A SIMPLE WINDER COUNTER
This article describes how to make a simple rubber model winder counter for use with hand drills and some dedicated winders.
It is based on a low cost pedometer as pictured. These are available from some dollar stores and also from:
for less than a dollar.
A magnet advances the pedometer count with every turn of the crank.
The photo sequence here shows how to modify the pedometer and ready it to count your rubber winds.
Open the case by removing the two case screws and then remove the internal screw to remove the belt clip.
Inside find a metal “swingie thingie” and a hair-like spring wire (look real close next to the “swingie thingie” in the photo). Lift both off and out.
Next prepare a reed switch for installation in the pedometer.
The reed switch shown is Electronic Goldmine part G20163B but similar switches should work as well. The listed part is only available in the smallest quantity of 25 pieces so having several folks participate makes sense. (See Notes below.)
The first step is to shape the switch leads approximately as pictured but DO NOT bend the leads by holding the glass switch body – it breaks easily. Rather grip the lead with small pliers near the glass body and then bend to shape. Scrub the pedometer metal parts shown with a pencil eraser or similar burnishing tool to ease solder tinning and then solder the switch leads in place as shown. Dress the switch so that the pedometer cover can be replaced without interference, and replace the cover and two screws.
With the reed switch oriented as shown the counter works best when a small magnet is passed near / by either end of the pedometer housing i.e. past the ends of the switch. This orientation is illustrated on the winders shown where the counters are held in place with “self-stick” Velcro pieces. Of course the actual rubber winds will be the winder gear ratio multiplied by the counter reading.
It is possible to turn the winder crank “too fast” such that the counter will miss about half the actual counts but this is actually quite hard to do and unlikely to happen routinely. Check out this possible “over speed” limit to your own satisfaction – and then go flying!
Notes: Reed switches can also be found on EBAY and AMAZON in various physical sizes and quantities. The one shown measures about 2mm dia. X 14 mm long. There is clearly room in the pedometer housing for somewhat larger switches. The Neodymium disk magnets pictured measure 0.1″ thick X 3/8″ dia. and are from RC Dude (excellent supplier of stuff!) One local counter builder found suitable disk magnets in a ACE hardware store. I suspect there are many other disk magnets that would function equally well though some experimentation may be needed.