn out,or it is a reversing drive and the noise is objectionable.
Spiral bevels,hypoid and other forms besides straight tooth gears,once set to the correct pattern should be run with the original settings until they wear out.Attempting to move them closer to take out backlash moves them from their mated/seated position and can lead to heel/toe/flank misalignment and excessive wear and breakage.That being said your drive may be very lightly loaded and not worn much,as already mentioned the marking from your bluing test will show how they are meshing if you know what you are looking at.
After you assemble them hold one gear shaft and turn the other both ways,a proper set up you will not feel the gear teeth engage,it will be smooth.
Another thing if your gears have depth and b/l markings on them,they were sold as a lapped , matched set and that is what they should be set at.
 
If your gears have a lot of time on them and have mated with a good pattern,do not attempt to take up any backlash from wear.You will put the gears on the unworn edges of the gear faces and depending on the load can cause noise or even breakage.
Backlash does not cause problems unless the gears are worn out,or it is a reversing drive and the noise is objectionable.
Spiral bevels,hypoid and other forms besides straight tooth gears,once set to the correct pattern should be run with the original settings until they wear out.Attempting to move them closer to take out backlash moves them from their mated/seated position and can lead to heel/toe/flank misalignment and excessive wear and breakage.That being said your drive may be very lightly loaded and not worn much,as already mentioned the marking from your bluing test will show how they are meshing if you know what you are looking at.
After you assemble them hold one gear shaft and turn the other both ways,a proper set up you will not feel the gear teeth engage,it will be smooth.
Another thing if your gears have depth and b/l markings on them,they were sold as a lapped , matched set and that is what they should be set at.

Thank you ! The gears seem new or have very little time on them. My concern is that the shims coming with the gears might not be the right ones - some sort of mix up happened 15 years or so ago. There are markings on the gears but they tell me nothing - I'll take some pics.
Thank you, again.
 








 
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