Braiding rubber motors

19 February 2025

(Revised)

Making the simplest braided rubber of 2 strands for peanut scale.

1. Cut a strand of 1/16" rubber to a length approximately 2.5 times the distance between the nose block to motor peg. Make a simple loop at each end of the strand, the loops are temporary and have to be released later. An overhand knot would work.
2. Place one loop end in a secured hook, stretch the rubber strand by pulling from the other loop end and wind 4 turns per inch. Let's say the nose-peg distance is 8": the strand is 20" and we wind 80 turns.
3. Now bring the other loop end to the same secured hook, the rubber strand will braid on itself, tug along the braided length to even out the braiding. 
4. Pinch the 2 loop ends together and remove from secured hook, release the loops and tie a square knot with the 2 free ends.
5. Tug and pull the square knot to tighten and add a small bit of superglue to better secure the knot.
6. The basic braided rubber is now completed, and we turn our attention to how we will be able to fit the knotted rubber to the motor peg.
7. We could just insert the motor peg through the knotted end and end it here. It is not as if the braided rubber will be replaced that often.
8. Alternately, we could also use a loose peg which is a cylinder (sort of a bobbin) that can fit loosely over the motor peg. We insert this loose peg through braided rubber at the knotted end by twisting to open up the end. This adds a bit of weight at the tail, but the main advantages are: 1) allows the turns to be freed up at the rear end thus less weight shift as the motor unwinds; 2) easier insertion of motor peg which allows easier motor replacement.
9. With the knotted end in the tail and secured by the motor peg, pull the braided but unwound rubber out with a wire hook. 
10. Twist to open up the end to hook it to a motor winder, when the braided rubber is wounded, remove the motor winder and hook the end to the propeller shaft's hook, then insert the nose block to the fuselage.

Note that if the braided rubber (unwounded) is short of the nose opening, you can pull it out with a wire hook.

If it is too long, it may not be a problem, but it is a problem if the rubber will thrash against the bottom of the fuselage.

Therefore, we would like a braid (unwounded) that hangs on the propeller shaft's hook and motor peg, and clears the bottom of the fuselage. 

17 February 2025

For the simplest rubber loop of 2 strands for peanut scale:

• know the distance between motor hook and peg.
• this can only be an estimate: Take twice plus half the distance, this is the length of a single rubber strand that, when braided, will result in about 110% length of motorhook to peg.
• Mark the centre of the single rubber strand with a permanent marker, slip in a small O-ring (can be a short section of any tube shaped soft plastic), place it near the centre, using sewing thread to wrap the rubber around the O-ring, tie off loosely.
• Hold one end in a binder clip or something that can hold the end securely temporarily.
• Twist the single strand from the other end, the O-ring is still in the centre.
• Bring the end to the secured end, now both ends are together, tug on the o-ring occasionally so that the rubber will wind itself evenly.
• Slip in another o-ring to the end, unsecure the first end, tie in a figure-8 knot, bit of superglue on the rubber.
• Now I have a braided loop of rubber, 2 strands, and about 10% longer than the distance between hook and peg. How much braiding and how big the o-rings will also affect the length. The two o-rings allow easy engagement of hook and peg.

2nd method?:

• know the distance between motor hook and peg.
• this can only be an estimate: Take twice plus half the distance, this is the length of a single rubber strand that, when braided, will result in about 110% length of motorhook to peg, how much braiding and size of loops will also affect the length.
• Tie a loop in the centre of the single rubber strand, you could use an overhand knot, or just directly tie the rubber with a few windings of button sewing thread and superglue. The second method is preferred for simplicity and lightness because you don't carry the extra weight of rubber knot. If you have a suitable o-ring, you can also tie it to the centre, just that o-ring is weight and the real usable length is shortened.
• Loop the loop over a dowel, and twist from each end, if the right strand is twisted towards you, then the left strand is also twisted towards you. The key is to twist both strands in equal number of turns.
• Tie the 2 ends together with an overhand knot but leaving a loop. If there is not going to be a loop, a S-hook can be used later, tie 2 ends together with figure - 8 knots.
• Let free both ends and the twisted rubber will braid itself. Tug the loops a few times and the braiding will be even.
• Unloop the loop from the dowel. Now you have 2 loops, one to the hook (the single loop first created) and the second to the peg (the double loop just created).

Gemini says:

Think of it this way:

• First method: Like building a finely crafted, hand-stitched garment. Higher quality, but more work.
• Revised second method: Like a well-made, machine-sewn garment. Good quality, faster and easier to produce.