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Some crown gear damage


bnbaz

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Good day,

 

My crown gear main bearing required replacement. Used the chisel method until there was sufficient room to fit the bearing puller. While chiseling, the protection I had put between the crown and the workbench fell out and I didn't notice in time. Result: a small piece of the crown broke off (see pic).

 

Not ideal, but it could be worse. My thoughts:

  • The damaged part is on the 'back' of the large crown
  • The damage is quite small
  • The damage is a the tip of the tooth
  • Other teeth have some residue in the location of the damage, indicating the shaft part does not touch here
  • The damage is clean: no cracks, no bits sticking out
  • Wheel balance effects at this scale cannot be noticeable
  • A crown gear set is hella expensive

 

So, I want to stick it back in like this. Probably not for another 100.000 miles, but should be good for a while. Opinions?

 

Cheers.

 

20201206_150125 - Copy.jpg

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1 hour ago, bnbaz said:

Good day,

 

My crown gear main bearing required replacement. Used the chisel method until there was sufficient room to fit the bearing puller. While chiseling, the protection I had put between the crown and the workbench fell out and I didn't notice in time. Result: a small piece of the crown broke off (see pic).

 

Not ideal, but it could be worse. My thoughts:

  • The damaged part is on the 'back' of the large crown
  • The damage is quite small
  • The damage is a the tip of the tooth
  • Other teeth have some residue in the location of the damage, indicating the shaft part does not touch here
  • The damage is clean: no cracks, no bits sticking out
  • Wheel balance effects at this scale cannot be noticeable
  • A crown gear set is hella expensive

 

So, I want to stick it back in like this. Probably not for another 100.000 miles, but should be good for a while. Opinions?

 

Cheers.

 

1 hour ago, bnbaz said:

Good day,

 

My crown gear main bearing required replacement. Used the chisel method until there was sufficient room to fit the bearing puller. While chiseling, the protection I had put between the crown and the workbench fell out and I didn't notice in time. Result: a small piece of the crown broke off (see pic).

 

Not ideal, but it could be worse. My thoughts:

  • The damaged part is on the 'back' of the large crown
  • The damage is quite small
  • The damage is a the tip of the tooth
  • Other teeth have some residue in the location of the damage, indicating the shaft part does not touch here
  • The damage is clean: no cracks, no bits sticking out
  • Wheel balance effects at this scale cannot be noticeable
  • A crown gear set is hella expensive

 

So, I want to stick it back in like this. Probably not for another 100.000 miles, but should be good for a while. Opinions?

 

Cheers.

 

 

 

Evening  bnbaz

 

Not good, at least it's on the coast side, it probably does contact that very area on the drive side so if there is any minor cracking or underlying structure damage then you could  have issues.  

 

Personally I would put a different used drive in it but if you are intent on trying to use that gear then___

 

First, use  Dremel or small sander to lightly round off the rough edges of that break.

 

Then use some gear contact marking compound (like red lead or yellow lead, or the newer non-lead  gear contact marking compound, then re-assemble & rotate under as much hand load a you can, then disassemble & see if it is actually missing that area. 

 

If it passes that above then re-assemble & ride that bike for a thousand miles or so, then remove the side cover & inspect the ring gear & inspect the pinion gear for scoring in that running area. 

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Hi dirtrider,

 

Yes, painful mistake. Your advice makes sense. The sanding bit I was planning to do. Will definitely add your gear marking check and take it apart again after a short while (and perhaps if it's still ok an extra oil change too).

 

As for cracking and surface damage, would you expect this to be visible under closer visual inspection? I.e. using optic aid.

 

Cheers

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16 minutes ago, bnbaz said:

Hi dirtrider,

 

Yes, painful mistake. Your advice makes sense. The sanding bit I was planning to do. Will definitely add your gear marking check and take it apart again after a short while (and perhaps if it's still ok an extra oil change too).

 

As for cracking and surface damage, would you expect this to be visible under closer visual inspection? I.e. using optic aid.

 

Cheers

Evening bnbaz

 

If I absolutely needed to use that gear I would  probably clean that area to be squeaky clean, then lightly heat & clean again. 

 

Then I would do a Zyglow  Dye Penetrant Inspection (Google Zyglow) as that shows most non-visible cracking if done correctly.  I'm not sure it is worth buying but I have access to it so personally I would Zyglow it. 

 

Added: most machine shops have Zyglow (or a similar product), if you have a friendly local  one they might do you a favor & give it a quick hit.  

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