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Finally....the '82 rolls
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Mike9311  



Joined: 14 Dec 2004
Posts: 839
Location: Chicago-ish

PostPosted: Fri Dec 20, 2019 9:56 am    Post subject: Reply with quote

Titanium is starting to dribble in over here. Full Ti exhaust planned after the down tube.




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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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Mike9311  



Joined: 14 Dec 2004
Posts: 839
Location: Chicago-ish

PostPosted: Sat Feb 29, 2020 4:46 am    Post subject: Reply with quote

So with a hard finish date looming in April (of this year i should add ),
Several things have been in the works. This one I may have only mentioned and it isn't a dream. There is actually work going on

I developed rebuild-able bearing carriers for the torque tubes. Aluminum or stock. They may or may not be interchangeable but easy enough to adjust the two dimensions needed during a production run. Will know for sure soon enough. The final width of the carriers will be reduced for production ease. Maybe for some further light-weighting but really it will simply save time and tooling.

This car will get the first Alu test tube and eventually a billet flange instead of having to find a donor.





First bit of the original Flange Modifications

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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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Mike9311  



Joined: 14 Dec 2004
Posts: 839
Location: Chicago-ish

PostPosted: Sat Feb 29, 2020 4:54 am    Post subject: Reply with quote

Flange Scan... This was the first one. The software (and me for that matter) was having an issue with scan alignment. I kept fighting because it looked warped. Someone walked in and looked at the flange and said "isn't this bent?".... ... why yes it is. Exactly what the scan was telling me all along and its since been redone plus compared with probing results for the holes just to be sure. First test fixture out of wood was spot on. Next fixture is being made in aluminum since it will be needed for machining.


_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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Mike9311  



Joined: 14 Dec 2004
Posts: 839
Location: Chicago-ish

PostPosted: Sun Mar 15, 2020 10:18 am    Post subject: Reply with quote

Started welding today. Surprisingly decent considering having to weld to cast flange. Even with cleaning and pre-tigging to float casting garbage I was expecting worse behavior. Will need to finish fixture which will be used to fine bore this newly welded section so it can receive the main tube section. Also ran a bunch of bearing carriers re-sized slightly smaller in width from the first design.


_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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Mike9311  



Joined: 14 Dec 2004
Posts: 839
Location: Chicago-ish

PostPosted: Wed Mar 18, 2020 3:02 am    Post subject: Reply with quote

Didn't realize someone was taking pictures

https://www.reddit.com/r/Welding/comments/fjvmta/are_we_still_posting_self_made_welding_tables/

Caught in action welding the torque tube


_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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Mike9311  



Joined: 14 Dec 2004
Posts: 839
Location: Chicago-ish

PostPosted: Sat Apr 04, 2020 7:58 am    Post subject: Reply with quote

Got the fixture done that has the holes and pilots that match the transmission exactly since they are based off of the crossed checked scan and probed hole data.

I finally got my answer as to why there are C5 clearance bearings in the torque tubes. The tolerances are crazy so they compensated with the C5 clearance.

Precision boring the flange tube to accept a machined aluminum torque tube. Bye bye crazy tolerances and bearings with excessive clearance requirements.

https://vimeo.com/403857385
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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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CÚdric  



Joined: 27 Aug 2004
Posts: 1976
Location: Sweden

PostPosted: Sat Apr 04, 2020 4:17 pm    Post subject: Reply with quote

Fun projects, C5 bearings was a bit of an odd choice, o thought it would have been the other way since the shaft is so long.

Btw, theres now an aluminium torque tube on the market that they guys from rev line racing put together, that's not everyday you can buy one of those
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Mike9311  



Joined: 14 Dec 2004
Posts: 839
Location: Chicago-ish

PostPosted: Mon Apr 27, 2020 11:14 pm    Post subject: Reply with quote

Cedric, we have been doing a lot of measuring and runnout ("rundlauf" is the German word) with dial indicators. There is a lot off and slop built into the system. This is totally why they chose C5 clearances. If there wasn't all these issues to provide preload to the bearings, I'd be freaking out spinning the the driveshaft up cold especially in cold weather. The balls wouldn't want to roll, they would just push the grease. Overall I am very impressed these shafts go 100k+ miles

This aluminum tube is being built holding much tighter tolerances. The side effect in all of this is my hope that the pilot shaft and pilot bearing are no longer stressed so much. Once assembled it will be checked and trued in a lathe in its assembled form.

Today I will be checking a 3D printed coupon (looks like a gasket) with the hole pattern taken from the bellhousing scan. I'm sure it will check out but its good to check. I have already modeled the flange. Just need to mill it out.


_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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Mike9311  



Joined: 14 Dec 2004
Posts: 839
Location: Chicago-ish

PostPosted: Wed May 20, 2020 10:54 pm    Post subject: Reply with quote

Should have the body together and welded up today. The aluminum tube has been straightened (no small feat). Both flanges are ready. Tube is being machined this morning before fitment for welding. Also in the works and nearly ready for the same, is a tube for a G31 box for the CS. The centering pins will be bushed to match up to the new tube.


_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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jacobroufa  



Joined: 18 Nov 2016
Posts: 267
Location: Rockford, IL

PostPosted: Thu May 21, 2020 12:38 am    Post subject: Reply with quote

Whoa... So if I understand correctly this is an entirely new type of torque tube with more precise fit bearings? or more easily rebuildable bearings? or both?

Do you think this is easily repeatable / is this going to be offered to the community along with your other projects/developments eventually? Asking for a friend.
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1981 Porsche 924 Weissach
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 903
Location: Maysville, Colorado

PostPosted: Thu May 21, 2020 1:42 am    Post subject: Reply with quote

I made a .dxf file of the strut tower top bolt setup for making a strut tower brace if you would like it. I had to make my own as the local machine shop was too busy and couldn't get to it.
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Mike
Poco a Poco, #033 '78 Vintage racer, SCCA Dp-81
'77 924
cricketdesigns.com
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Mike9311  



Joined: 14 Dec 2004
Posts: 839
Location: Chicago-ish

PostPosted: Thu May 21, 2020 1:53 am    Post subject: Reply with quote

jacobroufa wrote:
Whoa... So if I understand correctly this is an entirely new type of torque tube with more precise fit bearings? or more easily rebuildable bearings? or both?

Do you think this is easily repeatable / is this going to be offered to the community along with your other projects/developments eventually? Asking for a friend.


So throughout the history of these cars there have been aluminum torque tubes. Factory GTR's ran these but also reported trouble with failures. DP cars ran them and several people have made them. Cedric just mentioned someone in europe who makes them. You can buy one for a 928 right now from 928 International ( I think thats the name)

There is also an aftermarket bearing carrier available that is very nice. For me though I would never run a larger bearing. I know this will eventually lead to a 'discussion' which I personally don't even want since bearings are a massive part of what I do. It will be over before it starts

The original bearing has larger internal clearances. This means its sloppier or more loose inside. This was necessary due to the tolerances of the oem tubes being all over the place. Of course the OEM bearings are very hard to find. In the case of the aluminum torque tube being built here, we will use a slightly tighter toleranced bearing readily available. This aluminum tube is straighter than the OEM so the driveshaft won't snake all over or at least that is the plan and can use these bearings just fine. When assembled it might get spun up to 9000rpm on a table.

If everything eventually works out and it can be done economically, then yes, it would be cool to offer for sale. The carriers are rebuild-able and there can even be the option for different durometer rubber in the slots of the carriers.

Originally, I was hoping to offer the carriers for stock rebuilds too but we have to be careful with the bearing used. We can cross that bridge down the road

Stay tuned, I am hoping the outside of this thing is ready today
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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jacobroufa  



Joined: 18 Nov 2016
Posts: 267
Location: Rockford, IL

PostPosted: Thu May 21, 2020 2:13 am    Post subject: Reply with quote

Mike9311 wrote:
If everything eventually works out and it can be done economically, then yes, it would be cool to offer for sale. The carriers are rebuild-able and there can even be the option for different durometer rubber in the slots of the carriers.

Originally, I was hoping to offer the carriers for stock rebuilds too but we have to be careful with the bearing used. We can cross that bridge down the road


Very cool! This is a topic I've been researching since I got my first 924.. Having never had a transaxle car before the noise produced by the driveshaft is really just outrageously loud! I've thought about ponying up for a set of those BlackSea bearings commonly referenced in the aftermarket, but it's an expensive proposition with very little transparency in terms of testing and results. Not having any untoward side effects but loud whirring noise, I'm not rushing to get it done..

Hearing that bearings are in your wheelhouse (if you'll excuse the pun) I'm curious to know what got you on this path, especially given aluminum torque tube failures? And (hope I'm not pushing my luck here) what makes you reticent to use a larger bearing?
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1981 Porsche 924 Weissach
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Mike9311  



Joined: 14 Dec 2004
Posts: 839
Location: Chicago-ish

PostPosted: Thu May 21, 2020 3:59 am    Post subject: Reply with quote

I put myself inside the bearing. Larger balls pushing thru grease and having to spin up (accelerate) and spin down drives me nuts especially when cold. Blacksea had to go that route to get the clearances from commercially available bearings. There was no need to go 'heavy duty' on the bearings since they do very little actual work. Maybe its just me having lived with the G31 1st gear synchro issues including tearing mine down and replacing everything for $1000+ back in the day. No need to add anything that stresses that system. The S2 tranny handles all this easier

We don't know what happened to the old GTR tube failures other than they happened.

This is why I simply want to try myself. Test, get data, and see what we get.
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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CÚdric  



Joined: 27 Aug 2004
Posts: 1976
Location: Sweden

PostPosted: Thu May 21, 2020 4:13 am    Post subject: Reply with quote

The Swedish guy who built one had it in his 968 time attack car, with almost 1000hp, it worked after the strengthened the clamp between the transaxle shaft and gear box input shaft. I guess you will have less power than that

For you other guys, this is a mad mans project, probably nr 205 on the list of improvements you should do on your car. There's so much other stuff to sort fist if you just want to go fast but it's cool, that's for sure
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