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I am rebuilding several SIT units and have noticed that the field and the armature combination for a 1947 version gets very hot to the touch even when it runs with no load. I have changed fields and armatures and have not changed the temperature. The 1947 field has 12 metal plates and the armature has 10 steel plates. My 1946 armatures and fields have 9 plates each, so I believe that I have the correct plate and field combination for 1947. Is there a 1947 armature with more plates (12?) that would match the field? Any observations or suggestions would be appreciated. I do not believe that the motor would survive running such high temperatures.
 

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I can look up all the specifics for the SIT motors when I get home, which will be Monday PM. I am relctant to reply from memory. The motors will definitely get hot. Try touching the motor parts in a Gilbert diesel when the shell is off, just be careful, they can burn you quickly.
 

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I am rebuilding several SIT units and have noticed that the field and the armature combination for a 1947 version gets very hot to the touch even when it runs with no load. I have changed fields and armatures and have not changed the temperature. The 1947 field has 12 metal plates and the armature has 10 steel plates. My 1946 armatures and fields have 9 plates each, so I believe that I have the correct plate and field combination for 1947. Is there a 1947 armature with more plates (12?) that would match the field? Any observations or suggestions would be appreciated. I do not believe that the motor would survive running such high temperatures.
I currently have a ‘46 & a ’47. Just tried them both at 15v for over 5 minutes with the load of the smoke unit. Both are only somewhat warm to the touch with the ‘47 being the cooler of the two.
 

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I do not like "really hot" when it comes to electrical items. I had, well still have, a 282 steamer that the motor ran too hot. Very hot. It got so hot it scorched the inside of the boiler shell. And was running slower than it should at given volts. Sounds like you have done what I did to find the problem. I did parts changing till the problem was found. Turned out to be a bad armature. Now I can run the engine fast and hard and motor will not even get warm. Keep changing parts till problem found. Change one at a time and test run. Good luck. There is a problem I just have no guess of what it is.

By the way my armature tested good on my meter, but it wasn't.

Check your wiring. Shorts will cause heat. Reface armature, check brushes
and springs, Clean the grooves between the segments on armature face. small drop of oil on each end of armature.
 

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Returning to the original question, there are two different motors used in SIT engines. The early version has a 9/32" armature stack with an 8/32" field stack. The later version motor has a 10/32" armature stack and a 10/32" field stack. The early and late armatures are wound almost the same and have the same DC resistance.The fields are wound differently and the later field has a 15% greater DC resistance.
 
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