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914World.com _ 914World Garage _ Trailing Arm Spherical Bearing
Posted by: yeahmag Jan 21 2020, 03:25 PM
It seems to me that the trailing arms are ripe for a spherical bearing mod. The way the rear toe is set leaves much to be desired, even with (if not more) with Delrin/Teflon bushings.
Has anyone tried to modify the inner ears to allow for a spherical bearing?
Posted by: Mark Henry Jan 21 2020, 03:56 PM
I think it's been done in needle bearings, I have McMarks Full Motion fronts that are NLA.
Elephant has the ploy/bronze bushings with grease zerks that include the shafts.
Posted by: yeahmag Jan 21 2020, 04:01 PM
I have the Rebel Racing units and while they are great, I cringe at the idea of running such a small thrust surface as I increase toe in. You can envision how the thrust surface gets smaller and smaller as the angle increases. Now think about the forces I'm putting through it on A7's!
For a long time I thought about self aligning washers (which I use on the RR front teflon bushings for collinearity), but it seems that lots of work would still need to be done to get those to fit. A simple spherical bearing would be an easy fix, especially if someone already has an ovaled out inner ear.
Posted by: sixnotfour Jan 21 2020, 04:06 PM
Armondo's GT build has em,, "914-6 GT pbase" https://pbase.com/9146gt/image/25824874
needs more surface area..ie bushing or roller bearing.....IMHO
http://forums.pelicanparts.com/porsche-914-914-6-technical-forum/632760-last-new-914-6-gt-project-3.html
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Posted by: Mark Henry Jan 21 2020, 04:12 PM
Armondo's GT build has em,, "914-6 GT pbase" https://pbase.com/9146gt/image/25824874
needs more surface area..ie bushing or roller bearing.....IMHO
https://pbase.com/9146gt/image/36445933
Posted by: jd74914 Jan 21 2020, 04:47 PM
I've done that. Haven't driven yet, but check out my build thread.
http://www.914world.com/bbs2/index.php?showtopic=227430
Posted by: jd74914 Jan 21 2020, 04:51 PM
Sorry, can't find pictures of the real parts for some reason. 
Posted by: yeahmag Jan 21 2020, 04:55 PM
Very cool! Is the new rod running through the trailing arm fixed in someway to the arm itself?
Posted by: tygaboy Jan 21 2020, 04:59 PM
My buddy Martin was over the other day looking at my Tangerine rear pick up point install and he asked "why don't you add a spherical bearing at the end that "adjusts"?
He used to design and fab ProStock drag bike frames for Kosman so has experience with Harley stuff and he pointed me at the Harley Soft Tail swing arm bearing, of all things. Pictured below.
It would require fabbing a "cup" that would weld to the suspension ear, house the bearing and secure it with a circlip.
Something to consider, anyway.
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Posted by: Mikey914 Jan 21 2020, 06:17 PM
We are actually working on a similar product right now. We are in machining right now.
Posted by: yeahmag Jan 21 2020, 06:21 PM
Well then. Let me know if you need some severe duty testing!
Posted by: Superhawk996 Jan 21 2020, 06:41 PM
No spherical for me for street use - no thank you
For racing use sure.
Posted by: jd74914 Jan 21 2020, 10:19 PM
Very cool! Is the new rod running through the trailing arm fixed in someway to the arm itself?
It’s not quite like that in real life. The tube running through the middle is representative of the trailing arm tube with the rolled lips removed. The other parts are then welded into an assembly for each side which was then pressed into the trailing arm and TIG welded around the perimeter.
Posted by: Jeff Hail Jan 21 2020, 10:56 PM
My buddy Martin was over the other day looking at my Tangerine rear pick up point install and he asked "why don't you add a spherical bearing at the end that "adjusts"?
He used to design and fab ProStock drag bike frames for Kosman so has experience with Harley stuff and he pointed me at the Harley Soft Tail swing arm bearing, of all things. Pictured below.
It would require fabbing a "cup" that would weld to the suspension ear, house the bearing and secure it with a circlip.
Something to consider, anyway.
Why not a bolt on solution that's simple and doesn't have a lot of moving parts?
Well at least for the folks that have modified the pickups already. Toe in and toe out on both the inner and outer pivots as well as camber adjustment on both ends.
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Posted by: 914forme Jan 22 2020, 10:41 AM
Even for a stock outer that would work. Flip the bracket over. Rod ends have some advantages in this application. Ready avlibility, easy R&R, heck don't even need to remove the arm to replace the bearing, all win win in my book.
Inside becomes a bit of an issue, but plenty of bearings to do just that at the local farm supply store.
In reality, I would Move the bearing into the arm on the inner side and let it go.
"Very cool! Is the new rod running through the trailing arm fixed in someway to the arm itself?" the bearing would turn ssepart of the arm shaft, just like it does not.
These are the exact same.
So now what are we missing. Roller bearings in the arm make pvferct sense as it keeps the arm and the bearing and shaft all in alignment. The issue is the angle at the end. Just use two pieces maybe 4 to solve the problem. Since you want the nut o the shaft to be seated flat to keep your settings. a semi circle washer with corresponding cup, on both sides solves your issue, and keeps everything working correctly while providing the movement you desire from the arm. You may need some thrust bearings on the outside. Muellers kit had them, and then everything works perfectly.
Look something like this. Concept, not final engineered solution.
BTW, that will cost you roughly $25K in consulting if you use the design or idea. 
Posted by: Toby May 25 2020, 09:30 PM
I'm trying to find the geometry of the rear swing arm and got good info from seeing Jeff Hail's setup. I don't have a 914 but I want to duplicate it's suspension movement, using a bearing and brake from a Pontiac Bonneville SSEi and the drivetrain (mid engine mount).
I'm hoping that you would evaluate the geometry as is for the 914 and make any suggestions for improvement.
Questions I have are camber and caster, toe in and out, does the frame mount horizontally or is there a different angle from the plane of the wheels? For a street machine are rubber bushings the way to go or does it need the precision of needle.
I've read the above posts and hope you guys will direct me to a thread, if this is not a good place to ask for some engineering help. Thanks
Posted by: mbseto May 26 2020, 02:26 PM
Maybe a dumb question but is the goal to
1) allow this to float all the time
OR
2) just allow it to be locked into place after toe adjustment without putting a constant stress on the ear
?
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