Still another 911 e-brake thread, there are many like it but this one is mine.... Options

[John]

Eric, since you asked so nicely in the thread that we hijacked, here are some pics of my e-brakes using stock 914 brake cables. I just finished them up, and there are some slightly fuzzy pics, but here they are..... (pre-blog even)

[John]

andys,

Since the return springs are what retract the brake shoes (as is the case in all drum brakes), I made the decision to eliminate the "helper spring" between the two "bow ties".

Considering the amount of tension that the "helper spring" provides (very little) the decision to eliminate it seems legitimate. As long as the stock cables are in good shape, the tension provided by the return springs (which are quite strong) should be sufficient to retract the shoes and prevent them from dragging.

I made the decision to eliminate one of the bow ties because the design does not require two. Since my cable has a fixed end (unlike the 911 design which uses the second bow tie to anchor the cable end via the spacer tube) only one bow tie is required to spread the shoes. After reviewing the design of the bow ties, I determined that the strength of one bow tie is more than sufficient to spread the shoes and keep them spread as the angle of the opposing arms approach 180 degrees, the forces on the pivot points of the bow tie becomes less.

Only time will tell, but my decisions to modify the 911 design were carefully reviewed. It is not my intention to use the e brake as an e brake as much as I am a parking brake. "Helper springs" can always be added if necessary without much change, but if the cables are kept in good condition, this should not be an issue.

As a parking brake, the modifications that I made are more than sufficient as all the items will only see static forces. In the case where the car is attempted to be moved while the brake is set, the anchor block provides the resistance, as does the bow tie.

I will not go into some of the critical design issues that I see with the addition of the willwood spot calipers.