Early A body Front Drum Exterior spring????????

[604]

Any one happen to know the purpose of the spring that goes around the outside of the stock early A body drums?? I figured it was ether a heat sink for cooling, or had something to do with harmonics. Any one know for sure?????

 

[C130 Chief]

Vibration damping was primary reason. I would have helped with cooling some too. Replacements are as close as the nearest screen door.

 

[65dartcharger]

What I heard of cooling the drum the reason. At least I was told that by a Chrysler mecanic here in Sweden.

 

[nuttyprof]

It would be harmonics, under certain conditions the drum will ring like a wine glass and when that happens the shoes will not make good contact with the drums and you can guess what happens next.

 

[cudamark]

Yup, harmonic vibration damping is what the spring is for. If you've used a brake lathe without using the damper band, you know what kind of noise it will make!

 

[604]

Thanks all!
I wonder if that is a problem on the new drums that do not have them?

 

[cudamark]

Most of the replacement drums don't have a groove for the spring.

 

[nuttyprof]

They can tune the drums so the harmonic is beyond the range of normal service. You still need the strap when turning them on a lathe but they are unlikely to ring in service.