[Fot] Fwd: Crown and pinion gear break in

Mon Sep 17 07:51:08 MDT 2018

 That's definitely not a "normal" failure; the ring gear doesn't look too bad, all considered, compared to the pinion damage.
That pattern doesn't look that bad either, with .005 minimum backlash, I don't think it had anything to do with the failure.
The only other possible variable would be related to (lack of) pinion preload, but if that was the case I would expect to see more ring damage.

I agree with Barry, the teeth do look like they are almost melted, I wonder if it could be a hardness issue?
Glen

-----Original Message-----
From: barry rosenberg via Fot <fot at autox.team.net>
To: Greg Blake <gblake58tr3 at icloud.com>; Fot <fot at autox.team.net>
Sent: Mon, Sep 17, 2018 8:45 am
Subject: Re: [Fot] Fwd: Crown and pinion gear break in

>From the pictures, I see melted teeth, not broken. It also looks like the front pinion bearing may have spun on the shaft. The ring gear is not nearly as worn as the pinion. I have seen this melting teeth trick and pattern only once before and it was caused by loss of fluid. I used to keep the melted pinion but have lost it over the past two moves.

Barry

 From: Greg Blake via Fot <fot at autox.team.net>
 To: Fot <fot at autox.team.net> 
 Sent: Sunday, September 16, 2018 8:53 PM
 Subject: Re: [Fot] Fwd: Crown and pinion gear break in

I meant to say, looking at the gear mesh, I thought I was close. In fact I started closer to 0.731 pinion depth and reduced it until I got a better mesh pattern. 

Sent from my iPhone

On Sep 16, 2018, at 1:47 PM, Greg Blake via Fot <fot at autox.team.net> wrote:

Here are my setup notes and a few photos from the failed unit. 

Backlash averaged 0.0055” measured at 4 locations 90 degrees apart each. Largest being 0.006 smallest 0.005. 

Depth from bottom of saddle to top of pinion head 0.726”. 

Pictures of gear mesh with this setup. 

Picture of failed pinion gear. 

And companion ring gear. 

I made a hell of a mess.

It looks like I set the pinion too deep into the case by the write ups I’ve reviewed. But looking at the gear mess, it looks like I was pretty close. 

What do y’all think?

Thanks. 

Sent from my iPhone

On Sep 13, 2018, at 3:45 PM, Michael Porter <mdporter at dfn.com> wrote:

On 9/13/2018 4:52 AM, Greg Blake wrote:

      Speaking of pattern, Chris mentioned that the Bastuck gear sets      are Oerlikon        as opposed to Gleason gears. Apparently they require a different        mesh pattern. Does anyone have a good resource for pictures of        the proper mesh pattern for the Oerlikon type gears?  I can not        find one. I contacted Bastuck with no luck there.       

        This might help:

https://www.cartechbooks.com/techtips/ring-and-pinion-gear-selection-for-optimal-performance/

    Note that in the section on hobbed gears (Oerlikon type), I think    the first photo has the toe and heel conditions reversed in the    description, and it looks to me as if they're using the same set of    photos for both types of gear (the hobbed gear has uniform tooth    height and the top of the tooth changes thickness from heel to toe,    while the milled gear has non-uniform tooth height and uniform tooth    thickness at the top, but to me, the dimensions of the teeth look    the same in both sets of photos).  There's also general    recommendations on break-in.

    This is the closest I've come to finding a comparison of the meshing    of the two types, even if it has errors, and some shortcuts in the    descriptions.  This, though, is simpler, and might be helpful:

    http://canadawideparts.com/downloads/dana_tooth_pattern.pdf

    Truthfully, I don't see much difference in the two sets of    examples.  With regard to set-up, the crucial difference in the two    types is where optimum tooth thickness occurs in relation to optimum    backlash.  One thing that these guides don't say is that hypoid    gears, whether with standard helical pinions or worm-gear pinions,    don't tolerate lack of backlash.  I once worked in the shipping    department of Boston Digital in Massachusetts as a lowly temp back    in the mid-`80s, and my boss was grumbling about how the company was    in trouble and it was going to affect his profit-sharing.  So, what    happened?  "Big troubles with the fifth-axis on the 5-axis milling    machines."  And?  "They use a hypoid worm and ring gear to operate    it and it's failing early."  And?  "The engineers don't understand    why."  It turned out that they'd set up the ring gear set to zero    backlash to eliminate the slop in the gear set because the encoders    they were using couldn't compensate, and, of course, the gears wore    out prematurely, and because none of them had an automotive    background, they didn't understand that they'd created the failure    themselves through bad design.  And, they were Indian, like the rest    of management, and the culture in India is that the upper classes    are never wrong, so they simply couldn't acknowledge that they'd    created the problem.  The answer was to use absolute measurement    such as flexible glass rules (which require no correction) and add    backlash, but I don't know that they ever did that.

    Cheers.

-- 

Michael Porter
Roswell, NM

Never let anyone drive you crazy when you know it's within walking distance....

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