Grantville Gazette, Volume 96 by Bjorn Hasseler

Author:Bjorn Hasseler [Hasseler, Bjorn]
Language: eng
Format: epub, mobi
Publisher: Ring of Fire Press
Published: 2021-06-30T04:00:00+00:00

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The simplest tethering system has each tether attached at the ground end to some kind of anchor (which might be just a tree). However, it is not desirable that a slack rope get tangled with trees or even people. (Bryan had to cut his balloon's tether to free an entangled ground crewman.) So it is better if the tether runs up from the anchor to some sort of winch by which rope can be let out or taken in as needed.

The winch must be able to pay out the cable for the balloon to ascend, hold it against the wind, and haul it in at the end. The tether is bent around the drum of the winch, so the smaller the diameter of the drum, the more flexible the tether must be. Unfortunately, bending reduces the strength of the line—by 21% if the sheave diameter is ten times the rope diameter (Myers 92).

The problem with a hand winch is that it probably has a handle only long enough for use by one or two workers, which limits the haul-in speed. For this reason, Lowe probably used a pulley and a snatch block on each line, rather than a winch. Multiple soldiers could then pull on each line.

WW1 kite balloon winches made use of steam, gas, and electric power. Some sort of dynamic braking is desirable, to control the ascent (Tucker 259). They were horse-drawn or motor vehicle-mounted (Streckfuss 43).

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We also need to consider the nature of the attachment at the high end. It may seem logical, at least with a single tether, to attach to the bottom of the balloon car. However, in a wind, this would incline the car. And in a strong enough wind, with a wicker basket, it might pull out the bottom.

Lowe's balloons had an external suspension system, with cords holding a wooden spreader ring in place around the gas bag, and additional cords suspending the balloon car from the ring. Lowe's tethers were also, independently, attached to this ring (Tunis).

Note that with Lowe's multiple tethers, if the circle on which the ground anchors lie is of a diameter different from that of the spreader ring, then even without wind, the tethers run obliquely rather than vertically, and the maximum height is less than the tether length.

On the Navy "M" kite balloon there was a single towing cable, but it was attached to a bronze ring (the confluence point), which was bridled, via steel cables and Italian hemp ropes, to forty points of suspension on a suspension band on the balloon.

On Cameron balloons, the basket is suspended from the burner frame, which in turn is attached via V-bridles to flying cables that stretch across the envelope to a crown ring. If tethered, the three tethers are attached to rings on the V-bridles. The flight manual calls for ropes and anchors with a minimum strength of 8800 pounds, and deploying two of the three tethers on the upwind side.

Multiple tethers do not necessarily run from the ground directly to different suspension points on the balloon.

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