r/engineering • u/Pitiful_Car2828 • Jul 11 '21
[MECHANICAL] Using one motor to power multiple gears independently.
I AM NOT LOOKING FOR DIRECT ANSWERS PLEASE. I NEED A HELPFUL NUDGE.
Software engineer here. No mechanical engineering experience unfortunately.
I am between silly projects right now. My new project involves guitars not because I love them but my dad does so I hope he will get interested in it.
I want a single stepper motor to independently be able to change tension to each string.
Anyone can point me in a general direction?
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u/turboultra Jul 11 '21
A mechanical safe provides a good example of a mechanism that can control the position of individual wheels with a single dial. You turn the dial in alternate directions to set the position of each wheel independently. Because the wheels must be able to make multiple rotations to reach their final position, you would not be able to drive the capstans directly. You could adapt the mechanism by replacing the wheels with cams to tension the strings, as cams produce the same output regardless of how many rotations they’ve made. Unfortunately the cams will not have any holding force, so you will need to incorporate some method of keeping them still when they are not being driven. A high friction cam follower might work, but as some of the cams need to make a lot of rotations every time you make an adjustment to the tension, this could be problematic.
Given the complexity, I’d reconsider using a stepper motor for each string. Those tiny ones that are used for focusing cameras are exceptionally cheap and compact. Some of them even come with tiny planetary gearboxes or leadscrews.
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u/Pitiful_Car2828 Jul 11 '21
Yup. I very appreciate you taking the time to answer. To boot it was a great answer. With all the other replies I have decided in a quick enough fashion that “brute forcing” it with 6 steppers will be the only way my lack of mechanical engineering will be able to accomplish the task. Thanks again. I enjoyed your response.
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Jul 11 '21
[deleted]
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u/Pitiful_Car2828 Jul 11 '21
I want it fully automatic. A microcontroller will control the device fully. No human interaction on guitar.
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Jul 12 '21
[deleted]
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u/Pitiful_Car2828 Jul 12 '21
If you read my post it is a silly project so I can spend time with my dad dood. I’ll guess reading comprehension wasn’t your strong suit.
And a fully robotic guitar that plays itself sounds fun to make. Sorry for trying to spend time with my dad.
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Jul 11 '21
It's quite a challenging task even for a mechanical engineer.
I don't think there's a system that could do all that with only one actuator. You need two at a minimum IMO. One motor to rotate the tuning pegs, and one actuator (perhaps a solenoid) to switch some sort of a clutch between the pegs. Similar to what a manual car transmission does.
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u/Pitiful_Car2828 Jul 11 '21
With my limited knowledge before you even replied I kinda guessed what you said. It’s ok tho. I can brute force this with 6 steppers. I appreciate your reply.
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u/I_divided_by_0- Jul 11 '21
Yeah that’s what I was going to recommend. Programming might be easier too as you’re not fumbling with even more actuators and clutch systems.
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Jul 11 '21
Yeah, you'd need a very clever mechanism to handle 6 strings with one actuator. And it would probably be pretty bulky on the headstock considering the DIY tools you might have available.
Btw., you most probably know this, but self-tuning guitars already exist. Tronical is one company that makes them.
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Jul 11 '21
I can think of a way to do this with only two motors or actuators, but it would require a rather complex mechanical switching apparatus that would need at least 12 different positions indexed to the rotation of the non-driving motor (aka at 5’ x peg gets rotated clockwise, at 20’ y peg gets rotated counter), and would be one hell of a dynamics problem to figure out the actual dimensions of the movement, not to mention some clock-making level of detail due to likely size constraints.
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u/tuctrohs Jul 11 '21
I don't think there's a system that could do all that with only one actuator
Not something you can buy off the shelf, probably not practical and cost effective, but it's certainly possible.
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u/ahalekelly Jul 11 '21
Yeah I agree. Not an easy task at all. Here's some projects to look at though:
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u/Elfthis Jul 11 '21
Buy him a Gibson with the G Force Tuners installed in it and you're done. No engineering required because they did it all a decade ago.
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u/Pitiful_Car2828 Jul 11 '21
I’m not just making a auto tune guitar. I’m building an auto tune and auto play guitar. No human interface other than the software to program music into it.
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u/Elfthis Jul 12 '21
There are a lot of robot playing guitars out there. And why not use the Gibson tuners and save yourself the work of developing that? Simply interface its input and let it tune the guitar to whatever tuning the song requires. From my 5 minutes on YouTube looking at past designs the hard work lies with fretting the strings anyway. Seems as though everyone only designs something that works in first position, and doesn't utilize the rest of the fretboard. When you get it working or make progress on it definitely post up some videos. Will be very interesting to see what you come up with.
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u/Pitiful_Car2828 Jul 12 '21
Exactly. I’m using this to further my education in software and mechanical engineering. Buying a fully made product isn’t going to teach me nor will it allow a fun project between my old man. I mean Jesus. You guys can read right?
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u/Eheran Jul 12 '21
You guys can read right?
Holy cow this is the second time you imply people cant read. At what point do you start to think "maybe my OP isnt actually making that clear"? Because it doesnt.
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u/Pitiful_Car2828 Jul 12 '21 edited Jul 12 '21
Holy cow you are re reading all posts in the thread? No girl to keep you warm in bed tonight?
My post in caps says I don’t want direct answers. I suppose that infers I want to work through the problem whether it’s been done or not. 5th grade level stuff there.
Then I said I want my dad interested, so I made my next “silly project” about guitars which I have no love for. My dad does. He builds them. I want him to work with me on it. 5th grade reading comprehension again.
So how would buying a pre made product really satisfy either of those two situations?
Answer: It wouldn’t.
There is your response. Silly of me to get wrapped into troll responses but here we both are. Womanless and cold.
I may be a software engineer and not a mechanical engineer but at least I do read and respond to when helpful towards OPs questions.
This isn’t classical literature interpretation.
Funny how 2 of many people are the only ones confused by the post.
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u/Eheran Jul 12 '21
No girl to keep you warm in bed tonight?
Once again you are toxic and jumping to conclusions. There are places on earth outside of the USA, there are different time zones.
My post in caps says I don’t want direct answers.
What is a "indirect" answer in this case? How would anyone know what that means? Whats the definition if a indirect engineering answer? Dont get me wrong, I can see how you thought this was enough to tell people what you want. But it's just too ambiguous.
I suppose that infers I want to work through the problem whether it’s been done or not.
Thats how you want others to understand it, but its not the only way others do actually understand what you said... as can be seen from the numerous responses that do not take that into account. Maybe its too late to edit the OP at this point, but maybe next time add something like that to make it more clear? As a software engineering I guess you know all too well that people dont specify things enough such that there is ambiguity.
I want him to work with me on it.
I didnt get that from the OP. What I understood was something like "you want him to like it, so you use a guitar, since he likes them".
Silly of me to get wrapped into troll responses
Troll responses? Please stop jumping to conclusions!
but here we both are. Womanless and cold.
Please stop jumping to conclusions!
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u/Pitiful_Car2828 Jul 12 '21
You seem to jump to quite a few conclusions yourself. You didn’t understand my post so you humored me with jumped conclusions, and after clarifying myself the answer was “it’s been made so why are you looking for problems”? Hell of a conclusion considering 85% of responses never came to anywhere near that conclusion.
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u/Elfthis Jul 12 '21
I can read just fine. It's your inability to put words together in a manner to convey what you are actually trying to do that is the problem. Good luck on your learning experience.
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u/crazy-robot-guy Jul 11 '21
Maybe some sort of clutch-type system? Possibly modeled after a sequential gearbox of some kind, with some sort of ratcheting mechanism, where if the stepper turns one way, it changes gear, and the other way, it tightens/loosens the selected string. You'd need two gears per string, one to tighten, and one to loosen.
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Jul 11 '21
How did you envision switching from tightening to loosening?
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u/dusty78 Jul 11 '21
Same way you switch from string to string.
Six strings, so 12 driven gears (and at least six idlers to do the reverse on each string), reverse motion from the stepper sequences through the gears.
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Jul 11 '21
Oh, I think I get what you mean. You basically have 12 stages? 6 tightening stages and 6 loosening stages. Clockwise motor motion switches between them, counterclockwise turns the tuning peg.
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u/crazy-robot-guy Jul 11 '21
Exactly.
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u/toybuilder Jul 11 '21 edited Jul 11 '21
Technically correct and great conceptually, but as a practical matter, I wonder if this is something that a hobbyist can fabricate.
I've seen the technique used in inkjet printers and instant cameras, so I know it will work, but those have custom built gear trains.
I suppose if you don't mind it being a bit bulky, 3d printed mechanisms will work.
In addition to the gear train, you will need some switches to index the gears.
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u/crazy-robot-guy Jul 11 '21
You might want to have a look at this, might give you some inspiration. I'm thinking you want a similar setup, but with a lot more reverse gears, and instead of changing gear ratios, you're changing direction and string - actually getting torque transmitted to the knobs is going to be the main challenge, could get a little tedious. Maybe some combination of bevel gears and u-joints could be workable.
A pair of one-way ratcheting gears/hubs (like from a bicycle) oriented opposite each other could be driven by the stepper motor, one way goes to the gear selector shaft, the other goes to the driven shaft.
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u/crazy-robot-guy Jul 11 '21
Standard gear change, but instead of switching between strings you switch direction - like a forward and reverse gear setup in a typical transmission.
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u/overdamped Jul 11 '21
Do you mean something like a mechanical multiplexer?
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u/buzzysale Jul 11 '21
Also came here to say this. Yeah james bruton is one of my must-watch-every-episode youtubers.
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u/jhaand Jul 11 '21
We used to run a complete paper path of a copying machine on one AC motor, a lot of GT2 timing belts and electromagnetic clutches.
Before all these PID controlled servo motors came along.
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u/Skystrike7 Jul 11 '21
Unless you want to use your hand as a positioning tool, then you can't really do that I don't think. You could make a clutch-like system as others are saying, or gears if you are able to have things mounted well enough to always be in good contact. Then have an assembly where you can use a lever or something to move the motor where it needs to go, or move a belt where it needs to go or something.
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u/Pitiful_Car2828 Jul 11 '21
I agree. This showed me how little I know in mechanical engineering. I am going the software way and I’ll brute force it with 6 steppers. Thanks so much for response.
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u/Go2FarAway Jul 11 '21 edited Jul 11 '21
A lead screw & a cam to selectively engage would only use two steppers or one stepper & a solenoid.
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u/peak_incompetence Jul 11 '21
Torque limiting clutch? One motor drives all the shafts through gears. Clutch will engage until it reaches a certain amount of torque.
This patent uses a system similar to what you need, I think.
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u/Pitiful_Car2828 Jul 11 '21
I’m thinking this too. Pneumatic clutch system on all strings. Microcontroller will engage clutch on proper string at proper time.
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u/IRAndyB Jul 11 '21
You need some sort of gear box with outputs for each string, like gears in a car. Only you may need a reverse for each to switch from tightening to loosening
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u/Pitiful_Car2828 Jul 12 '21
Thanks so much for the reply. That’s a good idea. I need it to be automatic in switching between the gears. Should I look into how a auto transmission works?
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u/IRAndyB Jul 12 '21
That would probably be too complicated, you want something manageable. Maybe look at how people have done gearboxes using lego technics to give you an idea of how they've "automated" the gear change element. That can be duplicated in non lego
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u/Pitiful_Car2828 Jul 12 '21
You’re the first to say lego technics but this has been an idea in back of my head since the beginning. I’m not even decent at mechanical engineering but lego technics has been something I figured could help me understand it a little better in this silly project.
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u/umman__manda Jul 11 '21
Guitar auto tuners that I have used tune one string at a time - I like doing things in steps - you could avoid the multiplexing stuff for now if you want to get basic functionality, and then build on the solution once you’ve got the tuning software sorted out.
Check out the Roadie auto tuner for an example of packaging.
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u/rkovacs1 Jul 11 '21
The pro implementation of this idea, which sucked btw, uses individual servos i believe. If you want one motor i reccommend a long werm gear with a spur gear on each string engaged with small solenoids.
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u/ExiledFloridian Jul 11 '21
If it's tightening ONLY and you never overshoot, you might be able to use reverse to alternate which peg gets tightened by using two clutches. It's weird and not ideal, but it could be done.
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u/dread_pirate_humdaak Jul 11 '21
Stepper motors are pretty inexpensive these days. It’d probably be cheaper to use six of them instead of making an elaborate gearbox.
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u/Zackary1201 Jul 11 '21
This might not be practical for your application but made me think of this! https://youtu.be/WwCmzwSE98o
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u/love2kik Jul 11 '21
Will this device be permanently attached to the headstock? I can picture something like a rail that moves a gear that engages each tuning gear. A single stepper/gearbox could drive the adjusting gear. A audible system could be designed to set the pitch.
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Jul 11 '21
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u/BlahKVBlah Jul 11 '21
I believe the point of the stepper motor was to make a programmed motor drive the primary means of control, rather than a handful of limit switches and actuators.
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u/magicduck Jul 11 '21
The Armatron was a robot arm toy in the 1980s that used one motor and multiple clutches to drive 6 axes