Session Title Side Load Measurements Presented by: (First and Last name of presenter(s) H O S T E D B Y : C O - H O S T E D B Y :
A case history (1) To understand the importance of side load, it is useful to tell the story of events that actually occurred. Our story begins in the spring of 2013, when a presHgious motorcycle manufacturer is suddenly faced with numerous cases of engine valve failure. The situaHon is serious, with deliveries blocked and thousands of bikes held back by dealers around the world, all waiHng to understand the problem and to find a soluHon. The cause is not known and all the components of the engine head, including the valve spring, are invesHgated. For the confidenHality of our client, we will call this motorcycle maker ‘Xxbike’. Xxbike get in touch with MicroStudio and orders the measurement of several springs from different lots. Within a few hours, the first tests are complete and the results are conclusive. The springs belonging to a specific lot have a side load three Hmes higher than the others
A case history (2) Xxbike convenes an emergency meeHng at 6pm that same Friday at MicroStudio. Immagine molla valvola The results of the first measurements are presented and there is no doubt that the engines with issues all had springs coming from that lot. Xxbike takes immediate acHon, replacing the springs, and commissions from MicroStudio a complete study of the valve springs used up to that point. Now we need to understand how this could have happened.
The Not-axial-load (1) Normally we simply speak about Side-Load Today we will talk about a more complex set of forces:the Not-axial-load. The Side-load is not the only Not-axial-load: a spring can have different non-axial-load components with different effects on the device where it is mounted.
The Not-axial-load (2) • Normally we call Side-load that force component that EN 13906-1 (Norm that describes the calculaHon of cylindrical compression springs under an axial load) calls Fq. • Suppose a spring pressed from above and we see the reacHon on the base plate. • The tangent force of the support plane is called Fq Fq
The Not-axial-load (3) • But we also have a perpendicular moment to the support plane (Mt) due to a spring thrust that is not perfectly centered on its axis. • Mt= Off-Center x Fz Mt or Off-Center
The Not-axial-load (4) • In a compression spring, we will call Mo the physiological rotaHon component on its axis. • It normally does not reach problemaHc levels and is not, however, correctable by the spring maker. For this reason Mo is o]en neither considered nor measured. Mo • Disegno
Consequence of Fq The too high Fq causes: • The premature consumpHon of the device. • Excessive fricHon of the sliding. (The spring doesn’t move fluently during compression)
Consequence of the Off-Center A too high Off-Center, if the plate is not well guided, causes: • Arching of the plate. • The premature consumpHon of the device. • FricHon of the sliding
How to measure the Not-axial-load (1) Over Hme, various technologies have been developed but all have the purpose of having Fq and Off-Center values under the criHcality limits of the device. The choice of the control system must consider: • The device in which the spring is mounted (where the Fq may be more criHcal than the off-center) • The availability of control systems and technologies of the manufacturer rather than the user. • The Hme (cost) of measurement.
How to measure the Not-axial-load (2) Summary table Time of measure Method of control Effec/veness of the control (cost of the control) 1 Squareness and It is not a direct measure, it can parallelism in free not guarantee the real values of about 15 - 60 seconds condiHon the not-axial load of the spring compressed It is not a direct measure of the about 2 InclinaHon Under load Off-center (Mt) but useful to 30-60 seconds control it It is not a direct measure of the depending on the 3 Shi] under load side-load (Fq) but useful to device from 0 to 60 control it seconds 4 Direct measuring of Direct control of the not axial 0-60 seconds Fq and the Off-Center load
How to measure the Not-axial-load (3) 1 Squareness and parallelism in free condiHon Effec/veness of the control Time of measure Instrument Indirect control, less certainty of about AutomaHc instrument “3D” under load behavior 15-30 seconds or or Profile projector and special 30-60 seconds tools Foto di una molla su un LED3D
How to measure the Not-axial-load (4) 2 InclinaHon Under load Effec/veness of the control Time of measure Instrument It is not a direct measure of the Off- about Special instruments center (Mt) but useful to control it. 30-60 seconds Manual or automaHc disegno
How to measure the Not-axial-load (5) 3 Shi] under load Effec/veness of the control Time of measure Instrument It is not a direct measure of At the same Hme as the Special load tester the side-load (Fq) but useful loads are measured to control it <60 sec Special instrument disegno
How to measure the Not-axial-load (6) 4 Direct measurement of Fq and Off-Center Effec/veness of the control Time of measure Instrument Direct control of the not axial 0 - 60 seconds Special load tester load Today, there are tools that can perform Fq measurements, off-center and at the Foto interna del same Hme doing many other LED4D e LED4D 700 measurements and controls.
A case history (3) A]er measuring a great number of Xxbike’s springs, we discover that: There was only one bad lot, where the average Fq was • much higher than the average of the other lots. Within each lot, Fq values �differed slightly from spring to • Foto di Molla spring. valvola su LED3/4D The faulty springs were idenHfiable even with free spring • squareness measurements. The free spring squareness measurement did not allow • the idenHficaHon of springs with the highest Fq value within the same lot. In other words, the free spring squareness measurement allows only a rough, yet important, idenHficaHon of variaHons in spring Fq, with the relaHon between squareness and Fq varying with the spring geometry.
CondiHon of the test (1) To measure the non-axial force values of a spring, the device designer must define some test parameters: Spring guide: • Through internal guide pin • Through external bush • High and form of the guides (dimension of the guides) • Coupling tolerance (how many space is allowed between the guide and the internal/external spring’s diameter) In the case of tests without spring guide : 1. We can measure only Fq and not the Off-Center 2. The roughness of the plate could affect the results. 3. The designer should determine whether the spring slipping on the plate is acceptable or not. The spring that slides on the plates during compression generally causes a curve with hysteresis (different graph when compressing or releasing the spring) in the curve of Fq
CondiHon of the test (2) • What to measure: Fq, Off-Center or what else? • When to measure: – Maximum value detected in a certain Inserire disegno con field of length, grafico con isteresi – or a value at a given compression length? • In case of hysteresis (caused by sliding on the plates or on the guides) the measure must be during compression, releasing or the average of the two? • Are sekng cycles needed?
Parameters related to not-axial load (1) • The spring geometry is always linked to non-axial force values during compression. • The geometry, and specifically the shape of the end of the coils in constant pitch springs, determines the value of Fq and Off-Center. • For this reason it is very difficult to correct a too high Fq value without analyzing the shape of the spring.
Parameters related to not-axial load (2) • Together or alternaHvely to Not-axial-load requirements, the encumbrance limits of the spring are o]en prescribed, which are also related to the same factors that define Fq and Off-Center
Parameters related to not-axial load (3) • The Fq thrust changes direcHon by reducing the free coils. • In variable pitch springs this creates apparently strange behaviors. Esempio di Fq che ruota
Importance of shape and off-center in suspension springs (1) • The Off-Center value and its direcHon tell us where the spring is pushing. • In suspension spring, it is an essenHal parameter of its operaHon as it is mounted on a lever.
Importance of shape and off-center in suspension springs (2) • In the car suspension spring, even the shape of the spring under load becomes a criHcal parameter the shock absorber inside
A case history (4) In the following years, the Xxbike racing department commissioned us to select springs with the lowest Fq value within large lots. These were engines intended to be used in compeHHons, in order to minimize engine issues at high performance.
Reminders Wednesday, October 4 Exhibit Hall Open: 10:00AM – 5:00PM NESMA Special Networking Event: 5:30PM – 8:30PM **A$endees must be registered and have their 3ckets on hand prior to boarding the cruise. If you did not purchase a 3cket and interested in a$ending, please go to the registra3on desk to check if openings are available**
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