Wednesday, April 08, 2015

DRS, Accelerator Wheels, and Low Grist Yarns

Many of the commercial double drive wheels come with a differential rotation speed of ~1.6. this would seem to make them ideal for making singles for worsted weight 2-ply yarns.

However, such thick yarns rapidly change the effective diameter of the bobbin as they accumulate on the bobbin.  Changes in the effective diameter of the bobbin change the DRS,  To keep grist/twist within ~10%, DRS need to be kept within  ~10%.  When you accumulate 1/4" of yarn on the bobbin, the diameter changes by 1/2" and the DRS changes by a lot and one needs to either change flyer whorls or wind off or allow slippage.  Slippage is the easiest, but why go to the effort of having a DD system, if you are just going to let the drive band slip?  I mean, at these grists we do not have to worry about breaking fine singles.

My first choice for spinning a single with grist of less than 2,500 ypp is single drive, bobbin lead (Irish tension).  These yarns do not require at lot of twist, so one does not need the very high rpm that requires 2 drive bands.  With these yarns, two thousand rpm will produce 10 yards per minute, which is about as fast as you can draft quality yarn.  With 90 rpm as a comfortable treadling cadence, that means a good ratio is ~1:24.

Whorls less than 2" (50 mm) in diameter tend to slip, so if you really want 2,000 rpm, then you need a whorl of 2" and a drive wheel of  48"!!  Forty-eight inch drive wheels are a big pain.

Enter the accelerator wheel.

When I first went looking for more speed for fine singles, I went to higher ratios by decreasing the size of my whorls. It was more an education than a success.

Today, I use the Ashford Jumbo flyer in Scotch Tension mode with the accelerator wheel for plying, and I routinely ply at more than 2,000 rpm.  I could just as well be spinning singles at (more than)  9 yards per minute. I have done samples and tests but no production spinning with that plying setup. Since with Scotch tension, worsted yarn does not self assemble as it does with DRS, it is all long draw woolen, rather than worsted. The speed is limited by my drafting, rather than the speed of the equipment.

Since low grist worsted tends to be harsh, when I want thick worsted yarns, I ply them up from fine worsted singles and have no interest in trying to figure out how to use DRS to spin low grist yarns.  On the other hand, this means that I have a great desire for fine singles.

Bottom line -- DRS for low grist yarns is a waste of effort.  DD without DRS is a waste of effort.  The only reason that people do it is that they have heard myths about the power of  double drive wheels  And, DD does have power.

DD with DRS can do things that SD simply cannot.  DD with DRS is a very powerful tool for spinning singles in the range of 2,500 to 45,000 ypp (5 m/gram to 90 m/gram). With DRS, true worsted and true woolen can be spun with almost the same drafting technique - what differs is the fiber preparation. Woolen is spun from a pile of carded rolags and worsted is spun from a distaff of combed sliver.  In particular, DRS allows spinning true worsted singles faster than long draw woolen singles of the same grist can be spun. (Woolen requires more twist than worsted of the same grist.) With DD/DRS, true worsted 5,600 ypp singles (10s) can be hand spun at 10 yd/minute on a sustained basis.  However, this puts very high demands on fiber preparation to avoid "twittering", which is variation in thickness of a single as a result of variation in the density of the sliver being spun.  Even with minor twittering, DRS allows spinning 560 yard hanks that are consistently within 5% of the desired weight.

And now you know why I have such respect for Clemes and Clemes.  Better fiber preparation is at the core of better and faster spinning.

On the other hand, minor twittering will not affect the final quality of 5-ply sport weight yarn.  The folks who say it does do not make enough of such yarn to make many objects from it.

2 comments:

buckfastbee said...

Did you see the video of Abby's husband with the new e-spinner?
https://www.youtube.com/watch?v=Va2LsKxg3p4&feature=em-subs_digest
He brags in the end how fast it is - but that was without any fiber on it....

Aaron said...

Buckfastbee,
Thanks, I had not seen that. Now we know Abby's new spinner will go in either direction, fast or slow!! I love it.

However, the brake band adjustment is not fine enough for some of the fine yarns that I spin, and spinning worsted is limited by the speed of the spinners inch worm drafting.

This espinner is EXCELLENT for spinning low grist woolen yarn. These yarns do not require much twist, so I am sure that it can keep up with even a fast spinner long draw like Abby. (e.g. 15 yards/ minute => 3,000 rpm)

On the other hand, Scotch tension does not allow self assembly of worsted yarns so its warp speed is no more than a couple of hundred yards per hour.

My guess is that my wheel will spin a hank of 22,000 ypp worsted in 1/5 the time, and I will save $12 in gym fees.