Sunroof Kinematics

[CA2kMcoupe]

Hi Ben! Can I still buy some parts from you? Thanks!

[JBZ4]

Following

[rustnrot]

Subscribed. I hope these parts are available again in the future.

[ddbaker3]

Hi everyone! I've also fallen victim to broken sunroof parts on my 2.8 coupe. I'm developing a solution to this problem and it may take some time, but my goal is to have this ready before summer. I really want to make sure this is done properly and I'm hoping that this will help a lot of people preserve their coupes.

I'll keep everyone updated!

[30yrMbr]

Is this a M-coupe problem or is it affect the Z coupes as well?

Following in case ddbaker3 comes up with a solution.
THX

[s8ilver]

Is this a M-coupe problem or is it affect the Z coupes as well?

Following in case ddbaker3 comes up with a solution.
THX

They share the same sunroof. Problem is across the range.

[ddbaker3]

I've made some progress and I'm in the middle of finishing up prototypes right now. I think this solution will work well and it will avoid having to cut the factory crimp off as I couldn't find a new one that would work. The original broken part will be cut length-wise (w/ dremel) to free the cable. This will be a snap fit part and it fits very nicely into the aluminum channel.

The next step is to finalize the some details and where I'll source these from and then they should be ready to order. It's a struggle to upload photos to this forum, but there are a few more in this imgur album:

https://imgur.com/a/CiFq7Kh

Thanks everyone

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[MartyBtoo]

I'll be interested in one once you've completed testing. I would like to have it in my just-in-case-I-ever-need-it kit (already has Randy's subframe kit and a few other doodads).

Marty

[JBZ4]

I am also definitely interested, were these 3D metal? There are a few others attempting to manufacture but yours seem to be the closest to completion. Thanks for attempting this. JB

[ddbaker3]

The prototypes are 3D plastic just to verify the design, but 3D metal parts are currently in process

[Randy Forbes]

Nice work! I'd like to secure a pair of those too, you know, just in case I ever raise the sunroof again (last time was either when I did the Coupe seen earlier in this thread, or when I replaced the headliner with Alcantara.

I don't know the tensile strength of 3-D printed metal, can it handle the uneven pull on that cable attachment? Beside a snap-fit, are you planning a secondary means of attachment?

Based on what I've seen of the originals, do you really need a Dremel to free the cable? I think you could just crack it with a couple raps from a jeweler's hammer.

Lastly, can the 3-D printing be embedded with some kind of lubricant? Might be a good candidate to apply a dry-film lubricant to the little pad contact- points.

Like I said, nice work!

[ddbaker3]

Thanks!

I think you're right about the jeweler's hammer, the original metal is so brittle. The main thing is to keep the steel cable intact whatever method.

The 3D printed metal will be more than strong enough, I just may have to do some post-processing if the surface needs extra smoothing. The snap fit has worked really well so far and the channel in the track really doesn't allow it to move or come out once inside. That helps the snap fit case, but makes secondary attachment really difficult to solve. I'm still looking into maybe adding a through hole and tying the cable in place with a thin wire, but I'm not too worried about it. If you really wanted to, you could add some glue, JB Weld, Solder, etc. but I personally wouldn't want to do that. It seems like the steel cable wrapped with the pipe cleaner type material is the real item that would be impossible to replace so I want to keep mine as clean as possible.

As far as lubrication, I don't think there are any metal options that can have it embedded right now, at least at a reasonable cost. There are a few plastic options that I've tried, but they won't hold up long term. I'll try to find some small packets of grease to send with these so it can be an all-inclusive repair.

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[JBZ4]

Looking really good. Appreciate all the work you have into this project. I also don’t see any secondary way to hold the cable in place. While you could drill for lock wire I haven’t ever used any below 0.032”. With JB weld you are going to have to go light or contour it.Thanks again, looking forward to having an operational sunroof! JB

[Randy Forbes]

ddbaker, I've got you covered when it comes to "small packets of grease."

I used to include a couple of these with each shortened shift lever I'd sell. I probably had to buy 200 of them to meet their minimum, still have a bunch left, which you're welcome to.





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[ddbaker3]

I've got a few updates to post.

Firstly, thank you Randy for offering the packets of grease. Those look like they'd be perfect and I'll PM you about them once I think I'm at the point where I can ship some of these.

I've been experimenting with different types of 3D printed metals. There is quite a variety to choose from and this part is pretty intricate so it's been pretty difficult to nail down a good material. So far, I've tried a sintered aluminum (left), metal filament stainless steel (middle two), cast bronze (right), and I've also got a binder jet stainless steel part in the mail which should arrive in a few days.

As you can see, the sintered aluminum is pretty rough and required a lot of post processing and still didn't quite work. The metal filament parts were a bit nicer, but still not nearly clean enough to be usable. The layer lines can be too large to always be accurate and the slightest inconsistency makes it hard to work inside of the aluminum track. I'm hopeful that the binder jet stainless part will be much finer in quality, but I did have to approve with the printing company to go ahead and "print it anyway" because they noticed some risky areas based on the parameters of the binder jet material. Telling them to "print anyway" means that I'll receive whatever happened and it may be deformed or incomplete somehow, but I like to try it and it helps these companies to develop their processes when customers are willing to push the limits a bit.

So the cast bronze piece is great and I'm really happy with how it turned out. The part is first printed in wax and then the casting is created as if this was a piece of jewelry, so the resolution and accuracy is very good. The downside is that it's more expensive than any of the steel or aluminum materials, but still much much cheaper than trying to buy the whole OE sunroof assembly these days. If the binder jet steel part works, it'll be more affordable than the bronze. But if not, this part will definitely solve the problem with the added benefit of being a little bit flashy haha.

I still need to figure out a few more details and how to go about selling these. I'm sure I could get some kind of volume discount when ordering, but I'm not sure how many people might be interested yet. I also want to see if I can replace the pins and C-clips with something threaded to be able to remove the whole glass piece easily. Someone help me give credit to the original guy who machined some removable pins, I can't seem to find that post right now.

Thanks!

Check out a few pictures and this youtube video:



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[s8ilver]

Incredible work and dedication. Count me in for a set. That bronze casting is amazing (not that the others aren't), but clearly price will be a driver for many, not that they have an abundance of alternatives. Pay to play, as they say.

Ron Stygar offered the pins, but is no longer with us. R.I.P.

http://www.unofficialbmw.com/e36/ext...y_removal.html

[ddbaker3]

I got the binder jet steel parts in and they are unfortunately not consistent enough to be useful. They were so close to working well, but there was some warping in the base and the snap fit worked okay on one and was too tight on the other. If there's any warping in the part that holds the wire, it won't fit into the channel at all. So I can't go with this material.

I think I've exhausted my material choices unless I wanted to try and get a mold to actually die cast these, but that's way outside of my budget and probably outside of the demand for these as too. So cast bronze it is and I'm really happy with it. I also like the idea of bronze contacting the aluminum channel vs a steel part to limit the wear and tear.

I have been able to change the design quite a bit to remove material and it's really cut down on the cost of these. BMW probably didn't care since they weren't making one-off parts in bronze, but this should work just as well and will probably be even stronger. The 45 degree arm that usually breaks on the original part can now be merged into the front foot and I think this will help. As far as I can tell, there's no reason to have so much extra material and the most important thing is the relationship of the upper hole to the snap fit for the wire. As long as those two features don't change their location, I can really get a lot of the extra bronze out of this thing. The last version was 2798 cubic mm and the new version is only 1880 cubic mm.

This whole process is taking longer than I expected, but I'm still working on it!

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[JBZ4]

Thanks for the update and your hard work. Waiting patiently for the final product!!!

[cleanerPA]

Kudos to your work, but is bronze strong enough to not break the same way as the stock OEM pot metal pieces?

I paid the exorbitant price for the CNCed stainless steel pieces because I know they won't break like the pot metal ones and I'm not in the position to have stuff machined for me.

[ddbaker3]

That is a good point and I can't say for sure until I've had a chance to really test these, but I'm confident that they will work well. The original connection point is so thin and brittle and I've done my best to beef up that connection as much as possible. I've also been able to tie it into the front foot now for added strength so I think they will hold up over time. The key with this is to add some lubricant every 6 months to make sure that nothing is sticking or binding.

At the very least, I think I've been able to document this with a lot more detail than some other attempts and I do have 3D files now that I could get CNC'd, but for a much higher price. My goal is to get these at a price point where even if they do give out after a few years, you'd be able to replace them multiple times and still end up spending less than buying a whole new assembly and knowing for a fact that those OEM parts will break at some point.

So if the bronze doesn't work out, this project is still on as a CNC part, but it would maybe price some people out. I really want coupe owners to be able to open their sunroof again and keep these cars in full working condition.

[robb1887]

I haven't torn my sunroof open yet to see the kinematics in person, but is the 45* angle of the cable attachment not an interference to the track for the feet or does the track not come in that close to the upright section?

[ddbaker3]

If you scroll back up to post 112, there's a decent picture of what the track looks like. There isn't any interference and there was actually a lot of extra room with the original slider part so I'm not sure why BMW didn't make their 45 degree arm a bit larger.

[BrightEs]

Another alternative is steel or aluminum and leave the tabs slightly undersized allowing for an epoxy pot dip then cure on all four tabs. The rough surface finish of the casting could help to promote adhesion, and will provide a polymer barrier between the aluminum extrusion and the bracket. BMW took a similar route with the overmolded tabs, albeit in a more true mass production fashion.

+1 for all that's taking place here, this is a crazy amount of work you've already completed.

[JBZ4]

Hello, any updates?

[ddbaker3]

Sorry for the delay, it took quite a while for the new version of the part to show up. I think there was a slight delay in making the part, but shipping took forever.

I've finally received the new, smaller version and I'm happy with the results. None of the functionality has been lost and I believe that this part will be stronger than the original. Using the casting process has allowed me to add some interior ribs for strength and I've been able to join the 45 degree angled piece with the front foot of the slider. This 45 degree part seems to be the weak point in the original so I'm confident that this change will help. See the picture with the red circle drawn in.

I've got two of these and I'll be installing them on my car in the next day or two and should have some updates soon. If everything works as it should, I'm just about ready to take some orders.

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