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Balanced Bug Number Seven - Some New Features

by

WB9LPU

This is the latest in the series of semi-automatic keys that I call Balanced

Bugs. The name comes from the use of a statically-balanced pendulum in the dot-

generating mechanism. This property makes the Balanced Bugs immune to the

effects of gravity - they work as well on their sides or upside down as they do on

the flat and level. The present design approach uses elements of previous bug

families such as the RotoBugs and the PicoBugs, but here they are arranged

mechanically to look more like conventional bugs.

Some New Features

Each bug in this series has incorporated several new experimental design

features. Some features worked well, others did not, while others were not worth

the trouble and complexity of construction. But each bug did work well enough to

be used on the air and to develop mechanisms to add to the bag of tricks.

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Bug No. 7 is a dual-lever design, with separate paddles for dots and dashes.

Unlike its predecessors, the levers use ball bearings rather than the ball-pivot

approach. This was done to allow the bearings to support (with the lowest possible

friction) the relatively large axial forces set up by the pendulum magnets. Paddle

tension is set by adjustable compression springs.This bug uses the magnet follower mechanism that has been used in many

previous bugs from other families. In some of the previous designs, the magnetic

forces controlling the pendulum were applied from below. At high forces

(corresponding to high code speeds), this arrangement exerted a significant torque

on the paddle bearings. This may have led to some changes in the feel of the key

as the speed setting was changed. The ball-bearing design was an attempt to

overcome this problem, and it appears to have worked.

The current design places the pendulum magnets withinthe pendulum,

aligned with its long axis. One magnet is borne on a projection of the dot leverextending inside the pendulum, while the other is on the end of an adjusting screw

that is threaded into the end of the pendulum. This arrangement is shown below.

At higher speeds, the attraction between the lever and pendulum magnets is quite

substantial, but the combination of the axial orientation of the magnets and the

use of ball bearings in the lever and the pendulum insulates the operator from

these forces. Speed is adjusted by using the axial screw to change the internalmagnet spacing. There are no weights to add or re-position. The speeds range is

from 5 words per minute, through a comfortable QSO-friendly 17 wpm, to a brisk

25 wpm, all the way up to 37 wpm (at which speed my ability to send coherent CW

disappears). The maximal dot-rate corresponds to 45 wpm. There is only a small

change in the relative dot-weight over this range, and this is easily tweaked by

using the dot-lever travel (as in previous bugs that use the magnet follower type

of mechanism). The use of an aluminum pendulum of the same dimensions gives an

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increase in speeds across the range. While it has not been tested thoroughly, it

appears that the span of speeds would be less useful than those obtained with the

brass pendulum.

Here are a few more views of the bug. The base is made of Fortal, a very

hard aluminum alloy. The levers are of 2024-T4 aluminum (aircraft aluminum),while other parts are machined of C-360 brass. Contacts are of brass and polished

stainless steel. The anodized fingerpieces are by P. Begali, I2RTF.

The FISTS Club logo

covers a hole through

the top plate which

allows access to the

pendulum signal magnet.This allows the key to

be customized for

various uses.

The wiring under the

base is let into channels

that protect it against

damage. Wiring from

the magnetic reedswitch that detects

pendulum motion

extends through the

base.

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The overall length of the bug is 6-3/4 inches (7 cm); the width of the base

is 2-1/2 inches (7 cm), and it is 2-1/4 inches (6 cm) high. It weighs about 35

ounces (1 kg), which is heavy enough to keep it steady on the operating desk.

While this bug has not yet come to the silver screen, there are a couple of

YouTube videos that show the operation of other bugs in the Balanced Bug family.

They are at http://www.youtube.com/watch?v=2eggX60OEPk (Balanced Bug #4)and http://www.youtube.com/watch?v=-TG_J57LOWE (Balanced Bug #6, the

GoBug).

73 de Rich, WB9LPU

wb9lpu@arrl.net, http://wb9lpu.com

At the left is the initial test

set-up. These tests removed any

misgivings about its performance

- this is a well-behaved bug with a

light touch and a positive feel. It

can be adjusted to send CW with

whatever accent the operator

desires, and there is minimal

operator fatigue.

http://www.youtube.com/watch?v=2eggX60OEPkhttp://www.youtube.com/watch?v=-TG_J57LOWEmailto:wb9lpu@arrl.nethttp://wb9lpu.com/http://wb9lpu.com/mailto:wb9lpu@arrl.nethttp://www.youtube.com/watch?v=-TG_J57LOWEhttp://www.youtube.com/watch?v=2eggX60OEPk