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Originally Posted by StephGOD
First of all I think what you did here is totally awesome!! Great overall ingenuity and things like this are what make Bimmerpost the best car forum on the interwebz 
With all that being said I do have a couple concerns on the design however and just wanted to point them out before you start mass producing these.
1. The little plastic part circled below is the custom portion of the plastic base that is used to screw into the E9X paddles correct? If so, do you believe this piece is strong & robust enough to hold up to thousands of shifts overtime? Reason I believe this part might be the weak link of the design is because if you look at how the F8X paddles attach to the base you can see that there's a flat metal piece that extends from the paddle and this piece slides into the plastic base and screws in about 3/4" of the way down effectively strengthening the thin plastic OEM base. |
The weakest link (of the adapter plate) is at the bottom of the paddle where it begins to connect to the adapter for the new paddle. Close to what you have circled. I scaled the part down dramatically to find the failure point. however that only considers my paddle itself. There are other plastic components in the paddle shift assembly including a pin which is dramatically smaller as well as a PCB that you would be stressing when pulling on the paddle. If PUSHING against the paddle you are stressing two small tabs in the stock housing. All of these stock parts are MUCH MUCH smaller than the cross sectional area of the failure point on my adapter. They are also likely ABS or PC-ABS versus PC.
As I stated above I have literally stepped on a bracket with one side of it supported by a piece of wood and it didn't budge. I will freely admit I am not a heavy dude, but I assure you if I supported the stock pin or PCB in and stepped on a paddle I would break something.
As for longevity. That is an interesting question. But two things:
1) The stock paddle is actually an aluminum paddle impregnated with a plastic mounting surface.
2) If I look up papers on longevity of polycarbonate (honestly even ANY plastic I suspect) we aren't even in the picture of fatigue. I am including a study done on mechanical and thermal fatigue of PC done by those much smarter than myself (I am an engineer but not a mechanical or chemical engineer). Here is an excerpt:
"The Lexan141R material was injection moulded into tensile bars according to ASTM-D638, having a gauge length of 100 mm and crosssectional area of 3x10 mm2"
That cross sectional area is smaller than the failure point we are talking about here. Using that they collected long term failure data with a certain amount of stress which results in this graph:
Mine would follow the non-annealed line (lower of the two lines).
What does this say? Well it says the failure is not measureable below lets say 40MPa or so. The stress we put on the paddle is a few orders of magnitude smaller than 40 Mpa (~5800 psi).
Even leaving in some room for margin/error this certainly agrees with what I am seeing with physically standing on the part. Most importantly it shows that if you stay within reasonable limits of the part it simply doesn't fail due to applied stress.
https://pure.tue.nl/ws/files/1927251...3620967040.pdf
Quote:
Originally Posted by StephGOD
2. The angle at which the E9X paddles mount to the custom plastic base seems much greater in comparison to the stock OEM LCI paddles. How exactly did you calculate this angle? Just from the few photos you've post it looks like if you mounted everything up including the OEM plastic boot adapter piece that attaches over the electronics then the face of the E9X paddles wouldn't be parallel to the steering wheel. Would you be able to take a sideview photo of the paddles mounted up to the steering wheel?
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You are correct I did measure the stock F8x M3 paddle angle. That is what I started with. After quite a few iterations of the design I ended with an angle slightly more than the stock paddle... But only by a few degrees. You need this additional angle otherwise the paddle is too close to the wheel and will nearly rest on the back of your fingers when you place them on the wheel. Again we are talking about a few degrees here, just enough to offset it a few mm out at edge of the paddle.
Quote:
Originally Posted by StephGOD
3. This is just a thought but I believe if people have upgraded to an actual E9X M3 steering wheel the whole assembly might not physically mount up correctly. The reason I bring this up is because when I did my retrofit the E9X paddle assembly didn't mount seamlessly to the back of my OEM M-Sport steering wheel (i.e. there's a bit of a gap). This makes me think that the OEM plastic adapter boot piece would not work with an actual E9X M3 steering wheel. Could be totally wrong here though lol. Does anyone have any experience with this?
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Now this is probably the best question yet... All I know is the physical mounting surface (against the wheel) is the same between the two steering wheels. I am not sure where that physical mounting plate exists in coordinate space relative to the M-Sport wheel.
Interestingly enough I actually will be replacing my steering wheel with an E9x steering wheel since mine is a little chewed up and I found an M3 replacement for a reasonable cost. So this is something I could actually test out... and probably should considering I will be using these
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It may simply fit right up. If its a small tweak then I could offer two different types. If they are dramatically different then I agree it is possible that the adapter wouldn't work at all.