Arduino, and Mechanical Movement of Objects - a Newbie Question

Dave_Burrows:

  1. What determines when a hook needs to slide, and what do they do when the determination is made?
  2. Are the hooks expected to move independently of each other?
  3. Are we sliding side to side along the shaft or rotating around the shaft?
  1. Ideally, they would slide very slowly but continually back and forth as the crank is turned. "As the crank is turned" suggests a purely mechanical device might be better suited. I mean, I might need to answer the phone, pour more coffee, take a leak, and forget to turn off that motor. When I move them manually, it's in response to certain visual cues; the yarn is getting deep in a particular slice of the drum, and the "V" shape of the split yarn starts to move towards the place where it's mounding more deeply.

  2. As it is right now, yes, they move independently. Whether they are moved by purely mechanical means, or with the assistance of electronics, they would slide back and forth in unison. I anticipate a nearly perfect distribution of the yarn around the drum, and zero breakage.

  3. They slide side to side.

Ahhh! Now I understand. You want them to slide back and forth so that the yarn does not all accumulate in one spot on the spool. Duh! I should have realized that. Like a wire spooler or coil-winding machine.

Essentially, you want them to direct the yarn from one edge to the other creating a uniform layer. Actually, this makes mechanical means even more relevant. As you change the speed of the drum, you want to also increase the speed of the side to side movement. However, this will be in a ratio.

For every revolution of the drum, you want the yarn to move over one yarn width. When it reaches the end, you want it to do the same, but in reverse. This will distribute the yarn uniformly along the spool/drum. If the speed of the slides do not match the speed of the rotating spool, it will not distribute evenly. So you want these to work in unison.

So you need to determine the number of revolutions it takes to spool the yarn across one entire length. Controlling the tension will thin the yarn fibers out to make them a universal width. You want there to be tension so the yarn does not slip side to side and so it will be a constant width. A coil-winder uses a solenoid to provide this tension by rotating the axle that the eyelets are on. Too much tension, and it will break of course.

Once you determine how many revolutions it takes to spool an entire layer, you count the number of spirals. This will determine your gearing ratio.

But then, as the spool gets thicker, it will take more revolutions to wind the yarn, correct?

Yes, you do have it now. Sorry it took so long to explain it coherently. There are several variables, and you named one of them; that as the yarn gets thicker on the drum, it takes more yarn to make a single revolution around the drum. However, unless the thickness of the yarn increases or decreases, precisely the same number of revolutions will be required to move from point A to point B on layer 1 as it will take to move from point B to point A on layer 8.

Another variable is the thickness of a single ply. In GB, AU, NZ, and most if not all of Europe for that matter, ply has a specific meaning. So, the yarn we call "baby yarn", or "sock yarn" here in the states, is called "4 ply" in much of the rest of the world. We call it "worsted weight", most everyone else calls it "8 ply". Same word, same topic, but very different meaning. To further complicate things, there is no exacting standard. One mill might produce a worsted weight yarn that another mill down river a mile calls DK weight.

Folks in the US have invented a new wheel. It's called wraps per inch, or WPI. Ostensibly, it dares to set a standard. By wrapping a yarn around a ruler, and counting the wraps between any two inch marks, worshipers of the WPI standard can tell you in no uncertain terms what the weight of a yarn is. Unless they're pissed, wrap a little more tightly than usual, and cram an extra couple of wraps in there, or unless the individual who did the wraps was your demure gramma who wraps considerably more loosely than the average fiber artist because she knows not to ever wind yarn too tightly lest you stretch the life out of it.

Because precision on that level is impossible, I wouldn't mind if there was a half a yarn width gap between revolutions, or if there were an overlap of half a yarn width or more. Consistency is the goal, and it's also a very good reason to mechanize that aspect. You hit on a very important point when you said,

As you change the speed of the drum, you want to also increase the speed of the side to side movement.

Exactly right. And since the crank that turns the drum needs to be done by hand to respond immediately when something is amiss, creating an electronic component may possibly be counter productive. I wish it were as simple as adding 2 more pulleys and a belt connected to the existing power train, but I don't think it is because of the direction change that is required.

Anyway, thanks; good thinking!

Bah! Direction change is no big deal. Ever look inside an old cassette deck or VCR? The motor always moves in just one direction for forward and reverse. You simply pop a gear over based on a clutch. A center driven gear spins in one direction. You connect a gear to the left side and it rotates in one direction, you move that gear away and mesh a gear on the other side and it rotates in the opposite direction. The cam that decides which gear is meshed is just controlled by the ends of the movement (when it reaches an end, it pushes a lever which disengages one gear and meshes the other.) You don't think a car engine actually rotates in the opposite direction when you put it in reverse, do you? :wink:

I will look for a picture if that doesn't make sense. I can't draw worth a crap. But it is incredibly simple.

Well, first, I tore apart a laser printer, retained all the screws, PCBs, 2 motors, a bunch of gears, cams, rods, rollers, wires, springs, switches, and bits that moved that I don't know how to name. Next, I re-read these last two posts of yours. I brought the ritual to completion by wiggling my finger in front of my lips while humming softly. "Two more printers to go", I said, and then continued my autistic mannerisms by staring at nearby lights.

Several posts up, you said:

I'm sure you understand exactly how this works, but to someone unfamiliar with the process you are going to have to explain it like you are talking to a toddler. lol

I get the idea that you know how to do what I want to do, but after numerous Google searches, I'm not finding anything to help me catch up to you. It does make sense, just not enough to jump start the old engine. A photo, or drawing, or diagram would be great.

ok. I found a few good resources for this, but none of them make it as simple as you need it to be. So this is my attempt at drawing it:

http://www.flickr.com/photos/78906572@N05/8449613492/ (apparently I don't know how to embed an image)

Bascially, a gear connected to the driving gear will rotate in the opposite direction. So for one direction, you connect the driving gear directly to the output gear. To reverse direction, we move an idler gear in between the driven gear and the output gear. You do this with a simple pivot mechanism that just rotates enough to pop the idler gear in place. This lever is toggled by reaching the end points of your sliding mechanism.

So, by default, your output gear would be driving in the opposite direction of the driven gear. The idler gear makes the output gear travel in the same direction, reversing it.

That makes sense for a simple mechanical solution, but given the presence of the microcontroller and quite likely a stepper motor I wouldn't have thought that a reverse gearing mechanism would be required.

PeterH:
That makes sense for a simple mechanical solution, but given the presence of the microcontroller and quite likely a stepper motor I wouldn't have thought that a reverse gearing mechanism would be required.

I am describing a purely mechanical solution which ensures that as he turns the spool at a variable speed, the sliding mechanism will stay in sync providing a uniform layer. He already has power from the crank which he mentioned he would leave to manual power anyway. Of course, if he is going to use the microcontroller, the reversing gear wouldn't be needed.

Hey, man; thanks for having taken the time to work that out on paper for me. I think I understand the concept, or at least I thought I did. In the gizmo I'm building, there are 2 identical gears each engaged with the other. The output gear turns clockwise which means the driven gear turns counterclockwise. The driven gear is fixed to the large pulley, and via a belt, turns the small pulley. As desired, both pulleys turn counterclockwise.

In your drawing, there is a point that confuses me. Your output gear rotates counterclockwise. As drawn, it is engaged with pulley A which turns clockwise. I'm with you to this point. Then pulley A the driven gear is engaged with pulley B, the idler gear, which appears in your drawing to also be turning clockwise...and visa versa when the lever is toggled, and the idler gear engages directly with the output gear. I guess what I'm unclear about is that before the toggle, both A & B are turning clockwise, and after the toggle, both A & B are still turning clockwise.

That said, I think I found enough in the way of gears, and shafts to attempt to make something work. I'll stick close by so you can help me understand better what confuses me now.

I missed the second image at first. Is it some kind torque gaining, speed reducing doo-dad?

It looks like the upper larger gear is the driven gear, and the lower two are speed reducers? Or do I have that bass ackwards?

That second picture is another project I am working on, sorry....

Did I mess up my drawing? lol

Idler gear A is always connected to driven gear, but in one direction, it just "idles" off to the side not touching anything. When you want to reverse direction, you pivot the idler gear into connection with the output gear C and the output gear will now rotate in the same direction as the driven gear.

Yep. I did mess up my drawing. The idler gear would would turn in the opposite direction of the driven gear, always. I just drew it wrong.

Here is a tutorial: http://www.societyofrobots.com/mechanics_gears.shtml#rotdirection

But the take away is that for each gear in a chain of gears, each one will move in the opposite direction of the one driving it. By introducing a gear in between the driven gear and output gear, the third one will move in the same direction as the first.

This type of transmission would be perfect, since it would always be in sync and would would not require any sort of lever at all, but it's construction would be more difficult which is why I didn't show it last night. Basically you would have the run in one direction on half the gear and the run in the other direction on the other, inner half. When it reached the end of the spool, it would just reverse the direction on its own.

I've never seen a gear like this one before, and it's an interesting idea. The down side to using it is that, whether I was splitting a 4 ply into (2) x 2 ply yarns, a 6 ply into (3) x 2 ply yarns, or an 8 ply into (4) x 2 ply yarns, the yarns would always occupy the same real estate on the drum. I'd want to spread the yarns over almost all of the drum however many new plies the splitter makes. So, if I were making (2) x 2 ply yarns, each of the 2 plies would be distributed over almost half of the drum, and so on.

I'm happy to keep posting here; it's a friendly, well informed place. But as I lean away from using any Arduino hardware, or software, I'm wondering if I might be veering off topic too much? I'm guessing that there must be a forum that's better suited for amateur mechanical engineering topics such as this one is becoming.

For a purely mechanical option, couldn't you use something similar to the level-winders on overhead and baitcasting fishing reels? I couldn't find a decent image to show you how it works. But the shaft is cut like this:

I'm sure you could use some adjustable (and removable) stops on the shaft to set the end-points for when the hooks need to change direction. And also add/remove them depending how many drums you're filling.

ahh, yes, another great idea. Basically a spiral "screw" that your yarn would follow along with the groove. Pretty much a rotating "slide." I can see it working in one direction, trying to picture how it reverse, though. A double-helix perhaps?

As far as whether this discussion belongs here if you go purely mechanical, I am not sure. I am an old-school engineer that doesn't believe that a microcontroller is always the answer. You will find me suggesting mechanical methods all over, but not because I am anti-micro. I just think people way over-use stuff like the arduino to do things that really don't need it and tend to overcomplicate things.

I try to adhere to the KISS principles. You already have a crank providing driven rotation. You do not intend to motorize that. Adding a motor that needs to be synchronized to that crank requires sensors, limit switches, and other stuff as well as having to build mechanisms anyway....

Speaking of screws by the way... your hooks could be connected to bolts that fit on a threaded rod. As you rotate the rod, it will travel the nut up and down the length of the shaft. The mechanism I showed you would still handle the reversing of this threaded rod. To eliminate what they call 'backlash" which in your case would mostly happen when switching directions, the "nut" usually consists of inner ball bearings which roll inside the groves. Your pitch and rotation speed will determine how fast the movement moves up and down your roll. This application would not require a fine pitch.

Hey, Jabbado;

That is a good idea. Like you, I also looked for the fishing reel part image to no avail. My dad had a ratcheting screwdriver when we were kids that operated by way of a shaft with the same, or very similar groves. I'm a sort of old fashioned fisherman. You know; bait the hook, hang a bob on the line, cast it out a little ways, and be vewy, vewy quiet.

Howdy, Retroplayer;

That threaded rod idea is one I've also been contemplating. Using your illustration labels with C being the output gear, A the idler, and B the driven gear, would you use the threaded rod as the axle for A, or B? The "hooks" are currently made from 18 gauge stainless wire, hardened by heating over a gas range, and quenched in water; I'll try 14 ga. or 16 ga. next, but it would be easy enough to add a loop or two to extend below the present rod to a threaded rod.

Your nuts...where might I find those, and by what name? I haven't had any luck with locating them, but they sound perfect. Since I don't want for either the steel rod the steel rod, nor the threaded rod to move due to the hooks that connect them, I'm thinking of adding a 4th gear to the array. It will be below, and between A & B, and if I go this direction, the threaded rod will be it's axle, as well as the pivot point for A & B.

I haven't worked out yet what to make the trip levers from, nor how throwing the lever will move the bar that connects A & B. One step at a time. I appreciate the exchange of ideas. My thanks to both of you!

Oh, I almost forgot. Your comment about using the high tech approach when a low tech one would do just as well if not better is a wise one. I disassemble old sewing machines, re-plate (nickel) the parts that need it, sandblast the main casting, and repaint that with auto lacquer, reassemble, lube, and adjust tension, needle position, and generally just put things back in order again. I have 18 machines built from the late 50s to the late 70s. These machines are workhorses.

Beginning in the late 70s, the vast majority of machines were computerized. Rather than having exchangeable cams to make different stitch patterns, manufacturers offering dozens or even hundreds of stitches built in, and used electronics to accomplish the movement of the needles, and feed dogs. I haven't spoken to anyone who uses more than a couple of these no matter how many their machine can do. But if a component on a PCB goes, it often affects the whole machine, and it's rare that a user can isolate and repair the problem.

This guy did what I think you are trying to do with all mechanical parts.

Hey there;

Oh, that guy? His name is Goldberg; Rube was his grandfather. :grin: There are a couple of styles of swifts. The umbrella swift opens and closes like an umbrella, and the yarn wraps around the parts that cross. The Amish swift is like a large, wooden plus sign that sits on a table, and has a number of holes drilled part way into all four arms for pegs so as to accommodate varying sized skeins. Yarn can be wound onto or from either of these styles. There is also a weasel . It's a tall, narrow box on 4 short legs, and a wooden gear system inside. Attached to the front of the box is a hub with 6 or 8 spokes radiating from it, and each of these has a fixed dowel attached to the ends at 90 degree angles. One of the spokes has a dowel at about it's midway point, also at a 90 degree angle, and serves as a crank. The weasel is best for winding only, as it isn't adjustable like the other two. However the mechanism inside counts rotations and when some number is reached, "pop goes the weasel".

There are, of course, variations on all of these. The pedal-powered swift is not among them, and is a unique sort of device to be sure. It doesn't appear to be adjustable, occupies a considerable amount of floor space as compared to the other three, and is bound to make all passers by at the county fair's sheep to wool contest smile. With the exception of the steam, any of the other swifts will do the same thing. The in-line steamer is aimed at de-kinking the unraveled sweater yarn, I think. Some folk take a more pedestrian approach when they wash it.

The gadget I'm messing with isn't a swift. It's meant to split a 4 ply yarn into two 2 ply yarns, or four 1 ply yarns. The lady I'm making it for was my high school art teacher a whole bunch of years ago. She has struggled for years with a degenerative form of arthritis, and leaves her wheel chair only for moments at a time. The splitter I'm making is designed to sit between the arms of her chair on her lap. She has spent days hand splitting the yarn from a single sweater. There are at least two large improvements I still want to make, but she's down to about 3 hours now to split the plies of a sweater. I'd like to cut that in half again.