Factors Affecting Design extension springs
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W = Spring material width T = Spring material thickness L =Spring length (reference only) J = Minimum extension for constantforce H = Off-setdistance D2= Storage drum diameter D1= Outside diameter of spring when fully wound on storage drum > RECOMMENDED DISTANCEBETWEEN DRUM FLANGES EQUALS SPRING WIDTH (W+1) to 3mm SEE DETAILS OFSPRING ENDS The fatigue life has a directeffecton the size of the spring and themaximum load available in the leastspace.A comparison of various chartvalues illustrates the effectfatigue requirements have on the size of the spring.For any application the required number of cycles or reversals,should be estimated for the life of the equipmentor a replacementschedule.The fatigue life of a spring can be defined as either a full or partialextraction and retraction of the spring i.e.the spring can be exercised over its whole length and achieve the average life expectation,however if itis exercised over any one section of the spring repeatedly then thatsection can be expected to fatigue when the total number of cycles approaches the life predicted for the spring.Fatigue Life is nottime dependantunder normal operatingcircumstances;itis solely dependenton the number of operations.However pollutants even in low concentrations can have the effectofshortening the fatigue life through corrosion or chemical attack, please refer to the statements regarding uses and misuses of Spiroflex springs in our brochure and web site and refer to Spiroflex if in doubt. The free end of the extension spring should be guided to preventthe spring from wandering off the drum.The spring should be firmly attached to the moveable member (see diagrams). > Held flat or The Spiroflex spring will be held on the drum by its inherent gripping action.No other fixing is required,provided there is sufficientspring material remaining on the drum when fully extended.An exception to this is when the mechanism does nothave its own limiting stops,in which case we recommend the inner end be secured to the drum by the holes provided (drum should be stepped see diagram). > The Spiroflex spring can be used with an idler pulley provided itis positioned to suitthe natural curvature of the spring (see diagram). Extension springs should notnormally be bentback or reverse wound,as this will permanently damage the spring. > A low costmounting arrangementis the Spiroflex spring coil seated in a cavity the obvious disadvantage is the friction between the spring coil and the cavity surface.We would recommend the cavity to be lined with a low friction material.Another method is to use the free coil force againsta moveable member. > INCORRECTCORRECT Various standard methods of multiple mounting are shown below.Springs can also be laminated to provide an increase in force orfatigue life in a minimum space.Please apply to Spiroflex Sales Departmentfor further details.To discuss your needs please call our Technical Sales Departmentwho will be pleased to help. > There is almostno limitto the speed or acceleration to which the spring will coil and uncoil.However,tests should be carried outto satisfy yourself the spring will perform satisfactorily under your conditions. > Issue No.1 (Ext_spr_A/eng) size="-4">

Spring ends nottailed as shown SPRING MATERIAL Type 301 High Yield Stainless Steel NOTE:- Drums notsupplied > END BEND A END AEND B Spring as supplied resembles a tightroll of metal tapeOuter end of spring to be firstwrap on storage drum Drum mustbefree running > D1+30t2 JHHD12 D2D1+ 30tD1HJ TANDEM BACK TO BACK ChartExtensions Less by (D1+30t) Extensions as Charts FRONT TO FRONT ChartExtensions less by (D1+30t+J) Extension shortened by (D1+30t) > HHD2 D1 J HH D1 D2 D1+30tJ HH D1 D2 D1+30tJ Issue No.1 (Ext_spr_B/eng) BACK TO BACK & TANDEM >