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Unread 25-01-2006, 08:12
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Joe Johnson Joe Johnson is offline
Engineer at Medrobotics
AKA: Dr. Joe
FRC #0088 (TJ2)
Team Role: Engineer
 
Join Date: May 2001
Rookie Year: 1996
Location: Raynham, MA
Posts: 2,648
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Re: Window motors....

Quote:
Originally Posted by Leo 1529
we decided against using the window motors so we could use the Bosch motor for our robot and we were also concerned with the strippage that could occur within these motors
It is possible to strip the internal plastic gear but not easy.


We discovered this in 1999 when a failure cost us an easy win and eliminated us from the tournament at the Championships at EPCOT.

Do not run these motors into a brick wall at high speed.

We had an arm that lifted us off the ground. The arm used an "over center" linkage to lock our arm in place. What would happen is every time we lifted, the motor would drive this overcenter arm into a stop. We made no effort to slow the arm down, we just ran it into the stop. After a season of lifting perfectly, the motor developed a hard spot where the gear teeth were bent from repeated bashings. In our last match of the season, the robot just would not lift off the ground. Root cause analysis showed that the plastic gear was the problem. Note that a window motor would not have failed in this way because window motors are designed to be run into a brick wall at full speed -- they have an internal rubber coupling that prevents the full shock load from going into the plastic worm gear.

Bottom line... ...don't run power sliding door motors into a hard stop at high speed.

Note: for a conveyor application I doubt you will have to worry at all.

Joe J.
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