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Author Topic: Arduino, and Mechanical Movement of Objects - a Newbie Question  (Read 2284 times)
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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.
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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.
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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.
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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?
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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.

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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.
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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.
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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.
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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....
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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.
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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.
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This guy did what I think you are trying to do with all mechanical parts.
http://lifehacker.com/5962928/diy-bicycle+powered-machine-reclaims-yarn-from-sweaters
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Hey there;

Oh, that guy? His name is Goldberg; Rube was his grandfather.   smiley-mr-green  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.
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Yay! That makes me feel even better about offering help! smiley Good on you helping this lady out.

I think I have some questions above to answer...
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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!

I assume that you are asking about the "nuts" I am talking about and not trying to comment on my sanity (either is valid)?  Geez... I forget what they are called. Let me look. Ahh... ball screws and ball nuts (that doesn't sound like a safe search at work) : http://www.roton.com/ballscrews-ballnuts-nav.aspx?line=Recirculating


http://cncmentor.com/blog/2011/06/28/ball-nut/ gives you an inside view of a complex one. It wouldn't be too difficult to make a simple one. You just need some way to "capture" the bearrings and they need to be the right size to fit within the threads. The reason this cutaway is using a deflector is because it is using a complete ring of bearrings and it needs a way to pop them into the track as it spirals. With just two or four bearrings offset, you don't need to do that. This isn't a great picture, but it does show what the bearring capture of something simpler would look like. http://www.heli-tek.com/ball-nuts.php

Hope that helps.

Well, let's see... your crank is rotating the spool and we want to synchronize with the spool. So I would tap a feed of the spool axel for the driven gear (you could even reverse my drawing, the important part is that when a gear spins, the gear meshed with it will spin in reverse. So, the only magic is putting a gear in-between to reverse it again.) You would never hook up anything to the idler axel (or it wouldn't be called an idler.) It is always just meshed with the driven gear. In one direction, it just spins freely -- idling, in the other, it meshes with the output gear. You can swap the input and output gear, it doesn't really matter. But I would put the threaded rod on the output gear in my drawing since that is fixed. The other two gears are going to be mounted on a pivoting mechanism. You simply toggle that mechanism up or down to change which gear meshes directly with the output shaft.

To trigger it when it reaches the endstops, I would put something on your nuts that trip the lever. I would run the lever all way along  below the rod. If you do it right, you could even adjust the endstops as desired for the different spool widths you talked about. I am envisioning two wedges that bump each other and create a quick motion... I will have to think on it some and draw something up.
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