The setup I used to spin the loom stuff gave a "ratio" of ~20:1. I treadle at a little over 100 strokes per minute, resulting in a bobbin speed between 2,000 and 2,400 rpm. At that speed it took ~200 hours to spin the loom stuff or 3 hours/ weekday for 3 months.
At a ratio of 10:1 the bobbin speed would have been only just over 1,000 rpm and it would have taken me 3/hr /evening for 6 months. At a ratio of 5:1 it would have taken a year of weeknights to spin the stuff - and it is just hard to plan a project that long.
Spinning fast makes more projects plausible. It makes more, and finer plies feasible.
The weaving stuff has grist of about 2,800 ypp, and thus ~ 5 tpi. For a finer single needing more twist, I use a higher ratio. Now the wheel is set for spinning 5,600 ypp/ 9 tpi singles with a ratio closer to 30:1. I use a similar ratio to spin fines that want 23 tpi. That comes to less than 200 yards per hour production, which is ok for worsted but not really fast enough for woolen.
If I go much above that range of ratios, I start getting drive band slippage. And once a drive band starts slipping, it slips a lot. Once a drive band starts slipping, the nature of the friction between the drive band and the whorl it is slipping against changes. Dynamic friction is different than static friction.
Drive band slippage and actual speed is more important than the "ratio".
At a ratio of 10:1 the bobbin speed would have been only just over 1,000 rpm and it would have taken me 3/hr /evening for 6 months. At a ratio of 5:1 it would have taken a year of weeknights to spin the stuff - and it is just hard to plan a project that long.
Spinning fast makes more projects plausible. It makes more, and finer plies feasible.
The weaving stuff has grist of about 2,800 ypp, and thus ~ 5 tpi. For a finer single needing more twist, I use a higher ratio. Now the wheel is set for spinning 5,600 ypp/ 9 tpi singles with a ratio closer to 30:1. I use a similar ratio to spin fines that want 23 tpi. That comes to less than 200 yards per hour production, which is ok for worsted but not really fast enough for woolen.
If I go much above that range of ratios, I start getting drive band slippage. And once a drive band starts slipping, it slips a lot. Once a drive band starts slipping, the nature of the friction between the drive band and the whorl it is slipping against changes. Dynamic friction is different than static friction.
Drive band slippage and actual speed is more important than the "ratio".
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