calculate the force of clutch pedal

[kanibaltaki]

heeey
i start to make a small tester mechanism I want to calculate the force applied by the driver with his foot on the clutch pedal and the spring because I want take this force and apply it with a pneumatic cylinder to measure the cable life see attached picture

thank you

 

[LittleInch]

Why?

A simple search "clutch pedal foot force" provides many different versions of the same thing, e.g

http://www.perceptionenhancement.com/docs/papers/gb1997mot.pdf

Also you haven't actually asked a question....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[drawoh]

kanibaltaki,

Look up MIL-STD 1472 DESIGN CRITERIA HUMAN ENGINEERING. This is available free on the internet, and it will probably tell you want you want to know.

--
JHG

 

[chicopee]

So where is the pivot point, at the spring or at the ball joint?

 

[BUGGAR]

Having had a clutch cable failure in an old car on the middle of the Bay Bridge at rush hour, I would say pay the most attention to the cable attachment. Any bending in the cable must be avoided or minimized.

 

[SnTMan]

Measure it:

http://www.mcmaster.com/#spring-scales/=10kuyzw

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[BrianE22]

Put a bathroom scale between your foot and the pedal.

 

[MikeHalloran]

Note that your clutch pedal mechanism is grossly oversimplified.
Real clutch pedals use a pivot that may provide variable mechanical advantage, and also may include an overcenter assist spring to make the pedal effort lower while applying a greater force to mechanisms downstream, like a cable.

I.e., your layout should accurately reflect the situation in the vehicle for which the clutch cable is intended.


Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

Does your clutch cable have sufficient stiffness to transmit force in both tension and compression?

 

[BUGGAR]

"overcenter assist spring to make the pedal effort lower."

If your geometry is right and you cable stretchy enough, you can make your cable into an overcenter spring.
I hate a spongy clutch pedal. Why can't you just use a rod and stiffen it up?

 

[kanibaltaki]

hey
thank you all
i just want to test the cable life and i dont know how to do it the drawing is my idea and didnt know if its right or not
could anyone propose a mechanism to some example of testing the clutch cable life it will be helpful
thank you all

 

[chicopee]

I guess that someone must have been asleep during their physics, statics/dynamics, elements of machine design and vibration classes.

 

[3DDave]

That's not a realistic free-body diagram because it is missing a fixation for the pedal pivot. After that, the load on a clutch cable is a nearly constant value based on the spring in the clutch. Pressing further just moves the cable in the housing; it doesn't increase the load because the movement of the clutch is very small and the resulting motion is magnified by the leverage. Often in clutches there is some unloaded pre-travel that is used to ensure the clutch is fully engaged. This leaves the clutch cable unloaded, but the pedal has a separate return spring to prevent it from being loose so it seems like the user has to push harder as the pedal is depressed, but that has nothing to do with the cable tension.

 

[LittleInch]

IMO cable life should be infinite. If you design the cable right then it should be straight pull. Any bending forces could impose fatigue loading, but you won't find this with a test section. Cables tend to fail at the connection points.

Clutch cable failure was something serious 30 years ago. Nowadays, it just doesn't happen, a bit like the engine always fires first time. I don't understand why you're doing this.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BUGGAR]

You can send a segment of cable to almost any lab and have them do a pull test for you. Some have cyclical loaders for fatigue testing. If you bring a box of donuts to the lab, I'm sure they will show you around and you can see how it's supposed to be done.

 

[SnTMan]

Tough crowd

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[LittleInch]

Snt, your tag line says it all...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[RossABQ]

(LittleInch) Cables tend to fail at the connection points.

In automotive applications, corrosion is likely the primary culprit. The increasing drag between cable and housing fails the connections.

O/T -- worst cable design ever --- Ford Fox-body Mustangs. My left leg still aches.