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Spiral Springs; Power Springs and Clock Springs
Because constant force springs usually function like an extension spring you can look these up on this great web page- Constant Force Springs-Design, Types and Uses The other various types of spiral springs each require different design formulas. Let's look at them by their name.
Hairsprings are open wound spiral springs that are usually small in size. Their main character is the uniform spacing between the coils. This shape is know as the Hairsprings are normally used in the Imstrument Industry. This would include timing devices, meters, anti-backlash mechanisms between gears, etc.
The manufacture of this type of spring requires special equipment and special skills. This equipment and skill is different from those used for any other type of spring.
A good reference for this would be, A Practical Guide for Hairspring Design by T. Raedy in Machine Design May 12, 1966.
Brush Springs are called that because they have been used for such a long time to apply pressure to carbon brushes in electric motors and generators.
This is also an open wound spiral spring but it is made from much heavier material than a hairspring. Brush springs are characterized by having all coils active through most of the travel. The length to thickness ratio should be in the range of approximately 200 to 1,000.
In the standard formulas for brush springs the torque formula indicates a stright line load/deflection curve. This is true for small deflections, like 180 degrees, where the active length remains constant and the coils do not rub.
For larger deflections, like 360 degrees, this is still true. Except, the performance of the spring depends on other factors like-
A precise solution to this design problem would be too complicated to consider. The formulas we show above are approximate. They are based on-
Clock springs or power springs have a rotation starting at about five turns and a length/thickness ratio starting at about 2,700. Their names describe their applications and functions. As the strip material used becomes longer the spiral becomes larger and the space between coils becomes larger.
This is why it is necessary to retain the spring in some sort of housing.As the arbor rotates to wind the spring the coils gradually pull away from the housing. The gradient of the spring decreases because of the increase in active length. The usual spring spring formulas can not be used in designing this type of spring. The active length changes as the spring deflects. We will be adding information related to spiral springs, so please check back. Our team and visitors to spring-makers-resource.net will be contributing. Got some info you want to share? Send it our way -
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