Make your own projector belts using Polycord

Making a replacement belt for almost any movie or slide projector is easy when using the Swiss Synthetic Polycord belting material.

Polycord is available in 2 mm, 3 mm, and 4 mm thickness or diameter from Habasit International.
It has a slightly rough textured surface which gives good grip on all pulleys, even on those meant for
V-Belts. The belt material is resistant to oils, fats, water and most solvents (but avoid acetone and acids contamination).

A new belt is made by simultaneously heating the belt ends to melting point with a slicing tool or torch flame, then immediately aligning the ends which will fuse together after about 60 seconds.

Method 1 - using a splicing tool:

Make a splicing tool for melting the ends of the Polycord from an old simple soldering iron (without temperature control) with a 3-4 cm long tip.

Fold a piece of brass shim as shown below, to slide over the tip of the soldering iron.
It must fit snugly so heat is distributed well into the flat of the shim - call it the Splicing Plate.

To make a belt you choose a suitable thickness Polycord (as close to the original belt diameter as possible). If you are replacing a V-belt, the 4 mm Polycord is probably best.

Measure a length of cord by fitting it around the pulleys - avoid stretching it, just hold it tightly in place. At some point between the two pulleys make a mark where the two ends will meet and cut the ends squarely at that point. Recheck that the ends now meet nicely with the cord helt tight but not stretched.

Have the splicing plate well heated, then gently press the two ends of the Polycord onto the plate, one end each side.

When the Polycord starts to melt and the ends are just softening to the shape shown above, quickly remove the cord from the splicing plate, align and push the ends together. Within about 60 seconds the ends will have fused ...



... and the join will look like shown above. Leave it another 5 minutes to cure then trim off the excess of the splice and you have a finished belt.

Some projectors need to be dismantled to fit a belt, however, we often manufacture the belt while holding it inside but off the pulleys in projector. This avoids dismantling, and just requires another person to hold the soldering iron with the heating plate while you do the joining.

Method 2 - using a miniature torch:

With some care you can use one of the miniature butane torches, sold by hobby or electronic supply shops, to melt the ends of the Polycord. Take care, the cord melts quickly and gets very hot using this method.

Measuring the correct length:

Cut an appropriate length of belt and fit it around the pulleys. It should be held tight/firmly but not stretched. On a straight part of the belt mark the point where the two ends will meet, cut splice and fit to projector. The required tightness will be achieved when the ends are melted and spliced together. If the belt if particularly long it must be held quite tightly otherwise it may end up too loose (however, it it easily re-cut and re-spliced).

Described and illustrated by Ben Vang
Camera Check Point, Dubbo NSW Australia