Thursday, February 19, 2015

Cablecam rope considerations

This Blog post is one of an entire series
Motivation and Design
Download Link for CAD drawings (updated regular)
Bill of Materials
Motor and ESC considerations
CableCam rope
Building the DSLR CableCam
CableCam controller board

Rope to use

Initially we discussed various options, steel cables, different types of ropes and at the end after some trial and error the conclusion was, a Dyneema rope with sheath is what we need. It is strong and yet lightweight. Its surface allows for smooth driving without much vibrations. Most important: Its prolongation under load is under 5%.
But it is very expensive.

The best rope currently is this one

The 6mm rope has 2500daN maximum load, it should be used with no more than 60% of that, which is 1500daN or about 1.5tons.


The formula to calculate the rope force is shown here

Let's try a simple calculation.

The distance to cover is l=100m. The weight of our cablecam is p=3kg. The tolerated maximum slack when in the middle is f=1m.

sqrt( (3/2)² + (3*100/ (4*1)² ) = sqrt ( 1.5² + 75² ) = 75kg

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