External metal jacket on the Drill motor and FP motor, WHY?

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Posted by Dennis Hughes at 05/30/2001 2:01 PM EST


Other on team #27, Team Rush, from OSMTech Academy & MTA and TEXTRON Automotive.



Can anyone explain the purpose of the metal jacket on the Drill motor and the FP motors. Can you remove it and still get the same performance??

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Posted by Joe Taylor at 05/30/2001 6:39 PM EST


College Student on team #461, West Side Boiler Invasion, from West Lafayette High School and Purdue University .


In Reply to: External metal jacket on the Drill motor and FP motor, WHY?
Posted by Dennis Hughes on 05/30/2001 2:01 PM EST:



I think It's just there so the effect of the magnetic field from the motor is less dramatic to surrounding componentry. We've run without it with no apparent performance loss, and taking it offf actually aided in cooling the motor down.

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Posted by Mark Garver at 05/30/2001 8:04 PM EST


Student on team #68, Truck Town Terror, from Waterford Kettering/OSMTech Academy and General Motors Truck Group.


In Reply to: External metal jacket on the Drill motor and FP motor, WHY?
Posted by Dennis Hughes on 05/30/2001 2:01 PM EST:



Dennis,
My team has come to the conclusion that the metal jackets are strictly heat sinks. We have taken them off some of our motors and discovered that they do heat up alittle quicker, not much though. My team has also found that by taking this heat sink off and manufacturing our own heat sink (which are bigger and made out of alum.) the motor cools more quickly.

: Can anyone explain the purpose of the metal jacket on the Drill motor and the FP motors. Can you remove it and still get the same performance??

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Posted by Joe Johnson at 05/30/2001 9:57 PM EST


Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.


In Reply to: External metal jacket on the Drill motor and FP motor, WHY?
Posted by Dennis Hughes on 05/30/2001 2:01 PM EST:



The extra metal case is there to help strengthen the magnetic field in the path of the armature. It helps increase the output of the motors by a small but significant amount (10% is a good rule of thumb as I recall).

The normal case of the motor is not sufficient for the Mabuchi and the Johnson Electric motors to direct all the magnetic flux from the permanent magnets toward the armature. This extra magnetic material around the outside makes the PM magnets more effective. There is no benefit to having such extra pieces on motor housings that are thicker (such as all the other motors in the kit).

I may be wrong but I think these bits of metal are called flux yokes -- I was sure until I started to type this message and I got cold feet. Some other motor guru help me out here.

You can take them off if you like, but your are giving up motor performance if you do.

I can tell you that you aren't likely to see a Chief Delphi robot without them any time soon ;-)

Joe J.