BCA belt replacement

Hi BCA owners

My Mk111's belt has a crack in it at what looks like the joint about 50% through so only a matter of time before it goes. It is not the orignal belt but certainly pretty old, some poly* material I think.

I put a hot knife blade in the crack then pressed it together and held until it cooled but no sign of any join or weld.

I see on ebay there is round leather belting available, 5/16" dia with a staple to join, meant for sewing machines and I wondered if anyone had tried this at all and what the experience is. If not good then I will try some of the round poly belt that is available.

I would be greatful for any advice/experience in the belt replacement.

Andrew

Hello Andrew,

I have used round poly belting with good results but the material does stretch and needs sizing accordingly without having to resort to jockey pulleys to take up slack.

Tony Griffiths of www.lathes.co.uk sells made up belts for all manner of machines including round leather belts with a proper scarfed joint rather than a staple joint. It might pay you to take a look

Regards

Brian

Why not use the green belting that’s available, it has been on my t/c grinder and put for many years and is available in los of sizes.

Not familiar with BCA but if it is a round belt this might be suitable. They do a range of sizes.

Round belt

Not used them myself but I have used similar belt from an exhibition stand for my watchmakers lathe.

Thanks for the replies.

I wanted to avoid stripping out the main spindle and so not use a made up belt.

The only reason for looking at the leather belting was the mechanical joint sounds more dependable as I wonder about the effectiveness of the green belt joint by fusing together but sounds like it should not be any issue.

Andrew

Edited By AStroud on 31/10/2021 12:18:10

This stuff works quite well Round polyurethane belting It can be joined with a little barbed aluminium gizmo. It doesn't last forever, starts to crack after about 10 years.

HTH,

Rod

There are glues advertised in the internet which claim to glue almost anything to almost everything. Perhaps take up one of them on the claims?

.

Properly jointed, it should not be any problem.

I have the ‘genuine Swiss’ green belt [purchased, ready-joined, from Tenga Engineering] on mine … but the Chinese clone material, with the rough texture, is as near identical as I can tell.

MichaelG.

.

Useful ebay reference not included, for obvious reasons.

https://www.model-engineer.co.uk/conduct/

Edited By Michael Gilligan on 31/10/2021 13:12:40

I have a green plastic belt on mine from Tony Griffiths on the "Lathes" website.

It has been on for over five years with no problems at all.

Phil

I have used the smooth red poly solid belting to start a .40 glo boat engine because rubber ones perished due to the fuel.

Joined by melting both ends on a solder iron, then bringing them smartly together and paring off the excess with a craft knife it lasted years under considerable tension.

This green heat joint belting 5 mm dia is at its limit here driving
the internal grinding spindle at 28,000 rpm you can just see the joint frozen
in the flash on the top side ,the normal tension is set i think at 8% i
increased this to 15% to get the spindle to drive reliably at just
over 31,000 rpm ,its tough stuff this belting.

John

My BCA along with a few other machines run with the cheap polyurethane belt available on ebay, and other retailers I guess.

I join it with an old knife heated with a blowlamp, press the 2 ends either side of the blade and slide them both off together simultaneously to stick together. This does require a bit of practice. The knife only needs to be warm enough to melt the material, I used to get the knife red hot and when the plastic touched it almost seemed to boil, evidently this did not work at all well.

Another thing I have found, if you are trying to repair the initial joint forget it! cut about 10mm either side and start from scratch, same if the new joint doesn't work.

The expensive name brand stuff came with my first BCA and I really struggled to get a good join with it it never seemed to fully adhere to one another, I put this down to being quite old, peoples views above seem to reflect my experience. Also my Alexander D bit grinder came with an old name brand poly belt on it, it subsequently broke, I repaired it (I didn't have any new 4mm stuff so needs must) and it subsequently broke again and whipped me in the chest! (which was quite a painful experience) I doubled up a length of cheap 2mm belt and its still in use today!

I would strongly advise not to use a metal joiner on the BCA, it was designed for an "endless loop" so I would be concerned with wear on the pulleys etc, also I cant seem to find any larger diameter than 5mm, I use 8mm on my BCA it seems to fit nicely in the grooves and only slips when I am using a slitting saw on the lowest rpm( no bad thing really).

I hope that helps

William

As a side note is there anyone here who uses the genuine original belt material? I have one from home and workshop machinery and its too short for my MK3 (it was described as a BCA mk3 original belt) I suspect its from a MK2. Its an odd material that wants to coil it self up because of the way its made.

.

I still have the original [twisted cotton tapes ?] belt from my Mk 3 … I only replaced it because it was starting to fray.

… aside from that, it seems an excellent material

MichaelG.

I have had good results joining polyurethane by making a knife-edge bit for a soldering iron. Hold the heated iron fixed for example in a vice, apply cut ends of belt to opposite sides, then slide them together off the edge, and hold till set. This avoids exposing the melted PU to air. If necessary, trim flash with a scalpel.

We used to use the green belting to make rings about 50mm diameter to hold the jaws of nail guns closed. We had special vee jaws made to attach to some hand shear blades so the material was cut square. So cutting the ends square is important. We had a small teflon coated blade to fit on the end of a soldering iron. The ends were heated, and slid off the blade and held together to make the joints. It needed practice to do it, and we got used to it. One problem for the hobbyist is that one does not get the chance to practice.

We made thousands of them, it was the cheapest and most effective way of keeping the jaws closed until the nail was driven through. The ring would stretch and then contract to hold the jaws shut. Each ring would cycle 7 or 8K times a day. This shows the joints will perform if the joint is made correctly.

Chris Gunn