Source for Plastic Gears? - PeachParts Mercedes-Benz Forum

jgl1 · #1 03-01-2004, 02:08 PM

'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?

Cap'n Carageous · #2 03-01-2004, 02:24 PM

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.

G-Benz · #3 03-01-2004, 03:00 PM

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...

sbourg · #4 03-01-2004, 03:50 PM

How about a pic? Next to a scale?

Steve

stevebfl · #5 03-01-2004, 05:08 PM

How is this for a 140 chassis seat height picture:

stevebfl · #6 03-01-2004, 05:10 PM

Or this for scale:

greenacres2 · #7 03-01-2004, 05:57 PM

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.

Cap'n Carageous · #8 03-01-2004, 08:37 PM

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.

git0 · #9 03-01-2004, 08:57 PM

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???

stevebfl · #10 03-01-2004, 09:12 PM

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.

guydewdney · #11 03-02-2004, 04:56 AM

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

kel347 · #12 03-02-2004, 06:02 AM

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.

stevebfl · #13 03-02-2004, 07:40 AM

Pictures, anyone recognize the upper left gear?