Lego Yarn Ball Winder and Swift
Background
My girlfriend had a ton of yarn that she'd bought and dyed, but it was all still in hanks. A hank is like what you end up with if you just wrap yarn around your arm using your hand and elbow.
A hank isn't all that useful for knitting, since the yarn gets tangled as you pull it out of the loop. That's why people use yarn balls, because it keeps your yarn from getting tangled.
If you are super clever, you wind you yarn balls so that you can pull the yarn out from the center of the ball, not the edges. This is better because it keeps you from stretching the yarn, and having it lose its elasticity. ( I'm not the knitter so don't ask me!)
The Device
I had seen a design for a Lego ball winder a while back, and thought "Hey, I can build one of those!" About a year later, my girlfriend had progressed up through her knitting hobby to where she was starting to dye her own yarn and therefore needed a yarn ball winder.
However, I'd never seen a ballwinder in action! I had no idea how they worked. From examining the pictures of the above winder, I could deduce the mechanical motions involved: the ball both spun and revolved. I didn't have any idea what speed these two things should happen at, so I started my design using what I could figure out from the pictures.
Click on the thumbnail to bring up a fullsized image. Sorry, some of the images aren't focused all that well.
 | A very large wound ball. This is the first design. |
 | Here you can see how the yarn is fed, the platform, and the motor. You can also make out the gears for turning the ball on its spindle. |
 | another view of the winder |
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 | detail of spindle gears. |
 | another detail. Notice I had a one missed winding. |
 | a view of some of the support structure. |
 | The drive motor and switch. The platform has been rotated 90 degrees. |
 | The winder without a the cardboard tube spindle. |
 | later we realized that we needed to have a longer spindle to wind really large balls. This is made by putting two toiletpaper rolls end to end, then simple wrapping both with a piece of paper. |
 | I added a key to the tube to lock it to the rotating spindle, since it was slipping trying to turn the larger yarn balls. |
 | detail of the locking pin |
 | another view of the locking pin |
 | This was anothere piece of yarn that was much thinner than the brown yarn. You can see the locking pin in action in the bottom left corner of the photo. |
 | I also made a Lego swift to hold the yarn. After you've had to feed hundreds of yards of yarn by holding the hank in your hand and flipping your wrists back and forth, this becoming a very desirable tool. :) |
Videos
So if you are like I was a week or so ago, you're wondering "How does this thing work?" Well, I can sort of help. You'll need Quicktime to watch the videos.
Here are two videos I took. The first video (2.5M) shows an earlier version of the ball winder. You can hear it strain due to the imbalance of the platform caused by the large yarn ball and because I had the entire unit inclined. Also, yes, it really winds that fast. You need to have a hand near the off switch because if something gets caught, it gets ugly quick.
It doesn't hop around like that any more :)
The second video (5.1M) was taken at a wierd angle and sideways. It shows the swift in action and the latest version of the ball winder. You can't tell from the video, but the ball winder is now flat against the ground. That's me sitting there, with my foot to keep the ball winder from inching slowly into the swift, and my right hand on the switch to shut the thing down if it tangles.
You may have the impression that I have a death grip on the winder to keep it from moving about, but actually i'm just lightly touching it. We had so much yarn to wind, I had to strike a fairly comfortable pose. The yarn is green, white, and blue colored because thats the way my girlfriend dyed it.
Results
How did it turn out? Very nicely, thank you. The balls of yarn slide right off the spindle and pull from the center without tangling. And while this machine can't run unattended, it is fast enough to not be a chore to sit through several hanks of yarn.
Currently, the winder doesn't make the nice 'square' balls of yarn that I'd like it to. Also, when it gets to very large balls of yarn, the geometry of the winding action sort of breaks down and it tends to just loop around the spool.
It doesn't really take up many Lego peices, so I will probably build a second revision to experiement with the geometry of the winding action. Angle of yarn feed, tilt of the spindle, position of the spindle in relation to the center of the platform, and ratio of revolutions of the spindle to revolutions of the platform are all variables which can be optimized.