Side Load Measurements Presented by: (First and Last name of - - PowerPoint PPT Presentation

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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 :

Side Load Measurements

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

• f 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. 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.

Immagine molla valvola

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

• r

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.

• Disegno

Mo

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
• f 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

Method of control Effec/veness of the control Time of measure (cost of the control) 1 Squareness and parallelism in free condiHon It is not a direct measure, it can not guarantee the real values of the not-axial load of the spring compressed about 15 - 60 seconds 2 InclinaHon Under load It is not a direct measure of the Off-center (Mt) but useful to control it about 30-60 seconds 3 Shi] under load It is not a direct measure of the side-load (Fq) but useful to control it depending on the device from 0 to 60 seconds 4 Direct measuring of Fq and the Off-Center Direct control of the not axial load 0-60 seconds

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 under load behavior about 15-30 seconds

• r

30-60 seconds AutomaHc instrument “3D”

• r

Profile projector and special tools Foto di una molla su un LED3D

How to measure the Not-axial-load(4)

Effec/veness of the control Time of measure Instrument It is not a direct measure of the Off- center (Mt) but useful to control it. about 30-60 seconds Special instruments Manual or automaHc disegno

2 InclinaHon Under load

How to measure the Not-axial-load(5)

Effec/veness of the control Time of measure Instrument It is not a direct measure of the side-load (Fq) but useful to control it At the same Hme as the loads are measured Special load tester <60 sec Special instrument disegno

3 Shi] under load

How to measure the Not-axial-load(6)

Effec/veness of the control Time of measure Instrument Direct control of the not axial load 0 - 60 seconds Special load tester Foto interna del LED4D e LED4D 700 Today, there are tools that can perform Fq measurements, off-center and at the same Hme doing many other measurements and controls.

4 Direct measurement of Fq and Off-Center

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

spring.

• 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.

Foto di Molla valvola su LED3/4D

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 field of length, – 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?

Inserire disegno con grafico con isteresi

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
• f 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
• f 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

• n 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**