This is the setup I have been using to induce rotational pre-tension into Firefly’s rope bundles.  The multiple holes in the top of the spanner are to allow it’s lever arm to point in the correct direction independent of where the crossbars are.


This rotational torque is essential to generate power and is applied only after the springs have been stretched linearly.  Keeping the springs as straight as possible with a linear stretch can be likened to building a good foundation for the twisting procedure seen above.  In my experience, both are essential for developing power.  While we will attempt to improve the linear stretching of Phoenix’s bundles by use of a stretcher to address each strand as it is laid down, I have no doubt that the procedure seen here will still be vital to build up the final power of the machine as well as tuning the bundles to have equal thrust.

I would respectfully suggest that if you are a fellow torsion catapult reconstructor, and are having problems of weak performance, it is likely you are skimping on your rotational pre-tension.  Straight springs are great, it is just that they are not the whole story.     ………. And be careful,  this can all get pretty extreme in a hurry…….

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