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Link belt drive problems

Since I have had my Denford Viceroy I have never been happy with the belt drive. This is an A section Link Belt, a similar setup to the Boxford. The Belt suffers as Backgear oiling is preferred from points over the gears, the oil therefore gets on the belt! Even though the manual says oil I feel the best option for the future is grease the layshaft and use gear spray on the gears from time to time.

I stripped it apart today and noticed that the belt is not sitting down into either the top or bottom pulley grooves. In fact there are one and a half link thicknesses standing proud. Theoretically three link sides should always be in contact IMHO. The belt that I removed shows polishing soley on about 8mm of the thinner "tail", ie from the innermost part of the groove. The pulleys appear to be original Denford (certainly the top pulley on the backear setup) and an A section belt is supposedly the standard. Groove angle seems to be 38 degrees from a quick check I have done some calculations and it appears that an SPZ belt will handle the loadings. Obviously the SPZ will sit fully in the groove hopefully allowing a full drive.

I suppose that a 13mm belt may have been fitted as opposed to an A section, however I doubt that 12.7 compared to 13mm would make that much difference.

Has anyone seen anything similar before? Can anyone suggest my best course of action?

Reply to
Richard Edwards
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Richard

I'm no expert on these belts but having just checked my Boxford the belt is slightly less than one link thickness proud of the pulley outer diameter on each pulley. It never slips and has run like that without problem for the last two years. It is dry though. The tension on these belts is critical and it almost sounds if yours does not have sufficient tension to pull the belt into the groove fully. If my memory serves me with an A link belt (new) when you put the belt round the pulleys to find the length you then remove 1 in 11 of the links to set the basic tension; the belt is in effect 9% shorter than the free length. The other way is to measure the force to deflect the belt when fitted depending on the centre distance of the shafts. There is a chart about somewhere but I would need to find it for you. I know that the (high in my opinion) tension when fitted to my S7 gave me some cause for concern and I returned to the standard belt. The belt on my Boxford is very tight but I am less concerned due to the spindle and layshaft bearing arrangement. The other issue I have had when fitting new link belts is that they require frequent re-tensioning as they settle in through the first few months of operation, depending of course how many hours they run. All assuming of course that your belt is in fact the correct section for the pulleys.

Regards

Keith

Reply to
jontom_1uk

A section *is* 13mm

Maybe it's been fitted with B section (16mm)?

Be very careful if you're thinking of using a smaller section, if the belt bottoms in either pulley you'll get next to no drive at all.

Tim

Reply to
Tim Leech

Modern synthetic link belting stretches *much* less than the older types did.

Tim

Reply to
Tim Leech

As I understand it SPA is 12.7 A section Metric is 13mm (another ) However I would be happy to be proved incorrect

Thats what I assumed until I measured it.

Agreed, well aware of that, need to apply test sections at my local supplier.

Reply to
Richard Edwards

The problem on the Viceroy is then clipping it back together again!

No need you helped with a link a long while ago, I now have the pdf on my system.

That is the thing that cocerns me most. The facxt that your Boxford only shows less than one link indicates that I have something awry. I will check a neighbors Boxford. Regards

Reply to
Richard Edwards

The Fenner leaflet in front of me lists both A and SPA as 13 x 10, I've seen the 12.7 figure before but 0.3mm on a Vee belt is possibly within the allowed tolerance.

Tim

Reply to
Tim Leech

Note. A section belts are not 13mm, they are not 12.7 mm, they are half a bloody inch! Just like M or Z section belts are three eighths of one.

Mark Rand RTFM

Reply to
Mark Rand

I have it on good authority that M or Z section are actually 9.525mm

However back to the subject in hand. Considering that the Viceroy was designed in the '50s it SHOULD use a true imperial section belt, maybe this is the main problem. I am concerned though with the old belt indicating polishing on just the very inner section of the links. I assume that Nu-T-Link belts have the same included angle wether Metric or imperial.

Reply to
Richard Edwards

Do they offer both A and SPA sections in link belting? I was of course wrong earlier when I said they were both listed as 13 x 10, the main difference between them is the depth and the old A section is only 8mm depth (Sorry Mark, 5/16" ). The Viceroy was probably only built for A section, so if you can get true SPA section belting you ought to be OK as it will sit deeper into the pulleys - provided, of course, that it doesn't bottom but that sounds unlikely from your description.

I bottled out from changing the drive belt when I had a Viceroy, it was getting due but I weighed it up & passed the problem on to the new owner

Tim

Tim

Reply to
Tim Leech

Richard, I'm sorry but I missed this comment (and its potential significance) the first time round. If you are trying to clip the belt into its=92 normal running position it will most definitely not be sufficiently tensioned. I understand (I haven't done it myself) that the Viceroy access can be a problem but the belt needs joining when aligned over a smaller pulley or the shaft at one end and then easing over the matching pulley to create the normal running tension.

Apologies if I have misunderstood your comment.

Regards

Keith

Reply to
jontom_1uk

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