The Ford Barn

rotorwrench · 01-14-2025, 11:52 AM

The short stop circuit breakers that Ford used in the post war era were a simple bi-metallic switch. Heat is what reacts them. The bi-metallic strip gets hot real quick in a short situation. They had bi-metal switches down to a science pretty early on. King Seeley used this principle for their pressure and quantity indicator systems as early as 1936 when Ford started using them. They are very reliable but can be destroyed in a dead short situation.

Aircraft circuit breakers work on the same principle but they have a toggle mechanism that must be reset to restore current flow. If the short still exists after a trip then the bi-metallic switch won't allow it to reset as soon as it heats back up. A short stop automatically resets after the bi-metallic switch cools back down but will continue to trip as long as the short is still present. Bi-metallic switches are calibrated for the amount of heat they can take before bending. A smaller wire can take less heat so the switch is made to bend at a lower temperature.

01-14-2025, 11:52 AM	#1
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 17,410	Re: Electronic Circuit Breaker The short stop circuit breakers that Ford used in the post war era were a simple bi-metallic switch. Heat is what reacts them. The bi-metallic strip gets hot real quick in a short situation. They had bi-metal switches down to a science pretty early on. King Seeley used this principle for their pressure and quantity indicator systems as early as 1936 when Ford started using them. They are very reliable but can be destroyed in a dead short situation. Aircraft circuit breakers work on the same principle but they have a toggle mechanism that must be reset to restore current flow. If the short still exists after a trip then the bi-metallic switch won't allow it to reset as soon as it heats back up. A short stop automatically resets after the bi-metallic switch cools back down but will continue to trip as long as the short is still present. Bi-metallic switches are calibrated for the amount of heat they can take before bending. A smaller wire can take less heat so the switch is made to bend at a lower temperature.