Nick's Winder For Homemade Litz Wire
Hi it’s Nick again
I hope you enjoyed my multiband mystery radio and it gave you food for thought.
This article describes my simple machine for making twisted Litz wire, I don’t intend to go into the advantages of this wire configuration for radio receivers it is covered by Wikipoedia at the link below suffice to say it is worth using it. Typical Litz construction configurations are covered on the New England Wire company pages using the link below.
The machine is a bit agricultural and I have made no attempt to make it
aesthetically pleasing it’s a working animal !. It can be split into two main configurations:-
Coil and bobbin winding and wire twisting
No origionality is claimed for the design just the way it is put together and used.
The motors are slow speed (around 200RPM) and are controlled by a simple PWM motor speed control based around a 555 timer and power FET, the main reason for this “complexity” is to maintain the motor toque and hence the uniformity of winding speed, the only really critical aspect of winding your own Litz. Turns counters are triggered either electronically or by cams on the motor drive shaft.
Coil and Bobbin winding
This configuration is used for two main functions, bobbin and coil winding.
In both cases the “stroke” length and direction of the oscillating wire guide is controlled by the position of the two micro-switches and a self latching relay. Different lengths of securing bolt and wing nut arrangement allow coil winding also and by varying the relationship between the rotational speed and wire guide speed it is possible to wind both single and muli-layer coils both close wound and spaced, in theory it should be possible to also wind a basket weave pattern but I have not had the courage to try this, YET!!!!
Both the number of turns and number of layers are counted, The number of turns by a motor driven cam and the layers by signals from BOTH micro switches otherwise only half the layers would be counted.
The main intended use was to wind the wire bobbins for Litz manfacture.
Please note the wire supply spool is mounted on small bearings to reduce the friction and hence the tendancy for the wire to snap on start up, start with a slow speed and gently increase to max when winding.
The wire feed arrangement is quite simple in its concept the bobbins are arranged in a simple matrix the wire being combined using the wire guides (screw in hooks) and fed through the counter and out to the winding (clever) section. Please note the bobbins are Not restrained in any way they are allowed to move freely this allows the wire feed to “self correct” if it walks off the end of the bobbin.
The wire twisting section can be split into two main sections the twisting and pick up spools.
The wire twisting is achieved by mounting the sub-assembly on the winding motor and rotating it.
The pick-up spool is mounted as shown in the pictures and provides a slow continuous pick up of the twisted wire from the feed arrangement. The pick-up motor power being supplied by carbon brushes and a slip ring arrangement.
The twists per inch of the wire is controlled by the relationship between the twisting and pick-up speeds. If you intend to make one of these and use it, no problem but try to aim at a minimum of 10 twist per inch.
A typical litz wire is 66 strand.
This is made using three bundles of 22 wires.
Twist the separate 22 wire bundles and then twist these together “Instant 66 strand Litz”.
In theory there is No limit to the wire configurations that can be produced, at this moment in time I’ve successfully wound up to 165/44 Litz.
In conclusion this arrangement can make most Litz configurations as for cost effectiveness My experience is above around 20 Litz it is financially worth it, but I’ll leave it to you to decide. Keep the speeds reasonably low to aid uniformity of winding.
Ease of use =10, Masochism rating =10
73, Nick - G0CWA