20 or 40

[Grant_Waite]

9 minutes ago, Matthew P said:

$4-6k for just the gears?

Oh no, for the whole actuator, I have no idea what the gears are worth. 

[Echo]

11 hours ago, Matthew P said:

Good morning, still working the issue but feel that it's now become stonewalling. From what I understand, 60 years ago Mooney contracted to have the actuators made but using their engineered gear set which is manufactured by a 3rd party, so the drawings and specs are Mooney proprietary and Mooney will not release them nor say who they used to manufacture them, I have asked the CEO if they refuse to have them produced than why not license them to  i.e. Lasar so that 1, Mooney can make a little money and 2 we can get the frigging parts....all I got back thus far is a, I'll call you this afternoon, well, that was a week ago.  If anyone can send me an old set so I can get a metallurgy (destructive testing) report done, that would help as I already had a new set loaned to me and had them scanned and I have the CAD drawings for, I've also petitioned the FAA, Certification Branch, under the OPP guidelines, for a copy of the drawings and technical specifications since there is still an active SB and Mooney refuses to have the parts produces, so that's where we are at..wish I had better news and was closer that we were 4 months ago.

Thank you for your work on this Mathew.  Endevor to persevere...Mooney.  WTF!  Stand up and fly right!  Shame.

[Pinecone]

7 hours ago, MikeOH said:

@Pinecone

I don't agree.

1) Tcal indicates that wear was why they were taken out of service; consistent with excessive backlash.

2) My research on worm gear design on this site (https://khkgears2.net/catalog5/ has many drawings, photos, and descriptions that do NOT show any such tooth width variation.  They do discuss backlash and the tooth dimensions that cause it.  Again, the variation in tooth width, wide at the ends and narrow in the middle, is evidence of wear.

I'm willing to reconsider if you can cite some design information supporting your contention.

https://www.grainger.com/product/793AJ9?gucid=N:N:PS:Paid:GGL:CSM-2295:4P7A1P:20501231&gad_source=1&gclid=EAIaIQobChMIsaKag97ciAMV22lHAR1oXynEEAQYByABEgK0sfD_BwE&gclsrc=aw.ds

 

[Vance Harral]

7 hours ago, MikeOH said:

My guess (and it's only a guess) is that the gears that wear out were not regularly inspected and regreased properly.  Maybe the 40:1 will take that kind of abuse?

Every time you post this hypothesis that only poorly-maintained 20:1 gears wear out, I'm going to counter with my anecdotal story that our 20:1 gears wore to the point of failing the SB M20-190B inspection, despite regular maintenance and proper regreasing per the associated SB/AD, over many years of ownership.  We knew this was coming, as the backlash in the gear set got progressively worse over a period of multiple inspections.

Wear is obviously a function of gear cycles, and we put more on our airplane than most.  So I'm not surprised there are airframes with the original 20:1 gears, and lots more hours than ours.  I'm sure it's also true that poorly maintained gears wear faster.  But the 20:1 gears absolutely do wear out, even when maintained properly.

[MikeOH]

1 hour ago, Pinecone said:

https://www.grainger.com/product/793AJ9?gucid=N:N:PS:Paid:GGL:CSM-2295:4P7A1P:20501231&gad_source=1&gclid=EAIaIQobChMIsaKag97ciAMV22lHAR1oXynEEAQYByABEgK0sfD_BwE&gclsrc=aw.ds

 

@Pinecone

Ah, I see the issue.  I'm NOT referring to the vertical 'scalloping' which is absolutely part of the design.  I'm talking about the actual width of the teeth; your link shows teeth that are of constant width, while in the photo from Tcal it is clear that the teeth are worn in the middle.

[MikeOH]

5 minutes ago, Vance Harral said:

Every time you post this hypothesis that only poorly-maintained 20:1 gears wear out, I'm going to counter with my anecdotal story that our 20:1 gears wore to the point of failing the SB M20-190B inspection, despite regular maintenance and proper regreasing per the associated SB/AD, over many years of ownership.  We knew this was coming, as the backlash in the gear set got progressively worse over a period of multiple inspections.

Wear is obviously a function of gear cycles, and we put more on our airplane than most.  So I'm not surprised there are airframes with the original 20:1 gears, and lots more hours than ours.  I'm sure it's also true that poorly maintained gears wear faster.  But the 20:1 gears absolutely do wear out, even when maintained properly.

@Vance Harral

You are overstating my claim.  I'm stating that lack of maintenance may explain the premature wear.  I am NOT trying to claim they won't wear out at all!  Certainly, the 20:1 gears are under more load than 40:1 so it makes sense the 40:1 will last longer.

Of course backlash is going to increase with use whether 20:1 or 40:1.  My opinion is that there is nothing really wrong with 20:1 gears when properly inspected and maintained.  Mine have certainly soldiered on but will obviously need replacing sometime.  IOW, merely going to 40:1 gears doesn't 'solve' the issue; my understanding is that inspection and maintenance is still required even with 40:1 gears.  Will 40:1 last longer than 20:1?  No doubt, but is that 100 years instead of only 50?

[Nico1]

13 hours ago, Matthew P said:

Good morning, still working the issue but feel that it's now become stonewalling. From what I understand, 60 years ago Mooney contracted to have the actuators made but using their engineered gear set which is manufactured by a 3rd party, so the drawings and specs are Mooney proprietary and Mooney will not release them nor say who they used to manufacture them, I have asked the CEO if they refuse to have them produced than why not license them to  i.e. Lasar so that 1, Mooney can make a little money and 2 we can get the frigging parts....all I got back thus far is a, I'll call you this afternoon, well, that was a week ago.  If anyone can send me an old set so I can get a metallurgy (destructive testing) report done, that would help as I already had a new set loaned to me and had them scanned and I have the CAD drawings for, I've also petitioned the FAA, Certification Branch, under the OPP guidelines, for a copy of the drawings and technical specifications since there is still an active SB and Mooney refuses to have the parts produces, so that's where we are at..wish I had better news and was closer that we were 4 months ago.

Thanks for your perseverance! Huge public service. It makes zero sense for them to sit on this or make it difficult...

[Matthew P]

26 minutes ago, MikeOH said:

@Vance Harral

You are overstating my claim.  I'm stating that lack of maintenance may explain the premature wear.  I am NOT trying to claim they won't wear out at all!  Certainly, the 20:1 gears are under more load than 40:1 so it makes sense the 40:1 will last longer.

Of course backlash is going to increase with use whether 20:1 or 40:1.  My opinion is that there is nothing really wrong with 20:1 gears when properly inspected and maintained.  Mine have certainly soldiered on but will obviously need replacing sometime.  IOW, merely going to 40:1 gears doesn't 'solve' the issue; my understanding is that inspection and maintenance is still required even with 40:1 gears.  Will 40:1 last longer than 20:1?  No doubt, but is that 100 years instead of only 50?

Problem is, you can't get either the 20:1 or 40:1 

[MikeOH]

3 minutes ago, Matthew P said:

Problem is, you can't get either the 20:1 or 40:1 

100% aware of that!

It's why I'm meticulous about the 100/200 hour service interval...I need to make mine last until you solve this

[N201MKTurbo]

I bought my 40:1 gears in 05 they were about $250. I bet they will be way more than that if you can ever get them.

[Vance Harral]

34 minutes ago, MikeOH said:

My opinion is that there is nothing really wrong with 20:1 gears when properly inspected and maintained.

On that we agree.  We know they wear, but not at a rate of concern provided they're inspected and maintained.  I do think the speculation on how many years they might last is pointless, as it's not calendar time that causes them to wear.

36 minutes ago, MikeOH said:

Of course backlash is going to increase with use whether 20:1 or 40:1.

Are you certain of that?  Some closed, lubricated systems effectively form a constant thin film between the meshing surfaces, such that the surfaces never actually touch.  I'm mostly ignorant in such matters, and not claiming the 40:1 gears last "forever".  But I could believe it's possible to design a set of gears with a high enough ratio that the force between gear teeth is never sufficient to entirely displace the lubricant.

[Ragsf15e]

1 hour ago, MikeOH said:

@Pinecone

Ah, I see the issue.  I'm NOT referring to the vertical 'scalloping' which is absolutely part of the design.  I'm talking about the actual width of the teeth; your link shows teeth that are of constant width, while in the photo from Tcal it is clear that the teeth are worn in the middle.

My 20:1 gears were replaced ~5500 hours ttaf.  Im not sure about the maintenance prior because it wasn’t mine yet.  They eventually wear out but do appear robust.

[MikeOH]

9 minutes ago, Vance Harral said:

On that we agree.  We know they wear, but not at a rate of concern provided they're inspected and maintained.  I do think the speculation on how many years they might last is pointless, as it's not calendar time that causes them to wear.

Are you certain of that?  Some closed, lubricated systems effectively form a constant thin film between the meshing surfaces, such that the surfaces never actually touch.  I'm mostly ignorant in such matters, and not claiming the 40:1 gears last "forever".  But I could believe it's possible to design a set of gears with a high enough ratio that the force between gear teeth is never sufficient to entirely displace the lubricant.

I find it interesting that you find it pointless how long the gears last (we can quibble over whether years or hours is a better measure), but then suggest upping the ratio to a point where there is no wear so they would last 'forever'!

I'm sure dealing with replacing the gears that wore out was expensive and a hassle but if I had to replace my 20:1 gears tomorrow I'd be perfectly satisfied to put in another set of 20:1 gears should they last the same time!  IOW, I wouldn't trade more life for slower operation; I'm perfectly happy with the life of 20:1 gears.

The issue is there are NONE available at any gear ratio!!