Dear Clayton, I have 2 questions:
1. Is it necessary to have a full wind for successful long run time? 2. Is balancing wheels critical for proper operation ?Thanks for any info. Don
Answer to question 1) The length of the run time depends on a number of things, but the main factor in determining run time is the number of winds of the spring. The Neg'ator springs I recommend will give a run time of about 40 minutes. Other constant force springs may be used, however their length is usually much shorter (for example; 22" or 560mm versus 106" or 2690mm) and will give a proportionally shorter run time. (using these spring examples means a difference between an 8 minute of run time and the 40 minutes).
We have also found that the Zinnia run time can be dramatically increased by eliminating the grease from the bearings. For our light duty kinetic sculpture purposes the grease inside the bearings actually increases the internal friction and can cause shortened run times.
By soaking the bearings overnight in mineral spirits and washing out the grease we've been able to double (in some cases) the run time of the Zinnia.
I do recommend adding a drop of clock or light oil back into the bearings...but I think this may be mainly superstition as there is probably still sufficient lubrication for our purposes.
Answer to question 2) The wheels of the Zinnia are first balanced and then unbalanced with the unbalancing weights that are attached behind the wheels. Recommending that the wheels be balanced first allows me to specify in the Zinnia plans which arms are the best for the placement of the imbalancing weights.
Balancing is not particularly critical as the unbalancing weights can be placed on different arms to get the sculpture to run. However, I build my plans primarily for the beginner, and I must make sure that if my instructions are followed the chances of success are going to be good.
Experienced builders could (possibly) disregard my instructions and still make the sculpture work...so..."critical"...no, but recommended. Enjoy!