Introduction Edit

The cheiroballistra uses the little ladder as the lower support structure holding the field-frames at correct distance from each other, and for attaching the field-frames to the case. This article shows one easy way to make the steel parts of the little ladder. Making of the (probably wooden) cross-pieces and rungs is described in the assembling the little ladder article.

The process step-by-step Edit

Take two long pieces of relatively thin (~4mm) steel and mark the center, the ends of the little ladder beams and the width taper. Also leave some extra steel at the ends for the tenons:

Making little ladder beams - method 1 - 01

Making little ladder beams - method 1 - 02

Cut the width taper into the beams and mark the cross-piece and rung holes:

Making little ladder beams - method 1 - 03

Making little ladder beams - method 1 - 04

Heat the tenon ends in a forge and fold them lengthwise:

Forging little ladder tenons - method 1 - 01

Forging little ladder tenons - method 1 - 02

Reheat and forge the tenons until they're straight and rectangular:

Forging little ladder tenons - method 1 - 03

Forging little ladder tenons - method 1 - 04

Next file fairly deep and tight notches to the tenons for the field-frame bars:

Little ladder and field-frame - 01

Little ladder and field-frame - 01

The notches are needed for two reasons:

  • Prevent the tenons from sliding in the pi-brackets during pullback (for full discussion see my first and second blog posting about the subject)
  • Fix the field-frames to a correct distance from each other

While wedges alone can hold the field-frames in position for a while, the will eventually loosen without the notches.

Finally bend the beams slightly outward near the rungs and back inwards near the tenons:

Little ladder and field-frame - 03

The idea is to (have to) bend the beams slightly outwards when the little ladder is inserted into the pi-brackets: this ensures that the tenons lock tightly into place, even before any wedges are inserted.

Finally, make the outer holes for the rungs, and the hole for the cross-piece in the middle. The rungs holes are round, so they can be either drilled or punched. The cross-piece hole is rectangular, so punching with a rectangular punch is easiest. An alternative is to drill the hole and file it rectangular:

Assembling the little ladder - 02

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