Weak manual transmission, how to strengthen?

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ptuomov
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Re: Weak manual transmission, how to strengthen?

Post by ptuomov » Thu Sep 20, 2018 7:47 am

bigblockmopar wrote:
Sun Aug 26, 2018 7:25 am
Could the gears be heat treated too hard (for the current purpose)?
Would a softer heat-treatment make them hold up better and prevent chipping/breaking, eventhough they would wear faster.
John Kuhn just sent some gears to be tested here to find out if changing the heat treatment from too hard and brittle to something else would have any potential benefits:
5E0CD61F-6347-4AFB-8B76-B6ADD93A9D79.jpeg
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Re: Weak manual transmission, how to strengthen?

Post by vwchuck » Thu Sep 20, 2018 3:36 pm

The removal of all the teeth is the standard German gear failure. The German stock gears are hard as a rock and brittle as glass. My VW does the same thing when you dump the clutch at 6000 on stock gears. They go off like a bomb. You have to go to 9310 steel gear, 300m input shaft, etc.... All big bucks if it is one off.
In your case don't be stupid and just put a T-56 from a corvette in it. Getting into tranny re-engineering is not worth it if you have a T-56 solution.
Plus with 750lb/ft of torque you are still at the limit of the Porsche design even with modern metallurgy.

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Re: Weak manual transmission, how to strengthen?

Post by ptuomov » Thu Sep 20, 2018 8:08 pm

vwchuck wrote:
Thu Sep 20, 2018 3:36 pm
The removal of all the teeth is the standard German gear failure. The German stock gears are hard as a rock and brittle as glass. My VW does the same thing when you dump the clutch at 6000 on stock gears. They go off like a bomb. You have to go to 9310 steel gear, 300m input shaft, etc.... All big bucks if it is one off.
In your case don't be stupid and just put a T-56 from a corvette in it. Getting into tranny re-engineering is not worth it if you have a T-56 solution.
Plus with 750lb/ft of torque you are still at the limit of the Porsche design even with modern metallurgy.
Probably all true, but I’m actually enjoying this learning experience!
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU

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Re: Weak manual transmission, how to strengthen?

Post by ptuomov » Sat Sep 22, 2018 4:27 pm

At what surface hardness are steel gears usually the toughest in terms of ability to hold load? 400 on the Brinell scale?
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Re: Weak manual transmission, how to strengthen?

Post by Kevin Johnson » Sun Sep 23, 2018 11:33 am

Probably too late in light of the gears already being sent to be tested...

https://ntrs.nasa.gov/archive/nasa/casi ... 016828.pdf

Table 4 suggests that you should send samples of the identical gear from both the two new boxes and the failed box. This will allow within and between groups testing. The hypothesis to be rejected is that the failed gear has suffered a decline in hardness due to length of service at unknown but presumably normal temperature. You would want to do this before second guessing the OEM gear treatment. It goes without saying that the new gears should be non-destructively tested. If destructive testing is implicit then possibly new individual gears are still available from Porsche.
NASA_Helicopter_gears.gif
NASA_Helicopter_gears.gif (14.77 KiB) Viewed 644 times
Table_4.gif

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Re: Weak manual transmission, how to strengthen?

Post by ptuomov » Sat Sep 29, 2018 4:51 pm

So what conclusions to draw from this?
AF68BE9F-2407-4D36-A436-E66AA79B71A3.png
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Re: Weak manual transmission, how to strengthen?

Post by ptuomov » Sat Sep 29, 2018 5:21 pm

Here's from one reference:

"I. Hardness. The required surface and core hardness should be selected based on the application. Depending on the alloy used, the hardness can be as high as 760 KHN (62 HRC). Long life power gears which see high loads for something like 10^9 to 10^10 cycles need to be up to about 730 KHN (60 HRC), and the Core hardness should be in the range of 360 to 400 KHN (35 to 40 HRC). Gears which are subjected to shock loading and do not see too many cycles may be better off with a surface hardness which has been tempered back to 55 HRC in order to gain more toughness."
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Re: Weak manual transmission, how to strengthen?

Post by MadBill » Sat Sep 29, 2018 11:57 pm

Drag race-specific ring and pinion sets are often much softer than street/road race gears, enough so that I believe their life is measured in hundreds, not hundreds of thousands of miles. Determining the hardness of same and re-heat treating the glass-hard factory gears to some intermediate value might be effective.
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Re: Weak manual transmission, how to strengthen?

Post by ptuomov » Sun Sep 30, 2018 10:18 am

MadBill wrote:
Sat Sep 29, 2018 11:57 pm
Drag race-specific ring and pinion sets are often much softer than street/road race gears, enough so that I believe their life is measured in hundreds, not hundreds of thousands of miles. Determining the hardness of same and re-heat treating the glass-hard factory gears to some intermediate value might be effective.
By my reading, these factory gears aren’t glass-hard.
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Re: Weak manual transmission, how to strengthen?

Post by MadBill » Sun Sep 30, 2018 4:44 pm

I was just referencing vwchuck a few posts back...
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Re: Weak manual transmission, how to strengthen?

Post by Kevin Johnson » Sun Sep 30, 2018 5:17 pm

Are you allowed to post what Cincinnati Testing Lab determined?

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Re: Weak manual transmission, how to strengthen?

Post by Kevin Johnson » Sun Sep 30, 2018 5:17 pm

Are you allowed to post what Cincinnati Testing Lab determined?

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Re: Weak manual transmission, how to strengthen?

Post by ptuomov » Sun Sep 30, 2018 6:51 pm

Kevin Johnson wrote:
Sun Sep 30, 2018 5:17 pm
Are you allowed to post what Cincinnati Testing Lab determined?
Yes but they just took measurements and provided data. We’ll do a conference call with them later.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU

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Re: Weak manual transmission, how to strengthen?

Post by ptuomov » Tue Oct 09, 2018 9:03 pm

Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU

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