plastic belting

A simple question - I've bought some 5mm dia. plastic belting from RS. I know it can be joined by heat but not sure how much. Second question is how much tension to build in. I'm guessing cut to exact length minus minus 2 or 3 p/cent ? Lesson here, buy a bit extra to practice on, to late now. Any advice welcomed.

I always used a candle to keep my hands free

After a bit of care and practice you can get a virtually 100% strength join which looks like a small lump, then trim the excess off with a pair of nail clippers

It's pretty amazing stuff

The easiest way to join them is place a 40W soldering iron in a bench vice, hold the ends of the belt against the flat but clean part of the tip of the hot iron and when molten push them together. If you have a nice joint, which can take a few attempts, make it smooth by cutting away the surplus which is pushed out. It is more difficult making the belt to have a certain tension, it is much easier if the distance of the pulleys are adjustable. Niko.

I'm probably not the best person to advise you Gordon, as I didn't have too much luck with the plastic belting I tried.

I would think that 2-3% for stretch would not be enough (but I suspect this would also depend on how long the total length of the belting is). I was using a belt about 4ft long (before jointing) and it needed about 10% (although I did have a means of adjusting final tension). I think the other problem might be that there are probably different types of this plastic stuff around. Mine was a clear (translucent) 3/8th" type, that I also found quite hard to join (well). I was driving a Cowells drill with it and several times the joint gave way (I found it tricky to balance tension against slippage)

I'm sure others have had better experiences with this stuff and this might be a function of the "type" of plastic used. For my part, I found a source of leather (round) belting on eBay, made a simple scarf joint with adhesive and treated it with Neatsfoot Oil (just as Tubal Cain advised). This has been a good solution for my application (as it tensions well & doesn't slip) and I haven't looked for alternative/other types of plastic belting as a result. If the lengths involved were smaller, I would be inclined to look for another (fixed length) belting type - I use small 'Gates' belts on my smaller machines for instance).

However, I'm sure others here can offer you better advice, especially if they have used the RS stuff (which I didn't btw) Good Luck,

IanT

Hi

I followed a method I read some where which was; -

Make asimple jig to hold bolt ends in alignment, one end clamped, one able to slide, hold jig in a vice.

Cut and linish both ends of the belt square, flat and clean, Place each end in the jig with a small gap between.

Heat up a clean thin piece of metal (1 to 2mm) to a temperature that melts the plastic belting.

Place said hot piece of metal in the gap between the plastic belt ends, push the ends together against the hot piece of metal until the plastic starts to melt.

Remove the hot piece of metal and push the ends of the plastic belt together and hold.

You will get a very neat flash around the joint, your jig must provide some clearance for this flash to form.

Clean up the flash with a sharp knife and emery.

I use this belting on my quorn T & C Grinder and a small drill press, it's never failed.

Nigel

I can confirm the method that Nigel mentions above. We used to make thousands of rings from this material to use as cheap springs to hold nail gun jaws closed. We had a modified pair of snips with a vee guide attached to allow us to cut the material square, this is important if joining the material by hand, as a tapered cut can cause the materiel to slide sideways out of line when bringing the ends together. We had a modified pair of pliers with Vee jaws in which the material could be located in line and clamped. We had a soldering iron with a specially made flat tip coated with Teflon. This was held in the vice and warmed up, then the pliers would be brought to the vice to straddle the tip, and when the ends melted, the joint was slid off the tip, and the jaws squeezed together to make the joint. Like all things some practice made perfect. Our star ring maker would not bother with the pliers, as it was quicker to do it by hand, but he made thousands and had plenty of practice. One other thing to bear in mind is that if a mistake is made, one needs to cut out the bad joint and 5mm or so either side of the joint to get rid of the previously softened material before having another go. The Teflon tip was needed when making lots of joints, as the softened material can pick up on a plain steel tip, but should not be an issue when making one or two joints.

Chris Gunn

Thanks for all the ideas. After careful checking I think I will have a short length spare, so can get a bit of practice. A little jig is a good idea. This belt is only for a hand drive on a Wimshurst machine. I've already fixed the centers, was going to use a big O ring for drive but could not find the round rubber at a sensible price , I have made lots of O rings by gluing rubber section (using a factory made jig ). Will start on the long side and can always cut the joint out and remake. If all else fails can fit two jockey wheels.

RS also sell plastic belting in the form of a tube. This is joined using small aluminium joiners with sharp radial fins that grip the inside of the tubular belt. The joint is very strong. I have used this type with 100% success for many years when making drive belts for my old Drummond lathe.

This video shows a very easy to make jig in use for welding PU belting.

Hope that helps.

Russell.

Like Lambton, i use the hollow type on a drummond lathe - at least I tried to. I tried to join it using heat as described, with no success, so i went back to the supplier. He advised (contrary to the guy at the sales counter) that there were different types for plastic welding and the type i had needed a joiner, basically a barbed pin.

I eventually gave up trying to eliminate slip, and at the recommendation of the same helpful supplier got a length of round leather, but i just make a wire clip (out of an umbrella spoke...). the leather can conform better between the lathe pulley designed for a round belt and the countershaft expecting a V belt.

-russell

I use 3 mm green belting for driving things off my hot air engines(up to 10W), and 5 mm green for my Super Adept lathe.

for joining, I heat a strip of stainless steel sheet about 15 mm wide x .5 mm thick(used to use an old table knife), to just about red heat, touch both ends on the hot steel, slide of, bring them together and press until they bulge, hold still until cool, use nail clippers to trim the flash, then I like to leave it until the next day before using at full load.

Never had any trouble with the green belting, but the white(ish) stuff I had years ago, goes brittle after a few years. Ian S C

Hi Russell - and I was beginning to think I was the only one who liked leather around here!

The idea of using round leather belting does sound kind of 'old fashioned' (obsolete?) but it actually works very well and thanks to the Internet is not hard to obtain again these days. It is not expensive either. I've just searched eBay under "Sewing Machine Belting" - and currently 6ft of 3/16" leather belting is available for about £5 - not ideal for everything but I would suggest it is suitable for longer runs - for instance overheads and older drilling machines etc.

Mine came with a metal clip but the scarfing joint seemed more secure and I didn't want any annoying 'clicks'. I occasionally give it a wipe over with neatsfoot oil to keep it supple. It's certainly worth considering for some applications - sometimes the old ways are still the best..

Regards,

IanT

I have always used the method outlined by Peter Spenlove-Spenlove in MEW no 89 in 2003, involving the use of a hot knife to melt the cut ends.

However, for removing the mushroom of flash from around the joint I have found that using the bench grinder carefully results in a smooth joint. When trimming with a knife I always manage to nick the belt

Phil.

Re joining plastic extrusion.

When I was still at school we used to do skipping for exercise as part of PE. The ropes were extruded unreinforced plastic, They used to break. I devised a method using a short length of thin; I guess about 20 thou nichrome wire stretched between two insulated posts attached to a board. It was heated by a small power supply in this case the battery I used to fire up my glow plug engine But any appropriate power supply would do, the wire glowed a dull red.

To join the plastic extrusion the ends of the wire were held together and the line of the joint was steadily, at a speed that allows proper melting, passed through the wire fusing the plastic as it went through. The process worked well. I remember doing hundreds of them. The hole job only took a few seconds, then all that was left was to trim off the sprue.

The wire kept clean burning off the small amount of residue between joints.

Regards
john

Edited By John McNamara on 22/01/2014 14:28:38

At last the belting is installed. For anyone who may be interested- I marked the belt at the joint and cut with a craft knife. Made a little fitment/jig from ally. A groove to hold the belt while joining and a hole thru' to cut the belt square. I shortened the 24" long belting by 1/2", this with the melted ends is about 3/4" short. Heated with a quick heat soldering iron with flat bit, one end of belt clamped to jig using toolmakers clamp, hold other end for what seems a long time. This amount of tension seems about right for hand turning but might need more for motor drive.