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My case is not missing motor screw related but damage is the same. What seems to happen to this engine is that with regular use, wheels got loose and unaligned on their shafts. This cause them to stall b/c of  side rods hit one another and got locked. While gear on wheels couldn't move, DC motor tried spin it's shaft anyway causing damage to the worm gear. 

The thing is, that worm gear elements are made out of  two different materials.
Worm seems to be a steel and its complementary gear on the wheel axle is brass. 
Worm got shredded while gear is intact. How softer metal can destroy harder one ?
Steel should win but facts are opposite.

I'm sorry for theoretical questions, just trying to be logical and learn something from this repair case.

Chris.

Last edited by Chirss

Attaching close ups of worm gear to estimate damage. Worm is shredded, It's complementary gear has some tiny bites but should still work. I didn't find anything cheap on Ebay (only motor with worm posted for ca. $40+ shipping).
I would rather like to buy a worm gear, which is going to last longer than spent money for something what may break again very soon. Can you give me please any recommendations where such worm can be purchased ?

Motor:
Mabuchi RS-385PH-2465, RN500608

Worm:

Dimensions: 6mm x 20mm
Bore: 2mm
Module 0.5M (most likely)
Space between threads (thread pitch): 2mm

Gear:

Dimensions: 13.7mm x 4mm
Bore = 4mm
Teeth# = 21

Attachments

Images (3)
  • 20171110_112930[1]
  • 20171111_173759[1]
  • 20171110_112930[2]
Last edited by Chirss

There was some lubrication (gray grease) but I wiped it off after disassembling damaged parts.
In my opinion steel can't be chewed by brass (or bronze).  It's against law of physics - softer metal can't be used to change structure of harder one. The only possibility is that worm is fact made out of some alloy softer than real steel and bronze.

Last edited by Chirss

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