Newton's first law of motion, "An

object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force."

Objects "tend to keep on doing what they're doing." It is the natural tendency of objects to resist changes in their state of motion. This tendency is described as inertia.

Because of inertia, an unwinding bobbin can accelerate too rapidly or continue to rotate in the unwinding direction after the thread ceases to be pulled from the bobbin. This results in loosened turns of thread commonly known as "backlash." This backlash is responsible for unsightly looking stitches commonly referred to as loops, bird nests, etc.

Backlash or over spin occurs after the take-up lever has pulled the stitch tight. If allowed, the bobbin would continue to spin, causing the bobbin thread to be thrown out of the groove in the bobbin, creating very loose tension as the machine starts up again. Backlash is undesirable in all types of sewing machines and is especially troublesome with high speed quilting machines, where many starts, stops and changes in speed and direction are commonplace. Inertia is the primary cause of backlash.

Mass as a Measure of the Amount of Inertia

All objects resist changes in their state of motion. All objects have this tendency - they have inertia. But do some objects have more of a tendency to resist changes than others?

Absolutely yes! The tendency of an object to resist changes in its state of motion is dependent upon mass. Inertia is that quantity which is solely dependent upon mass. The more mass which an object has, the more inertia it has - the more tendency it has to resist changes in its state of motion.

Too little top tension will not bring the lower thread far enough, too much will pull the lower thread right through both layers of the quilt. Less bobbin inertia equals less necessary bobbin tension. Less bobbin tension then enables you to quilt with less top tension. The result is the beautiful stitch that is synonymous with all APQS long arm machines.

Some thread types bear up to this rubbing through the needle eye much better than others. Lower operating tensions reduce the level of rubbing friction. Lower friction enables you to enjoy the incredibly wide range of thread types that are available today, from the sturdier polyesters to the more delicate and fussy cottons, silks and specialty threads.

• Enjoys almost 50% less inertial mass.
• Very low moment of inertia allows high speed quilting at lower tension levels.
• Lower bobbin and top thread tensions produce beautiful looking stitches.

• Less inertial mass enable you to quilt with a wide variety of thread types.