915 Clutch Helper "Omega" Spring Function

[pmax]

Why did Porsche add the helper "omega" spring to the 915 clutch mechanism ?

If it is to reduce clutch effort, as far as I can tell, that remains the same sprung or unsprung though the pickup point is much lower, arguably better in fact, in the latter case.

[porschedude996]

Originally Posted by pmax

Why did Porsche add the helper "omega" spring to the 915 clutch mechanism ?

If it is to reduce clutch effort, as far as I can tell, that remains the same sprung or unsprung though the pickup point is much lower, arguably better in fact, in the latter case.

I think the spring helps lessen the peddle effort when first pushing the peddle in.

[Fab64]

I don't know what it is officially designed to do. However, that spring was broken when I bought my '84 Carrera. After I had it replaced, the clutch did seem to work a bit more smoothly, especially when first pushing it in - as porschedude said, above.

[walt]

It does give the pedal a snap action feel to it when first depressed.

[pmax]

So, a power mechanism which adds more force to the arms during the initial travel from sprung to unsprung.

Originally Posted by Fab64

I don't know what it is officially designed to do. However, that spring was broken when I bought my '84 Carrera. After I had it replaced, the clutch did seem to work a bit more smoothly, especially when first pushing it in - as porschedude said, above.

Curious, by smoother, do you mean easier ?

The reason I ask is that snap action leads to a non-linear feel in the sense that the foot feels the spring action first then the resistance of the short arm as it moves the TOB is the way I understand it.

[eastbay]

Drive a 75 or older car and you will understand. I've considered converting my old 74.

[pmax]

Originally Posted by eastbay

Drive a 75 or older car and you will understand. I've considered converting my old 74.

The earlier simpler mechanisms.




The later 915 standard clutch lever install with the dead space introduced by the two arm omega spring setup

Sorry about the "dirty" pic, not mine, a good example being harder to find that I expected.

In the later 915s there's a spring on the short arm in tension which preloads the TOB fork whereas the earlier variant's all in the clutch cable. Is the cable tension much higher in the latter ? The omega spring assists in the initiation of the clutch pedal movement but how much does it help if at all beyond that phase ? I believe by the time the omega reaches the "red" position, it is largely unsprung. And arguably the leverage of the later version has been lengthened somewhat so that helps.

So I suppose the combination of all these factors contribute to easier clutching. In my SC, the omega spring doesn't seem to do much for this purpose.

Threads of interest.
Examples of the clutch lever backdate, the advantages being elimination of the dead space caused by the 1/1.2mm gap contributing to a more direct linear feel in addition to simplifying the mechanism.
930 Clutch Throw Out Lever / Helper Spring Issue
Clutch Adjustment Help
https://forums.pelicanparts.com/porsche-911-technical-forum/1163942-what-can-you-tell-me-about-my-engine.html#post12278738
https://forums.pelicanparts.com/porsche-911-technical-forum/1178995-clutch-positioning-lever-broken-spring-attachment-2.html
https://forums.pelicanparts.com/porsche-911-technical-forum/417364-convert-early-915-clutch-arm.html#post4033069

Omega snap facilitates cable tensioning which allows long arm to "float".

[pmax]

Pic of the 74 setup
https://forums.pelicanparts.com/porsche-911-technical-forum/866073-seeking-advice-proper-adjustment-new-clutch-cable-non-omega-915-a.html#post8631169

Pic of the clutch arms at the pedal
https://forums.pelicanparts.com/porsche-911-technical-forum/1181129-915-clutch-cable-adjustment-challenges-2.html#post12532713

[KNS]

Mine just snapped one day. Not a bad idea to purchase a spare since they are 40 years old or more.