Monday, August 19, 2013

Math for Spinners, or, Maxxing out the Traddy

Spinning fine takes time. No joking. How much time?

I've run through some numbers, and for you math geeks here they are:

My goal is sock yarn: 400m 4-ply for a 100g hank. This means 1600m of singles (at least!) out of that 100g roving, which works out to a grist of about 8000 ypp (16 m/g in metric). 

I have the following:
  • maximum flyer whorl ratio 10:1 (I have a 1980's Traddy)
  • treadle speed 2/sec (this is about the maximum that is comfortable for me to maintain for any length of time), which, on the above ratio, means 20 rotations of the flyer per second. In other words, it's buzzing at 1200 RPM. Note that this is treadling very fast. A more comfortable rate is 90 treades/minute (1.5 treadles/sec). Slow treadling is 1 per second. I'm such a geek that I've actually used a metronome to establish treadling rates!
  • Drafting speed 2" or 5cm per second - this means inserted twist at ~10 twists per inch ("TPI") (actually probably a little less), which seems to be good for the type of yarn I'm getting so far (may have to go a little higher as a I get thinner). I find the drafting actually quite slow., to spin 1600m of singles will take me (at 5 cm/sec) about 9 hours. And, of course, more time still because it doesn't include the plying. Uh-oh.

So, you can appreciate why I am looking into getting additional equipment to boost the speed!

How about a lace flyer? This is a thin (more aerodynamic) flyer with a tiny whorl on it, that has a ratio of up to 40:1, according to the Ashford website. If I maintain the same treadling speed, this will cause the flyer to buzz around at 4800 RPM, so to maintain the same TPI I will have to draft 4x as fast (20 cm/second - not sure I can handle that worsted!), which will reduce my spinning time to a much more palatable 2-3 hours.

But, and this is a BIG but, I am not convinced that the Traddy can actually perform at 4800 RPM. The power required to drive the flyer to these speeds is not inconsiderable (which manifests itself in "it gets hard to treadle"), and I am sure that the kitchen string I'm currently using as a drive belt won't handle it (it's not grippy enough, it'll slip, heat up and break). No wonder there's a plastic drive belt included in Ashford's lace flyer kit. According to this gentleman, who has done actual tachometer measurements on his wheel, the Traddy, kitted out with a lace flyer and plastic drive band, maxes out at about 2000 RPM. No matter how hard he treadles...and he has a double-treadle setup, which allows him to use both of his legs to deliver power (I could deliver more power by putting both feet on my single treadle...). If this is true, then the actual, effective, highest ratio you can spin on a lace flyer is a mere 20:1 or so - only half of the rated spec! For perspective, the current flyer that ships with modern "Traddy's" has a top ratio of 17.5:1. Hm, I think I can see where this number comes from...and, it's clear that a better choice for me is simply to upgrade to a new flyer. That'll halve my spinning long as I can reach that 2000 RPM with a single-treadle setup! I think I may need to revisit my lubrication regime when I start pushing the Traddy like this though...

Spinners in days of yore used to spin this fine, I'm sure they did. In the very early days, they used "quill spindle" setups, which don't have a flyer and can go really fast (but don't wind "automatically"). By the 1800's, so-called "production" spinners were using bigger wheels with dual-drive setups, not lace flyers. I think I will have to learn more about those.


  1. I don't really understand maths;I enjoy the spinning on a more tactile level and mostly spin on instinct. You have really gone into the depths of spinning in your quest to spin fine yarn though and I can certainly appreciate the obsession. When I first learned to spin I dreamed drafting.
    Do you think a double belt drive might increase your speed? I have a scotch tension traditional a double belt drive traditional style wheel and the double belt drive lets me spin faster than the scotch tension; I use it for cotton mostly.

  2. I think the short answer to this is "yes", but likely not with the standard equipment from Ashford. The double-drive setup has more surface area for the belt to make contact and so it's possible to drive to higher speeds. The guy who did the tachometer tests on his lace-flyer-scotch-tension setup apparently regularly drives his double-drive setup much, much higher than 2000RPM (which is where the belt starts to slip on single-drive machines). But, he uses "custom" bobbins and whorls that he makes himself. So that's the other part of the equation. I don't have a woodshop...

  3. That's a pity; you could be flying (pun intended) in no time.