Source for Plastic Gears?
 

'91 500 SL ... power seat problems...

The electric motor that drives the seat's fore and aft movement connects via a flex rod to a "transmission" that is responsible for actually moving the seat. The transmission "failed" ... upon disassembly it was found that the flex rod connects to a spiral cut driveshaft via a hard plastic (nylon?) gear. The gear had cracked into two pieces and thus no power was being transmitted to the driveshaft; otherwise the transmission was flawless. The gear can easily be replaced.. if only it was available. M-B offers no repair parts for this transmission; cost for a new assembly is over $400.

Same situation for the seat's power head rest... the head rest motor drives a cable which in turn connects to a theaded rod assembly carrying the head rest. The metal threaded rod contains a plastic gear at the top.. and the gear has cracked and no repair parts are available from M-B.

Is there an alternate source for these gears?

I've contacted Odometer Gears Ltd (www.odometergears.com) and he's willing to have a go at this. However, there remains the question of strength... the seat travel gear must be capable of bearing the weight of an adult... and if his standard issue gear is too weak/soft, he states an injection molded process would be required. The mold for such could cost >$5K and the lead time might approach 2 months.

Any suggestions?

I have a failed right rear power window regulator that doesn't work because the plastic gear is stripped. I sure wish I could find one of those.

Have you seen the gear? Pretty weird looking...

...also flexible, not rigid. Not an off-the-shelf part at all!

My driver's seat rear height adjustment has the same failure...was quoted $350 at the dealer for a new motor assembly.

Broken shaft caused one side to raise and lower only, leaving the entire seat listing to one side.

So for now, I adjusted until it sits level then disconnected the harness from the module under the seat until I can find a suitable replacement...:rolleyes:

How about a pic? Next to a scale?

Steve

How is this for a 140 chassis seat height picture:

Or this for scale:

You might want to pose this question to Jeff at Odometer Gears Ltd in Virginia. Perhaps there is enough market for them to tool up a run. www.odometergears.com No personal interest, they just provided an unusual product and good service for me.

I'm not gonna ask the obvious question, why does the car "engineered like no other car in the world" use plastic gears? I'd like to ask that but I won't.

I wonder if it isn't possible to glue this together in order to form a silicon rubber mold and then run a production using a polymer resin final product.

Anyone in this line of plastics composite works???

Well from my engineering training and my technical experience, I would say they did it for noise suppression and smoothness of operation. It is also likely that by using a 10 times larger gear in plastic than a three times tougher gear in metal they designed a gear that last three times as long.

Even with my background I try not to "Monday Morning" engineer.

Obviously, the material used is a critical design component.

http://www.hpcgears.com/products/helical_gears.htm

there must be a company like this in the US - they make and stock plastic gears - just make it from nylon 66 or delrin - i would guess about 20 bucks tops.


or take the broken gear to "a.n. other engineering company inc." and ask them to make you a new one - or a dozen and sell 'em on here ;)

i had stripped gear in seat belt presenter and could not locate used unit subsequently had one made here(queensland,australia) from brass for aboutAUS$140(= US$110 approx.
i first tryed an off the shelf delrin gear that had to be machined to correct axle diameter.( it lasted two days).
cost of that exercise $80, hence the brass gear.
the lot that did the brass one are setup to do smalll gears but need sample. if anyone wants their address e-mail me.

Pictures, anyone recognize the upper left gear?