This technical information has been contributed by
Ace Wire Spring & Form Company, Inc.
Click on Company Name for a Detailed Profile

Drawbar Springs Specifications

In Ordering Give The Following Information As Completely As Possible:

• Assembly Length, Maximum, Minimum. Spring Length, Maximum, Minimum
• Controlling Diameter, Outside Diameter Maximum. Inside Diameter Minimum. Pitch Diameter. Works Inside (Dia. Hole). Works Over (Dia. Shaft).
• Number of Coils.
• Wire Size. Decimal size if possible. Material, Kind and Grade.
• Loads at deflected positions.
• Style of Ends. Standard, Strap, Eye, Enlarged
• Finish. Plain unless otherwise specified.
• Maximum Solid Length.
• Frequency of Compression.

How to Determine Rate For Drawbar Springs

Rate which is the change in load per unit deflection, may be determined by the following procedure:

1. Deflect spring to approximately 20 percent of available deflection and measure load (P₁) and spring length (L₁).
2. Deflect spring to approximately 80 percent of available deflection and measure load (P₂) and spring length (L₂). Be certain that no coils (other than closed ends) are touching L₂.
3. Calculate rate (R) lb./in. (N/mm)
   R = (P₂ - P₁) / (L₁ - L₂)

Design Hints

1. Compression springs are the easiest type to make, and can be made more rapidly and accurately than other types. Should be preferenced to other type of springs as well.

2. Avoid using open ends or open ends ground. Such springs usually tangle when shipped. They also buckle when deflected.

3. Use closed ends not ground whenever possible, especially on light wire, or where a large spring index prevails.

4. Use closed ends ground and state degree of squareness on important springs and on those used under diaphragms or in regulator valves, or where buckling might occur.

5. Use conical springs when a short, solid height is needed and to reduce buckling and surging.

6. Avoid using conical, barrel shaped, or other special shapes, including tangs on the ends, when a standard helical spring could be used.

7. Design springs with a reasonably safe stress when compressed solid so that they may be adaptable to other installations.

8. Hand - do not specify coiling right or left hand if it is not important. Specify right hand if it must be threaded onto a bolt. If a spring is used inside another one spring should be wound left and the other spring should be wound right. This prevents meshing of the coils.

9. There are four basic types of compression spring ends as shown above.  The particular type of ends specified affect the pitch, solid height, number of active and total coils, free length and seating characteristics of the spring.

10. Specify unusual conditions such as high or low temperatures, corrosive surroundings, impact force and fatigue life or number of cycles of deflection desired on drawings of springs.

This technical information has been contributed by
Ace Wire Spring & Form Company, Inc.
Click on Company Name for a Detailed Profile