kram submitted this idea :
Does anybody know how to tension garage doors correctly ? i.e. the large
spring in the middle My door only comes up half way and if you opened it
really quickly the cables would come off the cones and ravel up.

It sounds like it needs lubrication, rather than more tension on the
springs. If you find that it really does need more tension, then the
way I have done it in the past....

Is to attach a rope onto the spring of side you are trying to add
tension, get an helper to pull the rope easing the tension on the wire,
thus enabling you to take up some slack on the wire. Do be very
carefull - these springs store a lot of power.

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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.org