Cracked sport seat hinge gearbox - first prototype ready

BenGerman · Post by **BenGerman** » Jan 18, 2017 8:12 PM

After having problems with a "rocking" drivers seat in my 535is I also discovered that one of the hinge gearboxes of the seats in my M5 are broken.
They came in cast aluminium from the factory, which seams to have a weak point at the lower part where the two worm gears are mounted.

I thought about this when is first detected it but now it starts to make more sense.
I would like to have the whole gearbox remanufactured from billet aluminium. Maybe with a couple upgrades to strengthen that certain area for the future.
After some research I have found that this is a pretty common failure on these seats and it's usually fixed by replacing the parts with parts from donor seats. Since these are not going to be available forever and replacements parts are $300 from BMW NA each, I think it would make sense to come up with an improved part.

My question:
Would there be an interest in these parts here from anybody? Is it common that only the front plate of the housing brakes or is it also the back part?

I will have drawings made up soon and maybe a first prototype in a couple of weeks.

BenGerman · Post by **BenGerman** » Jan 19, 2017 10:15 AM

Took the cover of the three remaining seats yesterday, ALL of them show cracks in the lower part.
The material is so unstable, I'm afraid to break it in two pieces just by looking at it.

I'm working on the quote/drawing for the front plates right now. Will most likely order a couple more, if somebody is interested.

vandiesel · Post by **vandiesel** » Jan 19, 2017 10:45 AM

I'm interested. Post up what you find out.

Yojedi · Post by **Yojedi** » Jan 19, 2017 11:32 PM

Ditto, +1

BenGerman · Post by **BenGerman** » Feb 09, 2017 8:26 PM

Just a little teaser...

dcains · Post by **dcains** » Feb 09, 2017 9:38 PM

Impressively nice work. Please keep the thread updated.

Mike W. · Post by **Mike W.** » Feb 09, 2017 10:14 PM

I like it.

3D printing had crossed my mind, but I was thinking metal, even weak metal, has a variety of properties that often make plastic replacements inappropriate. But a redesign in plastic looks like a winner. You looking at making them or having them produced or what?

Is this the power sport or manual sport or both?

BenGerman · Post by **BenGerman** » Feb 10, 2017 2:02 AM

As of now the idea is to make it from Aluminium and strengthen the areas where it cracks.
The original plate is some kind of high magnesium alloy, super light weight. I'm not afraid to add a bit of weight for a good increase in strength.

It is just for the electric seats used in E28 and E24.
If there is appropriate demand for the manual seat, we can look into that.

The plan is to have the first prototype on the machine in the next couple of weeks.

Will keep you updated!

tn535i · Post by **tn535i** » Feb 10, 2017 9:44 AM

Once you generate a drawing I would think CNC from aluminum is the best way to go with thicker sections when possible. Is that what you are talking about?

Any plastic I can think of would be a sure fail over time if not instantly and ANY 3D printing other than very sophisticated stuff has no chance other than testing for fit.

I am curious to see what you come up with !

BenGerman · Post by **BenGerman** » Feb 14, 2017 11:46 AM

Yea, that's the plan. Might get to that next week.
I think a Aluminium solution is very feasible, no reason to go with plastic. Once the clamp for the part has been made, it is easy to produce them in bigger quantities.

I'm still thinking about also drawing up the back part. It is just way more complex and none of my seats really show an issue with it.

Pauly Walnuts · Post by **Pauly Walnuts** » Feb 15, 2017 12:59 PM

Mine aren't even cracked yet but I'm interested

tn535i · Post by **tn535i** » Feb 15, 2017 2:48 PM

Me too since my driver's seat is out and has been for repairs to the bolster and maybe I replace before putting back.

demetk · Post by **demetk** » Feb 15, 2017 2:56 PM

BenGerman wrote:

Just a little teaser...

Do those cracks go all the way to the other side or are they just casting cracks?

BenGerman · Post by **BenGerman** » Feb 16, 2017 6:11 PM

They show on the other side.
Also this is exactly were one of them broke for me.

I can imagine that the if the seat is reclined with (heavy) load in it, there is a lot of stress on those worm gears.
Since this is the weakest area on the part, that is were it starts to crack.

demetk · Post by **demetk** » Feb 16, 2017 6:35 PM

Thanks. Did you decide on the material? Aluminum, SS Steel? I would imagine that the CNC machining process will be the same no mater what material is used?

BenGerman · Post by **BenGerman** » Feb 16, 2017 9:11 PM

I don't see an advantage going Stainless, I think I will go 6061 Aluminium. Most likely dark grey anodized for a stealth OEM look.
Stainless would make the part more expensive and I don't see an advantage if I strengthen the weak spot on the part.

jhh925 · Post by **jhh925** » Feb 17, 2017 12:50 PM

Subscribed & interested in parts. Thanks!

BenGerman · Post by **BenGerman** » Feb 17, 2017 4:39 PM

Sample will be ready by sunday! I will keep you posted.

BenGerman · Post by **BenGerman** » Feb 19, 2017 8:44 AM

89bigcoupe · Post by **89bigcoupe** » Feb 22, 2017 1:21 PM

Both my cars have this issue and would love to see this project go through!

BenGerman · Post by **BenGerman** » Feb 23, 2017 10:00 PM

We are still working on it, just have lots of other stuff going on with the M5.
We should have a fully working sample ready by the end of next week. There are still a couple of things I need to figure out.

After I have tested it on the seat, it won't take long to run a batch of 10-15 pieces.

BenGerman · Post by **BenGerman** » Mar 06, 2017 9:15 PM

That stuff is just like good wine... the longer it sits...
Sorry for the delay, there is progress in the machine shop!

By the end of the week I have one test fitted.

They will be available anodized in dark grey or black.

BenGerman · Post by **BenGerman** » Mar 07, 2017 9:16 PM

Ladies and Gentlemen, there it is.

Next steps: Testfit, Mirror for other side, more testfitting, try it on my car, figure out pricing.
My goal is to have the first sets ready for shipping or in person delivery to the vintage, so mid may.

I will start a separate thread for ordering the parts and keep this updated.

BenGerman · Post by **BenGerman** » Mar 09, 2017 9:55 PM

There we go:

Still a couple more details to figure out, but it is working! Finally sitting straight up in the car again.

The the outside is not in the future finish yet. Left it raw for the prototype.

The other side is not done yet but seems like an exact mirror. So it should be pretty easy to do. I will do enough to equip my car for now and see how they work under load, but I don't expect any surprises. Assembly is pretty straight forward, but I do recommend taking the whole box off and getting that nasty, old, gummy grease out and filling the box with fresh grease.
Will do a How-To later.
15 min job and can be done while the seat is in the car, if you don't refresh the grease.

ElGuappo · Post by **ElGuappo** » Mar 10, 2017 12:59 PM

This is great stuff.
I love it that new solutions are still being figured out for old problems like this.

tn535i · Post by **tn535i** » Mar 10, 2017 6:02 PM

And isn't it interesting that it's still worth the effort of finding solutions to problems you would never have encountered if it wasn't worth keeping the car going for so long in the first place.

Just last night in parking lot (Harbor Freight btw) some guy said to me, "I had one of those cars once and loved it and should have kept it".

Pattonky · Post by **Pattonky** » Mar 10, 2017 6:35 PM

I am interested in this as well.

BenGerman · Post by **BenGerman** » Mar 11, 2017 7:32 AM

There is so many great fixes and mods for this car that got started on this board.
If there is a problem that can't be fixed easily and parts are hard to find, somebody will get so annoyed that he will start looking for a new solution. This is what happened here.

I don't think this will happen to a lot of newer cars in 20 years.

We are still working on the program and figuring out the details but I should have a cost estimate within the next two weeks.

Yojedi · Post by **Yojedi** » Mar 11, 2017 7:20 PM

BenGerman wrote:There is so many great fixes and mods for this car that got started on this board.
If there is a problem that can't be fixed easily and parts are hard to find, somebody will get so annoyed that he will start looking for a new solution. This is what happened here.

I don't think this will happen to a lot of newer cars in 20 years.

We are still working on the program and figuring out the details but I should have a cost estimate within the next two weeks.

jon roll · Post by **jon roll** » Mar 11, 2017 9:49 PM

I'm interested

Brian O · Post by **Brian O** » Mar 12, 2017 1:50 PM

Cant wait to see these available. I need two!

BenGerman · Post by **BenGerman** » Mar 18, 2017 12:13 PM

Pauly Walnuts · Post by **Pauly Walnuts** » Mar 18, 2017 4:40 PM

This may have been asked but I'm assuming the passenger and driver's side are the same?

BenGerman · Post by **BenGerman** » Mar 18, 2017 6:05 PM

They are both the same. There is a left and a right piece.

Brian O · Post by **Brian O** » Mar 18, 2017 11:36 PM

Any chance you will be doing the other half of the gearbox?

BenGerman · Post by **BenGerman** » Mar 19, 2017 12:32 AM

We have thought about it, but it requires quite a bit more machining.
The integrated gear set would be hard to do for a reasonable price.
I have an idea how to avoid it, but I will not have time to take care of it before later this summer.

So the answer is: maybe, but not in the beginning.

Do yours break in the back, where the transfer cables attach? Do you have a picture of the defect?

Brian O · Post by **Brian O** » Mar 19, 2017 1:18 PM

Yes it is where the cables attach and turn the plastic gears. I would love to hear a workaround

I'll post pics tonight

Here is the pic of one of the broken ones. [img][http://s44.photobucket.com/user/Brianeh ... ml?o=0/img]

BenGerman · Post by **BenGerman** » Mar 20, 2017 4:53 PM

I mounted them on the seat last night, super easy.
Will do the same thing in the car next week and check how they work.

There should available capacity on the machine by late April.
We also have a pricing figured out. I will make that official as soon as the plates have been tested on the road.
Is not a super cheap fix but way cheaper then buying the whole assembly or getting a used seat for it.
Plus you won't have to worry about them braking again.

They will by anodized dark grey or black.

duggi · Post by **duggi** » Mar 20, 2017 5:18 PM

Consider me impressed! When this thread first started I'll admit I was a bit skeptical, but damn, nice job! My driver's seat had this issue at some point before I got it, as it has a replacement gear box on it already with a more modern BMW sticker, but I'm sure the others will need attention eventually.

Now..next problem: is there any effort being made to reproduce the plastic covers that hide these boxes?

(fwiw that was a total joke, you've done more than enough just doing this!)

tn535i · Post by **tn535i** » Mar 20, 2017 8:13 PM

Very very nice work by the OP.

I guess those plastic covers can be 3D printed by someone.