Chains arrived, thanks Andy. Took 3 days from UK to Australia. Couldn't have done it much quicker if you'd bought 'em a seat on a plane and taxi each end!
It's interesting comparing different chains.
I have 4 different primary chains in front of me: An original Regina triplex, an IWIS triplex, an IRIS triplex, and the IWIS (Mercedes) big pin duplex.
Of the tripex chains, the most heavily constructed is the Regina. It weighs in at 922 grams on my (non calibrated) digital kitchen scale, compared with 804 grams for the IWIS, and 802 grams for the IRIS.
Being only two rows, the duplex is obviously much lighter in total weight at 670 grams, but its construction looks about the same as the Regina - big pins and hefty side plates.
Comparing the apparent construction got me thinking (a dangerous thing). If you take the weight of the IWIS (Merc) duplex and manipulate it through some complex arithmetic* to estimate what a triplex chain of the same construction would weigh, the answer comes out to 975 grams. So the IWIS duplex is actually built more heavily than the original Regina chain. It?s a pity they don?t make it in triplex. :sad:
* The complex arithmetic isn?t simply multiplying the weight of the duplex by 1.5. It?s a combination of multiplying the weight of the rollers and pins by a factor of 1.5 and the weight of the plates by 1.429 (380 plates in triplex / 266 plates in duplex). The trick is to know the weight distribution between plates, rollers and pins :wink:
Andy, I know you said the choice of primary chain is a ?no brainer?. I must have no brain because I?m hard to convince, but I think I?m now tending towards your opinion that the big pin duplex is the best primary drive option out of what?s available today.
I also have an old Regina cam chain and a new IWIS equivalent in front of me.
For what it's worth, I've made some observations in the tables below. Dunno whether any useful conclusions can be drawn from this. Note that the figures are approximate - dimensions measured roughly and rounded to one decimal, and weights from my crappy cheap kitchen scales.
Cheers,
Cam