Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Trad handbrake conundrum.

My question is - How does the front sheath of the handbrake cable increase in length when the handbrake is set on? "They all do that, Sir" will not be accepted as an answer!

My concept of the hand brake mechanism is as follows. I have replaced several handbrake cables on my +8 and 4/4. Both are basically the same. The handbrake cable runs from the handbrake lever through a sheath to the nearside brake drum and actuates the handbrake mechanism. This sheath is in two parts, the front sheath is anchored to the chassis at the front by a lock nut. It ends in a floating adjuster in the region of the back axle. This cable then enters a second sheath which is anchored in the region of the back axle and at the near side brake drum. The cable then actuates the near side hand brake.
The offside handbrake cable is attached to the adjuster and reaches the off side brake drum via a third sheath which is also anchored in the region of the back axle and at the off side brake drum. So far, so good.

All the cable sheaths appear to be of a fixed length. However, when I pull the hand brake lever on, the first sheath moves at the adjuster end by about a centimetre as if it increases in length. It is this apparant increase in length of the sheath which pulls the off side cable by about a centimeter and actuates the off side hand brake mechanism. At the same time the pulled main cable actuates the near side hand brake mechanism.

Hand brake off.



Hand brake on.



Do not be concerned that you do not recognise this hand brake set up, I am prating round with it as part of another project. Just concentrate on the movement in the pictures. The adjuster is disappearing off the picture on the left and the sheath to the near side brake drum is on the right.

What am I missing? How does a sheath of fixed length move as if increasing in length when the cable running through it is tightened?

Answers to me on the back of a £20 c/o TM.

If it wasn't still pouring with rain in Mid Wales, I'd crawl under the car and have a look for you.

But, here's a theory.

As the inner cable is pulled maybe it straightens the cable slightly thereby shortening the distance overall and as the inner is fixed the outer would have to move as the shortest distance between 2 point is a straight line.

Only a theory and if the cables are already straight then that theory goes straight out of the window.

The liner of the outer will be a tight wound coil under the plastic sheath ..... it shortens a little under compression but can open out as there's only the plastic sheath resisting stretch ..... the outer has a natural 'spring' ..... it may be this that's allowing the outer to expand.

On my old Harley which has a clutch that requires a serious pull I have a longitudinal clutch cable rather than a spring wound one to reduce 'lost motion' when the clutch is pulled that you can get as the spring-wound ones compress and shorten under load and expand again when the clutch is released.

K