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The motor driven etalon band needs a reduction in turning friction to function well. After thinking about it some more it occurred to me that there are alternatives to Teflon tape wrapping. As the o-rings are the only source of friction one should concentrate on those.I tried fitting only one o-ring and it made no discernible difference to friction. Fail.
Modification could include replacement with slightly thinner o-rings of the same diameter.
Or, thinning the original o-rings slightly by abrasion. Though I certainly would not recommend doing this in situ. The o-rings would need to be removed from the inner shell of the etalon housing. For reduction in overall diameter by sanding with a cylinder of abrasive paper.
A suitable mandrel would be required to hold the rings firmly [by stretching] for sandpapering. A perfectionist, with a lathe, could make a copy of the etalon inner shell complete with grooves. Though I doubt it would be necessary to make the grooves. Most o-rings, by their very nature, do not easily roll along a bar but remain in one orientation unless deliberately rolled from the side. Usually they just slide sideways without rolling. So sanding will slightly flatten only the curved, outer surface.
O-rings are available in a huge range of sizes and materials from specialists. The "mileage" they suffer in an etalon housing suggests the most common black rubber type is perfectly adequate.
The original PST O-rings in my own etalon housing are 51mm measured across the grooves x 2mm thick. Which suggests that 50 x 1.5mm might do the rick. I have checked the stock o-rings [locally] and their range includes 51mm x 1.6mm. A reduction of .8mm on overall diameter.
Whether these companies deal with private customers is the next hurdle. Many Danish businesses prefer to specialise in wholesale only. Leaving the private customer to find a source elsewhere. There is certainly no sales website for private customers to pay for small quantities of anything. Fail.
Which means going to eBay and the UK many times. With large postal charges for a signed-for service to avoid the career crooks. Who routinely say they never received the item and claim a refund. Then put the item on eBay. Fail.
Some companies sell round, rubber o-ring materials in long lengths to make your own o-rings. Now there's an idea! What everyday materials could replace the o-rings with something more slippery? Heavy, monofilament, nylon fishing line? Or grass strimmer line. Fine cord? Time to start looking!
I have been searching for plastic coated wire/flex in 1.5mm to replace the o-rings in the grooves. Amazingly difficult to find. Loads of 1.2mm or 2mm but nothing in between. So I used some 1.2mm and friction remained very low at the expense of a little extra slop. I have boxes and boxes of cables, from multiple disciplines, but no 1.5mm OD. The strimmer monofilament was also 1.2mm.
Tried 1.5mm brake cable, solid brass wire and solid copper wire. All too stiff. Copper cored, multi-strand flex is still the best so far.
For the truly adventurous there are stepped diameters of strimmer [grass trimmer] "wire" in monofilament nylon. 1.3 and 1.6mm are small change for a 15m length. Stiffness is unknown at 1.6mm but would seem an ideal candidate to remove the last of the outer drum slop. Not that it would matter with belt drive. It just seems a bit sloppy for my taste.
So another whole page of text dedicated to finding [about] 6" [15cm] of something better to replace the PST O-rings. It is Saturday and the nearest big DIY outlets close at 2pm. So it will just have to wait until Monday. This is weird! I searched online and none of the local DIY chains has 1.6mm nylon line in stock. I have had to order it online.
The original PST O-rings in my own etalon housing are 51mm measured across the grooves x 2mm thick. Which suggests that 50 x 1.5mm might do the rick. I have checked the stock o-rings [locally] and their range includes 51mm x 1.6mm. A reduction of .8mm on overall diameter.
Whether these companies deal with private customers is the next hurdle. Many Danish businesses prefer to specialise in wholesale only. Leaving the private customer to find a source elsewhere. There is certainly no sales website for private customers to pay for small quantities of anything. Fail.
Which means going to eBay and the UK many times. With large postal charges for a signed-for service to avoid the career crooks. Who routinely say they never received the item and claim a refund. Then put the item on eBay. Fail.
Some companies sell round, rubber o-ring materials in long lengths to make your own o-rings. Now there's an idea! What everyday materials could replace the o-rings with something more slippery? Heavy, monofilament, nylon fishing line? Or grass strimmer line. Fine cord? Time to start looking!
I have been searching for plastic coated wire/flex in 1.5mm to replace the o-rings in the grooves. Amazingly difficult to find. Loads of 1.2mm or 2mm but nothing in between. So I used some 1.2mm and friction remained very low at the expense of a little extra slop. I have boxes and boxes of cables, from multiple disciplines, but no 1.5mm OD. The strimmer monofilament was also 1.2mm.
Tried 1.5mm brake cable, solid brass wire and solid copper wire. All too stiff. Copper cored, multi-strand flex is still the best so far.
For the truly adventurous there are stepped diameters of strimmer [grass trimmer] "wire" in monofilament nylon. 1.3 and 1.6mm are small change for a 15m length. Stiffness is unknown at 1.6mm but would seem an ideal candidate to remove the last of the outer drum slop. Not that it would matter with belt drive. It just seems a bit sloppy for my taste.
So another whole page of text dedicated to finding [about] 6" [15cm] of something better to replace the PST O-rings. It is Saturday and the nearest big DIY outlets close at 2pm. So it will just have to wait until Monday. This is weird! I searched online and none of the local DIY chains has 1.6mm nylon line in stock. I have had to order it
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